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Background: Cannabis use has been associated with abnormalities in cerebellar mediated motor and non-motor (i.e. cognition and personality) phenomena. Since the cerebellum is a region with high cannabinoid type 1 receptor density, these impairments may reflect alterations of signaling between the cerebellum and other brain regions. Aims: We hypothesized that cerebellar-cortical resting-state functional connectivity (rsFC) would be altered in cannabis users, relative to their non-using peers. It was also hypothesized that differences in rsFC would be associated with cannabis use features, such as age of initiation and lifetime use. Methods: Cerebellar-cortical and subcortical rsFCs were computed between 28 cerebellar lobules, defined by a spatially unbiased atlas template of the cerebellum, and individual voxels in the cerebral regions, in 41 regular cannabis users (20 female) and healthy non-using peers ( N = 31; 18 female). We also investigated associations between rsFC and cannabis use features (e.g. lifetime cannabis use and age of initiation). Results: Cannabis users demonstrated hyperconnectivity between the anterior cerebellar regions (i.e. lobule I-IV) with the posterior cingulate cortex, and hypoconnectivity between the rest of the cerebellum (i.e. Crus I and II, lobule VIIb, VIIIa, VIIIb, IX, and X) and the cortex. No associations were observed between features of cannabis use and rsFC. Conclusions: Cannabis use was associated with altered patterns of rsFC from the cerebellum to the cerebral cortex which may have a downstream impact on behavior and cognition.

The goal of the study was to evaluate how repetitive head traumas sustained by athletes in contact sports depend on sport and level of play. A total of 16 middle school football players, 107 high school football players, and 65 high school female soccer players participated. Players were separated into levels of play: middle school (MS), freshman (FR), junior varsity (JV), junior varsity-varsity (JV-V), and varsity (V). xPatch sensors were used to measure peak translational and angular accelerations (PTA and PAA, respectively) for each head acceleration event (HAE) during practice and game sessions. Data were analyzed using a custom MATLAB program to compare metrics that have been correlated with functional neurological changes: session metrics (median HAEs per contact session), season metrics (total HAEs, cumulative PTA/PAA), and regressions (cumulative PTA/PAA versus total HAEs, total HAEs versus median HAEs per contact session). Football players had greater session ( p

Abnormalities of cerebellar function have been implicated in the pathophysiology of schizophrenia. Since the cerebellum has afferent and efferent projections to diverse brain regions, abnormalities in cerebellar lobules could affect functional connectivity with multiple functional systems in the brain. Prior studies, however, have not examined the relationship of individual cerebellar lobules with motor and nonmotor resting‐state functional networks. We evaluated these relationships using resting‐state fMRI in 30 patients with a schizophrenia‐spectrum disorder and 37 healthy comparison participants. For connectivity analyses, the cerebellum was parcellated into 18 lobular and vermal regions, and functional connectivity of each lobule to 10 major functional networks in the cerebrum was evaluated. The relationship between functional connectivity measures and behavioral performance on sensorimotor tasks (i.e., finger‐tapping and postural sway) was also examined. We found cerebellar–cortical hyperconnectivity in schizophrenia, which was predominantly associated with Crus I, Crus II, lobule IX, and lobule X. Specifically, abnormal cerebellar connectivity was found to the cerebral ventral attention, motor, and auditory networks. This cerebellar–cortical connectivity in the resting‐state was differentially associated with sensorimotor task‐based behavioral measures in schizophrenia and healthy comparison participants—that is, dissociation with motor network and association with nonmotor network in schizophrenia. These findings suggest that functional association between individual cerebellar lobules and the ventral attentional, motor, and auditory networks is particularly affected in schizophrenia. They are also consistent with dysconnectivity models of schizophrenia suggesting cerebellar contributions to a broad range of sensorimotor and cognitive operations.

Understanding the impact of concussion history on mental health—mood disorders and substance use—is an essential step in characterizing the psychological and behavioral consequences of concussion and in developing effective treatments. The objective of this study was to examine the association between the history of concussion and substance abuse by investigating both its direct and indirect association via mood disorder. A secondary objective was to determine whether gender moderates the association. A comprehensive survey was administered to 4849 college-age adults that assessed history of concussion; depression, anxiety, and panic disorders using the Patient Health Questionnaire (PHQ); and substance use using the Alcohol Use Disorders Identification Test (AUDIT) (alcohol) and Cannabis Use Disorders Identification Test-Revised (CUDIT) (cannabis). Regression models were used to examine the association between concussion history and substance use. Mood disorders were entered into the model as mediators and gender as a moderator variable. Those with a history of concussion had higher panic, AUDIT, and CUDIT scores than those with no history of concussion, and AUDIT and CUDIT scores showed an interaction between concussion history and gender. The regression models revealed significant direct and indirect (via depression and panic disorder) effects of concussion history on alcohol and cannabis use, which was moderated by gender. Concussion can have long-term psychological consequences and appears to affect both mood and substance use. The results presented demonstrate that the relationship between concussion and substance use is complex with mood disorder mediating the effect.

fMRI has been used as an outcome measure in dementia treatment studies, with many previous studies comparing only single pre- and post-treatment fMRI scans to determine treatment-induced neural changes, while utilizing single subject experimental designs. The purpose of the current study was to evaluate fMRI test-retest reliability in dementia patients and typical older adults using noun and verb confrontation naming to evaluate the validity of using a single pre/post-treatment scan comparison. Seven individuals with dementia and 9 control participants were tested three times over two months using the same fMRI procedures. Differences in individual and group level activation patterns were observed that varied across time. Additionally, the extent of variability fluctuated across individuals, groups, and the grammatical category of target words. Our findings suggested that one time fMRI scanning may inadequately represent an individual's typical brain activation pattern, particularly an individual with dementia. Thus, multiple imaging baselines are recommended.

The research on the neural correlates underlying the language system has gradually moved away from the traditional Broca-Wernicke framework to a network perspective in the past 15 years. Language processing is found to be supported by the co-activation of both core and peripheral brain regions. However, the dynamic co-activation patterns of these brain regions serving different language functions remain to be fully revealed. The present functional magnetic resonance imaging (fMRI) study focused on sentence processing at different syntactic complexity levels to examine how the co-activation of different brain networks will be modulated by increased processing costs. Chinese relative clauses were used to probe the two dimensions of syntactic complexity: embeddedness (left-branching vs. center-embedded) and gap-filler dependency (subject-gap vs. object-gap) using the general linear model (GLM) approach, independent component analysis (ICA) and graph theoretical analysis. In contrast to localized activation revealed by the GLM approach, ICA identified more extensive networks both positively and negatively correlated with the task. We found that the posterior default mode network was anti-correlated to the gap-filler integration costs with increased deactivation for the left-branching object relative clauses compared to subject relative clauses, suggesting the involvement of this network in leveraging the cognitive resources based on the complexity level of the language task. Concurrent activation and deactivation of networks were found to be associated with the higher costs induced by center-embedding and its interaction with gap-filler integration. The graph theoretical analysis further unveiled that center-embeddedness imposed more attentional demand on the subject relative clause, as characterized by its higher degree and strength in the ventral attention network, and higher processing costs of syntactic reanalysis on the object relative clause, as characterized by increased intermodular connections of the language network with other networks. The results suggest that network activation and deactivation profiles are modulated by different dimensions of syntactic complexity to serve the higher demand of creating a coherent semantic representation.

There is accruing evidence of cerebellar abnormalities in individuals with schizophrenia as measured by performance on a variety of tasks believed to be dependent on cerebellar integrity, including delay eyeblink conditioning. There is also evidence of cerebellar dysfunction on a neural level in schizophrenia from both task-based and resting state neuroimaging studies, however few studies have examined cerebellar neural function while the cerebellum is directly recruited in individuals with schizophrenia. In the current pilot study, we examined neural activity during an explicitly cerebellar task in individuals with schizophrenia or schizoaffective disorder and non-psychiatric controls. Participants underwent delay eyeblink conditioning during fMRI. Results indicated eyeblink conditioning impairment in patients as evidenced by a group by time interaction for conditioned responses. A significant cluster of cerebellar activation was present in controls but not patients during the first half of conditioning; there were no significant differences in activation between groups. An ROI analysis focused on the cerebellum in patients revealed two significant clusters that were inversely associated with negative symptom severity. These results are broadly consistent with the theory of cognitive dysmetria, wherein cerebellar abnormalities are theorized to contribute to motor as well as cognitive and affective disturbances in schizophrenia.

Introduction A prominent effect of acute cannabis use is impaired motor coordination and driving performance. However, few studies have evaluated balance in chronic cannabis users, even though density of the CB1 receptor, which mediates the psychoactive effects of cannabis, is extremely high in brain regions critically involved in this fundamental behavior. The present study measured postural sway in regular cannabis users and used rambling and trembling analysis to quantify the integrity of central and peripheral nervous system contributions to the sway signal. Methods Postural sway was measured in 42 regular cannabis users (CB group) and 36 non-cannabis users (N-CB group) by asking participants to stand as still as possible on a force platform in the presence and absence of motor and sensory challenges. Center of pressure (COP) path length was measured, and the COP signal was decomposed into rambling and trembling components. Exploratory correlational analyses were conducted between sway variables, cannabis use history, and neurocognitive function. Results The CB group had significantly increased path length and increased trembling in the anterior-posterior (AP) direction. Exploratory correlational analyses suggested that AP rambling was significantly inversely associated with visuo-motor processing speed. Discussion Regular cannabis use is associated with increased postural sway, and this appears to be predominantly due to the trembling component, which is believed to reflect the peripheral nervous system’s contribution to the sway signal.

Prominent conceptual models characterize schizophrenia as a dysconnectivity syndrome, with recent research focusing on the contributions of the cerebellum in this framework. The present study examined the role of the cerebellum and its effective connectivity to the cerebrum during sensorimotor synchronization in schizophrenia. Specifically, the role of the cerebellum in temporally coordinating cerebral motor activity was examined through path analysis. Thirty-one individuals diagnosed with schizophrenia and 40 healthy controls completed a finger-tapping fMRI task including tone-paced synchronization and self-paced continuation tapping at a 500 ms intertap interval (ITI). Behavioral data revealed shorter and more variable ITIs during self-paced continuation, greater clock (vs motor) variance, and greater force of tapping in the schizophrenia group. In a whole-brain analysis, groups showed robust activation of the cerebellum during self-paced continuation but not during tone-paced synchronization. However, effective connectivity analysis revealed decreased connectivity in individuals with schizophrenia between the cerebellum and primary motor cortex but increased connectivity between cerebellum and thalamus during self-paced continuation compared with healthy controls. These findings in schizophrenia indicate diminished temporal coordination of cerebral motor activity by cerebellum during the continuation tapping portion of sensorimotor synchronization. Taken together with the behavioral finding of greater temporal variability in schizophrenia, these effective connectivity results are consistent with structural and temporal models of dysconnectivity in the disorder.

Objectives Though sub-concussive impacts are common during contact sports, there is little consensus whether repeat blows affect brain function. Using a “lifetime exposure” rather than acute exposure approach, we examined oculomotor performance and brain activation among collegiate football players and two control groups. Our analysis examined whether there are group differences in eye movement behavioral performance and in brain activation during smooth pursuit. Methods Data from 21 off-season Division I football “starters” were compared with a) 19 collegiate cross-country runners, and b) 11 non-athlete college students who were SES matched to the football player group (total N = 51). Visual smooth pursuit was performed while undergoing fMRI imaging via a 3 Tesla scanner. Smooth pursuit eye movements to three stimulus difficulty levels were measured with regard to RMS error, gain, and lag. Results No meaningful differences were found for any of the standard analyses used to assess smooth pursuit eye movements. For fMRI, greater activation was seen in the oculomotor region of the cerebellar vermis and areas of the FEF for football players as compared to either control group, who did not differ on any measure. Conclusion Greater cerebellar activity among football players while performing an oculomotor task could indicate that they are working harder to compensate for some subtle, long-term subconcussive deficits. Alternatively, top athletes in a sport requiring high visual motor skill could have more of their cerebellum and FEF devoted to oculomotor task performance regardless of subconcussive history. Overall, these results provide little firm support for an effect of accumulated subconcussion exposure on brain function., Highlights • Elite collegiate football players have identical smooth eye movements in comparison to cross country runners and controls. • There is more activation in ocularmotor structures in football players in comparison to cross country runners or controls.

Cognitive mechanisms for sign language lexical access are fairly unknown. This study investigated whether phonological similarity facilitates lexical retrieval in sign languages using measures from a new lexical database for American Sign Language. Additionally, it aimed to determine which similarity metric best fits the present data in order to inform theories of how phonological similarity is constructed within the lexicon and to aid in the operationalization of phonological similarity in sign language. Sign repetition latencies and accuracy were obtained when native signers were asked to reproduce a sign displayed on a computer screen. Results indicated that, as predicted, phonological similarity facilitated repetition latencies and accuracy as long as there were no strict constraints on the type of sublexical features that overlapped. The data converged to suggest that one similarity measure, MaxD, defined as the overlap of any 4 sublexical features, likely best represents mechanisms of phonological similarity in the mental lexicon. Together, these data suggest that lexical access in sign language is facilitated by phonologically similar lexical representations in memory and the optimal operationalization is defined as liberal constraints on overlap of 4 out of 5 sublexical features-similar to the majority of extant definitions in the literature.

Human and animal studies have shown that heavy cannabis (CB) use interacts with glutamatergic signaling. Additionally, recent studies have suggested that glutamate (Glu) may drive resting state functional connectivity (RSfc). The aims of the current preliminary study were to: 1) determine whether dorsal anterior cingulate cortex (dACC) Glu is related to RSfc between the dACC and two nodes of the reward network, the nucleus accumbens (NAc) and hippocampus (Hp); and 2) determine whether CB use interacts with the relationship between dACC Glu and RSfc. A group of 23 chronic CB users and 23 healthy controls participated in this multimodal MRI study. Glu levels were assessed in the dACC using magnetic resonance spectroscopy (MRS). Linear regression models were used to determine whether dACC Glu and CB use predicts RSfc between the dACC and the NAc and Hp. While the effect size is small, the results showed that the connectivity between the dACC and right NAc was predicted by the interaction between dACC Glu levels and monthly CB use. Additionally, while there is some suggestion that dACC Glu is correlated with dACC-hippocampal connectivity, unlike for dACC/NAc connectivity the relationship between them does not appear to be affected by CB use. These preliminary findings are significant in that they demonstrate the need for future studies with larger sample sizes to better characterize the relationship between resting state connectivity and neurochemistry as well as to characterize how CB use interacts with that relationship.

BACKGROUND Magnetic resonance imaging (MRI) studies have shown differences in volume and structure in the brains of individuals with alcohol use disorder (AUD). Most research has focused on neuropathological effects of alcohol that appear after years of chronic alcohol misuse. However, few studies have investigated white matter (WM) microstructure and diffusion MRI-based (DWI) connectivity during early stages of AUD. Therefore, the goal of this work was to investigate WM integrity and structural connectivity in emerging adulthood AUD subjects using both conventional DWI metrics and a novel connectomics approach. METHODS Twenty-two AUD and 18 controls (CON) underwent anatomic and diffusion MRI. Outcome measures were scalar diffusion metrics and structural network connectomes. Tract-Based Spatial Statistics was used to investigate group differences in diffusion measures. Structural connectomes were used as input into a community structure procedure to obtain a coclassification index matrix (an indicator of community association strength) for each subject. Differences in coclassification and structural connectivity (indexed by streamline density) were assessed via the Network Based Statistics Toolbox. RESULTS AUD had higher fractional anisotropy (FA) values throughout the major WM tracts, but also had lower FA values in WM tracts in the cerebellum and right insula (pTFCE

Accumulating evidence relates finger gnosis (also called finger sense or finger gnosia), the ability to identify and individuate fingers, to cognitive processing, particularly numerical cognition. Multiple studies have shown that finger gnosis scores correlate with or predict numerical skills in children. Neuropsychological cases as well as magnetic stimulation studies have also shown that finger agnosia (defects in finger gnosis) often co-occurs with cognitive impairments, including agraphia and acalculia. However, our knowledge of the structural and functional correlates, and the development of finger gnosis is limited. To expand our understanding of structural brain features that are associated with finger gnosis, we conducted a voxel-based morphometry study with 42 seven- to 10-year-old children, where we investigated the correlation between finger gnosis scores and whole-brain gray matter volume (GMV). Correlations between finger gnosis and GMV were found in a set of frontoparietal, striatal, and cerebellar areas. We also found sex differences in how GMV is associated with finger gnosis. While females showed a more distributed and extensive set of frontal and parietal clusters, males showed two striatal clusters. This study provides the first findings on structural brain features that correlate with finger gnosis.

The impact of fingers on numerical and mathematical cognition has received a great deal of attention recently. However, the precise role that fingers play in numerical cognition is unknown. The current study explores the relationship between finger sense, arithmetic and general cognitive ability. Seventy-six children between the ages of 5 and 12 participated in the study. The results of stepwise multiple regression analyses demonstrated that while general cognitive ability including language processing was a predictor of addition performance, finger sense was not. The impact of age on the relationship between finger sense, and addition was further examined. The participants were separated into two groups based on age. The results showed that finger gnosia score impacted addition performance in the older group but not the younger group. These results appear to support the hypothesis that fingers provide a scaffold for calculation and that if that scaffold is not properly built, it has continued differential consequences to mathematical cognition.

The aim of the present study was to characterize effects of learning a sign language on the processing of a spoken language. Specifically, audiovisual phoneme comprehension was assessed before and after 13 weeks of sign language exposure. L2 ASL learners performed this task in the fMRI scanner. Results indicated that L2 American Sign Language (ASL) learners' behavioral classification of the speech sounds improved with time compared to hearing nonsigners. Results indicated increased activation in the supramarginal gyrus (SMG) after sign language exposure, which suggests concomitant increased phonological processing of speech. A multiple regression analysis indicated that learner's rating on co-sign speech use and lipreading ability was correlated with SMG activation. This pattern of results indicates that the increased use of mouthing and possibly lipreading during sign language acquisition may concurrently improve audiovisual speech processing in budding hearing bimodal bilinguals.

Subconcussive head impacts have emerged as a complex public health concern. The oculomotor system is sensitive to brain trauma; however, neuro-ophthalmologic response to subconcussive head impacts remains unclear.To examine whether subconcussive head impacts cause impairments in neuro-ophthalmologic function as measured by the King-Devick test (KDT) and oculomotor function as measured by the near point of convergence.In this randomized clinical trial, adult soccer players were randomized into either a heading group or kicking (control) group. The heading group executed 10 headers with soccer balls projected at a speed of 25 mph. The kicking-control group followed the same protocol but with 10 kicks. Peak linear and rotational head accelerations were assessed with a triaxial accelerometer. The KDT speed and error and near point of convergence were assessed at baseline (preheading or prekicking) and at 0, 2, and 24 hours after heading or kicking.Ten soccer-ball headings or kicks.The primary outcome was the group-by-time interaction of KDT speed at 0 hours after heading or kicking. The secondary outcomes included KDT speed at 2 hours and 24 hours after heading or kicking, KDT error, and near point of convergence.A total of 78 individuals enrolled (heading group, n = 40; kicking-control group, n = 38). Eleven individuals (heading group: 4 women; mean [SD] age, 22.5 [1.0] years; kicking-control group, 3 women and 4 men; mean [SD] age, 20.9 [1.1] years) voluntarily withdrew from the study. Data from 67 participants with a mean (SD) age of 20.6 (1.7) years were eligible for analysis (heading, n = 36; kicking-control, n = 31). Mean (SD) peak linear accelerations and peak rotational accelerations per impact for the heading group were 33.2 (6.8) g and 3.6 (1.4) krad/s2, respectively. Conversely, soccer kicking did not induce a detectable level of head acceleration. Both groups showed improvements in KDT speed (heading group: 0 hours, -1.2 [95% CI, -2.2 to -0.1] seconds; P = .03; 2 hours, -1.3 [95% CI, -2.6 to 0] seconds; P = .05; 24 hours, -3.2 [95% CI, -4.3 to -2.2] seconds; P .001; kicking-control group: 0 hours, -3.3 [95% CI, -4.1 to -2.5] seconds; P .001; 2 hours, -4.1 [95% CI, -5.1 to -3.1] seconds; P .001; 24 hours, -5.2 [95% CI, -6.2 to -4.2] seconds; P .001). Group differences occurred at all postintervention points; the kicking-control group performed KDT faster at 0 hours (-2.2 [95% CI, -0.8 to -3.5] seconds; P = .001), 2 hours (-2.8 [95% CI, -1.2 to -4.4] seconds; P .001), and 24 hours after the intervention (-2.0 [95% CI, -0.5 to -3.4] seconds; P = .007) compared with those of the heading group.These data support the hypothesis that neuro-ophthalmologic function is affected, at least in the short term, by subconcussive head impacts that may affect some individuals in some contact sports. Further studies may help determine if these measures can be a useful clinical tool in detecting acute subconcussive injury.ClinicalTrials.gov Identifier: NCT03488381.

Cellular studies indicate that endocannabinoid type-1 retrograde signaling plays a major role in synaptic plasticity. Disruption of these processes by delta-9-tetrahydrocannabinol (THC) could produce alterations either in structural and functional brain connectivity or in their association in cannabis (CB) users. Graph theoretic structural and functional networks were generated with diffusion tensor imaging and resting-state functional imaging in 37 current CB users and 31 healthy non-users. The primary outcome measures were coupling between structural and functional connectivity, global network characteristics, association between the coupling and network properties, and measures of rich-club organization. Structural-functional coupling was globally preserved showing a positive association in current CB users. However, the users had disrupted associations between structural-functional coupling and network topological characteristics, most perturbed for shorter connections implying region-specific disruption by CB use. Rich-club analysis revealed impaired structural-functional coupling in the hippocampus and caudate of users. This study provides evidence of the abnormal structural-functional association in CB users. The effect was predominant in shorter connections of the brain network, suggesting that the impact of CB use or predispositional factors may be most apparent in local interconnections. Notably, the hippocampus and caudate specifically showed aberrant structural and functional coupling. These structures have high CB1 receptor density and may also be associated with changes in learning and habit formation that occur with chronic cannabis use.

Bilinguals activate both languages when they intend to speak even one language alone (e.g., Kroll, Bobb, & Wodniekca, 2006). At the same time, they are able to select the language they intend to speak and switch back and forth between languages rapidly, with few production errors. Previous research utilizing behavioral (Linck, Kroll, & Sunderman, 2009) and neuroimaging techniques (ERPs and fMRI; Guo, Liu, Misra, & Kroll, 2011; Misra, Guo, Bobb, & Kroll, 2012) suggest that successful bilingual speech production is enabled by active inhibition of the language not in use. Results showing an asymmetric switching cost for the L1 compared to the L2 (with a larger cost -reflected in longer naming latencies-when switching from the L2 to the L1) have been taken as evidence that the L1 (usually the dominant language for bilinguals who learned their second language later in life) may need to be inhibited when speaking in the L2. However, there is still little research on the scope of this inhibitory process. The goal of this event-related functional magnetic resonance imaging study is to understand how the recruitment of neural areas implicated during bilingual language processing are shaped by the scope of language use. The results show that bilinguals engage a wide functional control network that is hierarchically engaged in local control for single lexical items, but extends further to the broader semantic level, and finally to the whole language. This functional network is modulated by proficiency in the L2.

Growing evidence suggests that glutamate neurotransmission plays a critical role in alcohol addiction. Cue-induced change of glutamate has been observed in animal studies but never been investigated in humans. This work investigates cue-induced change in forebrain glutamate in individuals with alcohol use disorder (AUD). A total of 35 subjects (17 individuals with AUD and 18 healthy controls) participated in this study. The glutamate concentration was measured with single-voxel (1)H-MR spectroscopy at the dorsal anterior cingulate. Two MRS sessions were performed in succession, the first to establish basal glutamate levels and the second to measure the change in response to alcohol cues. The changes in glutamate were quantified for both AUD subjects and controls. A mixed model ANOVA and t-tests were performed for statistical analysis. ANOVA revealed a main effect of cue-induced decrease of glutamate level in the anterior cingulate cortex (ACC). A significant interaction revealed that only AUD subjects showed significant decrease of glutamate in the ACC. There were no significant group differences in the level of basal glutamate. However, a negative correlation was found between the basal glutamate level and the number of drinking days in the past 2 weeks for the AUD subjects. Collectively, our results indicate that glutamate in key areas of the forebrain reward circuit is modulated by alcohol cues in early alcohol dependence.

A disturbance in the integration of information during mental processing has been implicated in schizophrenia, possibly due to faulty communication within and between brain regions. Graph theoretic measures allow quantification of functional brain networks. Functional networks are derived from correlations between time courses of brain regions. Group differences between SZ and control groups have been reported for functional network properties, but the potential of such measures to classify individual cases has been little explored. We tested whether the network measure of betweenness centrality could classify persons with schizophrenia and normal controls. Functional networks were constructed for 19 schizophrenic patients and 29 non-psychiatric controls based on resting state functional MRI scans. The betweenness centrality of each node, or fraction of shortest-paths that pass through it, was calculated in order to characterize the centrality of the different regions. The nodes with high betweenness centrality agreed well with hub nodes reported in previous studies of structural and functional networks. Using a linear support vector machine algorithm, the schizophrenia group was differentiated from non-psychiatric controls using the ten nodes with the highest betweenness centrality. The classification accuracy was around 80%, and stable against connectivity thresholding. Better performance was achieved when using the ranks as feature space as opposed to the actual values of betweenness centrality. Overall, our findings suggest that changes in functional hubs are associated with schizophrenia, reflecting a variation of the underlying functional network and neuronal communications. In addition, a specific network property, betweenness centrality, can classify persons with SZ with a high level of accuracy.

Fingers are used as canonical representations for numbers across cultures. In previous imaging studies, it was shown that arithmetic processing activates neural resources that are known to participate in finger movements. Additionally, in one dual-task study, it was shown that anatomically ordered finger tapping disrupts addition and subtraction more than multiplication, possibly due to a long-lasting effect of early finger counting experiences on the neural correlates and organization of addition and subtraction processes. How arithmetic task difficulty and tapping complexity affect the concurrent performance is still unclear. If early finger counting experiences have bearing on the neural correlates of arithmetic in adults, then one would expect anatomically and non-anatomically ordered tapping to have different interference effects, given that finger counting is usually anatomically ordered. To unravel these issues, we studied how (1) arithmetic task difficulty and (2) the complexity of the finger tapping sequence (anatomical vs. non-anatomical ordering) affect concurrent performance and use of key neural circuits using a mixed block/event-related dual-task fMRI design with adult participants. The results suggest that complexity of the tapping sequence modulates interference on addition, and that one-digit addition (fact retrieval), compared to two-digit addition (calculation), is more affected from anatomically ordered tapping. The region-of-interest analysis showed higher left angular gyrus BOLD response for one-digit compared to two-digit addition, and in no-tapping conditions than dual tapping conditions. The results support a specific association between addition fact retrieval and anatomically ordered finger movements in adults, possibly due to finger counting strategies that deploy anatomically ordered finger movements early in the development.

Gender differences in brain structure and function have long been an interest to neuroscientists. One region where these differences have been reported is in the band of white matter that connects the two cerebral hemisphere, the corpus callosum. The current study explores the possibility that differences in cognitive ability contribute to the observed gender effects. The focus here is on visuo-spatial processing as measured by mental rotation which has also been found to have significant gender differences. The results reported show that two segments of the corpus callosum revealed gender differences, the rostrum and the anterior midbody. Both segments connect cortical regions that have been implicated in mental rotation. Additionally, the gender effect found in the rostrum appears to be due to visuo-spatial processing while the anterior midbody appears to be affected by both visuo-spatial processing and gender. These results suggest that because neural structure and cognition are intimately intertwined, cognition should be accounted for when making group comparisons of neural structure.

White matter abnormalities in schizophrenia have been revealed by many imaging techniques and analysis methods. One of the findings by diffusion tensor imaging is a decrease in fractional anisotropy (FA), which is an indicator of white matter integrity. On the other hand, elevation of metabolic rate in white matter was observed from positron emission tomography (PET) studies. In this report, we aim to compare the two structural and functional effects on the same subjects. Our comparison is based on the hypothesis that signal fluctuation in white matter is associated with white matter functional activity. We examined the variance of the signal in resting state fMRI and found significant differences between individuals with schizophrenia and non-psychiatric controls specifically in white matter tissue. Controls showed higher temporal signal-to-noise ratios clustered in regions including temporal, frontal, and parietal lobes, cerebellum, corpus callosum, superior longitudinal fasciculus, and other major white matter tracts. These regions with higher temporal signal-to-noise ratio agree well with those showing higher metabolic activity reported by studies using PET. The results suggest that individuals with schizophrenia tend to have higher functional activity in white matter in certain brain regions relative to healthy controls. Despite some overlaps, the distinct regions for physiological noise are different from those for FA derived from diffusion tensor imaging, and therefore provide a unique angle to explore potential mechanisms to white matter abnormality.

Previous studies have reported anticipatory effects during sentence processing. However, the source of these effects has not been clearly characterized. This study investigated the hypothesis that one source of anticipatory effects, particularly during verb processing, is the automatic triggering of argument structure processes. If argument structure processes are automatically triggered it was hypothesized that the task need not require the initiation of the process, as such a primed lexical decision task was used that examined the neural priming of cross-grammatical class prime pairs (e.g., verb-noun priming). While previous studies, as does the current study, have revealed behavioral priming for cross-grammatical class and within-class (noun-noun and verb-verb) prime/target pairs, the current results revealed significant activation differences. Enhancement effects were observed for cross-grammatical class priming in the language network, particularly the inferior frontal gyrus (BA 47), and the posterior temporal cortex. Both regions have been linked to argument structure processing previously. Within-class priming resulted in neural suppression of the inferior temporal/occipital regions. Together, the data presented suggest the automatic triggering of argument structure representations and demonstrate that priming is a fruitful mechanism to explore aspects of sentence processing.

The impact of handedness on language processing has been studied extensively and the results indicate that there is a relationship between the two variables; however, the nature of the relationship is not at all clear. In the current study we explored degree of handedness (DH) opposed to direction in a group of right-handed individuals. fMRI was used to explore the impact of DH on the sentence comprehension network. The results revealed that during sentence comprehension activation in regions linked to semantic memory (e.g., anterior temporal cortex) were modulated by DH. Also, unexpectedly the precuneus/posterior cingulate gyrus which has been linked to episodic memory was also affected by DH. These results extend those reported previously by showing that the neural architecture that supports sentence comprehension is modulated by DH. More specifically, together the results presented here support the hypothesis proposed by Townsend, Carrithers, and Bever (2001) that DH interacts with the language system and impacts the strategy used during sentence comprehension.

Visual word recognition has been studied for decades. One question that has received limited attention is how different text presentation orientations disrupt word recognition. By examining how word recognition processes may be disrupted by different text orientations it is hoped that new insights can be gained concerning the process. Here, we examined the impact of rotating and inverting text on the neural network responsible for visual word recognition focusing primarily on a region of the occipto-temporal cortex referred to as the visual word form area (VWFA). A lexical decision task was employed in which words and pseudowords were presented in one of three orientations (upright, rotated or inverted). The results demonstrate that inversion caused the greatest disruption of visual word recognition processes. Both rotated and inverted text elicited increased activation in spatial attention regions within the right parietal cortex. However, inverted text recruited phonological and articulatory processing regions within the left inferior frontal and left inferior parietal cortices. Finally, the VWFA was found to not behave similarly to the fusiform face area in that unusual text orientations resulted in increased activation and not decreased activation. It is hypothesized here that the VWFA activation is modulated by feedback from linguistic processes.

Here, we explored the impact of finger counting habits on arithmetic in both adults and children. Two groups of participants were examined, those that begin counting with their left hand (left-starters) and those that begin counting with their right hand (right-starters). For the adults, performance on an addition task in which participants added 2 two-digit numbers was compared. The results revealed that left-starters were slower than right-starters when adding and they had lower forward and backward digit-span scores. The children (aged 5-12) showed similar results on a single-digit timed addition task-right-starters outperformed left-starters. However, the children did not reveal differences in working memory or verbal and non-verbal intelligence as a function of finger counting habit. We argue that the motor act of finger counting influences how number is represented and suggest that left-starters may have a more bilateral representation that accounts for the slower processing.

This study used repetition priming to examine the influence of lexical processing on sentence comprehension processing. In order to do that the effect of the lexical priming of nouns and verbs on active compared to passive sentences was investigated. The results revealed that facilitating lexical access resulted in the facilitation of sentence comprehension processes. More specifically it was found that while lexical priming of the nouns and verbs within a sentence aids sentence comprehension processes - reduced reaction time to the comprehension probe - verb priming appears to have a greater impact, particularly on syntactic level processes. This is demonstrated by a priming effect observed in left BA 44, a region that has been linked to syntactic level processing, only for verb repetition. These results also support previous studies that have reported a differential neural representation for nouns and verbs; priming effects for these two grammatical classes were observed in different brain regions.

The aim of the current study was to explore the effects of problem structure, namely goal hierarchy and number of optimal solution paths, on the neural architecture that supports problem-solving and planning. Here, six-move problems with both an unambiguous and ambiguous goal hierarchy and single and multiple optimal solution paths were examined. In the task used, participants were encouraged to generate a solution plan before execution. The behavioral results revealed that problem-solving time and accuracy were both affected by both problem parameters. The fMRI activation results revealed three major findings. First, the right prefrontal cortex revealed a significantly different activation pattern than the other regions examined. This was the only region that revealed a larger response during the execution phase than the planning phase. Second, the effect of goal hierarchy was strongest during the execution phase. Finally, while there was no main effect of number of optimal solution paths, this parameter interacted with goal hierarchy in a number of regions across the brain. The present study also suggests that the minimum number of moves may not be the best measure of problem difficulty and that greater care be taken in the selection of TOL problems for both experimental studies as well as clinical assessment.

The present study tracked activation pattern differences in response to sign language processing by late hearing second language learners of American Sign Language. Learners were scanned before the start of their language courses. They were scanned again after their first semester of instruction and their second, for a total of 10 months of instruction. The study aimed to characterize modality-specific to modality-general processing throughout the acquisition of sign language. Results indicated that before the acquisition of sign language, neural substrates related to modality-specific processing were present. After approximately 45 h of instruction, the learners transitioned into processing signs on a phonological basis (e.g., supramarginal gyrus, putamen). After one more semester of input, learners transitioned once more to a lexico-semantic processing stage (e.g., left inferior frontal gyrus) at which language control mechanisms (e.g., left caudate, cingulate gyrus) were activated. During these transitional steps right hemispheric recruitment was observed, with increasing left-lateralization, which is similar to other native signers and L2 learners of spoken language; however, specialization for sign language processing with activation in the inferior parietal lobule (i.e., angular gyrus), even for late learners, was observed. As such, the present study is the first to track L2 acquisition of sign language learners in order to characterize modality-independent and modality-specific mechanisms for bilingual language processing.

The roles of visual sonority and handshape markedness in sign language acquisition and production were investigated. In Experiment 1, learners were taught sign-nonobject correspondences that varied in sign movement sonority and handshape markedness. Results from a sign-picture matching task revealed that high sonority signs were more accurately matched, especially when the sign contained a marked handshape. In Experiment 2, learners produced these familiar signs in addition to novel signs, which differed based on sonority and markedness. Results from a key-release reaction time reproduction task showed that learners tended to produce high sonority signs much more quickly than low sonority signs, especially when the sign contained an unmarked handshape. This effect was only present in familiar signs. Sign production accuracy rates revealed that high sonority signs were more accurate than low sonority signs. Similarly, signs with unmarked handshapes were produced more accurately than those with marked handshapes. Together, results from Experiments 1 and 2 suggested that signs that contain high sonority movements are more easily processed, both perceptually and productively, and handshape markedness plays a differential role in perception and production.

The present study investigates whether the inferior frontal gyrus is activated for phonetic segmentation of both speech and sign. Early adult second language learners of Spanish and American Sign Language at the very beginning of instruction were tested on their ability to classify lexical items in each language based on their phonetic categories (i.e., initial segments or location parameter, respectively). Conjunction analyses indicated that left-lateralized inferior frontal gyrus (IFG), superior parietal lobule (SPL), and precuneus were activated for both languages. Common activation in the left IFG suggests a modality-independent mechanism for phonetic segmentation. Additionally, common activation in parietal regions suggests spatial preprocessing of audiovisual and manuovisual information for subsequent frontal recoding and mapping. Taken together, we propose that this frontoparietal network is involved in domain-general segmentation of either acoustic or visual signal that is important to novel phonetic segmentation.

Comprehension of complex sentences is necessarily supported by both syntactic and semantic knowledge, but what linguistic factors trigger a readers' reliance on a specific system? This functional neuroimaging study orthogonally manipulated argument plausibility and verb event type to investigate cortical bases of the semantic effect on argument comprehension during reading. The data suggest that telic verbs facilitate online processing by means of consolidating the event schemas in episodic memory and by easing the computation of syntactico-thematic hierarchies in the left inferior frontal gyrus. The results demonstrate that syntax-semantics integration relies on trade-offs among a distributed network of regions for maximum comprehension efficiency.

This study triangulates executive planning and visuo-spatial reasoning in the context of the Tower of London (TOL) task by using a variety of methodological approaches. These approaches include functional magnetic resonance imaging (fMRI), functional connectivity analysis, individual difference analysis, and computational modeling. A graded fMRI paradigm compared the brain activation during the solution of problems with varying path lengths: easy (1 and 2 moves), moderate (3 and 4 moves) and difficult (5 and 6 moves). There were three central findings regarding the prefrontal cortex: (1) while both the left and right prefrontal cortices were equally involved during the solution of moderate and difficult problems, the activation on the right was differentially attenuated during the solution of the easy problems; (2) the activation observed in the right prefrontal cortex was highly correlated with individual differences in working memory (measured independently by the reading span task); and (3) different patterns of functional connectivity were observed in the left and right prefrontal cortices. Results obtained from the superior parietal region also revealed left/right differences; only the left superior parietal region revealed an effect of difficulty. These fMRI results converged upon two hypotheses: (1) the right prefrontal area may be more involved in the generation of a plan, whereas the left prefrontal area may be more involved in plan execution; and (2) the right superior parietal region is more involved in attention processes while the left homologue is more of a visuo-spatial workspace. A 4CAPS computational model of the cognitive processes and brain activation in the TOL task integrated these hypothesized mechanisms, and provided a reasonably good fit to the observed behavioral and brain activation data. The multiple research approaches presented here converge on a deepening understanding of the combination of perceptual and conceptual processes in this type of visual problem solving. © 2003 Elsevier Science Ltd. All rights reserved.

A verbal reasoning problem at the intersection of verbal working memory, problem-solving, and language comprehension was examined using event-related fMRI to distinguish differences in the differential timing of the response of the various cortical regions that compose the working memory network. Problems were developed such that the process demand as well as the timing of the manipulation of the contents of working memory (i.e., a demanding computation) was varied. Activation was observed in several regions including the dorsolateral prefrontal cortex, the inferior frontal gyrus, and the parietal lobe. Examination of the MR amplitude response revealed that the regions do not all activate simultaneously; instead, their activation time courses reveal differential responses that correspond to their theoretical processing role in the problem-solving task. The coordination of cortical area responses reveals how the various cortical regions synchronize and collaborate in order to accomplish a given cognitive function.

Recent studies of schizophrenia have revealed cognitive and memory deficits that are accompanied by disruptions of neuronal connectivity in cortical and subcortical brain regions. More recently, alterations of topological organization of structural networks in schizophrenia are also being identified using graph theoretical analysis. However, the role of the cerebellum in this network structure remains largely unknown. In this study, global network measures obtained from diffusion tensor imaging were computed in the cerebella of 25 patients with schizophrenia and 36 healthy volunteers. While cerebellar global network characteristics were slightly altered in schizophrenia patients compared with healthy controls, the patients showed a retained small-world network organization. The modular architecture, however, was changed mainly in crus II. Furthermore, schizophrenia patients had reduced correlations between modularity and microstructural integrity, as measured by fractional anisotropy (FA) in lobules I–IV and X. Finally, FA alterations were significantly correlated with the Positive and Negative Syndrome Scale symptom scores in schizophrenia patients. Taken together, our data suggest that schizophrenia patients have altered network architecture in the cerebellum with reduced local microstructural connectivity and that cerebellar structural abnormalities are associated symptoms of the disorder.

Although there has been great interest in the neuroanatomical basis of reading, little attention has been focused on auditory language processing. The purpose of this study was to examine the differential neuroanatomical response to the auditory processing of real words and pseudowords. Eight healthy right‐handed participants performed two phoneme monitoring tasks (one with real word stimuli and one with pseudowords) during a functional magnetic resonance imaging (fMRI) scan with a 4.1 T system. Both tasks activated the inferior frontal gyrus (IFG), the posterior superior temporal gyrus (pSTG) and the inferior parietal lobe (IPL). Pseudoword processing elicited significantly more activation within the posterior cortical regions compared with real word processing. Previous reading studies have suggested that this increase is due to an increased demand on the lexical access system. The left inferior frontal gyrus, on the other hand, did not reveal a significant difference in the amount of activation as a function of stimulus type. The lack of a differential response in IFG for auditory processing supports its hypothesized involvement in grapheme to phoneme conversion processes. These results are consistent with those from previous neuroimaging reading studies and emphasize the utility of examining both input modalities (e.g., visual or auditory) to compose a more complete picture of the language network. Hum. Brain Mapping 14:39–47, 2001. © 2001 Wiley‐Liss, Inc.

This study explores the interaction between working memory systems and language processing by examining how differences in working memory capacity (WMC) modulates neural activation levels and functional connectivity during sentence comprehension. The results indicate that two working memory systems may be involved in sentence comprehension, the verbal working memory system and the episodic buffer, but during different phases of the task. A sub-region of the left inferior frontal gyrus (BA 45) was correlated with WMC during the probe and not during sentence reading while the only region to reveal a correlation with WMC during sentence reading was the posterior cingulate/precuneus area, a region linked to event representation. In addition, functional connectivity analysis suggests that there were two distinct networks affected by WMC. The first was a semantic network that included the middle temporal cortex, an anterior region of the inferior frontal gyrus and the inferior parietal region. The second included the posterior cingulate and BA 45 of the inferior frontal gyrus. We propose here that high capacity readers may generate an event representation of the sentence during reading that aids in comprehension and that this event representation involves the processing of the posterior cingulate cortex.

Functional magnetic resonance imaging was used to investigate the role of phonology in visual word recognition (VWR). A group of children between the ages of 7 and 13 participated in a lexical decision task in which lexical frequency and homophony were manipulated. A significant homophone effect was observed for the high-frequency condition, indicating that phonology does indeed play a significant role in VWR. The brain activation patterns also support this idea in that regions that have been linked to phonological processing, the inferior frontal gyrus and the inferior parietal lobe, also revealed a homophone effect. Additionally, the posterior superior temporal cortex showed a homophone effect; however, this activation is argued to be related to lexical competition generated by the high-frequency homophone via the activation of multiple semantic representations.

It has long been thought that word problems are more difficult to solve than number/equation problems. However, recent findings have begun to bring this broadly believed idea into question. The current study examined the processing differences between these two types of problems. The behavioral results presented here failed to show an overwhelming advantage for number problems. In fact, there were more errors for the number problems than the word problems. The neuroimaging results reported demonstrate that there is significant overlap in the processing of what, on the surface, appears to be completely different problems that elicit different problem-solving strategies. Word and number problems rely on a general network responsible for problem-solving that includes the superior posterior parietal cortex, the horizontal segment of the intraparietal sulcus which is hypothesized to be involved in problem representation and calculation as well as the regions that have been linked to executive aspects of working memory such as the pre-SMA and basal ganglia. While overlap was observed, significant differences were also found primarily in language processing regions such as Broca's and Wernicke's areas for the word problems and the horizontal segment of the intraparietal sulcus for the number problems.

The sentences we process in normal conversation tend to refer to information that we are familiar with rather than abstract, unrelated information. This allows for the use of knowledge stores to help facilitate comprehension processes. In many sentence comprehension studies, the stimuli are designed such that the use of world knowledge is limited. Here, we investigated how the semantic relatedness of sentence constituents influences sentence processing. A three factor design was employed in which processing phase (sentence vs. probe), syntactic complexity (object-relative vs. conjoined active) and the semantic relatedness of the nouns within the sentence was examined. We found a differential effect in two sub-regions of the left inferior frontal gyrus (LIFG). BA 44 revealed an effect of syntactic complexity while inferior portions of the LIFG (BA 47) revealed an effect of relatedness as well as an interaction between complexity and relatedness during the probe phase. In addition, significant differences in activation were observed when comparing the sentence processing and probe phases with the sentence phase eliciting stronger semantic related activation while the probe phase elicited stronger working memory related activation.

The aim of this study was to better characterize the influence of the comprehension probe on syntax‐related activation patterns observed in fMRI studies of sentence comprehension. In this study, sentence comprehension was assessed by presenting a true/false statement after each sentence. To disassociate the sentence reading from the comprehension probe activation, a 6‐s delay was placed between these processing phases. Two factors were manipulated, one affected the sentence and the other affected the probe. The sentences were manipulated by varying their syntactic complexity; conjoined‐active and object‐relative sentences were examined. The comprehension probes asked whether one of the first two mentioned nouns in the preceding sentence performed the action of one of the two verbs. The probes were manipulated by varying the distance (number of intervening words) between the noun and verb within the sentence; there were three probe types: short distance, long distance, and false statements. The results, which focused on the processing taking place during the probe, showed that the distance manipulation resulted in significant differences in both behavioral and brain activation measures. This was particularly true of BA 44, which revealed an interaction between complexity and distance such that the complexity effect was all but eliminated for the long‐distance condition. Additionally, we replicated our previous finding of syntactic complexity effects during the probe phase. Finally, post hoc analysis revealed that participants used two distinct strategies during sentence reading; significant effects of strategy use on both behavioral and brain activation data were observed. Hum Brain Mapp 2009. © 2009 Wiley‐Liss, Inc.

Only recently has there been any consideration of the influence of the problem structure on Tower of London task (TOL) performance. Not surprisingly, these few studies that have investigated this issue have found significant differences in the cognitive demands of individual TOL problems. Based on these previous findings, the aim of the current study was to further explore the effects of two problem characteristics on the planning process - namely, goal hierarchy and the number of optimal solution paths. A number of performance measures when solving six-move problems were examined, including preplanning time, movement time, and accuracy. Analysis of the preplanning time revealed that it was significantly affected by goal hierarchy but not the number of solution paths. The individual movement times, however, revealed effects for both goal hierarchy and the number of optimal solution paths. The number of paths only affected movement times at specific moves: those corresponding to the initiation of a subgoal chunk. The results are discussed in terms of the influence of preplanning on subsequent performance. The present study also suggests that greater care be taken in the selection of TOL problems.

This study used functional MRI (fMRI) to examine the neural effects of willfully allocating one's attention to one of two ongoing tasks. In a dual task paradigm, participants were instructed to focus either on auditory sentence comprehension, mental rotation, or both. One of the major findings is that the distribution of brain activation was amenable to strategic control, such that the amount of activation per task was systematically related to the attention-dividing instructions. The activation in language process- ing regions was lower when attending to mental rotation than when attending to the sentences, and the activation in visuospatial processing regions was lower when attending to sentences than when attending to mental rotations. Additionally, the activation was found to be underadditive, with the dual-task condition eliciting less activation than the sum of the attend sentence and attend rotation conditions. We also observed a laterality shift across conditions within language-processing regions, with the attend sentence condition showing bilateral activation, while the dual task condition showed a left hemispheric dominance. This shift suggests multiple language-processing modes and may explain the underadditivity in activation observed in the current and previous studies. Hum Brain Mapp 28:109 -117, 2007. © 2006 Wiley-Liss, Inc.

Two experiments are reported that used fMRI to compare the brain activation during the imagery of material and geometric object features. In the first experiment, participants were to mentally evaluate objects along either a material dimension (roughness, hardness and temperature; e.g., Which is harder, a potato or a mushroom?) or a geometric dimension (size and shape; e.g., Which is larger, a pumpkin or a cucumber?). In the second experiment, when given the name of an object and either a material (roughness and hardness) or geometric (size and shape) property participants rated the object on a scale from 1 to 4. Both experiments were designed to examine the underlying neural substrate that supports the processing of material object properties with respect to geometric properties. Considering the relative amount of activation across the two types of object properties, we found that (1) the interrogation of geometric features differentially evokes visual imagery which involves the region in and around the intraparietal sulcus, (2) the interrogation of material features differentially evokes the processing of semantic object representations which involves the inferior extrastriate region, and (3) the lateral occipital cortex (LOC) responds to shape processing regardless of whether the feature being queried is a material or geometric feature.

This study examined brain activation while participants read or listened to high-imagery sentences like The number eight when rotated 90 degrees looks like a pair of spectacles or low-imagery sentences, and judged them as true or false. The sentence imagery manipulation affected the activation in regions (particularly, the intraparietal sulcus) that activate in other mental imagery tasks, such as mental rotation. Both the auditory and visual presentation experiments indicated activation of the intraparietal sulcus area in the high-imagery condition, suggesting a common neural substrate for language-evoked imagery that is independent of the input modality. In addition to exhibiting greater activation levels during the processing of high-imagery sentences, the left intraparietal sulcus also showed greater functional connectivity in this condition with other cortical regions, particularly language processing regions, regardless of the input modality. The comprehension of abstract, nonimaginal information in low-imagery sentences was accompanied by additional activation in regions in the left superior and middle temporal areas associated with the retrieval and processing of semantic and world knowledge. In addition to exhibiting greater activation levels during the processing of low-imagery sentences, this left temporal region also revealed greater functional connectivity in this condition with other left hemisphere language processing regions and with prefrontal regions, regardless of the input modality. The findings indicate that sentence comprehension can activate additional cortical regions that process information that is not specifically linguistic but varies with the information content of the sentence (such as visual or abstract information). In particular, the left intraparietal sulcus area appears to be centrally involved in processing the visual imagery that a sentence can evoke, while activating in synchrony with some core language processing regions.

Discrepancies in the patterns of cortical activation across studies may be attributable, in part, to differences in baseline tasks, and hence, reflect the limits of the subtractive logic underlying much of neuroimaging. To assess the extent of these effects, three of the most commonly used baseline conditions (rest, tone monitoring, and passive listening) were compared using phoneme discrimination as the experimental task. Eight participants were studied in a fMRI study with a 4.1 T system. The three baseline conditions systematically affected the amount of activation observed in the identical phoneme task with major affects in Broca's area, the left posterior superior temporal gyrus, and the left and right inferior parietal regions. Two central findings were: 1) a differential effect of baseline within each region, with the rest baseline condition producing the greatest amount of activation and the passive listening condition producing the least, and 2) systematic baseline task activation in the inferior parietal regions. These results emphasize the relativity of activation patterns observed in functional neuroimaging, and the necessity to specify the baseline processes in context to the experimental task processes. Hum. Brain Mapping 14:228–235, 2001. © 2001 Wiley‐Liss, Inc.