Search

Tests of fluid intelligence predict success in a wide range of cognitive activities. Much uncertainty has surrounded brain lesions producing deficits in these tests, with standard group comparisons delivering no clear result. Based on findings from functional imaging, we propose that the uncertainty of lesion data may arise from the specificity and complexity of the relevant neural circuit. Fluid intelligence tests give a characteristic pattern of activity in posterolateral frontal, dorsomedial frontal, and midparietal cortex. To test the causal role of these regions, we examined fluid intelligence in 80 patients with focal cortical lesions. Damage to each of the proposed regions predicted fluid intelligence loss, whereas damage outside these regions was not predictive. The results suggest that coarse group comparisons (e.g., frontal vs. posterior) cannot show the neural underpinnings of fluid intelligence tests. Instead, deficits reflect the extent of damage to a restricted but complex brain circuit comprising specific regions within both frontal and posterior cortex. neuropsychology | frontoparietal cortex | focal brain lesions | cognitive control | IQ doi/ 10.10731pnas.1007928107

A differential impact of hemispheric side (left vs right) on cognitive measures, specifically Verbal and Performance IQ, has been described previously for both focal onset seizures and lateralized brain lesions. This study revealed a differential effect on intra-individual variability, measured as subtest scaled-score range, on the Dutch WISC-R and WISC-III, in children with epilepsy. The presence of documented brain lesion was associated with elevated variability on the Verbal Scale for the left hemisphere seizure group and with decreased variability on the Verbal and Full Scales for the right hemisphere seizure group. DOI 10.2466/03.04.15.PR0.107.4.113-119

Orienting in large-scale space depends on the interaction of environmental experience and preconfigured, possibly innate, constructs. Place, head-direction, and grid cells in the hippocampal formation provide allocentric representations of space. Here we show how these cognitive representations emerge and develop as rat pups first begin to explore their environment. Directional, locational, and rhythmic organization of firing are present during initial exploration, including adultlike directional firing. The stability and precision of place cell firing continue to develop throughout juvenility. Stable grid cell firing appears later but matures rapidly to adult levels. Our results demonstrate the presence of three neuronal representations of space before extensive experience and show how they develop with age. doi: 10.1126/science.1188224

The basal ganglia play a central role in cognition and are involved in such general functions as action selection and reinforcement learning. Here, we present a model exploring the hypothesis that the basal ganglia implement a conditional information-routing system. The system directs the transmission of cortical signals between pairs of regions by manipulating separately the selection of sources and destinations of information transfers. We suggest that such a mechanism provides an account for several cognitive functions of the basal ganglia. The model also incorporates a possible mechanism by which subsequent transfers of information control the release of dopamine. This signal is used to produce novel stimulus-response associations by internalizing transferred cortical representations in the striatum. We discuss how the model is related to production systems and cognitive architectures. A series of simulations is presented to illustrate how the model can perform simple stimulus-response tasks, develop automatic behaviors, and provide an account of impairments in Parkinson's and Huntington's diseases. Keywords: basal ganglia, neural networks, computational modeling, procedural learning DOI: 10.1037/a0019077

Accomplishing even simple tasks depend on neuronal circuits to configure how incoming sensory stimuli map onto responses. Controlling these stimulus-response (SR) mapping rules relies on a cognitive control network comprising the anterior cingulate cortex (ACC). Single neurons within the ACC convey information about currently relevant SR mapping rules and signal unexpected action outcomes, which can be used to optimize behavioral choices. However, its functional significance and the mechanistic means of interaction with other nodes of the cognitive control network remain elusive and poorly understood. Here, we report that core aspects of cognitive control are encoded by rhythmic theta-band activity within neuronal circuits in the ACC. Throughout task performance, theta-activity predicted which of two SR mapping rules will be established before processing visual target information. Task-selective theta-activity emerged particularly early during those trials, which required the adjustment of SR rules following an erroneous rule representation in the preceding trial. These findings demonstrate a functional correlation of cognitive control processes and oscillatory theta-band activity in macaque ACC. Moreover, we report that spike output of a subset of cells in ACC is synchronized to predictive theta-activity, suggesting that the theta-cycle could serve as a temporal reference for coordinating local task selective computations across a larger network of frontal areas and the hippocampus to optimize and adjust the processing routes of sensory and motor circuits to achieve efficient sensory-motor control. cognitive control | theta-synchronization | attention | oscillation | antisaccade doi: 10.1073/pnas.0906194107

This study investigated the relationship of tactile abilities within the framework of a hierarchical structure of mental abilities. Data were analysed from 229 participants who were administered tactile measures from the Dean-Woodcock Sensory Motor Battery along with a battery of conormed cognitive measures representative of the Cattell-Horn-Carroll (CHC) model of intelligence. Multiple measures of tactile performance were used including Palm Writing and Object Identification, and each measure included a lateralized measure (i.e., right/left). Factor analytic results suggest tactile measures have a significant relationship with measures of cognitive ability. In this study, tactile measures involving object identification were more related to cognitive measures of visual processing-speed and overall processing speed; whereas, tactile measures involving the recognition of numbers written on the palm of the hand produced high loadings on a separate factor. Results from this study suggest different tactile measures may differentially load on cognitive factors depending on the common processing demands of the tactile and cognitive measures. Suggestions for differentiating common processing demands between tactile and cognitive measures are discussed. Keywords: tactile, intelligence, cognitive abilities DOI: 10.1037/a0015845

The effects of advanced age and cognitive resources on the course of skill acquisition are unclear, and discrepancies among studies may reflect limitations of data analytic approaches. We applied a multilevel negative exponential model to skill acquisition data from 80 trials (four 20-trial blocks) of a pursuit rotor task administered to healthy adults (19-80 years old). The analyses conducted at the single-trial level indicated that the negative exponential function described performance well. Learning parameters correlated with measures of task-relevant cognitive resources on all blocks except the last and with age on all blocks after the second. Thus, age differences in motor skill acquisition may evolve in 2 phases: In the first, age differences are collinear with individual differences in task-relevant cognitive resources; in the second, age differences orthogonal to these resources emerge. Key Words: Aging--Motor performance--Multilevel model Negative exponential learning function--Pursuit rotor--Skill acquisition--Working memory. doi: 10.1093/geronb/gbp126

We examined whether higher levels of neuroticism in adolescence were associated with poorer cognitive function in midlife in 2,071 members of the British 1946 birth cohort. Higher neuroticism at age 13 was associated with poorer performance on tests of verbal ability, verbal fluency, and verbal memory at age 53 in sex-adjusted analyses. However, higher neuroticism was also associated with poorer cognitive performance at age 8. After adjustment for childhood cognition or educational attainment, the associations between neuroticism at age 13 and midlife cognition ceased to be statistically significant. The link between neuroticism and subsequent cognitive ability may be a reflection of a long-standing correlation between the stable aspects of these traits since childhood, but further measurements of both traits are needed to confirm this. Key Words: Personality--Neuroticism--Cognition--Life course and developmental change. doi: 10.1093/geronb/gbp082.

During early adulthood, a phase in which the central nervous system displays considerable plasticity and in which important cognitive traits are shaped, the effects of exercise on cognition remain poorly understood. We performed a cohort study of all Swedish men born in 1950 through 1976 who were enlisted for military service at age 18 (N = 1,221,727). Of these, 268,496 were full-sibling pairs, 3,147 twin pairs, and 1,432 monozygotic twin pairs. Physical fitness and intelligence performance data were collected during conscription examinations and linked with other national databases for information on school achievement, socioeconomic status, and sibship. Relationships between cardiovascular fitness and intelligence at age 18 were evaluated by linear models in the total cohort and in subgroups of full-sibling pairs and twin pairs. Cardiovascular fitness, as measured by ergometer cycling, positively associated with intelligence after adjusting for relevant confounders (regression coefficient b = 0.172; 95% CI, 0.168-0.176). Similar results were obtained within monozygotic twin pairs, in contrast, muscle strength was not associated with cognitive performance. Cross-twin cross-trait analyses showed that the associations were primarily explained by individual specific, non-shared environmental influences ([greater than or equal to] 80%), whereas heritability explained aerobic fitness | intelligence | muscular strength | twin analysis | exercise doi/10.1073/pnas.0905307106

We review the growing literature on health numeracy, the ability to understand and use numerical information, and its relation to cognition, health behaviors, and medical outcomes. Despite the surfeit of health information from commercial and noncommercial sources, national and international surveys show that many people lack basic numerical skills that are essential to maintain their health and make informed medical decisions. Low numeracy distorts perceptions of risks and benefits of screening, reduces medication compliance, impedes access to treatments, impairs risk communication (limiting prevention efforts among the most vulnerable), and, based on the scant research conducted on outcomes, appears to adversely affect medical outcomes. Low numeracy is also associated with greater susceptibility to extraneous factors (i.e., factors that do not change the objective numerical information). That is, low numeracy increases susceptibility to effects of mood or bow information is presented (e.g., as frequencies vs. percentages) and to biases in judgment and decision making (e.g., framing and ratio bias effects). Much of this research is not grounded in empirically supported theories of numeracy or mathematical cognition, which are crucial for designing evidence-based policies and interventions that are effective in reducing risk and improving medical decision making. To address this gap, we outline four theoretical approaches (psychophysical, computational, standard dual-process, and fuzzy trace theory), review their implications for numeracy, and point to avenues for future research. Keywords: risk perception, risk communication, mathematical cognition, intuition, dual processes DOI: 10.1037/a0017327

The striatum is a vital substrate for performance, procedural memory, and learning. The ventral and medial striatum are thought to be critical for acquisition of tasks while the dorsolateral striatum is important for performance and habitual enactment of skills. Evidence based on cortical, thalamic, and amygdaloid inputs to the striatum suggests a medio-lateral zonation imposed on the classical dorso-ventral distinction. We therefore investigated the functional significance of dopaminergic signaling in cognitive tasks by studying dopamine-deficient (DD) mice and mice with dopamine signaling restored to only the dorsolateral (DL) striatum by viral rescue (vrDD-DL mice). Whereas DD mice failed in all of the tasks examined here, vrDD-DL mice displayed intact discriminatory learning, object recognition, visuospatial learning and spatial memory. Acquisition of operant behavior for food rewards was delayed in vrDD-DL mice and their motivation in a progressive ratio experiments was reduced. Therefore, dopaminergic signaling in the dorsolateral striatum is sufficient for mice to learn several different cognitive tasks although the rate of learning some of them was reduced. These results indicate that dopaminergic signaling in the ventromedial striatum is not absolutely necessary for mastery of these behaviors, but may facilitate them. knockout | learning | memory | tyrosine hydroxylase | viral gene transfer

Is human thought fully embedded in language, or do some forms of thought operate independently? To directly address this issue, we focus on inference-making, a central feature of human cognition. In a 3T fMRI study we compare logical inferences relying on sentential connectives (e.g., not, or, if ... then) to linguistic inferences based on syntactic transformation of sentences involving ditransitive verbs (e.g., give, say, take). When contrasted with matched grammaticality judgments, logic inference alone recruited 'core' regions of deduction [Brodmann area (BA) 10p and 8m], whereas linguistic inference alone recruited perisylvian regions of linguistic competence, among others (BA 21, 22, 37, 39, 44, and 45 and caudate). In addition, the two inferences commonly recruited a set of general 'support' areas in frontoparietal cortex (BA 6, 7, 8, 40, and 47). The results indicate that logical inference is not embedded in natural language and confirm the relative modularity of linguistic processes. fMRI | logic | reasoning | semantics | syntax

The human brain's capacity for cognitive function is thought to depend on coordinated activity in sparsely connected, complex networks organized over many scales of space and time. Recent work has demonstrated that human brain networks constructed from neuroimaging data have economical small-world properties that confer high efficiency of information processing at relatively low connection cost. However, it has been unclear how the architecture of complex brain networks functioning at different frequencies can be related to behavioral performance on cognitive tasks. Here, we show that impaired accuracy of working memory could be related to suboptimal cost efficiency of brain functional networks operating in the classical [beta] frequency band, 15-30 Hz. We analyzed brain functional networks derived from magnetoen-cephalography data recorded during working-memory task performance in 29 healthy volunteers and 28 people with schizophrenia. Networks functioning at higher frequencies had greater global cost efficiency than low-frequency networks in both groups. Superior task performance was positively correlated with global cost efficiency of the [beta]-band network and specifically with cost efficiency of nodes in left lateral parietal and frontal areas. These results are consistent with biophysical models highlighting the importance of [beta]-band oscillations for long-distance functional connections in brain networks and with pathophysiological models of schizophrenia as a dysconnection syndrome. More generally, they echo the saying that 'less is more': The information processing performance of a network can be enhanced by a sparse or low-cost configuration with disproportionately high efficiency. efficiency | graph theory | schizophrenia | working memory | magnetoencephalography

Patients with remitted bipolar disorder (BD) have persistent cognitive deficits, but the nature and specificity of this deficit remain unclear. The authors evaluated the executive hypothesis of BD by determining whether (a) patients' executive deficits qualify as differential deficits, that is, that these significantly exceed deficits in other cognitive domains; (b) deficits in particular executive functions are evident, and (c) executive difficulties mediate declarative memory deficits in BD. The cognitive performance of 63 prospectively verified euthymic bipolar patients was compared with controls, using J. Baron and R. Trieman's (1980) method of testing for differences in nonindependent correlations. There were no differential deficits within the executive domain. Patients' generic executive performance was differentially impaired relative to primary verbal memory and retention in declarative memory, but not relative to their declarative recall, recognition, or their psychomotor performance. However, patients' executive deficit was not an artifact of their poor psychomotor performance. Executive performance accounted for all but a trivial portion of the between-group variance in declarative memory. Persistent cognitive difficulties in euthymic bipolar disorder (EBD) are thus usefully characterized as a generic dysexecutive syndrome. Keywords: bipolar disorder, euthymic, cognition, executive function, differential deficit

The authors review a viewpoint on human functional brain development, interactive specialization (IS), and its application to the emerging network of cortical regions referred to as the social brain. They advance the IS view in 2 new ways. First, they extend IS into a domain to which it has not previously been applied--the emergence of social cognition and mentalizing computations in the brain. Second, they extend the implications of the IS view from the emergence of specialized functions within a cortical region to a focus on how different cortical regions with complementary functions become orchestrated into networks during human postnatal development. Keywords: cognitive brain development, face processing, interactive specialization, social cognition

Education and cognitive ability are studied as predictors of female age at first birth (AFB) among Danish twins. Variance in AFB emerges from differences between families and is located within shared environments.

Certain cognitive functions differ in men and women, although the anatomical and functional substrates underlying these differences remain unknown. Because neocortical activity is directly related with higher brain function, numerous studies have focused on the cerebral cortex when searching for possible structural correlates of cognitive gender differences. However, there are no studies on possible gender differences at the synaptic level. In the present work we have used stereological and correlative light and electron microscopy to show that men have a significantly higher synaptic density than women in all cortical layers of the temporal neocortex. These differences may represent a microanatomical substrate contributing to the functional gender differences in brain activity. electron microscopy | neocortex | neuronal density | sex

Cognitive flexibility is a crucial human ability allowing efficient adaptation to changing task challenges. Although a person's degree of flexibility can vary from moment to moment, the conditions regulating such fluctuations are not well understood. Using a task-switching procedure with fMRI, we found several brain regions in which neural activity preceding each trial predicted subsequent cognitive flexibility. Specifically, as pretrial activity increased, performance improved on trials when the task switched but did not improve when the task repeated. Regions from which flexibility could be predicted reliably included the basal ganglia, anterior cingulate cortex, prefrontal cortex, and posterior parietal cortex. Although further analysis revealed similarities across the regions in how flexibility was predicted, results supported the existence of multiple independent sources of prediction. These results reveal distinct neural mechanisms underlying fluctuations in cognitive flexibility. basal ganglia | fMRI | task switching | cognitive control

Byline: Lisiane Tuon (1), Clarissa M. Comim (1), Fabricia Petronilho (2), Tatiana Barichello (2), Ivan Izquierdo (4), Joao Quevedo (1), Felipe Dal-Pizzol (2) Keywords: Sepsis; Learning; Memory; Depression; Anxiety; Central nervous system Abstract: Objective To evaluate the cognitive performance in rats that survived sepsis induced by cecal ligation and puncture (CLP) after 10, 30 and 60 days. Design Prospective, controlled experiment. Setting Animal basic science laboratory. Subjects Male Wistar rats, weighing 300--350 g. Interventions The rats were sham-operated or submitted to CLP (sepsis group) with 'basic support' (saline, s.c. at 50 mL/kg immediately and 12 h after CLP plus ceftriaxone, s.c. at 30 mg/kg and clindamycin, s.c. at 25 mg/kg 6, 12 and 18 h after CLP). Measurements and main results The animals underwent six behavioral tasks 10, 30 and 60 days after surgery: (a) habituation to the open field (b) inhibitory avoidance task (c) continuous multiple trials step-down inhibitory avoidance task (d) object recognition (e) elevated plus-maze and (f) forced swimming test. We demonstrated that survivors 10 days after CLP presented deficits on the habituation to the open field, step-down inhibitory avoidance, continuous multiple-trials step-down inhibitory avoidance, object recognition and forced swimming. After 30 days of sepsis induction, survivors maintained deficits on the step-down inhibitory avoidance, continuous multiple-trials step-down inhibitory avoidance and forced swimming. However, after 60 days all behavior deficits were reversed. Conclusions These results indicate that the impairment of memory and learning, demonstrated 10 days after the induction of sepsis, persist 30 days after the CLP. The cognitive impairments did not persist after 60 days suggesting that this model can help in the understanding of the biological mechanisms associated with sepsis-induced sickness behavior. Author Affiliation: (1) Laboratorio de Neurociencias, Programa de Pos-Graduacao Ciencias da Saude, Unidade Academica de Ciencias da Saude, Universidade do Extremo Sul Catarinense, 88806-000, Criciuma, SC, Brazil (2) Laboratorio de Fisiopatologia Experimental, PPGCS, UNASAU, Universidade do Extremo Sul Catarinense, 88806-000, Criciuma, SC, Brazil (4) Centro de Memoria, Instituto de Pesquisas Biomedicas, Pontificia Universidade Catolica do Rio Grande do Sul, 90610-000, Porto Alegre, RS, Brazil Article History: Registration Date: 11/04/2008 Received Date: 28/11/2007 Accepted Date: 08/04/2008 Online Date: 30/04/2008 Article note: Supported, in part, by UNESC (Brazil), FAPESC (Brazil) and CNPq (Brazil).

Background. Among persons with white matter lesions (WMLs), there is a range of cognitive function. We examine whether participation in leisure activities modifies the effect of WML load on cognitive function. Methods. Data are from 2300 men and women (aged 66-92 years) participating in the population-based Age Gene/ Environment Susceptibility-Reykjavik Study. Subcortical WML load was calculated as a weighted sum, based on size of lesions in the four lobes. Periventricular WML load was calculated as the sum of lesion scores, based on size, for the frontal caps, occipitoparietal caps and bands. The upper quartile of lesion load in either area was compared to the lower three quartiles. Composite scores of memory (MEM), speed of processing (SP), and executive function (EF) were constructed from a battery of neuropsychological tests. Frequency of participation in nine cognitively stimulating leisure activities was assessed via questionnaire; the upper quartile was compared to the lower three quartiles. Multiple regression, controlling for demographic and health factors and brain infarcts, was used to test the main effects and interaction of WMLs and leisure activity on cognitive function. Results. High leisure activity was associated with higher performance in all three cognitive abilities: MEM [beta] = 0.20, 95% confidence interval [CI], 0.11-0.29; SP [beta] = 0.37, 95% CI, 0.29-0.45; and EF [beta] = 0.23, 95% CI, 0.15-0.29. High WML load was associated with significantly lower performance in SP ([beta] = -0.06, 95% CI, -0.13 to -0.01). The effect of WMLs on SP performance was modified by high leisure activity (p for interaction < .05). Conclusion. Participation in cognitively stimulating leisure activity may attenuate the effect of WML pathology on cognitive performance. Key Words: Epidemiology--Cognition--White matter lesions--Leisure activity.

During a 20-year longitudinal study, 5,842 participants aged 49 to 93 years significantly improved over two to four successive experiences of the Heim AH4-1 intelligence test (first published in 1970), even with between-test intervals of 4 years and longer. After we considered significant attrition by death and dropout and the effects of gender, socioeconomic advantage, and recruitment cohort, we found that participants with high intelligence test scores showed greater improvement than did those with lower intelligence test scores. Practice gains also reduced with age, even after we took into consideration the individual differences in intelligence test scores. This emphasizes the methodological point that neglect of individual differences in improvement during longitudinal studies underestimates age-related changes in younger and more able participants and the theoretical point that, like all experiences during everyday life, participation in longitudinal studies alters the ability of aging humans to cope with cognitive demands to different extents according to their baseline abilities. Key Words: Cognitive gain--Longitudinal study--Practice gains.

White matter is the brain region underlying the gray matter cortex, composed of neuronal fibers coated with electrical insulation called myelin. Previously of interest in demyelinating diseases such as multiple sclerosis, myelin is attracting new interest as an unexpected contributor to a wide range of psychiatric disorders, including depression and schizophrenia. This is stimulating research into myelin involvement in normal cognitive function, learning and IQ. Myelination continues for decades in the human brain; it is modifiable by experience, and it affects information processing by regulating the velocity and synchrony of impulse conduction between distant cortical regions. Cell-culture studies have identified molecular mechanisms regulating myelination by electrical activity, and myelin also limits the critical period for learning through inhibitory proteins that suppress axon sprouting and synaptogenesis.

Background. Although several studies have investigated the association between cholesterol and dementia, few have examined cholesterol and decline across cognitive domains. We examined serum total and high-density lipoprotein (HDL) cholesterol, total-to-HDL ratio, and trajectories across cognitive domains. Methods. Participants were 436 community-residing women (70-79 years old) in the Women's Health and Aging Study II; they were screened to be physically high-functioning and cognitively intact at baseline. Cognition and other health-related variables were assessed at five intervals spanning 9 years. Cognitive assessments included Trail Making Test Parts A (TMT-A) and B (TMT-B), Hopkins Verbal Learning Test-Revised, Purdue Pegboard, and Mini-Mental State Examination (MMSE). The association between baseline levels of serum lipids and cognitive trajectories were evaluated using Generalized Estimating Equations (GEE). Covariates included age, education, race, vascular disease, serum creatinine, depression, and lipid-lowering medications. Results. In multivariate analyses, baseline higher total (p = .02) and HDL (p = .03) cholesterol were associated with better performance on the Purdue Pegboard. Using clinical cholesterol cutoffs, baseline serum total cholesterol levels > 240 mg/dL were associated with the best performance (p = .02). Baseline lipids were not associated with any other cognitive tests; there were no Lipid x Time interactions. Conclusion. Higher baseline serum lipid levels predicted better performance over time on a measure of motor speed, but not memory or psychomotor or executive functioning in this population of elderly women. This association suggests that peripheral cholesterol levels, measured in late-life, may not be a good predictor of subsequent cognitive decline. Future research examining peripheral cholesterol over the life span and its relationship with cognition is needed. Key Words: Cholesterol--Cognition--Motor speed--Biological aging.

RNA editing appears to be the major mechanism by which environmental signals overwrite encoded genetic information to modify gene function and regulation, particularly in the brain. We suggest that the predominance of Alu elements in the human genome is the result of their evolutionary co-adaptation as a modular substrate for RNA editing, driven by selection for higher-order cognitive function. We show that RNA editing alters transcripts from loci encoding proteins involved in neural cell identity, maturation and function, as well as in DNA repair, implying a role for RNA editing not only in neural transmission and network plasticity but also in brain development, and suggesting that communication of productive changes back to the genome might constitute the molecular basis of long-term memory and higher-order cognition.

This study recorded visual fixation performance and event related brain potentials (ERPs) to examine processing of novel visual information in 6- to 7-mo.-old infants as well as to test attention- or memory-related hypotheses of the functional significance of the Nc-ERP component. Separate groups of infants were presented two versions of a novelty-probe task with three types of visual stimuli: (a) a frequent face on 70% of the trials, (b) an oddball face on 15% of the trials, and (c) novel probe stimuli on the remaining 15% of the trials. The novelty probes were faces in one group and irregular shapes in the second group. Analysis showed longer fixations and Nc responses of greater amplitude occurred to oddball and novel stimuli. It was concluded that Nc reflects a top-down, controlled processing mechanism that flexibly allocates attentional resources.

Interpretations of cross-cultural differences in performance on cognitive tasks tend to rely on broad concepts, such as general intelligence or cultural modes of thinking. In this study, the authors examine two proximate parameters, stimulus complexity and task exposure, using reaction time (RT) and event-related brain potentials (ERPs) recorded during various tasks. Five tasks differed in complexity but had similar stimulus content; one task had stimuli of different appearance. Test trials were administered across three days. Participants were trained on most tasks for two days. There were three samples, rural Venda youngsters in South Africa with little schooling, Venda university students, and Dutch university students. Cross-cultural differences in RT increased with task complexity and decreased with exposure. Substantial correspondence was found between patterns of RT and latency of the N2, an ERP component related to stimulus categorization. Our results fit an explanation in terms of task familiarity. Implications for culture-cognition relationships are discussed. Keywords: cognitive tasks; cross-cultural differences; reaction time; N2; event-related potentials; lateralized readiness potential; stimulus categorization; stimulus familiarity; task familiarity

Little is known about genetic regulation of the development of white matter. This knowledge is critical in understanding the pathophysiology of neurodevelopmental syndromes associated with altered cognition as well as in elucidating the genetics of normal human cognition. The hemideletion of [approximately equal to] 25 genes on chromosome 7q11.23 that causes Williams syndrome (WS) includes genes that regulate cytoskeletal dynamics in neurons, especially LIMK1 and CYLN2, and therefore offers the opportunity to investigate the role of these genes in the formation of white matter tracts. We used diffusion tensor imaging to demonstrate alteration in white matter fiber directionality, deviation in posterior fiber tract course, and reduced lateralization of fiber coherence in WS. These abnormalities are consistent with an alteration of the late stages of neuronal migration, define alterations of white matter structures underlying dissociable behavioral phenotypes in WS, and provide human in vivo information about genetic control of white matter tract formation. development | LIMK1 | neuronal growth cone | neuronal migration | tractography

In human and nonhuman primates, structural variants of the gene encoding the serotonin transporter [5-hydroxytryptamine transporter (5-HTT)] affect the transcription and functional efficacy of 5-HTT. Prior work has shown that structural variants differentially affect function of the amygdala and ventromedial prefrontal cortex (VMPFC), regions important for the regulation and expression of emotion. However, relatively little is known about the impact of 5-HTT allelic variants on cognition. To address this question, we tested rhesus monkeys carrying orthologous structural variants of 5-HTT on a battery of tasks that assess cognitive flexibility, reward processing, and emotion. Here we show that rhesus monkeys carrying two copies of the short allele (SS) of the rhesus 5-HTT gene-linked polymorphic region (rh5-HTTLPR) show significantly reduced cognitive flexibility as measured by two tasks in the battery: object discrimination reversal learning and instrumental extinction. Monkeys with the SS genotype also displayed alterations in socioemotional behavior. Genotype variation was not related to visual perceptual abilities, valuation of food rewards, or the ability to express a wide range of defensive responses. Although emotional alterations associated with 5-HTT variation have been described as the primary phenotype, the present study reports differences in at least one type of cognitive flexibility, which has not been described previously. Because behaviors modulated by the 5-HTTLPR are a subset of those dependent on the VMPFC, analysis of structural and functional correlates of gene variation in this region may inform the nature of the genetic modulation of cognition. aggression | extinction | orbital prefrontal cortex | reversal learning | serotonin

Microscopic study of the human brain has revealed neural structures, enhanced wiring, and forms of connectivity among nerve cells not found in any animal, challenging the view that the human brain is simply an enlarged chimpanzee brain. On the other hand, cognitive studies have found animals to have abilities once thought unique to the human. This suggests a disparity between brain and mind. The suggestion is misleading. Cognitive research has not kept pace with neural research. Neural findings are based on microscopic study of the brain and are primarily cellular. Because cognition cannot be studied microscopically, we need to refine the study of cognition by using a different approach. In examining claims of similarity between animals and humans, one must ask: What are the dissimilarities? This approach prevents confusing similarity with equivalence. We follow this approach in examining eight cognitive cases--teaching, short-term memory, causal reasoning, planning, deception, transitive inference, theory of mind, and language--and find, in all cases, that similarities between animal and human abilities are small, dissimilarities large. There is no disparity between brain and mind. animal/human | Darwin

Visual attention provides a means of selecting among the barrage of information reaching the retina and of enhancing the perceptual discriminability of relevant stimuli. Neurophysiological studies in monkeys and functional imaging studies in humans have demonstrated neural correlates of these perceptual improvements in visual cortex during attention. Importantly, voluntary attention improves the discriminability of visual cortical responses to relevant stimuli. Recent work aimed at identifying sources of attentional modulation has implicated the frontal eye field (FEF) in driving spatial attention. Subthreshold microstimulation of the FEF enhances the responses of area V4 neurons to spatially corresponding stimuli. However, it is not known whether these enhancements include improved visual-response discriminability, a hallmark of voluntary attention. We used receiver-operator characteristic analysis to quantify how well V4 responses discriminated visual stimuli and examined how discriminability was affected by FEF microstimulation. Discriminability of responses to stable visual stimuli decayed over time but was transiently restored after microstimulation of the FEF. As observed during voluntary attention, the enhancement resulted only from changes in the magnitude of V4 responses and not in the relationship between response magnitude and variance. Enhanced response discriminability was apparent immediately after microstimulation and was reliable within 40 ms of microstimulation onset, indicating a direct influence of FEF stimulation on visual representations. These results contribute to the mounting evidence that saccade-related signals are a source of spatial attentive selection. cognition | gain control | oculomotor | prefrontal cortex | visual perception

Abstract Recent studies have investigated the rote of attentional biases and memory in alcohol and other drugs of dependence and the relationship between the motivation to use alcohol or other [...]