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Functional somatic syndromes are characterized by high morbidity due to various, fluctuating symptoms without objective somatic findings. There is increasing evidence for the contribution of emotional and cognitive functions to symptom formation, which has been well established in the perception of pain. In addition to their involvement in various other cognitive and emotional processes, the anterior cingulate and insular cortex are thought to contribute to the so-called "pain neuromatrix". Recent data suggest that these areas appear also to be involved in symptom manifestation in multiple chemical sensitivity. Here we used functional Magnetic Resonance Imaging (fMRI) to test whether this network is also involved in the induction of unpleasant perceptions by sham mobile phone radiation in subjectively electrosensitive patients. This design enabled us to completely dissociate the unpleasant subjective perception from any real physical stimulus. Fifteen subjectively electrosensitive patients and 15 age- and gender-matched healthy controls were exposed to sham mobile phone radiation and heat as a control condition. The perceived stimulus intensities were rated on a five-point scale. During anticipation of and exposure to sham mobile phone radiation increased activations in anterior cingulate and insular cortex as well as fusiform gyrus were seen in the electrosensitive group compared to controls, while heat stimulation led to similar activations in both groups. Symptom manifestation during sham exposure to mobile phone radiation was accompanied by specific alterations of cortical activity in anterior cingulate and insular cortex in subjectively electrosensitive patients further supporting the involvement of these areas in the perception of unpleasantness and generation of functional somatic syndromes.

Smooth pursuit eye movements (SP) are driven by moving objects. The pursuit system processes the visual input signals and transforms this information into an oculomotor output signal. Despite the object's movement on the retina and the eyes' movement in the head, we are able to locate the object in space implying coordinate transformations from retinal to head and space coordinates. To test for the visual and oculomotor components of SP and the possible transformation sites, we investigated three experimental conditions: (I) fixation of a stationary target with a second target moving across the retina (visual), (II) pursuit of the moving target with the second target moving in phase (oculomotor), (III) pursuit of the moving target with the second target remaining stationary (visuo-oculomotor). Precise eye movement data were simultaneously measured with the fMRI data. Visual components of activation during SP were located in the motion-sensitive, temporo-parieto-occipital region MT+ and the right posterior parietal cortex (PPC). Motor components comprised more widespread activation in these regions and additional activations in the frontal and supplementary eye fields (FEF, SEF), the cingulate gyrus and precuneus. The combined visuo-oculomotor stimulus revealed additional activation in the putamen. Possible transformation sites were found in MT+ and PPC. The MT+ activation evoked by the motion of a single visual dot was very localized, while the activation of the same single dot motion driving the eye was rather extended across MT+. The eye movement information appeared to be dispersed across the visual map of MT+. This could be interpreted as a transfer of the one-dimensional eye movement information into the two-dimensional visual map. Potentially, the dispersed information could be used to remap MT+ to space coordinates rather than retinal coordinates and to provide the basis for a motor output control. A similar interpretation holds for our results in the PPC region.

Using fMRI, we explored cortical responses to dichoptically presented random-dot (RD) stimuli which formed a checkerboard by means of horizontal disparity (Julesz). Depth reversals occurred every 800 ms by appropriate horizontal shifting of a subset of the RD pattern. We compared cortical blood oxygen level dependent (BOLD) responses of five subjects under conditions with and without binocular disparity. The results indicate that only extrastriate, but not striate, areas responded more to the stimuli with binocular disparity. We further found that the BOLD signal increased with increasing disparity level only in dorsal areas of occipito-parietal and prefrontal cortex. These results suggest that the fMRI BOLD response can reflect the processing of relative binocular disparity in extrastriate cortex.

We examined whether the frontal eye fields (FEF) are involved in the suppression of reflexive saccades. Simultaneous recording of horizontal eye movements and functional magnetic resonance imaging enabled us to perform a randomized pro- and antisaccade task and to sort blood oxygenation level dependent (BOLD) time series on the basis of task performance. Saccadic reaction time distributions were comparable across tasks indicating a similar effort in preprocessing of the saccades. Furthermore, we found similar BOLD activation in FEF during both correctly performed pro- and antisaccades. Frontal eye field activation started prior to target presentation and saccade generation. While we observed only few erroneous antisaccades, these were associated with a decrease in BOLD activity prior to target presentation, and increased BOLD activity after target presentation relative to correctly performed antisaccades. These findings are consistent with a role of the FEF in the suppression of reflexive saccades. The increase in activity after target presentation for antisaccade errors can only be indirectly linked to such a role but may also reflect activity related to the generation of a correction saccade. Frontal eye field BOLD activity may further represent general arousal, preparatory set, short-term memory, or salience-map related activity.

The auditory and visual perception systems have developed special processing strategies for ecologically valid motion stimuli, utilizing some of the statistical properties of the real world. A well-known example is the perception of biological motion, for example, the perception of a human walker. The aim of the current study was to identify the cortical network involved in the integration of auditory and visual biological motion signals. We first determined the cortical regions of auditory and visual coactivation (Experiment 1); a conjunction analysis based on unimodal brain activations identified four regions: middle temporal area, inferior parietal lobule, ventral premotor cortex, and cerebellum. The brain activations arising from bimodal motion stimuli (Experiment 2) were then analyzed within these regions of coactivation. Auditory footsteps were presented concurrently with either an intact visual point-light walker (biological motion) or a scrambled point-light walker; auditory and visual motion in depth (walking direction) could either be congruent or incongruent. Our main finding is that motion incongruency (across modalities) increases the activity in the ventral premotor cortex, but only if the visual point-light walker is intact. Our results extend our current knowledge by providing new evidence consistent with the idea that the premotor area assimilates information across the auditory and visual modalities by comparing the incoming sensory input with an internal representation., Posted Online November 29, 2011

Selectively retrieving a target memory among related memories requires some degree of inhibitory control over interfering and competing memories, a process assumed to be supported by inhibitory mechanisms. Evidence from behavioral studies suggests that such inhibitory control can lead to subsequent forgetting of the interfering information, a finding called retrieval-induced forgetting [Anderson, M. C., Bjork, R. A., & Bjork, E. L. Remembering can cause forgetting: Retrieval dynamics in long-term memory. Journal of Experimental Psychology: Learning, Memory & Cognition, 20, 1063–1087, 1994]. In the present functional magnetic resonance imaging study, we investigated the neural processes underlying retrieval-induced forgetting and, in particular, examined the extent to which these processes are retrieval (i.e., selection) specific. Participants actively retrieved a subset of previously studied material (selection condition), or were re-exposed to the same material for relearning (nonselection condition). Replicating prior behavioral work, selective retrieval caused significant forgetting of the nonretrieved items on a delayed recall test, relative to the re-exposure condition. Selective retrieval was associated with increased BOLD responses in the posterior temporal and parietal association cortices, in the bilateral hippocampus, and in the dorsolateral prefrontal cortex. Medial and lateral prefrontal areas showed a strong negative linear relationship between selection-related neural activity and subsequent forgetting of competitors. These findings suggest reduced demands on inhibitory control processes when interference is successfully resolved during early selective retrieval from episodic memory.

During language comprehension, readers or listeners routinely infer information that has not been stated literally in a given text or utterance in order to construct a coherent mental representation (situation model). We used a verification task in a behavioral study and in an event-related functional magnetic resonance imaging (fMRI) experiment to investigate the inference construction process. After having read sentences that mention the outcome of an event explicitly, implicitly, or not at all, participants verified the plausibility of short statements with respect to the context of the just read sentence. The results of the behavioral study established the verification task as a valid method for studying inferences. In the fMRI study, the dorsomedial prefrontal cortex was the most prominent area that was involved in the processing of inference statements. Regions in the left and right temporal lobes were associated with comparison processes that are based on the propositional representations of context sentence and test statements. The results are discussed with respect to levels of representations and the memory systems that underlie the verification process in the different sentence conditions.

Blood oxygenation-level dependent changes in the cerebral cortex were measured using event-related functional magnetic resonance imaging in participants while they performed triple-step memory-guided saccades. To explore the role of dorsolateral prefrontal cortex in the manipulation of the contents of working memory, the sequence of saccade targets in the memory-guided task was either constant or was manipulated using coloured cues. The dorsolateral prefrontal cortex was significantly activated only during the period when participants had to reorder the locations of the saccade targets and not during the maintenance of spatial locations. This finding suggests that dorsolateral prefrontal cortex is primarily involved in the manipulation, and to a lesser extent, in the maintenance of the contents of working memory.

Background Dorsolateral prefrontal cortex (DLPFC), posterior parietal cortex, and regions in the occipital cortex have been identified as neural sites for visual working memory (WM). The exact involvement of the DLPFC in verbal and non-verbal working memory processes, and how these processes depend on the time-span for retention, remains disputed. Methods We used functional MRI to explore the neural correlates of the delayed discrimination of Gabor stimuli differing in orientation. Twelve subjects were instructed to code the relative orientation either verbally or non-verbally with memory delays of short (2 s) or long (8 s) duration. Results Blood-oxygen level dependent (BOLD) 3-Tesla fMRI revealed significantly more activity for the short verbal condition compared to the short non-verbal condition in bilateral superior temporal gyrus, insula and supramarginal gyrus. Activity in the long verbal condition was greater than in the long non-verbal condition in left language-associated areas (STG) and bilateral posterior parietal areas, including precuneus. Interestingly, right DLPFC and bilateral superior frontal gyrus was more active in the non-verbal long delay condition than in the long verbal condition. Conclusion The results point to a dissociation between the cortical sites involved in verbal and non-verbal WM for long and short delays. Right DLPFC seems to be engaged in non-verbal WM tasks especially for long delays. Furthermore, the results indicate that even slightly different memory maintenance intervals engage largely differing networks and that this novel finding may explain differing results in previous verbal/non-verbal WM studies.

Using functional magnetic resonance imaging, we compared responses during visually guided saccades with those evoked during memory-guided saccades, in which participants executed saccades to remembered locations. Eye movements were recorded in the magnetic resonance tomograph. Significantly stronger activation during memory-guided saccades was observed in the posterior portion of the right inferior frontal gyrus, in the left inferior frontal eye field, in the posterior parietal cortex, as well as in the right posterior superior temporal gyrus. The posterior part of the dorsal anterior cingulum and a small voxel cluster in the dorsolateral prefrontal area, anterior to the left inferior frontal eye field, were only active in the memory-guided condition.

Using an uncertainty paradigm and functional magnetic resonance imaging (fMRI) we studied the effect of nonspatial selective and divided visual attention on the activity of specific areas of human extrastriate visual cortex. The stimuli were single ovals that differed from an implicit standard oval in either colour or width. The subjects’ task was to classify the current stimulus as one of two possible alternatives per stimulus dimension. Three different experimental conditions were conducted: “colour-certainty”, “shape-certainty” and “uncertainty”. In all experimental conditions, the stimulus differed in only one stimulus dimension per trial. In the two certainty conditions, the subjects knew in advance which dimension this would be. During the uncertainty condition they had no such previous knowledge and had to monitor both dimensions simultaneously. Statistical analysis of the fMRI data (with SPM2) revealed a modest effect of the attended stimulus dimension on the neural activity in colour sensitive area V4 (more activity during attention to colour) and in shape sensitive area LOC (more activity during attention to shape). Furthermore, cortical areas known to be related to attention and working memory processes (e.g., lateral prefrontal and posterior parietal cortex) exhibit higher activity during the condition of divided attention (“uncertainty”) than during that of selective attention (“certainty”).

The processing of optic flow fields in motion-sensitive areas in human visual cortex was studied with BOLD (blood oxygen level dependent) contrast in functional magnetic resonance imaging (fMRI). Subjects binocularly viewed optic flow fields in plane (monoptic) or in stereo depth (dichoptic) with various degrees of disparity and increasing radial speed. By varying the directional properties of the stimuli (expansion, spiral motion, random), we explored whether the BOLD effect reflected neuronal responses to these different forms of optic flow. The results suggest that BOLD contrast as assessed by fMRI methods reflects the neural processing of optic flow information in motion-sensitive cortical areas. Furthermore, small but replicable disparity-selective responses were found in parts of Brodmann's area 19.

Using functional magnetic resonance imaging (fMRI), we explored the binocular interactions occurring when subjects viewed dichoptically presented checkerboard stimuli. A flickering radial checkerboard was presented to each eye of the subject, while T2*-weighted images were acquired over the visual cortex with gradient-echo, echoplanar sequences. We compared responses in striate and extrastriate visual cortex under four conditions: both eyes were stimulated at the same time (binocular condition), each eye was stimulated in alternation (monocular condition) or first the one eye then the other eye was stimulated (left eye first - right eye trailing, or vice versa). The results indicate that only the striate area, in and near the calcarine fissure, shows significant differences for these stimulation conditions. These differences are not evident in more remote extrastriate or associational visual areas, although the BOLD response in the stimulation-rest comparison was robust. These results suggest that the effect could be related to inhibitory interactions across ocular dominance columns in striate visual cortex.