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Awareness in Primary Visual Cortex
Full text linkThe neural processes that give rise to visual awareness are currently the subject of much debate. One brain region in particular, the primary visual cortex (also known as striate cortex or V1), has been implicated in the neural interactions that give rise to conscious perception. This region, located in and around the calcarine fissure in the occipital lobe, was long regarded merely as a relay station for visual cortical input, with visual awareness believed to arise from the activity of highly specialized visual areas in the parietal and temporal lobes. The perceptual consequences of V1 lesions, however, reveal the indispensable role of this area in conscious perception, and this view is supported by recent neurodisruption and neuroimaging studies carried out in neurologically normal observers. Here we review findings from neuropsychology, cognitive neuroscience, and electrophysiology, and discuss what they reveal about the role of V1 in visual awareness
Dissociable neural representations of grammatical gender in Broca's area investigated by the combination of satiation and TMS
No full textAlong with meaning and form, words can be described on the basis of their grammatical properties. Grammatical gender is often used to investigate the latter as it is a grammatical property that is independent of meaning. The left inferior frontal gyrus (IFG) has been implicated in the encoding of grammatical gender, but its causal role in this process in neurologically normal observers has not been demonstrated. Here we combined verbal satiation with transcranial magnetic stimulation (TMS) to demonstrate that subpopulations of neurons within Broca's area respond preferentially to different classes of grammatical gender. Subjects were asked to classify Italian nouns into living and nonliving categories; half of these words were of masculine and the other half of feminine grammatical gender. Prior to each test block, a satiation paradigm (a phenomenon in which verbal repetition of a category name leads to a reduced access to that category) was used to modulate the initial state of the representations of either masculine or feminine noun categories. In the No TMS condition, subjects were slower in responding to exemplars to the satiated category relative to exemplars of the nonsatiated category, implying that the neural representations for different classes of grammatical gender are partly dissociable. The application of TMS over Broca's area removed the behavioral impact of verbal (grammatical) satiation, demonstrating the causal role of this region in the encoding of grammatical gender. These results show that the neural representations for different cases of a grammatical property within Broca's area are dissociabl
Using state-dependency of transcranial magnetic stimulation (TMS) to investigate letter selectivity in the left posterior parietal cortex: a comparison of TMS-priming and TMS-adaptation paradigms
No full textState-Dependent TMS Reveals Representation of Affective Body Movements in the Anterior Intraparietal Cortex
Full text linkIn humans, recognition of others' actions involves a cortical network that comprises, among other cortical regions, the posterior superior temporal sulcus (pSTS), where biological motion is coded and the anterior intraparietal sulcus (aIPS), where movement information is elaborated in terms of meaningful goal-directed actions. This action observation system (AOS) is thought to encode neutral voluntary actions, and possibly some aspects of affective motor repertoire, but the role of the AOS' areas in processing affective kinematic information has never been examined. Here we investigated whether the AOS plays a role in representing dynamic emotional bodily expressions. In the first experiment, we assessed behavioral adaptation effects of observed affective movements. Participants watched series of happy or fearful whole-body point-light displays (PLDs) as adapters and were then asked to perform an explicit categorization of the emotion expressed in test PLDs. Participants were slower when categorizing any of the two emotions as long as it was congruent with the emotion in the adapter sequence. We interpreted this effect as adaptation to the emotional content of PLDs. In the second experiment, we combined this paradigm with TMS applied over either the right aIPS, pSTS, and the right half of the occipital pole (corresponding to Brodmann's area 17 and serving as control) to examine the neural locus of the adaptation effect. TMS over the aIPS (but not over the other sites) reversed the behavioral cost of adaptation, specifically for fearful contents. This demonstrates that aIPS contains an explicit representation of affective body movements
Contrasting early visual cortical activation states causally involved in visual imagery and short-term memory
No full textOverlapping representations of numerical magnitude and motion direction in the posterior parietal cortex: A TMS-adaptation study
No full textThe causal role of category-specific neuronal representations in the left ventral premotor cortex (PMv) in semantic processing
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Processing of featural and configural aspects is lateralized in dorsolateral prefrontal cortex: a TMS study
No full textFacial recognition relies on distinct and parallel types of processing: featural processing focuses on the individual components of a face (e.g., the shape or the size of the eyes), whereas configural (or "relational") processing considers the spatial interrelationships among the single facial components (e.g., distance of the mouth from the nose). Previous neuroimaging evidence has suggested that featural and configural processes may rely on different brain circuits. By using rTMS, here we show for the first time a double dissociation in dorsolateral prefrontal cortex for different aspects of face processing: in particular, TMS over the left middle frontal gyrus (BA8) selectively disrupted featural processing, whereas TMS over the right inferior frontal gyrus (BA44) selectively interfered with configural processing of faces. By establishing a causal link between activation in left and right prefrontal areas and different modes of face processing, our data extend previous neuroimaging evidence and may have important implications in the study of face-processing deficits, such as those manifested in prosopagnosia and autistic spectrum disorder
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