Search results for "visual"
showing 10 items of 7386 documents
Automatic numerical-spatial association in synaesthesia: An fMRI investigation
2016
A horizontal mental number line (MNL) is used to describe how quantities are represented across space. In humans, the neural correlates associated with such a representation are found in different areas of the posterior parietal cortex, especially, the intraparietal sulcus (IPS). In a phenomenon known as number-space synaesthesia, individuals visualise numbers in specific spatial locations. The experience of a MNL for number-space synaesthetes is explicit, idiosyncratic, and highly stable over time. It remains an open question whether the mechanisms underlying numerical-spatial association are shared by synaesthetes and nonsynaesthetes. We address the neural correlates of number-space assoc…
Distributed BOLD-response in association cortex vector state space predicts reaction time during selective attention.
2006
Human cortical information processing is thought to be dominated by distributed activity in vector state space (Churchland, P.S., Sejnowski, T.J., 1992. The Computational Brain. MIT Press, Cambridge.). In principle, it should be possible to quantify distributed brain activation with independent component analysis (ICA) through vector-based decomposition, i.e., through a separation of a mixture of sources. Using event-related functional magnetic resonance imaging (fMRI) during a selective attention-requiring task (visual oddball), we explored how the number of independent components within activated cortical areas is related to reaction time. Prior to ICA, the activated cortical areas were d…
Meaningful physical changes mediate lexical-semantic integration: top-down and form-based bottom-up information sources interact in the N400
2011
Models of how the human brain reconstructs an intended meaning from a linguistic input often draw upon the N400 event-related potential (ERP) component as evidence. Current accounts of the N400 emphasise either the role of contextually induced lexical preactivation of a critical word (Lau, Phillips,& Poeppel, 2008) or the ease of integration into the overall discourse context including a wide variety of influencing factors (Hagoort & van Berkum, 2007). The present ERP study challenges both types of accounts by demonstrating a contextually independent and purely form-based bottom-up influence on the N400: the N400 effect for implausible sentence-endings was attenuated when the critical sente…
Bodily self-relatedness in vicarious touch is reflected at early cortical processing stages.
2019
Studies have suggested that there is a strong link between the bodily self and the mechanisms underlying vicarious representations. Here, we used somatosensory ERPs to investigate the temporal dynamics of vicarious touch for stimuli that are more or less related to one's own body (human hands vs. rubber gloves). We found that vicarious touch effects were restricted to self-relatable events (human hands) at early implicit stages of somatosensory processing (P45). At later more cognitive stages of processing (late positive complex, LPC), the vicarious touch effect was stronger for self-relatable events (touch on human hands) than nonself-relatable events (touch on rubber gloves) but present f…
Is that me in the mirror? Depersonalisation modulates tactile mirroring mechanisms
2016
Our sense of self is thought to develop through sensory-motor contingencies provided, not only by observing one's own body, but also by mirroring interactions with others. This suggests that there is a strong link between mirroring mechanisms and the bodily self. The present study tested whether this link is expressed at early, implicit stages of the mirroring process or at later, more cognitive stages. We also provide, to the best of our knowledge, the first demonstration of how inter-individual differences in our sense of bodily self may affect mirroring mechanisms. We used somatosensory event-related potentials (SEPs) to investigate the temporal dynamics of mirroring highly self-related …
Early use of phonological codes in deaf readers: An ERP study.
2017
Previous studies suggest that deaf readers use phonological information of words when it is explicitly demanded by the task itself. However, whether phonological encoding is automatic remains controversial. The present experiment examined whether adult congenitally deaf readers show evidence of automatic use of phonological information during visual word recognition. In an ERP masked priming lexical decision experiment, deaf participants responded to target words preceded by a pseudohomophone (koral - CORAL) or an orthographic control prime (toral - CORAL). Responses were faster for the pseudohomophone than for the orthographic control condition. The N250 and N400 amplitudes were reduced fo…
Early access to abstract representations in developing readers: evidence from masked priming
2013
A commonly shared assumption in the field of visual-word recognition is that retinotopic representations are rapidly converted into abstract representations. Here we examine the role of visual form vs. abstract representations during the early stages of word processing - as measured by masked priming - in young children (3rd and 6th Graders) and adult readers. To maximize the chances of detecting an effect of visual form, we employed a language with a very intricate orthography, Arabic. If visual form plays a role in the early stages of processing, greater benefit would be expected from related primes that have the same visual form (in terms of the ligation pattern between a word's letters)…
Segregation of areas related to visual working memory in the prefrontal cortex revealed by rTMS.
2002
The functional organization of working memory (WM) in the human prefrontal cortex remains unclear. Storage and processing functions might be segregated in ventral and dorsal areas of the prefrontal cortex, respectively. If so, storage functions might be spared, irrespective of informational domain, following damage or dysfunction in dorsolateral areas. Alternatively, WM and prefrontal function in general might be segregated according to informational domains (e.g. spatial versus object-based information). In the present study we used repetitive transcranial magnetic stimulation (rTMS) to directly test these competing hypotheses. We applied rTMS to transiently and selectively disrupt the fun…
Chronometry of parietal and prefrontal activations in verbal working memory revealed by transcranial magnetic stimulation.
2003
We explored the temporal dynamics of parietal and prefrontal cortex involvement in verbal working memory employing single-pulse transcranial magnetic stimulation (TMS). In six healthy volunteers the left or right inferior parietal and prefrontal cortex was stimulated with the aid of a frameless stereotactic system. TMS was applied at 10 different time points 140-500 ms into the delay period of a two-back verbal working memory task. A choice reaction task was used as a control task. Interference with task accuracy was induced by TMS earlier in the parietal cortex than in the prefrontal cortex and earlier over the right than the left hemisphere. This suggests a propagation of information flow…
Low-frequency rTMS inhibitory effects in the primary motor cortex: Insights from TMS-evoked potentials
2014
The neuromodulatory effects of repetitive transcranial magnetic stimulation (rTMS) have been mostly investigated by peripheral motor-evoked potentials (MEPs). New TMS-compatible EEG systems allow a direct investigation of the stimulation effects through the analysis of TMS-evoked potentials (TEPs).We investigated the effects of 1-Hz rTMS over the primary motor cortex (M1) of 15 healthy volunteers on TEP evoked by single pulse TMS over the same area. A second experiment in which rTMS was delivered over the primary visual cortex (V1) of 15 healthy volunteers was conducted to examine the spatial specificity of the effects. Single-pulse TMS evoked four main components: P30, N45, P60 and N100. M…