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Tactile sensitivity enhancement (TSE) observed in blind people is probably a result of intensified tactile training. Although many researchers consider TSE in the blind to be an example of use-dependent plasticity, it is unclear whether the effects of training (Braille reading) are specific, i.e. restricted to the trained function and hand, or if they are more general. To examine this issue further, blind Braille readers, low-vision subjects (Braille readers and non-Braille readers) and sighted controls were tested in two tasks: a texture task resembling the Braille system and a dissimilar groove orientation task. Braille readers, both blind and those with low vision, performed better in both tasks than low-vision non-Braille readers or sighted controls. However, the difference was significant only for the blind (more experienced) Braille readers. In the groove orientation task, the positive influence of training was detectable irrespective of the hand used in the test, but in the coarse texture task this influence was limited to the hand trained in Braille. Thus, it appears that tactile training is of significance in TSE but its effects are, to a large extent, task- and hand-specific.
Event-related potentials were used to examine if the brain response (N400 component) in dyslexic children is modulated by phonological or semantic priming, similarly to age-matched controls. ERPs were recorded while the children listened to word lists in which the semantic and phonological congruency of the terminal words were manipulated. Dyslexics exhibited a dissociation of priming effects depending on whether semantically or phonologically loaded primes were used. An enhancement of N400 amplitude to semantically incongruent words was observed, although this effect was reduced and delayed compared to that seen in controls. Direct comparison of the performance of the two groups in the semantic priming task revealed that they differed only in their response to semantically incongruent words. In the phonological priming task, rather than an enhancement of the N400 amplitude found in controls, dyslexics displayed a reduction of the N400 to the incongruent condition in comparison to the congruent condition. In this task, the studied groups differed in both the phonologically congruent and incongruent conditions. These results suggest that when faced with phonological priming, dyslexics have problems with both matching for similarities (integration into context) and incongruency detection. In the case of semantic priming, the integration of semantic context seems relatively intact in dyslexics, but they experience diffi culties in detecting the shift from one semantic category to another.
The ability to “read” the information about facial identity, expressed emotions, and intentions is crucial for non-verbal social interaction. Neuroimaging and clinical studies consequently link face perception with fusiform gyrus (FG) and occipital face area (OFA) activity. Here we investigated face processing in an adult, patient PK, diagnosed with both high functioning autism spectrum disorder (ASD) and developmental prosopagnosia (DP). Both disorders have a significant impact on face perception and recognition, thus creating a unique neurodevelopmental condition. We used eye-tracking and functional magnetic resonance imaging (fMRI) method. Eye-tracking and fMRI results of PK were compared to results of control subjects. Patient PK showed atypical gaze-fixation strategy during face perception and typical patterns of brain activations in the FG and OFA. However, a significant difference between PK and control subjects was found in the left anterior superior temporal sulcus/middle temporal gyrus (aSTS/MTG). In PK the left aSTS/MTG was hypo-activated in comparison to the control subjects. Additionally, functional connectivity analysis revealed decreased inter-hemispheric connectivity between right and left aSTS/MTG in ‘ASD and DP’ patient during face recognition performance as compared to the control subjects. The lack of activity in the left aSTS/MTG observed in the case of the clinical subject, combined with the behavioral, eye-tracking, and neuropsychological results, suggests that impairment of the cognitive mechanism of face recognition involves higher level of processing. It seems to be related to insufficient access to semantic knowledge about the person when prompted by face stimuli.
Previous imaging studies have identified many brain regions activated during reasoning, but there are differences among the findings concerning specific regions engaged in reasoning and the contribution of language areas. Also, little is known about the relation between task complexity and neural activation during reasoning. The present fMRI study investigated brain activity during complex four-term transitive reasoning with abstract material (determinate or partially indeterminate) and compared the resulting images to those obtained during a memorization task. The memory condition required subjects to memorize unrelated elements whereas the reasoning conditions required them to integrate information from premises and to infer relations between elements. After contrasting the two kinds of reasoning conditions with the memory condition we found that right prefrontal and bilateral parietal regions are specifically activated during reasoning. We also demonstrated that different reasoning requirements - the possibility of constructing one (determined reasoning) versus several (undetermined reasoning) models of a situation during task solving - lead to different patterns of brain activity, with higher prefrontal (PFC) activity accompanying undetermined reasoning. We interpret the PFC activity as a reflection of simultaneous maintenance and manipulation of information in reasoning. These findings provide new evidence that specific forms of reasoning (abstract and undetermined) demand recruitment of right PFC and hemispheric coordination and lend new support to the mental model theory of relational reasoning.
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