Search results for "Cerebral hemisphere"
showing 10 items of 19 documents
Intra- and Interhemispheric Electroencephalogram Coherence in Siblings Discordant for Schizophrenia and Healthy Volunteers
1997
Former studies had pointed to an increased electroencephalogram (EEG) coherence in schizophrenics, but it remained unsolved whether this deviation represents the premorbid state or is only a consequence of the current or previous schizophrenic episodes. To clarify this question, we tested the hypothesis that subjects at elevated risk also reveal higher coherences compared to healthy controls. For that, intra- and interhemispheric EEG coherences were investigated in untreated schizophrenics, their healthy siblings, and healthy controls. Differences were only found regarding the intrahemispheric coherences. Both in schizophrenics and, even though to a lesser degree, in their siblings signific…
Time and spatial attention: Effects of prism adaptation on temporal deficits in brain damaged patients
2011
Growing evidence indicates that the representations of space and time interact in the brain but the exact neural correlates of such interaction remain unknown. Neuroimaging and neuropsychological studies show that processing of temporal information engages a distributed network in the right hemisphere and suggest a link between deficits in spatial attention and deficits in time perception. In the present study we used the procedure of prismatic adaptation (PA) to directionally manipulate spatial attention in order to explore the effect of attentional deviation on time perception in patients with right (RBD) vs. left (LBD) brain damage. In a first experiment, two groups of RBD and LBD patien…
Lexical competition is enhanced in the left hemisphere: Evidence from different types of orthographic neighbors
2007
Two divided visual field lexical decision experiments were conducted to examine the role of the cerebral hemispheres in orthographic neighborhood effects. In Experiment 1, we employed two types of words: words with many substitution neighbors (high-N) and words with few substitution neighbors (low-N). Results showed a facilitative effect of N in the left visual field (i.e., right hemisphere) and an inhibitory effect of N in the right visual field (left hemisphere). In Experiment 2, we examined whether the inhibitory effect of the higher frequency neighbors increases in the left hemisphere as compared to the right hemisphere. To go beyond the usual N-metrics, we selected words with (or witho…
Localization of emotional and volitional facial paresis.
1992
Emotional facial paresis is characterized by impaired activation of face muscles with emotion but normal voluntary activation. We report seven patients with this sign. Their lesions involved the frontal lobe white matter, the striatocapsular territory, the anterolateral thalamus and insula, the posterior thalamus and operculum, and the mesial temporal lobe and insula each in one patient, and the posterior thalamus in two patients. Volitional facial paresis affects facial movements with voluntary effort, sparing activation on emotion. We report four such patients, with lesions involving the motor cortex in one and the pyramidal tract in the cerebral hemisphere in three.
Perceptual, affective, and cognitive judgments of odors: pleasantness and handedness effects.
2003
International audience; The present study sought to examine the differential processing of pleasant, neutral, and unpleasant odors. The effects of the nostril stimulated (left or right) and the type of judgment (perceptual, affective, or cognitive) performed on the olfactory stimuli were also studied. To this end, 64 subjects were asked to smell pleasant, neutral, and unpleasant odors under four conditions (detection, intensity, pleasantness, and familiarity tasks). The participants were to perform these tasks as quickly as possible, while response times were recorded. The results showed that (i) unpleasant odors were assessed more rapidly than neutral or pleasant odors, and that this was s…
Lateralized effects of self-induced sadness and happiness on corticospinal excitability.
1997
We studied the changes in excitability of the corticospinal projection evoked by self-induced sad and happy thoughts. Corticospinal excitability was probed using focal, single-pulse transcranial magnetic stimulation (TMS) applied to the optimal scalp position for evoking motor potentials in the contralateral first dorsal interosseus muscle. Fourteen right-handed subjects were studied while counting mentally, thinking sad thoughts, or thinking happy thoughts. In each of these three conditions TMS was applied in each subject randomly, 20 times to the right and 20 times to the left hemisphere. Sad thoughts resulted in a significant facilitation of the motor potentials evoked by left-hemispheri…
Eye position tunes the contribution of allocentric and egocentric information to target localization in human goal-directed arm movements.
1997
Subjects were required to point to the distant vertex of the closed and the open configurations of the Muller-Lyer illusion using either their right hand (experiment 1) or their left hand (experiment 2). In both experiments the Muller-Lyer figures were horizontally presented either in the left or in the right hemispace and movements were executed using either foveal or peripheral vision of the target. According to the illusion effect, subjects undershot and overshot the vertex location of the closed and the open configuration, respectively. The illusion effect decreased when the target was fixated and when the stimulus was positioned in the right hemispace. These results confirm the hypothe…
Lateral differences in GABA binding sites in rat brain.
1988
An asymmetric distribution of GABA binding sites was found in the cerebral cortex, hippocampus, cerebellar hemispheres, striatum, and thalamus. Higher levels of [3H]GABA binding were observed in the left-side of most brain areas and in a greater percentage of adult rats, but the opposite asymmetry was found in the thalamus. A similar left-right difference in cerebral hemispheres was also found in five day-old rats, suggesting the genetic predetermination of asymmetry.
Embedded word priming elicits enhanced fMRI responses in the visual word form area.
2018
Lexical embedding is common in all languages and elicits mutual orthographic interference between an embedded word and its carrier. The neural basis of such interference remains unknown. We employed a novel fMRI prime-target embedded word paradigm to test for involvement of a visual word form area (VWFA) in left ventral occipitotemporal cortex in co-activation of embedded words and their carriers. Based on the results of related fMRI studies we predicted either enhancement or suppression of fMRI responses to embedded words initially viewed as primes, and repeated in the context of target carrier words. Our results clearly showed enhancement of fMRI responses in the VWFA to embedded-carrier …
Electrophysiological and hemodynamic mismatch responses in rats listening to human speech syllables
2016
International audience; Speech is a complex auditory stimulus which is processed according to several time-scales. Whereas consonant discrimination is required to resolve rapid acoustic events, voice perception relies on slower cues. Humans, right from preterm ages, are particularly efficient to encode temporal cues. To compare the capacities of preterms to those observed in other mammals, we tested anesthetized adult rats by using exactly the same paradigm as that used in preterm neonates. We simultaneously recorded neural (using ECoG) and hemodynamic responses (using fNIRS) to series of human speech syllables and investigated the brain response to a change of consonant (ba vs. ga) and to …