Biomedical subjects

Denis Brunet

Publications and source records attributed to Denis Brunet.

4 recordsLinked to original sources

PubMed2007

Rhyme processing in the brain: an ERP mapping study.

The event-related potential (ERP) N450 component has been described in rhyme detection tasks as a negative response elicited by non-rhyming words in comparison to rhyming ones. This response, which peaked around 450 ms over the midline and right hemisphere recording sites, has been subsequently suggested to start already at approximately 300 ms. Moreover, although, the phonological N450 has first been linked to the semantic N400 component, its cognitive nature and cerebral origin remained debated. In this study, we re-investigated the time course of the electrophysiological responses to rhyming and non-rhyming words and estimated their cerebral generators using source localization methods. Waveform analysis showed that, prior to the N450 response to non-rhyming, a slightly earlier negativity characterized the rhyming condition over left fronto-temporal electrodes and peaked at approximately 350 ms. The analysis of the ERP map series in terms of functional microstates revealed a specific map segment in the rhyming condition and another one in the non-rhyming condition. Source localization indicated that the rhyming-elicited microstate engaged predominantly left frontal and temporal areas while the non rhyming-specific response recruited temporal and parietal regions bilaterally. Our results suggest that, similar to the N400 component that is also induced by mismatch contexts, the N450 might rely on temporal generators.

Adult↗

PubMed2006

A case of Lewis-Sumner syndrome with conduction abnormalities only in the brachial plexus and roots.

We present a case of subacute weakness of one hand with unusual sensory involvement including the upper thorax. Despite normal distal conduction studies, a clinical diagnosis of Lewis-Sumner syndrome was made and the patient responded well to intravenous immunoglobulins. Repeated studies after clinical exacerbation finally proved the demyelinating nature of the neuropathy using proximal magnetic nerve stimulation. This case underlies the importance of seeking proximal conduction blocks in patients with suspected demyelinating neuropathy.

Action Potentials↗

PubMed2005

Adrenomyeloneuropathy: report of a new mutation in a French Canadian female.

BACKGROUND: X-linked adrenoleukodystrophy is a peroxisomial disorder caused by mutations in the ABCD1 gene. Adrenomyeloneuropathy is the second most frequent phenotype (25-46%) of this disease and classically presents in adulthood with spastic paraparesis. Female heterozygotes can be symptomatic, but they are frequently misdiagnosed as having multiple sclerosis. CASE REPORT: We report a novel missense mutation in the ABCD1 gene in a 47-year-old French-Canadian female with spastic paraparesis and no confirmed family history of X-linked adrenoleukodystrophy. The mutation is located on exon 1 and causes the amino acid substitution of a valine for an alanine in a region of the protein highly conserved between mouse and man. CONCLUSION: Adrenomyeloneuropathy must be considered in the differential diagnosis of spastic paraparesis in men or women. This is an initial report of an ABCD1 gene mutation in the French-Canadian population, which should lead to the recognition of other cases in the future.

ATP Binding Cassette Transporter, Subfamily D, Mem↗

PubMed2004

Rapid discrimination of visual and multisensory memories revealed by electrical neuroimaging.

Though commonly held that multisensory experiences enrich our memories and that memories influence ongoing sensory processes, their neural mechanisms remain unresolved. Here, electrical neuroimaging shows that auditory-visual multisensory experiences alter subsequent processing of unisensory visual stimuli during the same block of trials at early stages poststimulus onset and within visual object recognition areas. We show this with a stepwise analysis of scalp-recorded event-related potentials (ERPs) that statistically tested (1) ERP morphology and amplitude, (2) global electric field power, (3) topographic stability of and changes in the electric field configuration, and (4) intracranial distributed linear source estimations. Subjects performed a continuous recognition task, discriminating repeated vs. initial image presentations. Corresponding, but task-irrelevant, sounds accompanied half of the initial presentations during a given block of trials. On repeated presentations within a block of trials, only images appeared, yielding two situations-the image's prior presentation was only visual or with a sound. Image repetitions that had been accompanied by sounds yielded improved memory performance accuracy (old or new discrimination) and were differentiated as early as approximately 60-136 ms from images that had not been accompanied by sounds through generator changes in areas of the right lateral-occipital complex (LOC). It thus appears that unisensory percepts trigger multisensory representations associated with them. The collective data support the hypothesis that perceptual or memory traces for multisensory auditory-visual events involve a distinct cortical network that is rapidly activated by subsequent repetition of just the unisensory visual component.

Adolescent↗