Biomedical subjects

Shirley Fecteau

Publications and source records attributed to Shirley Fecteau.

12 recordsLinked to original sources

PubMed2006

A sham-controlled trial of a 5-day course of repetitive transcranial magnetic stimulation of the unaffected hemisphere in stroke patients.

BACKGROUND AND PURPOSE: It has been recently shown that a single session of repetitive transcranial magnetic stimulation (rTMS) of the unaffected hemisphere can improve motor function in stroke patients; however, this improvement is short-lasting. We therefore conducted a randomized, sham-controlled, phase II trial to evaluate whether five sessions of low-frequency rTMS can increase the magnitude and duration of these effects and whether this approach is safe. METHODS: Fifteen patients with chronic stroke were randomized to receive active or sham rTMS of the unaffected hemisphere. A blinded rater assessed motor function and corticospinal excitability at baseline, during and after 2 weeks of treatment. Safety was assessed using a neuropsychologic battery and electroencephalogram. RESULTS: Active rTMS resulted in a significant improvement of the motor function performance in the affected hand that lasted for 2 weeks. These effects were not observed in the sham rTMS group (affected and unaffected hand) and in the unaffected hand in the active rTMS group. Corticospinal excitability decreased in the stimulated, unaffected hemisphere and increased in the affected hemisphere. There was a significant correlation between motor function improvement and corticospinal excitability change in the affected hemisphere. Cognitive performance and electroencephalogram were not changed significantly throughout the trial in both groups of treatment. CONCLUSIONS: These results support and extend the findings of previous studies on rTMS in stroke patients because five consecutive sessions of rTMS increased the magnitude and duration of the motor effects. Furthermore, this increased dose of rTMS is not associated with cognitive adverse effects and/or epileptogenic activity.

Adult↗

PubMed2006

Intrahemispheric dysfunction in primary motor cortex without corpus callosum: a transcranial magnetic stimulation study.

BACKGROUND: The two human cerebral hemispheres are continuously interacting, through excitatory and inhibitory influences and one critical structure subserving this interhemispheric balance is the corpus callosum. Interhemispheric neurophysiological abnormalities and intrahemispheric behavioral impairments have been reported in individuals lacking the corpus callosum. The aim of this study was to examine intrahemispheric neurophysiological function in primary motor cortex devoid of callosal projections. METHODS: Intracortical excitatory and inhibitory systems were tested in three individuals with complete agenesis of the corpus callosum and sixteen healthy individuals. These systems were assessed using transcranial magnetic stimulation (TMS) protocols: motor threshold at rest, paired-pulse curve, and cortical silent period. RESULTS: TMS revealed no difference between the patient and control groups on the motor threshold measure, as well as intracortical facilitation and intracortical inhibition systems as tested by paired stimulation. However, intrahemispheric inhibitory function was found to be abnormal in participants without callosal projections, as the cortical silent period duration was significantly increased in the patient group. CONCLUSION: These data suggest that in addition to previously reported impaired interhemispheric function, patients lacking the entire corpus callosum also display abnormal intrahemispheric excitability of the primary motor cortex.

Adult↗

PubMed2006

Homeostatic effects of plasma valproate levels on corticospinal excitability changes induced by 1Hz rTMS in patients with juvenile myoclonic epilepsy.

OBJECTIVE: The preliminary results of noninvasive brain stimulation for epilepsy treatment have been encouraging, but mixed. Two important factors may contribute to this heterogeneity: the altered brain physiology of patients with epilepsy and the variable presence of antiepileptic drugs. Therefore, we aimed to study the effects of 1 Hz rTMS on corticospinal excitability in patients with juvenile myoclonic epilepsy (JME) in two different conditions: low- or high-plasma valproate levels. METHODS: Fifteen patients with JME and 12 age-matched healthy subjects participated in this study. Corticospinal excitability before and after 1 Hz rTMS was assessed in JME patients with low- and high-plasma valproate levels; and these results were compared with those in healthy subjects. RESULTS: In patients with chronic use of valproate and low-plasma concentrations, 1 Hz rTMS had a similar significant inhibitory effect on corticospinal excitability as in healthy subjects. However, in the same patients when the serum valproate concentration was high, 1 Hz rTMS increased the corticospinal excitability significantly. In addition, there was a significant positive correlation between plasma valproate levels and the motor threshold changes after 1 Hz rTMS. CONCLUSIONS: Our findings can be accounted for by mechanisms of homeostatic plasticity and illustrate the dependency of the modulatory effects of rTMS on the physiologic state of the targeted brain cortex. SIGNIFICANCE: The therapeutic use of rTMS in epilepsy should take into consideration the interaction between rTMS and drugs that change cortical excitability.

Adolescent↗

PubMed2006

Autism spectrum disorder: seeing is not understanding.

Impairments in social and emotional skills are a defining feature of autism spectrum disorder. Recent research shows that structural and functional abnormalities within the neural system that matches observation and execution of actions--the mirror neuron system--may explain the social aspects of the pathophysiology of autism spectrum disorder.

Autistic Disorder↗

PubMed2006

Paradoxical facilitation of attention in healthy humans.

Transcranial magnetic stimulation (TMS)-induced virtual lesions in healthy subjects can be used to test neurofunctional models of disease. The interhemispheric rivalry model of heminglect is well suited for such investigations, as simple predictions derived from clinical data can be tested without the caveats normally associated with lesion studies. One of these predictions is that release from contralateral inhibition should lead to increased parietal responsiveness, which, in turn, would enhance spatial attention. Here, we detail studies showing TMS-induced paradoxical functional facilitation of attention in healthy individuals and highlight their contribution to the understanding and treatment of neglect syndromes.

Attention↗

PubMed2005

Modulation of motor cortex excitability during action observation in disconnected hemispheres.

The degree of involvement of the right and left hemispheres in the system matching perception and execution of actions remains unclear. Some studies have proposed that action observation involves a bilateral network of brain areas, whereas others have suggested left-hemisphere dominance. We explored hemispheric lateralization associated with action observation using transcranial magnetic stimulation over primary motor cortex devoid of callosal influences. We assessed corticospinal excitability related to observation of finger movements in one split-brain patient and six controls. Results revealed that the left hemisphere of the split-brain patient shows enhanced excitability during action observation, whereas no enhancement was found in the right hemisphere. The controls showed increased excitability in both hemispheres during action observation. Our findings suggest a left-hemisphere dominance for mirror-neuron function in the absence of a corpus callosum.

Adolescent↗

PubMed2005

Sensitivity to voice in human prefrontal cortex.

We report two functional MRI (fMRI) experiments showing sensitivity to human voice in a region of human left inferior prefrontal cortex, pars orbitalis. The voice-enhanced response was observed for speech as well as non-linguistic vocalizations and was stronger for emotional than neutral vocalizations. This region could constitute a human prefrontal auditory domain similar to the one recently identified in the macaque brain.

Acoustic Stimulation↗

PubMed2005

Judgment of emotional nonlinguistic vocalizations: age-related differences.

Humans make extensive use of vocal information to attribute emotional states to other individuals. To date, most studies exploring perception of vocal emotions have done so in the context of speech prosody, although nonlinguistic emotional vocalizations represent an important, perhaps more universal, means to express emotions. Here, we explored the perception of emotional nonlinguistic vocalizations in healthy individuals, with an emphasis on potential age- and sex-related differences. Sixty participants rated 563 positive (e.g., laughs, sexual vocalizations), negative (e.g., cries, screams of fear), and neutral vocalizations (e.g., coughs), according to the valence, intensity, and authenticity of the emotion expressed. Ratings were consistent among individuals, suggesting that valence is an adequate measure of emotional categorization. An important effect of age emerged: (a) age by vocalization category interactions were observed for both valence and intensity ratings, and (b) younger participants rated stimuli as more emotional than older individuals (i.e., higher valence for positive, lower for negative, and more intense for both positive and negative). We also found a sex effect in the authenticity ratings: older women rated the vocalizations as less authentic than younger women whereas authenticity judgments did not differ between the two age groups in men. Taken together, these findings suggest that, as previously observed for facial expressions and prosody, the judgments of emotional vocalizations may vary with age.

Adult↗

PubMed2004

Priming of non-speech vocalizations in male adults: the influence of the speaker's gender.

Previous research reported a priming effect for voices. However, the type of information primed is still largely unknown. In this study, we examined the influence of speaker's gender and emotional category of the stimulus on priming of non-speech vocalizations in 10 male participants, who performed a gender identification task. We found a significant priming effect, which was greater for female than male vocalizations. In contrast, the emotional category of the stimuli did not appear to modulate the magnitude of priming. These data suggest that different aspects of the information conveyed in non-speech vocalizations may contribute differently to behavioral priming, possibly influenced by task relevance.

Adult↗

PubMed2004

Is voice processing species-specific in human auditory cortex? An fMRI study.

Recent studies suggested a sensitivity of regions of the human superior temporal sulcus (STS) to the sound of the human voice. However, the question of the species specificity of this response is still open. Healthy adult volunteers were scanned in an event-related fMRI design to compare responses in the STS to human and animal vocalizations, as well as to control nonvocal sounds (e.g., musical instruments). Bilateral activation of anterior STS was observed for human vocalizations, when contrasted with both nonvocal sounds and animal vocalizations. Animal vocalizations, compared to nonvocal sounds, elicited a more restricted left STS activation, although this region responded even more strongly to human vocalizations. This study provides the first evidence suggesting a species specificity in STS responses to vocalizations in humans.

Acoustic Stimulation↗

PubMed2004

Thinking the voice: neural correlates of voice perception.

The human voice is the carrier of speech, but also an "auditory face" that conveys important affective and identity information. Little is known about the neural bases of our abilities to perceive such paralinguistic information in voice. Results from recent neuroimaging studies suggest that the different types of vocal information could be processed in partially dissociated functional pathways, and support a neurocognitive model of voice perception largely similar to that proposed for face perception.

Auditory Perception↗

PubMed2003

Developmental changes of autistic symptoms.

The study examined developmental changes in autistic symptoms retrospectively in a sample of 28 verbal children and adolescents with autism. Individuals with Asperger syndrome, PDD-NOS, and related medical conditions were not included in the study. We compared autistic symptoms present at the retrospective assessment and during the 4- to 5-year age period using the ADI-R. Our findings revealed a significant improvement in the three domains relevant for the diagnosis of autism, independent of age or IQ level. Improvement occurred in more symptoms from the social than the communication domain, and for more symptoms from the latter than the restricted interest and repetitive behavior domains. The finding that improvement was not linked to level of functioning and was found in individuals still positive for a diagnosis of autism suggests that improvement belongs to the 'natural history' of the handicap.

Adolescent↗