La thèse de madame Samson portait sur les mécanismes cérébraux impliqués dans la perception auditive chez les personnes autistes. Plus les stimuli auditifs sont simples, plus les personnes autistes obtiennent des performances supérieures à celles des personnes non-autistes. Cela est associé à une activité plus grande du gyrus de Heschl, la première région corticale où l’information auditive est traitée. Chez les personnes autistes, il y a aussi moins de distinction dans l’activité cérébrale associée aux sons purs et aux sons complexes.
Le résumé de la thèse de Mme Samson >>>
Les articles de la thèse de Mme Samson
Atypical processing of auditory temporal complexity in autistics.
Samson F, Hyde KL, Bertone A, Soulières I, Mendrek A, Ahad P, Mottron L, Zeffiro TA.
Centre d'Excellence en Troubles Envahissants du Développement de l'Université de Montréal (CETEDUM), Montréal, QC, Canada.
Neuropsychologia. 2011 Feb;49(3):546-55. Epub 2010 Dec 28.
PMID: 21465627 [PubMed - as supplied by publisher]
Autistics exhibit a contrasting combination of auditory behavior, with enhanced pitch processing abilities often coexisting with reduced orienting towards complex speech sounds. Based on an analogous dissociation observed in vision, we expected that autistics' auditory behavior with respect to complex sound processing may result from atypical activity in non-primary auditory cortex. We employed fMRI to explore the neural basis of complex non-social sound processing in 15 autistic and 13 non-autistics, using a factorial design in which auditory stimuli varied in spectral and temporal complexity. Spectral complexity was modulated by varying the harmonic content, whereas temporal complexity was modulated by varying frequency modulation depth. The detection task was performed similarly by autistics and non-autistics. In both groups, increasing spectral or temporal complexity was associated with activity increases in primary (Heschl's gyrus) and non-primary (anterolateral and posterior superior temporal gyrus) auditory cortex Activity was right-lateralized for spectral and left-lateralized for temporal complexity. Increasing temporal complexity was associated with greater activity in anterolateral superior temporal gyrus in non-autistics and greater effects in Heschl's gyrus in autistics. While we observed similar hierarchical functional organization for auditory processing in both groups, autistics exhibited diminished activity in non-primary auditory cortex and increased activity in primary auditory cortex in response to the presentation of temporally, but not of spectrally complex sounds. Greater temporal complexity effects in regions sensitive to acoustic features and reduced temporal complexity effects in regions sensitive to more abstract sound features could represent a greater focus towards perceptual aspects of speech sounds in autism.
Can spectro-temporal complexity explain the autistic pattern of performance on auditory tasks?
Samson F, Mottron L, Jemel B, Belin P, Ciocca V.
Pervasive Developmental Disorders Specialized Clinic, Rivière-des-Prairies Hospital, & Fernand Seguin Research Center, University of Montréal, QC, Canada.
J Autism Dev Disord. 2006 Jan;36(1):65-76.
PMID: 16382329 [PubMed - indexed for MEDLINE]
To test the hypothesis that level of neural complexity explain the relative level of performance and brain activity in autistic individuals, available behavioural, ERP and imaging findings related to the perception of increasingly complex auditory material under various processing tasks in autism were reviewed. Tasks involving simple material (pure tones) and/or low-level operations (detection, labelling, chord disembedding, detection of pitch changes) show a superior level of performance and shorter ERP latencies. In contrast, tasks involving spectrally- and temporally-dynamic material and/or complex operations (evaluation, attention) are poorly performed by autistics, or generate inferior ERP activity or brain activation. Neural complexity required to perform auditory tasks may therefore explain pattern of performance and activation of autistic individuals during auditory tasks.
Stimulus complexity and categorical effects in human auditory cortex: an activation likelihood estimation meta-analysis.
Samson F, Zeffiro TA, Toussaint A, Belin P.
Centre d'Excellence en Troubles Envahissants du Développement de l'Université de Montréal Montréal, QC, Canada.
Front Psychol. 2010;1:241. Epub 2011 Jan 17.
PMID: 21833294 [PubMed - in process] PMCID: PMC3153845
Investigations of the functional organization of human auditory cortex typically examine responses to different sound categories. An alternative approach is to characterize sounds with respect to their amount of variation in the time and frequency domains (i.e., spectral and temporal complexity). Although the vast majority of published studies examine contrasts between discrete sound categories, an alternative complexity-based taxonomy can be evaluated through meta-analysis. In a quantitative meta-analysis of 58 auditory neuroimaging studies, we examined the evidence supporting current models of functional specialization for auditory processing using grouping criteria based on either categories or spectro-temporal complexity. Consistent with current models, analyses based on typical sound categories revealed hierarchical auditory organization and left-lateralized responses to speech sounds, with high speech sensitivity in the left anterior superior temporal cortex. Classification of contrasts based on spectro-temporal complexity, on the other hand, revealed a striking within-hemisphere dissociation in which caudo-lateral temporal regions in auditory cortex showed greater sensitivity to spectral changes, while anterior superior temporal cortical areas were more sensitive to temporal variation, consistent with recent findings in animal models. The meta-analysis thus suggests that spectro-temporal acoustic complexity represents a useful alternative taxonomy to investigate the functional organization of human auditory cortex.