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Research Unit in Cognitive Neurosciences
UNESCOG investigates the organisation and functioning of the language and cognitive system while taking its biological substrate into account.Experimental psychologists, neuropsychologists and electrophysiologists work on both normal and brain-damaged individuals in the following domains: audio-visual interactions, auditory and visual attention, speech perception and recognition, reading disturbances, cognitive consequences of schooling, literacy and ageing, organisation of the semantic system, retrieval of information from memory (in particular episodic and prospective), re-education of working memory, impairments of executive functions and of social representations due to brain lesion. Besides experimental approaches from cognitive psychology and neuropsyclology, UNESCOG's researchers employ methods of neuropsychological patient examination and of cerebral imagery (recording of evoked potentials and of hemodynamic changes).
Speech perception in congenitally profound deaf children
Behavioral and electrophysiological investigation of the processes and neural substrates underlying audiovisual speech perception in congenitally profound deaf children benifiting from a cochlear implant. We will particularly examine the effect of early vs late implantation as well as the effect of the utilisation of Cued Speech on the quality of phonological representations underlying speech learning.
The neurophysiological correlates of voicing in French-speaking adults
We explore the voicing neural code in French-speaking subjects so as to get some insight into the auditory mechanisms at the root of voicing perception. /d_/ and /t_/ syllables with a VOT value varying evenly from -75 and +75 ms are presented to French-speaking adults while recording scalp recorded auditory evoked-potentials. Specifically, the morphology and peak latencies measures of N1b and Na (two N100 subcomponents) recorded at midline and temporal electrodes are assessed.
Electrophysiological study of the mechanisms underlying the auditory discrimination of duration contrasts
This research is designed to examine the accuracy with which a change in the moment of detection of a duration deviance is reflected in the Mismatch Negativity (MMN) peak latency. MMNs were recorded using the oddball paradigm on healthy adults. Different standard stimulus durations are used and deviants are 50% shorter or longer. Beside the temporal resolution of the MMN latency as a function of the theoretical moment of deviance direction, standard duration as well as deviance directions effects on MMN amplitude and latency are also examined.
Audiovisual interaction in the analysis of the spatial scene and in speech.
Behavioral and electrophysiological studies are carried out to specify the constraints and the neural basis of the audiovisual interactions involved both in spatial scene analysis (ventriloquism effect : interaction between visual and auditory data coming from different spatial sources) and in speech perception (McGurk effect : conflict between auditory speech and lipreading).
The development of categorical perception: comparison between voicing, colours and facial expressions
The aim of this research is to compare categorical precision (i.e. the steepness of the identification slope) and categorical perception (i.e. the correspondence between identification and discrimination tasks) scores for three different continua (/d-t/ ; yellow-green ; happy-sad). Specifically, this research is designed to test the reading hypothesis (Burnham, Earnshaw & Clark, 1991; Burnham, 2003) according to which the onset of reading is responsible for the development of categorical perception of voicing and the general cognitive hypothesis (Karmiloff Smith, 1991; Lalonde & Werker, 1995) according to which categorical perception evolves in synchronicity with other abilities through the influence of cognitive maturation.
Investigation of phonological discrimination evolution in 4 and 8 months old babies by heart rate recordings
Before six months, chidren are able to discriminate all phonemes of all languages. However, from six months, children select only the sounds that are pertinent for their native language. In order to objectively examine this change, we study, thanks to heart rate recordings, phonemic discrimination abilities of 4 and 8 months-old babies presented with syllables from a VOT (Voice Onset Time) continuum.
Development of neurophysiological measures allowing objective characterisation of neural code distortions in sensori-neural hearing losses
Besides increased thresholds, partial sensori-neural haring losses are associated to more or less significant distortions of the neural code, which represents the stimulus in the cochlear nerve. Hearing aids, in their current use, do not restore the effects of these distortions. Whereas hearing aids improve speech detection threshold, they often fail to improve speech reception threshold in presence of sensori-neural hearing losses. Hence, because of these distortions, patients with sensori-neural hearing losses do not fully benefit from hearing aid rehabilitation. The quantification of these distortions relies upon complex psychophysical procedures that can not be applied to prelingual paediatric populations. This research aims at developing objective methods based on the recording of auditory evoked potentials and able to characterise the different distortions in prelingual paediatric populations. Once these distortions are defined, treatments options integrating digital signal processing may be provided in order alleviate their effects.
Neural mechanisms of rhythm perception
When we listen to rhythms, as in music, we often synchronize body movements with it. To do so, we detect regularities in the temporal pattern of sounds. To perceive this regularity, the sound's durations have to be equal or proportional in terms of integer numbers ratios, mostly binary (e.g. 1/2). Studies on cerebral imaging shows that neural mechanisms underlying auditory rhythm processing involve cerebral motor areas such as the cerebellum, the basal ganglia and the supplementary motor area. The contribution of these motor areas depends on the regularity that we perceive. Our research explores the neural representation of rhythms and the way they relate with the motor system. Using neurophysiological data, our work showed that the representation of rhythmical rules is already present in sensory memory, when no attention and no calls to motor response are required. We are now inrerested in studying the neural representation of regular and irregular rhythms at this processing level to determine if it relies on these motor areas. In addition, in order to identify their functional role, we will explore the effect s of rhythmic motor training on discrimination performance and the neural representation of rhythms.
Behavioral and electrophysiological study of the phonological and natural categorical boudaries using a VOT (voice onset time) continuum.
The aim of this project is to study the potential residual sensitivity of French speakers to natural, but not phonological, VOT contrasts. For this purpose, we use behavioral methods (identification and discrimination of syllables from a VOT continuum) as well as electrophysiological methods (recording of the MMN).