Différenciation hémisphérique auditive par analyse de potentiels évoqués auditifs

- Par opposition aux études subjectives adressant le problème de la spécialisation hémisphérique auditive, le but de ce travail est de proposer des mesures objectives permettant de différencier le comportement des deux hémisphères vis-à-vis des stimuli. Pour ce faire, nous disposons de signaux intracérébraux enregistrés en réponse à divers stimuli. Ce papier ne traite que des réponses aux sons verbaux voisé /ba/, non voisé /pa/ et à la voyelle /a/ et présente trois méthodes. La première calcule le coefficient de corrélation entre les réponses à deux stimuli, recueillies sur le même plot. La seconde porte sur l'évolution de la corrélation au cours du temps. Sur les valeurs de corrélation obtenues est effectuée une analyse factorielle des correspondances (AFC) suivie d'une classification hiérarchique ascendante appliquée sur les facteurs de l'AFC. Finalement, les réponses sont caractérisées selon le nombre d'extrema en fonction de l'hémisphère et du stimulus considérés. Les trois méthodes permettent de mettre en avant certains paramètres révélateurs de différence de comportement des deux hémisphères

Individual Differences in Sound-in-Noise Perception Are Related to the Strength of Short-Latency Neural Responses to Noise

Important sounds can be easily missed or misidentified in the presence of extraneous noise. We describe an auditory illusion in which a continuous ongoing tone becomes inaudible during a brief, non-masking noise burst more than one octave away, which is unexpected given the frequency resolution of human hearing. Participants strongly susceptible to this illusory discontinuity did not perceive illusory auditory continuity (in which a sound subjectively continues during a burst of masking noise) when the noises were short, yet did so at longer noise durations. Participants who were not prone to illusory discontinuity showed robust early electroencephalographic responses at 40–66 ms after noise burst onset, whereas those prone to the illusion lacked these early responses. These data suggest that short-latency neural responses to auditory scene components reflect subsequent individual differences in the parsing of auditory scenes

Electrophysiological evidence for an early processing of human voices

<p>Abstract</p> <p>Background</p> <p>Previous electrophysiological studies have identified a "voice specific response" (VSR) peaking around 320 ms after stimulus onset, a latency markedly longer than the 70 ms needed to discriminate living from non-living sound sources and the 150 ms to 200 ms needed for the processing of voice paralinguistic qualities. In the present study, we investigated whether an early electrophysiological difference between voice and non-voice stimuli could be observed.</p> <p>Results</p> <p>ERPs were recorded from 32 healthy volunteers who listened to 200 ms long stimuli from three sound categories - voices, bird songs and environmental sounds - whilst performing a pure-tone detection task. ERP analyses revealed voice/non-voice amplitude differences emerging as early as 164 ms post stimulus onset and peaking around 200 ms on fronto-temporal (positivity) and occipital (negativity) electrodes.</p> <p>Conclusion</p> <p>Our electrophysiological results suggest a rapid brain discrimination of sounds of voice, termed the "fronto-temporal positivity to voices" (FTPV), at latencies comparable to the well-known face-preferential N170.</p

Reconstructing Speech from Human Auditory Cortex

Direct brain recordings from neurosurgical patients listening to speech reveal that the acoustic speech signals can be reconstructed from neural activity in auditory cortex

A Blueprint for Real-Time Functional Mapping via Human Intracranial Recordings

International audienceBACKGROUND: The surgical treatment of patients with intractable epilepsy is preceded by a pre-surgical evaluation period during which intracranial EEG recordings are performed to identify the epileptogenic network and provide a functional map of eloquent cerebral areas that need to be spared to minimize the risk of post-operative deficits. A growing body of research based on such invasive recordings indicates that cortical oscillations at various frequencies, especially in the gamma range (40 to 150 Hz), can provide efficient markers of task-related neural network activity. PRINCIPAL FINDINGS: Here we introduce a novel real-time investigation framework for mapping human brain functions based on online visualization of the spectral power of the ongoing intracranial activity. The results obtained with the first two implanted epilepsy patients who used the proposed online system illustrate its feasibility and utility both for clinical applications, as a complementary tool to electrical stimulation for presurgical mapping purposes, and for basic research, as an exploratory tool used to detect correlations between behavior and oscillatory power modulations. Furthermore, our findings suggest a putative role for high gamma oscillations in higher-order auditory processing involved in speech and music perception. CONCLUSION/SIGNIFICANCE: The proposed real-time setup is a promising tool for presurgical mapping, the investigation of functional brain dynamics, and possibly for neurofeedback training and brain computer interfaces

Interaction between Attention and Bottom-Up Saliency Mediates the Representation of Foreground and Background in an Auditory Scene

Bottom-up (stimulus-driven) and top-down (attentional) processes interact when a complex acoustic scene is parsed. Both modulate the neural representation of the target in a manner strongly correlated with behavioral performance

GÉNÉRATEURS DES POTENTIELS ÉVOQUÉS AUDITIFS CORTICAUX CHEZ L'HOMME

Des potentiels évoqués en réponse à des stimulations auditives ont été enregistrés avec des électrodes intracérébrales en différents sites du Gyrus Temporal Transverse (gyrus de Heschl) et du Planum temporale chez des patients épileptiques, candidats à une chirurgie. Les résultats montrent qu'il existe une ségrégation anatomique des réponses évoquées en fonction de leur latence. Les réponses à courte latence (13-17 msec) sont enregistrées préférentiellement dans la région dorso-médiane du gyrus de Heschl, les réponses à moyenne latence (50-70 msec) dans la partie plus latérale et les réponses à longue latence (>100 msec) dans le Planum Temporale. Il apparaît que ce sont les réponses à moyenne latence qui codent pour la fréquence tonale.Auditory evoked potentials have been recorded with depth electrodes in different sites in Temporal Transverse Gyrus (Heschl's gyrus) and in Planum Temporale in epileptic patients that are candidates for neurosurgical corticectomy. Our results show that there exists an anatomical segregation of the evoked response as a function of latency. Short latency responses (13-17 msec) are recorded in the dorso-medial part of the gyrus, middle latency responses (50-70 msec) in the more lateral part and long latency responses (>100 msec) in the Planum Temporale. Only middle latency evoked potentials vary with the tonal frequency

Identification Reaction Times of Voiced/Voiceless Continua: A Right-Ear Advantage for VOT Values near the Phonetic Boundary

International audienceWe explored the degree to which the duration of acoustic cues contributes to the respective involvement of the two hemispheres in the perception of speech. To this end, we recorded the reaction time needed to identify monaurally presented natural French plosives with varying VOT values. The results show that a right-ear advantage is significant only when the phonetic boundary is close to the release burst, i.e., when the identification of the two successive acoustical events (the onset of voicing and the release from closure) needed to perceive a phoneme as voiced or voiceless requires rapid information processing. These results are consistent with the recent hypothesis that the left hemisphere is superior in the processing of rapidly changing acoustical information