Biology subjects

Gutschalk, A.

Publications and source records attributed to Gutschalk, A..

4 recordsLinked to original sources

bioRxiv2024

Reduction of right-hemispheric auditory cortex activity in response to speech in more experienced paediatric cochlear implant users

In case of severe hearing loss early in life or congenital deafness, cochlear implants (CIs) represent the method of choice to restore hearing and enable language acquisition. While speech intelligibility has been shown to improve during the first year after implantation to then reach a plateau, the underlying neuroplastic changes are poorly understood. Here, we longitudinally compared the cortical processing of speech stimuli in a case-control design with two groups of pre-lingually deafened CI users (4.4 vs. 25.8 months of CI experience) and an age-matched control group with normal hearing (NH; mean group ages [~]9 years). In two experiments, participants were presented with running speech and vowel sequences while fNIRS and EEG data were obtained simultaneously. Despite trends in this direction, cortical activity did not increase significantly with more CI experience and did not approach the higher levels observed in the NH controls. However, in the speech experiment, the less experienced CI group showed an abnormal shift of activity to the right hemisphere not observed in the other two groups. These results hence imply that adaptation to CI-based hearing is not characterised by a gradual increase of activity in left-hemispheric language network, but a reduction of abnormal activity elsewhere.

neuroscience↗

bioRxiv2024

Perceptual awareness of near-threshold tones scales gradually with auditory cortex activity and pupil dilation

Perceptual awareness covaries with negative-going responses in sensory cortex, but the derived concept of perceptual awareness negativity has been criticized a.o. because of its presence for undetected stimuli. To evaluate this objection, we combined magnetoencephalography, electroencephalography, and pupillometry to study the roles of sustained attention and response criterion on the auditory awareness negativity. Participants first detected distractor sounds and denied hearing task-irrelevant near-threshold tones, which evoked neither awareness negativity nor pupil dilation. These same tones evoked responses when task-relevant, stronger for hit but also present for miss trials. To explore if response criterion could explain the presence of responses for miss trials, participants rated their perception on a six-point scale. Decreasing perception ratings were associated with gradually reduced evoked responses, consistent with signal detection theory. These results support the concept of an awareness negativity that is modulated by attention, but does not exhibit a non-linear threshold mechanism.

neuroscience↗

bioRxiv2023

Hemispheric decoupling of awareness-related activity in human auditory cortex under informational masking and divided attention

The conditions under which sensory stimuli require selective attention to reach awareness is a fundamental question of cognitive neuroscience. We examined this question in the context of audition utilizing M/EEG and a dual-task informational-masking paradigm. Listeners performed a demanding primary task in one ear - detecting isochronous target-tone streams embedded in random multi-tone backgrounds and counting within-stream deviants - and retrospectively reported their awareness of secondary, masker-embedded target streams in the other ear. Irrespective of attention or ear, left-AC activity strongly covaried with target-stream detection starting as early as 50 ms post-stimulus. In contrast, right-AC activity was unmodulated by detection until later, and then only weakly. Thus, under certain conditions, human ACs can functionally decouple, such that one - here, right - is automatic and stimulus-driven while the other - here, left - supports perceptual and/or task demands, including basic perceptual awareness of nonverbal sound sequences.

neuroscience↗

bioRxiv2023

A role for retro-splenial cortex in the task-related P3 network

ObjectiveThe P3 is an event-related response observed in relation to task-relevant sensory events. Despite its ubiquitous presence, the neural generators of the P3 are controversial and not well identified. MethodsWe compared source analysis of combined magneto- and electroencephalography (M/EEG) data with functional magnetic resonance imaging (fMRI) and simulation studies to better understand the sources of the P3 in an auditory oddball paradigm. ResultsOur results suggest that the dominant source of the classical, postero-central P3 lies in the retro-splenial cortex of the ventral cingulate gyrus. A second P3 source in the anterior insular cortex contributes little to the postero-central maximum. Multiple other sources in the auditory, somatosensory, and anterior midcingulate cortex are active in an overlapping time window but can be functionally dissociated based on their activation time courses. ConclusionThe retro-splenial cortex is a dominant source of the parietal P3 maximum in EEG. SignificanceThese results provide a new perspective for the interpretation of the extensive research based on the P3 response.

neuroscience↗