Biology subjects

Hillyard, S. A.

Publications and source records attributed to Hillyard, S. A..

3 recordsLinked to original sources

bioRxiv2024

Feeling Senseless Sensations: A Crossmodal study of mismatching tactile and virtual visual experience

To create highly immersive experiences in virtual reality (VR) it is important to not only include the visual sense but also to involve multimodal sensory input. To achieve optimal results, the temporal and spatial synchronization of these multimodal inputs is critical. It is therefore necessary to find methods to objectively evaluate the synchronization of VR experiences with a continuous tracking of the user. In this study a passive touch experience was incorporated in a visual-tactile VR setup using VR glasses and tactile sensations in mid-air. Inconsistencies of multimodal perception were intentionally integrated into a discrimination task. The participants electroencephalogram (EEG) was recorded to obtain neural correlates of visual-tactile mismatch situations. The results showed significant differences in the event-related potentials (ERP) between match and mismatch situations. A biphasic ERP configuration consisting of a positivity at 120 ms and a later negativity at 370 ms was observed following a visual-tactile mismatch. This late negativity could be related to the N400 that is associated with semantic incongruency. These results provide a promising approach towards the objective evaluation of visual-tactile synchronization in virtual experiences.

neuroscience↗

bioRxiv2024

Fifty Years After: The N1 Effect Travels Down to the Brainstem

Fifty years ago, it was reported that selective attention affects the N1 wave in auditory event-related potentials. We revisited the original study design but integrated the state of the art knowledge on short auditory stimuli and neural signal processing. In particular, one series of tone bursts has been replaced by chirp stimuli which are optimized to evoke consistent brainstem potentials at low and medium stimulation levels. Auditory selective attention affected the chirp- evoked response in subcortical structures, even at level of the inferior colliculi. A single-trial time-frequency analysis of the full-range (0-250ms) event-related potentials showed that selective attention increases the spectrotemporal consistency across trials in the corticofugal auditory pathway, at least from the N1 wave down to the auditory brainstem response.

neuroscience↗

bioRxiv2023

Linear modeling of brain activity during selectiveattention to continuous speech: the critical role of the N1 effect in event-related potentials to acoustic edges

Recent work in the field of neural speech tracking provided evidence for a cortical rep-resentation of speech through superposition of event-related responses to acoustic edges, an idea closely related to the popular linear modeling approach to study cortical syn-chronization to speech via magneto- or electroencephalography (M/EEG). However, it is still unclear to what extent speech-evoked event-related potentials (ERPs) including well-established phenomena, e.g., the N1 selective attention effect, contribute to the regression-based analyses. Here, we addressed this question by analyzing an EEG dataset obtained during a simple multispeaker selective attention task in which participants were cued to attend to only one of two competing speakers. Segmenting the ongoing EEG based on acoustic edges, we were able to replicate previous findings of event-related responses to speech in MEG data with particularly clear P1-N1-P2 complexes. Crucially, speech-evoked ERPs exhibited significant effects of attention in line with the auditory N1 effect. Comparing speech-evoked ERPs to the linear regression results revealed two major find-ings. First, temporal response functions (TRFs) obtained from forward modeling were strongly temporally as well as spatially correlated with corresponding true ERPs. Sec-ond, effects of attention demonstrated by the stimulus reconstruction (SR) accuracies obtained from backward modeling appeared to be driven by a consistent generation of speech-evoked ERPs including the N1 effect. Taken together, our observations reveal a direct link between ERPs to acoustic edges in speech and the linear TRF and SR mod-eling techniques. We emphasize the enhancement in signal-to-noise ratio provided by repeatedly evoked N1 responses to be a critical factor in facilitating the tracking and subsequent higher-order processing of selectively attended speech. In addition to that, the findings imply a cortical speech representation through superimposed speech-evoked ERPs in accordance with recent arguments promoting the neural evoked-response speech tracking model.

neuroscience↗