Biology subjects

Ince, R. A. A.

Publications and source records attributed to Ince, R. A. A..

4 recordsLinked to original sources

bioRxiv2018

Early Neural Correlates of an Auditory Pitch - Visual Size Cross-modal Association

Research has shown participants associate high pitch tones with small objects, and low pitch tones with large objects. Yet it remains unclear when these associations emerge in neural signals, and whether or not they are likely the result of predictive coding mechanisms being influenced by multisensory priors. Here we investigated these questions using a modified version of the implicit association task, 128-channel human EEG, and two approaches to single-trial analysis (linear discriminant and mutual information). During two interlaced discrimination tasks (auditory high/low tone and visual small/large circle), one stimulus was presented per trial and the auditory stimulus-response assignment was manipulated. On congruent trials preferred pairings (high tone, small circle) were assigned to the same response key, and on incongruent trials non-preferred pairings were (low tone, small circle). The results showed participants (male and female) responded faster during auditory congruent than incongruent trials. The EEG results showed that acoustic pitch and visual size were represented early in the trial (~100 ms and ~220 ms), over temporal and frontal regions. Neural signals were also modulated by congruency early in the trial for auditory (<100ms) and visual modalities (~200ms). For auditory trials, EEG components were predictive of reaction times, but for visual trials they were not. These EEG results were consistent across analysis methods, demonstrating they are robust to the statistical methodology used. Overall, our data support an early origin of cross-modal associations, and suggest that these may originate during early sensory processing potentially due to predictive coding mechanisms.

neuroscience↗

bioRxiv2018

Neural Processing of the Same, Behaviourally Relevant Face Features is Delayed by 40 ms in Healthy Ageing

Fast and accurate face processing is critical for everyday social interactions, but it declines and becomes delayed with age, as measured by both neural and behavioural responses. Here, we addressed the critical challenge of understanding how ageing changes neural information processing mechanisms to delay behaviour. Young (20-36 years) and older (60-86 years) adults performed the basic social interaction task detecting a face vs. noise while we recorded their electroencephalogram (EEG). In each participant, using a new information theoretic framework we reconstructed the features supporting face detection behaviour, and also where, when and how EEG activity represents them. We found that occipital-temporal pathway activity dynamically represents the eyes of the face images for behaviour [~]170 ms post-stimulus, with a 40 ms delay in older adults that underlies their 200 ms behavioural deficit of slower reaction times. Our results therefore demonstrate how ageing can change neural information processing mechanisms that underlie behavioural slow down.\n\nAuthor summaryOlder adults are consistently slower than young adults in a variety of behavioural perceptual tasks. So far, it has been unclear if the underlying cause of the behavioural delay relates to attentional or perceptual differences in encoding visual information, or slower neural processing speed, or other neural factors. Our study addresses these questions by showing that in a basic social interaction task (discriminating faces from noise), young and older adults encoded the same visual information (eyes of the face) to perform the task. Moreover, early brain activity (within 200 ms following stimulus onset) encoded the same visual information (again, eyes of the face) in both groups, but was delayed and weaker in older adults. These early delays in information encoding were directly related to the observed behavioural slowing in older adults, showing that differences in early perceptual brain processes can contribute to the motor response.

neuroscience↗

bioRxiv2017

Entrained audiovisual speech integration implemented by two independent computational mechanisms: Redundancy in left posterior superior temporal gyrus and Synergy in left motor cortex

Information integration is fundamental to many aspects of human behavior, and yet its neural mechanism remains to be understood. For example, during face-to-face communication we know that the brain integrates the auditory and visual inputs but we do not yet understand where and how such integration mechanisms support speech comprehension. Here we show that two independent mechanisms forge audiovisual representations for speech comprehension in different brain regions. With a novel information theoretic measure, we found that theta (3-7 Hz) oscillations in the posterior superior temporal gyrus/sulcus (pSTG/S) code speech information that is common (i.e. redundant) to the auditory and visual inputs whereas the same oscillations in left motor and inferior temporal cortex code synergistic information between the same inputs. Importantly, redundant coding in the left pSTG/S and synergistic coding in the left motor cortex predict behavior - i.e. speech comprehension performance. Our findings therefore demonstrate that processes classically described as integration effectively reflect independent mechanisms that occur in different brain regions to support audiovisual speech comprehension.

neuroscience↗

bioRxiv2016

Contributions of local speech encoding and functional connectivity to audio-visual speech integration

Seeing a speakers face enhances speech intelligibility in adverse environments. We investigated the underlying network mechanisms by quantifying local speech representations and directed connectivity in MEG data obtained while human participants listened to speech of varying acoustic SNR and visual context. During high acoustic SNR speech encoding by entrained brain activity was strong in temporal and inferior frontal cortex, while during low SNR strong entrainment emerged in premotor and superior frontal cortex. These changes in local encoding were accompanied by changes in directed connectivity along the ventral stream and the auditory-premotor axis. Importantly, the behavioural benefit arising from seeing the speaker's face was not predicted by changes in local encoding but rather by enhanced functional connectivity between temporal and inferior frontal cortex. Our results demonstrate a role of auditory-motor interactions in visual speech representations and suggest that functional connectivity along the ventral pathway facilitates speech comprehension in multisensory environments.

neuroscience↗