Biology subjects

Chait, M.

Publications and source records attributed to Chait, M..

4 recordsLinked to original sources

bioRxiv2017

Auditory Figure-Ground Segregation is Impaired by High Visual Load

Figure-ground segregation is fundamental to listening in complex acoustic environments. An ongoing debate pertains to whether segregation requires attention or is automatic and pre-attentive. In this magnetoencephalography (MEG) study we tested a prediction derived from Load Theory of attention1 that segregation requires attention, but can benefit from the automatic allocation of any leftover capacity under low load. Complex auditory scenes were modelled with Stochastic Figure Ground stimuli (SFG2) which occasionally contained repeated frequency component figures. Naive human subjects passively listened to these signals while performing a visual attention task of either low or high load. Whilst clear figure-related neural responses were observed under conditions of low load, high visual load essentially abolished the neural response to the figure in auditory cortex (Planum Temporale, Heschls gyrus). We conclude that fundamental figure-ground segregation in hearing is not automatic but draws on shared resources across vision and audition.

neuroscience↗

bioRxiv2017

Enhanced deviant responses in patterned relative to random sound sequences

How are brain responses to deviant events affected by the statistics of the preceding context? We recorded electroencephalography (EEG) brain responses to frequency deviants in matched, regularly-patterned (REG) versus random (RAND) tone-pip sequences. Listeners were naive and distracted by an incidental visual task. Stimuli were very rapid so as to limit conscious reasoning about the sequence order and tap automatic processing of regularity.\n\nDeviants within REG sequences evoked a substantially larger response (by 71%) than matched deviants in RAND sequences from 80 ms after deviant onset. This effect was underpinned by distinct sources in right temporal pole and orbitofrontal cortex in addition to the standard bilateral temporal and right pre-frontal network for generic frequency deviance-detection. These findings demonstrate that the human brain rapidly acquires a detailed representation of regularities within the sensory input and evaluates incoming information according to the context established by the specific pattern.

neuroscience↗

bioRxiv2017

Sensitivity to statistical structure facilitates perceptual analysis of complex auditory scenes

The notion that sensitivity to the statistical structure of the environment is pivotal to perception has recently garnered considerable attention. Here we investigated this issue in the context of hearing. Building on previous work (Sohoglu & Chait, 2016b), stimuli were artificial sound-scapes populated by multiple (up to 14) simultaneous sources ( auditory objects) comprised of tone-pip sequences, each with a distinct frequency and pattern of amplitude modulation. Sequences were either temporally regular or random.\n\nWe show that listeners ability to detect abrupt appearance or disappearance of a source is facilitated when scene sources were characterized by a temporally regular fluctuation pattern. The patterning of the changing source as well as that of the background (non-changing) sources contribute independently to this effect. Remarkably, listeners benefit from regularity even when they are not consciously aware of it. These findings establish that perception of complex acoustic scenes relies on the availability of detailed representations of the regularities automatically extracted from each scene source.

neuroscience↗

bioRxiv2017

The impact of visual gaze direction on auditory object tracking

Subjective experience suggests that we are able to direct our auditory attention independent of our visual gaze, e.g when shadowing a nearby conversation at a cocktail party. But what are the consequences at the behavioural and neural level? While numerous studies have investigated both auditory attention and visual gaze independently, little is known about their interaction during selective listening. In the present EEG study, we manipulated visual gaze independently of auditory attention while participants detected targets presented from one of three loudspeakers. We observed increased response times when gaze was directed away from the locus of auditory attention. Further, we found an increase in occipital alpha-band power contralateral to the direction of gaze, indicative of a suppression of distracting input. Finally, this condition also led to stronger central theta-band power, which correlated with the observed effect in response times, indicative of differences in top-down processing. Our data suggest that a misalignment between gaze and auditory attention both reduce behavioural performance and modulate underlying neural processes. The involvement of central theta-band and occipital alpha-band effects are in line with compensatory neural mechanisms such as increased cognitive control and the suppression of task irrelevant inputs.

neuroscience↗