Biology subjects

Bizley, J. K.

Publications and source records attributed to Bizley, J. K..

5 recordsLinked to original sources

bioRxiv2018

Training listeners to detect auditory-visual temporal coherence enhances their ability to exploit visual information for auditory scene analysis

The ability to use temporal relationships between cross-modal cues facilitates perception and behavior. Previously we observed that temporally correlated changes in the size of a visual stimulus and the intensity in an auditory stimulus influenced the ability of listeners to perform an auditory selective attention task (Maddox et al., 2015). In this task participants detected timbral changes in a target sound while ignoring those in a simultaneously presented masker. When the visual stimulus was temporally coherent with the target sound, performance was significantly better than when it was temporally coherent with the masker sound, despite the visual stimulus conveying no task-relevant information. Here, we trained observers to detect audiovisual temporal coherence and asked whether this improved their ability to benefit from visual cues during the auditory selective attention task. We observed these listeners improved performance in the auditory selective attention task and changed the way in which they benefited from a visual stimulus: after training performance was better when the visual stimulus was temporally coherent with either the target or the masker stream, relative to the condition in which the visual stimulus was coherent with neither auditory stream. A second group which trained to discriminate modulation rate differences between temporally coherent audiovisual streams improved task performance, but did not change the way in which they used visual information. A control group did not change their performance between pretest and post-test. These results provide insights into how crossmodal experience may optimize multisensory integration.

neuroscience↗

bioRxiv2017

Pitch discrimination performance of ferrets and humans on a go/no-go task.

Animal models are widely used to examine the neurophysiological basis of human pitch perception, and it is therefore important to understand the similarities and differences in pitch processing across species. Pitch discrimination performance is usually measured using two-alternative forced choice (2AFC) procedures in humans and go/no-go tasks in animals, potentially confounding human-to-animal comparisons. We have previously shown that pitch discrimination thresholds of ferrets on a 2AFC task are markedly poorer than those reported for go/no-go tasks in other non-human species (Walker et al., 2009). To better compare the pitch discrimination performance of ferret with other species, here we measure pitch change detection thresholds of ferrets and humans on a common, appetitive go/no-go task design. We found that ferrets pitch thresholds were ~10 times larger than that of humans on the go/no-go task, and were within the range of thresholds reported in other non-human species. Interestingly, ferrets thresholds were 100 times larger than human thresholds on a 2AFC pitch discrimination task using the same stimuli. These results emphasize that sensory discrimination thresholds can differ across tasks, particularly for non-human animals. Performance on our go/no-go task is likely to reflect different neurobiological processes than that on our 2AFC task, as the former required the subjects only to detect a pitch change while the latter required them to label the direction of the pitch change.\n\nABBREVIATIONS\n\nHIGHLIGHTSO_LIPitch discrimination thresholds of ferrets were 10 times larger than those of humans on a go/no-go task\nC_LIO_LIFerrets pitch thresholds are similar to those reported for a range of other mammals\nC_LIO_LIPitch thresholds of ferrets, but not humans, were drastically better on the go/no-go task than a 2AFC task using the same stimuli\nC_LI

animal behavior and cognition↗

bioRxiv2017

Neural correlates of perceptual constancy in Auditory Cortex

Perceptual constancy requires neural representations that are selective for object identity, but also tolerant for identity-preserving transformations. How such representations arise in the brain and contribute to perception remains unclear. Here we studied tolerant representations of sound identity in the auditory system by recording multi-unit activity in tonotopic auditory cortex of ferrets discriminating the identity of vowels which co-varied across orthogonal stimulus dimensions (fundamental frequency, sound level, location and voicing). We found that neural decoding of vowel identity was most successful across the same orthogonal dimensions over which animals generalized their behavior. We also decoded orthogonal sound features and behavioral variables including choice and accuracy to show a behaviorally-relevant, multivariate and multiplexed representation of sound, with each variable represented over a distinct time-course. Finally, information content and timing of sound feature encoding was modulated by task-engagement and training, suggesting that tolerant representations during perceptual constancy are attentionally and experience-dependent.

neuroscience↗

bioRxiv2017

Integration of visual information in auditory cortex promotes auditory scene analysis through multisensory binding

How and where in the brain audio-visual signals are bound to create multimodal objects remains unknown. One hypothesis is that temporal coherence between dynamic multisensory signals provides a mechanism for binding stimulus features across sensory modalities. Here we report that when the luminance of a visual stimulus is temporally coherent with the amplitude fluctuations of one sound in a mixture, the representation of that sound is enhanced in auditory cortex. Critically, this enhancement extends to include both binding and non-binding features of the sound. We demonstrate that visual information conveyed from visual cortex, via the phase of the local field potential, and is combined with auditory information within auditory cortex. These data provide evidence that early cross-sensory binding provides a bottom-up mechanism for the formation of cross-sensory objects and that one role for multisensory binding in auditory cortex is to support auditory scene analysis.

neuroscience↗

bioRxiv2017

Egocentric and Allocentric Representations in Auditory Cortex

A key function of the brain is to provide a stable representation of an objects location in the world. In hearing, sound azimuth and elevation are encoded by neurons throughout the auditory system and auditory cortex is necessary for sound localization. However the coordinate frame in which neurons represent sound space remains undefined: classical spatial receptive fields in head-fixed subjects can be explained either by sensitivity to sound source location relative to the head (egocentric) or relative to the world (allocentric encoding). This coordinate frame ambiguity can be resolved by studying freely moving subjects and here we recorded spatial receptive fields in auditory cortex freely moving ferrets. We found two distinct populations of neurons: While the majority ([~]80%) of spatially tuned neurons represented sound source location relative to the head, we provide novel evidence for a group of neurons in which space was represented in an allocentric world-centered coordinate frame. We also use our ability to measure spatial tuning in moving subjects to explore the influence of sound source distance and speed of head movements on auditory cortical activity and spatial tuning. Modulation depth of spatial tuning increased with distance for egocentric but not allocentric units, whereas for both populations modulation was stronger at faster movement speeds. Our findings argue that auditory cortex is involved in the representation of both sound source location relative to ourselves and sound location in the world independent of our own position.

neuroscience↗