Neural Bases for Working Memory of Natural Sound Textures

Holding sound objects in mind is critical to understanding the sound world around us. Auditory texture perception is thought to rely on extracting statistical properties of sounds over time, raising the question of how encoding duration influences subsequent maintenance of auditory texture information. We investigated this question using behavioural performance and fMRI while participants performed two delayed match-to-sample tasks: a texture discrimination and a comparison loudness discrimination task. In the texture task, participants judged whether two sequentially presented sounds belonged to the same texture type, whereas in the loudness task, participants judged whether the sounds, drawn from the same texture type, had the same loudness. Stimuli were presented for either 0.1s or 2s. Discrimination sensitivity increased with duration in both tasks, but more strongly for texture discrimination. fMRI analysis revealed distinct effects of duration on univariate and multivariate activity in the auditory cortex and medial temporal lobe (MTL) during maintenance. We found no univariate duration effect in the auditory cortex during maintenance, but multivariate patterns encoded texture category more strongly for longer stimuli, regardless of task. In contrast, MTL activity was modulated by sound duration in both tasks, but there was no effect of duration on texture category decoding. There was a task effect in MTL where multivariate patterns in posterior hippocampal and parahippocampal regions distinguished texture from loudness tasks following 2s stimuli. Together, these findings show effects of duration on sound texture representations during maintenance and that MTL representations reflect the behavioural context in which that information is maintained.