The influence of whisker stimulation and active whisking on auditory cortical processing and perception

Thesis

Sensory processing is profoundly influenced by its behavioural context, and the primary sensory cortices are recognised as dynamic integrators of multisensory and motor-related inputs. In rodents, whiskers are critical for near-field exploration, and mounting evidence demonstrates that somatosensory inputs can modulate auditory processing even at early subcortical stages. However, how these interactions impact perception and how behavioural relevance and motor activity reshape cross-modal influences in the auditory cortex is not yet known.

In this thesis, I explore the impact of passive whisker stimulation and active whisking on auditory cortical processing and perception in mice, and ask how behavioural demands and stimulus relevance dynamically tune tactile–auditory interactions. Firstly, using a combination of two-photon calcium imaging and near-threshold behavioural tasks, I confirm that whisker stimulation consistently suppresses sound-evoked activity in the auditory cortex during goal-directed behavior. Despite this suppression, detection performance remains stable across both tone and broadband noise stimuli, while frequency discrimination improves during simultaneous whisker stimulation, suggesting that divisive suppression sharpens spectral representations without impairing detectability.

Building on these results, I examine how the behavioural relevance of whisker input modulates cross-modal suppression. Mice trained to detect whisker stimulation exhibit reduced somatosensory-auditory suppression compared to those detecting sounds, contrary to the hypothesis that reward association would amplify tactile gating. Instead, whisker-driven suppression was strongest when whisker input was behaviourally irrelevant, suggesting instead, that suppression at the thalamocortical level reflects learned prioritisation of sensory modalities rather than fixed circuit properties.

Finally, I demonstrate that active whisking itself modulates auditory cortical responses in a context-dependent manner. A subset of neurons responds robustly to spontaneous whisking—accompanied by pupil dilation and brain state changes—but not to sound-triggered whisking of similar kinematics, revealing that brain state transitions, rather than motor output per se, might shape auditory cortical activity. Whisking-sensitive neurons encode spontaneous and stimulus-evoked movements differently, highlighting the flexible integration of motor, arousal, and sensory signals in the auditory cortex.

Together, these studies establish that subcortical tactile-auditory suppression is not static but dynamically reweighted by behavioural context, behavioural state and task demands.

Authors: Zimmer-Harwood, P

• DOI: 10.5287/ora-w4kq7bqxx
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford
• Language: English
• Keywords: auditory cortex; somatosensory-auditory suppression; active whisking; whisker stimulation; multisensory integration
• Subjects: Auditory cortex; Auditory pathways; Neurosciences; Perception; Somatosensory neurons; Auditory evoked response; Sensorimotor integration