| Summary: | Sequestered deep beneath the cortex, the claustrum is the most densely connected structure in the brain. This tantalizing anatomy has spawned a wide range of hypotheses regarding the function of the claustrum, but technological and biological constraints have hindered research. In this thesis, I have investigated the activity and behavioural function of the claustrum. I developed a novel preparation for recording claustrum activity using two-photon calcium imaging of claustrum axons in dorsal cortex. I show that claustrum axons display stimulus-locked changes in activity following uni- and multimodal sensory stimuli. While some axons were selective to one sensory modality, most were promiscuously responsive to multiple sensory modalities. I then investigated the behavioural consequences of silencing the claustrum. I detected no effects of claustrum silencing on home-cage activity, circadian behaviour, or a battery of tests assessing a wide range of behavioural domains. Finally, I investigated the impact of claustrum silencing on two behavioural tasks. While I detected no effects on a reversal learning task, I found that claustrum silencing reduced animals’ sensitivity to multimodal stimuli in a classical conditioning-like paradigm. Collectively, these results support the hypothesis that the claustrum may be involved in processing multimodal information and highlight the need for more research into the function of the claustrum.
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