| Achoimre: | <p>The brains of higher organisms are composed of anatomically and functionally
distinct regions performing specialised tasks. However, individual regions do not
operate in isolation. Hence, the orchestration of complex behaviours requires
communication between brain regions and reliable transmission of information
between them. In this thesis I explore how we can study this process directly
by generating neural activity that propagates between brain regions and drives
behaviour, allowing me to assess how populations of neurons in sensory cortex act in
concert to transmit information. I achieved this by imaging two hierarchically organised and densely interconnected regions, the primary and secondary somatosensory
cortex (S1 and S2) in mice while performing two-photon photostimulation of S1
neurons and assigning behavioural salience to the photostimulation. I found that the
probability of perception is determined by both the variance of the S1 network and
the strength of the photostimulation. Conceptually this means that maximising the
signal-to-noise ratio of an incoming stimulus is critical to its continued propagation
downstream. Further, I show that propagated, behaviourally salient activity elicits
balanced, persistent and generalised activation of the downstream region, consistent
with inhibitory stabilised network models with dense recurrent connectivity. Hence,
my work adds to existing understanding of cortical function by identifying how
population activity is formatted to ensure robust transmission of information,
allowing specialised brain regions to communicate and coordinate behaviour.</p>
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