How does the brain represent sensory input? When stimuli move across sensor surfaces, such as a light source moving across the retina, sound moving between the ears, or contact moving over the skin, patterns of activation propagate across sheets of neurons that form the primary sensory cortices. Understanding how the movement of stimuli across the sensor surfaces relates to the activation of the cortical sheet is a fundamental problem in neuroscience.
The thesis presents a series of computational neuroscience studies, addressing how sensory stimuli are represented in mammalian primary sensory cortex. Each study constructed a model of how tactile stimuli, experienced by rodents via the array of facial whiskers, are encoded in the barrel cortex area of the primary somatosensory cortex. Each explains how the responses of cortical neurons to sensory stimuli can be predicted from their location in the cortical sheet. In each case, simple organising principles, based on cortical connection geometry and/or local learning rules, could account for how neuronal responses vary according to sensory stimuli.
The success of these highly simplified descriptions of cortical circuitry at explaining complex neurophysiological data suggests an important role for sensory experience and neural inter-connection geometry in neural computation. The roles of both have been largely overlooked in recent large-scale efforts to model somatosensory cortical processing, which have focussed instead on cataloguing descriptions of neural tissue in increasing levels of detail. Using a top-down approach to modelling, the thesis generates specific hypotheses about the functional organisation of the sensory cortex, that can be used to guide future experimental work. The contribution of the thesis will therefore have been to lay the foundations of a theoretical framework for studying tactile stimulus processing in the somatosensory cortex, which is emerging as one of the most popular model systems in modern neuroscience.
