Brown, APY;
(2016)
Intrinsic and Visually-Evoked Properties of Layer 2/3 Neurons in Mouse Primary Visual Cortex and Their Dependence on Sensory Experience.
Doctoral thesis , UCL (University College London).
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Abstract
Neurons in Primary Visual Cortex (V1) are known to respond strongly to visual stimuli. Studies of neuronal responses in V1, carried out first in cats, but later primates and other mammals, have demonstrated that bars of light at particular orientations evoke strong, reliable responses in terms of increased firing rate of action potentials. Tuning of neuronal responses to certain stimulus parameters, such as orientation but also spatial and temporal frequencies, as well as the apparent dichotomy between simple and complex responses, have given rise to a number of influential models not just of V1 function, but more generally in the field of cortical physiology and computer vision. Owing to its small size and the plethora of available molecular and genetic tools, the visual cortex of the mouse may be a more tractable model system than that of much larger animals. Recent studies of neuronal responses in mouse V1 have shown that these are broadly similar to those of primates and carnivores, although not identical in all aspects. My thesis aims firstly to characterise intrinsic and sensory-evoked properties in regularspiking, putative pyramidal neurons in L2/3 of the mouse visual cortex using whole-cell patch clamp recording in vivo . In addition, the anatomical connectivity of individual neurons is characterised using virus-assisted circuit mapping. The majority of these neurons are found to be simple cells. Orientation tuning (the degree to which neuronal responses are selective to stimuli of a preferred orientation) is found to be quite variable, even within this singular group of neurons. The potential roles of intrinsic diversity, functional connectivity, and sensory experience in setting the orientation tuning of a particular neuron are investigated. These findings provide an insight in to how diverse responses to sensory stimuli can be generated in an apparently homogenous group of neurons.
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