Neuronal growth patterns in states of learning and activity blockade

The role of activity on the formation of neural networks during development is known to be critical. In the research conducted for this dissertation the effect of experience was probed at the single neuron level. First, a method for selecting neurons based on their responses to a visual stimulus and electroporating the selected neurons in a somata dense region was developed. This method was then used to select neurons responsive to a predetermined visual stimulus and the growth behavior of the neuronal arbor was observed in the presence of visual stimuli. When neurons were trained to better discern the visual stimulus the plasticity of the neuron was correlated with the dendritic growth behavior. In general, responsive neurons tended to prune their dendritic arbors while non-responsive neurons tended to grow. Interestingly, neurons that acquired a response with training tended to grow before acquiring a response and prune after. Blockade of NMDA receptors abolished these effects. In a separate set of experiments dendritic growth patterns were observed while all excitatory activity was blocked pharmacologically. These experiments showed that short-term (1.5 hours) excitatory activity blockade does not alter dendritic growth patterns. However, 30 minutes after the start of the activity blockade, the density of filopodia increased, suggesting that the neuron was compensating for the lack of activity.