Date of Graduation
School of Medicine
Physiology, Pharmacology & Neuroscience
Charles L. Rosen.
Throughout the mammalian cortex, neurons of similar response characteristics group together into topographic functional domains. The genesis and role of this organization remains in question, but it has been proposed to affect the mixed properties of neurons. These types of neurons possess multiple receptive field preferences, such as a cell responding to a color and an oriented stimulus. To examine the functionality of clustered organization and their effect in generation of neurons possessing mixed properties, this dissertation examined the secondary visual cortex (V2) of the Macaca fasicularis. This particular cortex is comprised of domains organized according to distinct visual stimulus components, specifically clusters of neurons partitioned by color and orientation preferences within a close proximity. In the first series of experiments (Chapter 3), a computer model of a cortical area based upon macaque V2 investigated the effect of clusters of like-preferring neurons on the probability of two different preference terminals synapsing on a particular cell. These results indicate that presence of at least one cluster significantly increases the probability of multiple preferences arriving at a neuron. The second series of experiments (Chapter 4) used single unit electrophysiology to investigate the temporal properties of V2 neurons in response to achromatic and colored oriented stimuli. With the addition of color to the stimulus, an increase in latency, an increase to the time point of the maximum rate of firing, and a decreased initial-phase response with a sustained later-phase response were observed. These studies indicate that functional clusters of neurons significantly increase the joint probability of the co-localization of differing preference terminals, potentially yielding neurons with mixed preferences through these intra-areal connections. Furthermore, the temporal characteristics of V2 neurons, as seen in observed latency and time of maximum spiking, support this idea of domain-enhanced intra-areal integration.
Cooper, Clinton Garret, "The Role of Clustered Organization and Generation of Mixed Properties in Macaque V2" (2012). Graduate Theses, Dissertations, and Problem Reports. 3581.