Electronic Thesis and Dissertation Repository

Degree

Doctor of Philosophy

Program

Neuroscience

Supervisor

Dr. Stefan Everling

Abstract

To thoroughly characterize any brain mechanism requires an appropriate animal model for invasive studies. An invaluable model system used toward a comprehension of cognitive neurophysiology is the macaque monkey. It is important to delineate similarities and limitations for this model in relation to the human brain and cognition. In this thesis, we have thus conducted three experiments to investigate putative generalizations between monkeys and humans regarding the neural processes associated with top-down action control in monkeys.

Our daily behaviour is largely comprised of automatic routine actions. The frequent repetition of certain behaviours in response to particular contexts can give rise to a potent external influence over action. Occasionally, however, automatic actions must be halted so that behaviour can be guided using attentive top-down control mechanisms. In the following chapters, we utilized a variant of an experimental task previously validated for use in monkeys to model top-down control over automatic action and investigated its neural basis in these subjects.

In Chapter Two, we used a macaque electroencephalogram preparation to demonstrate for the first time that evidence for the formation of a large-scale synchronized network can be detected during the engagement of top-down control in monkeys, a result that had previously only been demonstrated in human subjects. In Chapter Three, we employ reversible cryogenic deactivation to demonstrate a causal function for the dorso-lateral prefrontal cortex in the strategic control over response preparation. In Chapter Four, we confirm that, consistent with observations in human subjects, the macaque putamen contains neurons that modulate their firing patterns in relation to top-down guided saccadic eye movements. As such, the work described demonstrates three novel generalizations between the complementary bodies of literature on human and monkey cognitive neuroscience.