In a multi‐agent environment, animals must often adopt a stochastic mixed‐strategy approach to maximize reward and minimize costs; otherwise, competitive opponents can exploit predictable choice patterns. This thesis tested the hypothesis that the frontal eye field (FEF) are involved in selecting mixed‐strategy saccades. To this end, I recorded preparatory activity of single FEF neurons and manipulated the preparatory activity of neuronal ensembles within the FEF while a monkey played an oculomotor version of the mixed­‐strategy game ‘matching­‐pennies’. Each trial began with fixation on a central visual stimulus which was extinguished for a predetermined warning period before two targets were presented; one in the center and the other opposite the neuron’s response field. If both the monkey and the adaptive computer opponent chose the same target, the monkey received a liquid reward; otherwise the monkey received no reward for that trial. Like humans, monkeys chose each target in equal proportions but showed a ‘win‐stay’ bias in their choice patterns. Signal detection theory was used to analyze how accurately FEF preparatory activity predicted upcoming saccade choices. My data demonstrates that the accuracy by which FEF preparatory activity predicted upcoming strategic choices gradually increased as the time of saccade execution approached. This pattern of preparatory activity is consistent with an accumulation of evidence for each potential option towards a decision threshold. Subthreshold micro­‐stimulation biased mixed‐strategy saccadic choices, further suggesting a role for the FEF in choosing mixed­‐strategy saccades, albeit unexpectedly, in favor of saccades opposite the stimulation sites. Lastly, a particular advantage of my experiment is that the same monkey performed this task using neurophysiological experimentation in the FEF and intermediate layers of the superior colliculus (SCi). This allowed me to compare the timing and magnitude of neuronal selectivity and effects of subthreshold microstimulation across these two structures, during strategic decision‐making. My results indicate that the selection of mixed­‐strategy saccades occurred earlier and was greater in magnitude in the FEF compared to the SC, indicative of a decision process that occurs earlier in the frontal cortex before being relayed on to premotor regions in the midbrain. / Thesis (Master, Neuroscience Studies) -- Queen's University, 2012-03-28 10:57:30.638

A hallmark of human behaviour is that we can either couple or decouple our thoughts, decision and motor plans from actions. Previous studies have reported evidence of gating of information between intention and action that can happen at different levels in the central nervous system (CNS) involving the motor cortex, subcortical structures such as the basal ganglia and even in the spinal cord. In my research I examine the extent of this gating and its modulation by task context. I will present results obtained by data collected from (a) neck muscles and neural recording from frontal eye field (FEF) in macaque monkeys and (b) putative motor units (MUs) from high density electrode arrays using surface EMG signals in human to delineate the type of information that leaks into muscles in the periphery when subjects are involved in preparing eye and hand movements, respectively, and its modulation by task context Overall, my results reveal that we can assess some aspects of central planning in the activity of motor units Further, the recruitment of these motor units depend on task context.

Projections from medial agranular cortex to brain stem in rat were determined by use of the anterograde tracers Phaseolus vulgaris leucoagglutinin, or wheat germ agglutinin conjugated horseradish peroxidase. Axonal trajectories were also followed by means of the Wiitanen modification of the Fink-Heimer degeneration technique. AGm was identified on the basis of its cytoarchitectonics. AGm projected to the anterior pretectal nucleus, the rostral interstitial nucleus of the medial longitudinal fasciculus, the medial accessory oculomotor nucleus of Bechterew, the interstitial nucleus of Cajal, the nucleus of Darkschewitsch, the nucleus cuneiformis and subcuneiformis, intermediate and deep superior collicular layers, the paramedian pontine reticular formation (reticularis pontis oralis and caudalis, and reticularis gigantocellularis), and raphe centralis superior. Differences in connections between rostral and caudal injections were observed: pontine and medullary projections were lighter from the rostral portion of AGm than from the more caudal portions of AGm. The heaviest projections to the anterior pretectal nucleus were from the caudal portion of AGm. The subcortical projections were very similar to those described for the frontal eye field in monkeys, and the majority of them targeted areas thought to be involved in coordination of gaze with head and neck movements. Thus AGm in rats may contain the homologue of the primate frontal eye fields.

Behavioral and physiological correlates of hostility, such as cardiovascular lability and increased risk of cardiovascular disease, are vital when considering the possible health risks associated with high levels of hostility (Henry & Meehan, 1981; Matthew & Haynes, 1986; Johnson, 1990; Heller, 1993; Heilman, Bowers, & Valenstein, 1993; Demaree & Harrison, 1997; Demaree Harrison, & Rhodes, 2000; and Shenal & Harrison, 2001). By examining this issue through a functional cerebral systems approach, one is better able to conceptualize changes that occur when men with extreme hostility levels (e.g. high and low) carry out emotional regulation tasks. High and low hostile groups have been shown to differ in their auditory, visual, somatosensory, and motor processes. Moreover, they differ in lateralized cerebral functions within these modalities where high hostiles have shown a right cerebral/ negative affective bias while low hostiles have shown a left cerebral/ positive affective bias in perception and in motor functions to stress. Right cerebral activation in high hostiles has occurred with heightened reactivity and persistence in sympathetic tone and with cardiovascular changes in heart rate, blood pressure, and Galvanic skin response. In the present experiment, this systematic line of research (Harrison & Gorelczenko, 1990; Herridge & Harrison. 1996; Demaree & Harrison, 1997; Herridge, Harrison, & Demaree, 1997; Demaree, Higgins, Williamson, and Harrison, 2002; Williamson & Harrison, in press) was extended to the investigation of the premotor frontal eye fields using rapid directional eye movements toward the contralateral hemisphere. It was predicted that high hostiles would evidence right frontal deficits in lateral eye movements (LEM) resulting in decreased LEM toward and within the left hemispace. Moreover, concurrent processing of lateralized eye movements and regulation over cardiovascular responding was predicted to yield sympathetic dysregulation on leftward LEM (lLEM) and potentially parasympathetic dysregulation on rightward LEM (rLEM). Leftward LEM appeared to result in more fatigue effects than rightward LEM. However, the primary behavioral hypothesis was not supported. Moreover, the directional relationship predicted between left side LEM and sympathetic tone was not found. Instead, LEM in either direction occurred with corresponding reduction in sympathetic blood pressure. Diametrically opposite results were found for the non- directional cold pressor stressor. High hostiles were found to be more reactive in their cardiovascular response to stress than the low hostiles. / Master of Science / [The Beck Depression Inventory, p. 62-66, was removed March 22, 2010 GMc]