PREFRONTAL ACTIVITY IN COGNITIVE FUNCTION: MECHANISMS AND MATURATION

A number of cognitive abilities, including working memory and response inhibition, mature relatively late in life. These functions are thought to be controlled by the prefrontal cortex, which itself undergoes a number of anatomical and functional changes that last beyond adolescence, into early adulthood. The nature of these changes is poorly understood. Experiments in this dissertation investigated behavioral performance and neural activity in tasks that test working memory and response inhibition around the time of puberty and during adulthood, tracking non-human primates in a longitudinal fashion. The onset of puberty and the completion of developmental maturation of male rhesus monkeys were evaluated with a series of morphometric, hormonal, and radiographic measures. We evaluated working memory with the oculomotor delayed response task, which requires subjects to make an eye movement towards the location of a remembered stimulus, after a delay period. Peri-pubertal monkeys performed the task with relatively high behavioral accuracy. The appearance of a distractor stimulus in some sessions did not impact performance significantly. Neuronal activity recorded during this task was robust and was not eliminated by the presentation of a distracting stimulus. During adulthood, the same animals exhibited a further improvement in performance. This was associated with prefrontal increased activity during the delay period of the task. We evaluated response inhibition with an anti-saccade task, which requires animals to make an eye movement away from the location of a visual stimulus. A much greater behavioral improvement was observed for the anti-saccade task between adolescence and adulthood. This improvement in performance was associated with changes in activity that were evident already in the baseline fixation period of the anti-saccade task, prior to the presentation of the stimulus. In order to understand the nature of functional circuit changes in the prefrontal cortex, we performed analyses of spike train cross-correlations between simultaneously recorded neurons. The average magnitude of functional connections measured between neurons was lower overall in the prefrontal cortex of peri- pubertal monkeys compared to adults. This difference was because negative functional connections (indicative of inhibitory interactions) were both stronger and more prevalent in peri-pubertal compared to adult monkeys. Our results identify changes in behavior, neuronal activity, and connectivity between prefrontal neurons as underlying improvement in cognitive capacity during adolescent development.

Grantor dc:publisher

Wake Forest University

Year dc:date.issued

2014

Author dc:creator

• Zhou, Xin

• antisaccade

Language dc:language.iso

en

Handle dc:identifier.uri

http://hdl.handle.net/10339/47444

OAI identifier oai:identifier

oai:wakespace.lib.wfu.edu:10339/47444