Efecto dun estímulo potenciador na actividade neuronal da corteza motora, putamen e amígdala

RESUMO: O presente traballo de investigación propón describir as características da actividade neuronal da corteza premotora, o putamen e a amígdala durante a realización dunha tarefa visuomotora que require dun movemento para recibir unha recompensa. O obxectivo deste traballo é estudar a influenza da presentación de estimulación visual, xunto coa presencia ou ausencia dun estímulo potenciador, na actividade neuronal das citadas áreas. Para realizar este estudo rexistrouse a actividade unitaria neuronal de dous monos rhesus (Macaca mulatta) nas estructuras mencionadas durante a execución dunha tarefa visuomotora. ABSTRACT: The present research aims to describe the characteristics of the neuronal actvity of the premotor cortex, putamen and amygdala during the performance of a visuomotor task that requires a movement to obtain a reward. The objective of our work was to study the influence of visual stimulation along with an enhancer on neuronal activity of the above brain areas. To carry out this study single unit extracellular recordings were performed on two monkeys rhesus (Macaca mulatta) trained in the performance of a visuomotor task

Identifying neural mechanisms and behavioral effects of anxiety on attentional capture

Attention research has long investigated the mechanisms by which sensory information is selectively filtered for neural representation. Models for visual selective attention initially formed a theoretical dichotomy in which goal-oriented or salience-driven mechanisms were argued as the predominant modes for attentional selection. However, this theoretical dichotomy was challenged when new experimental findings could not be reduced to goal-oriented or salience-driven mechanisms. These results were grouped into a new component of attentional control by an experience-driven mechanism and expanded models of selective attention into a theoretical trichotomy under the third label selection history. In the context of attention research, threat has been investigated primarily by measuring rapid orienting towards threatening stimuli. Individuals with elevated state anxiety measured via self-report demonstrate increased attentional orienting towards threatening stimuli and enhanced attentional capture by physically salient stimuli. However, such findings are limited to attentional mechanisms toward the threatening nature of a stimulus and do not extend to more systemic changes in attentional control when the observer is in a threatened state. It is yet unknown whether elevated state anxiety globally modulates attentional capture through a core mechanism or whether such changes in observer state uniquely modulate different modes of attentional control. Furthermore, the mechanism by which threatening stimuli are afforded greater attentional priority in individuals with elevated state anxiety is still unclear. In this dissertation, I investigate how attentional priority can be modulated by changing the state of an individual by experimentally inducing anxiety through the Threat of Shock (ToS) paradigm. I first present a series of behavior experiments that investigate how unpredictable threat modulates the three predominant mechanisms of attentional selection: attentional capture by reward history (selection history), color (salience-driven), and strategic goals. Then, I present a neuroimaging experiment that investigates how the neural mechanisms of processing threat interacts with mechanisms of attentional selection by previously-reward associated stimuli. I conclude by expanding on the core findings of this dissertation and its implications concerning how changes in observer state modulates attentional control and how the identified mechanisms can be expanded to inform our understanding of attentional biases toward threatening stimuli

The human amygdala encodes value and space during decision making

Valuable stimuli are invariably localized in space. While our knowledge regarding the neural networks supporting value assignment and comparisons is considerable, we lack a basic understanding of how the human brain integrates motivational and spatial information. The amygdala is a key structure for learning and maintaining the value of sensory stimuli and a recent non-human primate study provided initial evidence that it also acts to integrate value with spatial location, a question we address here in a human setting. We measured haemodynamic responses (fMRI) in amygdala while manipulating the value and spatial configuration of stimuli in a simple stimulus-reward task. Subjects responded significantly faster and showed greater amygdala activation when a reward was dependent on a spatial specific response, compared to when a reward required less spatial specificity. Supplemental analysis supported this spatial specificity by demonstrating that the pattern of amygdala activity varied based on whether subjects responded to a motivational target presented in the ipsilateral or contralateral visual space. Our data show that the human amygdala integrates information about space and value, an integration of likely importance for assigning cognitive resources towards highly valuable stimuli in our environment

The human amygdala encodes value and space during decision making

Valuable stimuli are invariably localized in space. While our knowledge regarding the neural networks supporting value assignment and comparisons is considerable, we lack a basic understanding of how the human brain integrates motivational and spatial information. The amygdala is a key structure for learning and maintaining the value of sensory stimuli and a recent non-human primate study provided initial evidence that it also acts to integrate value with spatial location, a question we address here in a human setting. We measured hemodynamic responses (fMRI) in amygdala while manipulating the value and spatial configuration of stimuli in a simple stimulus-reward task. Subjects responded significantly faster and showed greater amygdala activation when a reward was dependent on a spatial specific response, compared to when a reward required less spatial specificity. Supplemental analysis supported this spatial specificity by demonstrating that the pattern of amygdala activity varied based on whether subjects responded to a motivational target presented in the ipsilateral or contralateral visual space. Our data show that the human amygdala integrates information about space and value, an integration of likely importance for assigning cognitive resources towards highly valuable stimuli in our environment