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dc.contributor.advisor Nicolelis, Miguel AL en_US
dc.contributor.author Pantoja, Janaina Hernandez en_US
dc.date.accessioned 2009-12-18T16:34:28Z
dc.date.available 2009-12-18T16:34:28Z
dc.date.issued 2009 en_US
dc.identifier.uri http://hdl.handle.net/10161/1648
dc.description Dissertation en_US
dc.description.abstract <p>Perception arises from sensory inputs detected by peripheral organs and processed in the brain by complex neuronal circuits required for the integration of external information with internal states such as expectation and attention. Stimulus discrimination requires activation of primary sensory areas in the brain, but expectation is traditionally associated with the activation of higher-order brain areas. Sensory information obtained by tactile organs is represented along the primary areas that comprise the trigeminal thalamocortical pathway. In anesthetized animals, neuronal activity in the somatosensory system has been extensively described over the past century. However, it is still unclear how the different thalamocortical structures contribute to active tactile discrimination and represent relevant features of the stimulus. It is also unknown whether expectation modulates tactile representations in these regions. In this dissertation, I investigated neuronal ensemble activity recorded from freely behaving rats performing a whisker-based tactile discrimination t-+ask. Multielectrode arrays were chronically implanted to record simultaneously from the main stages of the trigeminal thalamocortical pathways involved in whisking: the primary somatosensory cortex (S1), the ventral posterior medial nucleus of the thalamus (VPM), the posterior medial complex (POm) and the zona incerta (ZI). In Chapter 1 I describe the behavior of rats performing the tactile discrimination task, which requires animals to associate two different tactile stimuli with two corresponding choices of spatial trajectory in order for reward to be delivered. I found that both cortical and thalamic neurons are dynamically engaged during execution of the task. The data reveal a very complex mosaic of responses comprising single or multiple periods of inhibition and excitation. Thalamocortical activity was modulated during whisker stimulation as well as after stimulus removal, up until reward delivery. To investigate whether reward expectation plays a role in tactile processing at early processing stages, I also recorded neuronal activity from rats performing a freely-rewarded version of the tactile discrimination task. Comparing data from regularly-rewarded and freely-rewarded sessions, I show in chapter 2 that the activity of single neurons in the primary somatosensory thalamocortical loop is strongly modulated by reward expectation. Stimulus-related information coded by primary thalamocortical neurons is high when a correct association between stimulus and response is crucial for reward, but decreases significantly when the association is irrelevant. These results indicate that tactile processing in primary somatosensory areas of the thalamus and cerebral cortex is directly affected by reward expectation.</p> en_US
dc.format.extent 7478865 bytes
dc.format.mimetype application/pdf
dc.language.iso en_US
dc.subject Biology, Neuroscience en_US
dc.subject Corticothalamic en_US
dc.subject Electrophysiology en_US
dc.subject Neuronal ensemble en_US
dc.subject Rat en_US
dc.subject Reward en_US
dc.subject Somatosensory en_US
dc.title Neuronal Correlates of Reward Contingency in the Rat Thalamocortical System en_US
dc.type Dissertation en_US
dc.department Neurobiology en_US
duke.embargo.months 12 en_US
dc.date.accessible 2010-05-18T05:00:35Z

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