Pulvinar-cortical interactions for spatial perception and goal-directed actions in non-human primates

by Lydia Gibson
Doctoral thesis
Date of Examination:2017-12-21
Date of issue:2018-12-12
Advisor:Dr. Igor Kagan
Referee:Dr. Igor Kagan
Referee:Prof. Dr. Melanie Wilke
Persistent Address: http://dx.doi.org/10.53846/goediss-7181

 

 

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Abstract

English

The pulvinar nucleus, the largest thalamic nucleus in primates, has been shown to be involved in goal-directed visuomotor behavior related to the contralateral side of visual space. However, there is conflicting evidence on the pulvinar’s involvement in either the facilitation of visuomotor responses towards contralateral visual stimuli or the filtering of contralateral visual distractors. Using unilateral electrical microstimulation of the dorsal pulvinar in one male rhesus macaque performing a visuomotor response selection task including choices between visual targets and distractors we found that pulvinar stimulation led to changes in response selection in a time-dependent manner: stimulation starting before the onset of the visual stimuli was associated with a decreased number of saccade choices towards contralateral visual stimuli whereas stimulation starting after stimulus onset led to an increased number of contralateral saccade choices. Both effects, however, may be explained by the pulvinar’s involvement in facilitating visuomotor responses towards contralateral stimuli. Moreover, by including eye fixation as an additional response option, we could show that the pulvinar plays a general role in resolving competition between multiple response options. The combination of functional magnetic resonance imaging and microstimulation of the dorsal pulvinar further revealed that the pulvinar plays a functional role in the brain network dedicated to visual attention and visuomotor processing with its effective connectivity strongly overlapping with the connectivity pattern found for the lateral intraparietal area (LIP), a node of the same brain network but located in posterior parietal cortex. However, the magnitude of both pulvinar and LIP stimulation effects on neuronal activity in activated brain regions depended on the current cognitive task and the spatial tuning of the activated areas suggesting that stimulation-induced activity might be modulated depending on the extent of task responsiveness in both the stimulated region and other activated areas. This may result in changes in space representations in the activated brain network which might be neuronal correlates of stimulation-induced changes in visuomotor behavior.
Keywords: pulvinar; fMRI; visuomotor; microstimulation; effective connectivity
 
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