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The Impact of Learning on Goal Encoding in Premotor Cortex

Alemayehu, Berook (2016) The Impact of Learning on Goal Encoding in Premotor Cortex. Doctoral Dissertation, University of Pittsburgh. (Unpublished)

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The dorsal aspect of the premotor cortex (PMd) is a key node in the cortical pathway for visually-guided reaching. As such, one of the functions it may contribute to is the conversion from visual (input) to muscle (output) coordinates. My central question is whether or not the task that the animal is trained to perform may affect the tuning properties of PMd neurons. To address this, we recorded from PMd of two Rhesus monkeys while they performed a delayed reaching task. The animals were not trained to fixate. We found that tuning in PMd for reach target location relative to the direction of gaze was quite weak. We recorded neural activity using a 96-channel Blackrock microelectrode array. Nine sessions with 447 well-isolated neurons were analyzed. We first used a planar regression to determine neural tuning. We found that tuning to the location of the target relative to the hand (TH) and target relative to the eye (TE) exhibited statistically significant regression fits (F-test, p > 0.05). However, we recognized that our tuning measurements could be overestimates. We found that both animals exhibit consistent gaze behavior patterns during the task, and this meant that at least some of the TH or TE tuning we observed might be an artifact of the nonuniform gaze behavior. To check for this, we performed two additional analyses. We used a partial regression analysis to first remove the tuning due to one reference frame so we could investigate whether the residual variance was tuned in the other reference frame. When the effect of TH was removed, only 36\% of our cells exhibited significant but weak tuning to TE. In our second analysis, we built a simulated neural population with TH tuning measured from the real data, but no TE tuning. When those simulated neurons were analyzed like the real data, using the monkeys' actual gaze behavior, we found they exhibited TE tuning. Our results suggest that neural tuning to the target location relative to the eye is inherently quite weak, weaker still than has been appreciated so far.


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Item Type: University of Pittsburgh ETD
Status: Unpublished
CreatorsEmailPitt UsernameORCID
Alemayehu, Berookbea22@pitt.eduBEA22
ETD Committee:
TitleMemberEmail AddressPitt UsernameORCID
Committee ChairBatista, Aaronapb10@pitt.eduAPB10
Committee MemberColby, Carolccolby@pitt.eduCCOLBY
Committee MemberChase,
Committee MemberGandhi, Neerajneg8@pitt.eduNEG8
Committee MemberSmith, Matthewsmithma@pitt.eduSMITHMA
Date: 26 January 2016
Date Type: Publication
Defense Date: 19 November 2015
Approval Date: 26 January 2016
Submission Date: 3 December 2015
Access Restriction: No restriction; Release the ETD for access worldwide immediately.
Number of Pages: 68
Institution: University of Pittsburgh
Schools and Programs: Swanson School of Engineering > Bioengineering
Degree: PhD - Doctor of Philosophy
Thesis Type: Doctoral Dissertation
Refereed: Yes
Uncontrolled Keywords: premotor cortex, reference frames, goal encoding, eye-hand coordination, visual-motor transformation
Date Deposited: 26 Jan 2016 16:22
Last Modified: 15 Nov 2016 14:31


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