Dunn, Catherine Anne
(2009)
How the brain constructs stable visual representations: Cortical and subcortical mechanims.
Doctoral Dissertation, University of Pittsburgh.
(Unpublished)
Abstract
Our eyes are constantly moving yet our perception remains stable. Neurons in lateral intraparietal cortex (LIP) update spatial representations by "remapping" visual information at the time of an eye movement. In order for remapping to occur over a wide range of eye movements, neurons must have access to visual information from the entire visual scene. The forebrain commissures appear to be the primary pathway for the transfer of visual information across hemispheres but they are not necessary. If the forebrain commissures are transected, behavior dependent on accurate spatial updating is impaired, but recovers. In three sets of experiments we examined different mechanisms of spatial updating in split brain monkeys. First, we studied the relationship between neural activity in LIP and the behavior of the monkey. We found across the population a small but significant relationship between the activity in LIP and the performance of the split brain monkey on the double-step task. This result showed that information about the opposite visual field still reaches LIP, and this activity contributes to the overall behavior of the monkey.Second, we determined if LIP neurons in the split brain monkeys have bilateral receptive fields. One explanation for the observed across-hemifield remapping is that information from both visual fields are represented in a single hemisphere. We found no neurons in the split brain monkeys with ipsilateral representations. We concluded that there must be a subcortical source for the across-hemifield remapping observed in the split brain monkeys.Third, we examined the difference in spatial updating between intact and split brain monkeys in the superior colliculus (SC). In both the intermediate layers of the SC and LIP, neural activity is selectively reduced for the across-hemifield condition in split brain compared to intact animals. This suggest that remapping activity is passed from LIP to the intermediate layers of the SC. In contrast, remapping activity in the superfical layers did not differ between the intact and split brain monkeys. It may be that the superfical neurons contribute to recovered remapping activity observed in LIP.
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Details
| Item Type: |
University of Pittsburgh ETD
|
| Status: |
Unpublished |
| Creators/Authors: |
| Creators | Email | Pitt Username | ORCID  |
|---|
| Dunn, Catherine Anne | cad11@pitt.edu | CAD11 | |
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| ETD Committee: |
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| Date: |
30 September 2009 |
| Date Type: |
Completion |
| Defense Date: |
12 May 2009 |
| Approval Date: |
30 September 2009 |
| Submission Date: |
7 August 2009 |
| Access Restriction: |
No restriction; Release the ETD for access worldwide immediately. |
| Institution: |
University of Pittsburgh |
| Schools and Programs: |
Dietrich School of Arts and Sciences > Neuroscience |
| Degree: |
PhD - Doctor of Philosophy |
| Thesis Type: |
Doctoral Dissertation |
| Refereed: |
Yes |
| Uncontrolled Keywords: |
parietal cortex; perception; spatial updating; superior colliculus |
| Other ID: |
http://etd.library.pitt.edu/ETD/available/etd-08072009-002413/, etd-08072009-002413 |
| Date Deposited: |
10 Nov 2011 19:58 |
| Last Modified: |
19 Dec 2016 14:37 |
| URI: |
http://d-scholarship.pitt.edu/id/eprint/8974 |
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