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Comparison of the Role of Dopamine in Egocentric and Allocentric Learning, Two Subtypes of Navigation

Braun, Amanda Ann

Abstract Details

2015, PhD, University of Cincinnati, Medicine: Neuroscience/Medical Science Scholars Interdisciplinary.
Successful navigation requires interactions among multiple but overlapping neural pathways mediating distinct capabilities, including egocentric (self-oriented, route-based) and allocentric (external, map-based) learning. Multiple neurotransmitters are involved in both navigation types, including dopamine. These studies sought to elucidate the region-specific role of dopamine in egocentric and allocentric learning. The dopaminergic-rich dorsal striatum (dStr) is involved in both egocentric and allocentric navigation. We first tested whether dStr dopamine loss using bilateral 6- hydroxydopamine (6-OHDA) injection impaired one or both types of navigation. Direct dStr 6- OHDA injection resulted in 80% dStr dopamine depletion pre- and post-testing. Two weeks after 6-OHDA injections, rats began testing in the Cincinnati water maze (CWM) followed by Morris water maze (MWM), tests of egocentric and allocentric navigation, respectively. dStr 6- OHDA treatment significantly impaired CWM and MWM learning, but not MWM cued performance. These data support that dStr dopamine modulates both navigation types. The dStr is divided into two heterogeneous sub-regions, the dorsolateral (DLS) and dorsomedial (DMS) striatum. Both regions have been implicated in egocentric learning, with the DMS also involved in allocentric learning. We next tested how selective DMS or DLS dopamine loss via 6-OHDA injection would impact one or both types of navigation. Both DMS and DLS lesioned animals were significantly impaired in CWM, but not allocentric or cued MWM performance. Dopamine loss in the DMS (62%) and DMS (75%) were region specific indicating independent roles for DMS and DLS dopamine in egocentric, but not allocentric learning. While the DMS is involved in allocentric learning, these processes do not appear to depend on DMS dopamine. The nucleus accumbens (Nacc), another dopaminergic-rich striatal region, is involved in learning. Nacc dopamine depleted rats (60%) were tested in either the CWM or MWM. Nacc dopamine is implicated in reversal learning, thus this study tested allocentric reversal learning and egocentric reverse path CWM learning. Nacc dopamine depletion significantly impaired CWM, but not CWM reverse path performance. Lesioned animals were impaired in MWM acquisition, reversal, and cued trials. Off-target dopamine depletion in the dStr (20%) was at a sub-threshold level to influence egocentric or allocentric learning indicating a Nacc specific dopaminergic modulatory role in both navigation types. Egocentric learning is dependent on the medial prefrontal cortex (mPFC), however the role of mPFC dopamine in egocentric learning has not been tested. 6-OHDA lesioned animals were tested in the CWM followed by the MWM. mPFC dopamine depletion (88%) did not alter CWM or MWM learning. These findings suggest that while the mPFC is necessary for egocentric learning, it is not dependent on or modulated by mPFC dopamine. These data suggest independent roles for striatal sub-region (Nacc, dStr, DMS and DLS) dopamine involvement in egocentric learning. Allocentric learning is independently modulated by Nacc and dStr dopamine. Egocentric and allocentric learning do not appear to depend on mPFC dopamine levels.
Charles Vorhees, Ph.D. (Committee Chair)
Stephen Benoit, Ph.D. (Committee Member)
Kenneth Campbell, Ph.D. (Committee Member)
John Layne, Ph.D. (Committee Member)
Matthew Skelton, Ph.D. (Committee Member)
Michael Williams, Ph.D. (Committee Member)
211 p.

Recommended Citations

Citations

  • Braun, A. A. (2015). Comparison of the Role of Dopamine in Egocentric and Allocentric Learning, Two Subtypes of Navigation [Doctoral dissertation, University of Cincinnati]. OhioLINK Electronic Theses and Dissertations Center. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439281292

    APA Style (7th edition)

  • Braun, Amanda. Comparison of the Role of Dopamine in Egocentric and Allocentric Learning, Two Subtypes of Navigation. 2015. University of Cincinnati, Doctoral dissertation. OhioLINK Electronic Theses and Dissertations Center, http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439281292.

    MLA Style (8th edition)

  • Braun, Amanda. "Comparison of the Role of Dopamine in Egocentric and Allocentric Learning, Two Subtypes of Navigation." Doctoral dissertation, University of Cincinnati, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1439281292

    Chicago Manual of Style (17th edition)