The inferotemporal cortex of the macaque monkey mediates the recognition of objects in the visual world. The purpose of the research presented in this dissertation was to investigate the neural mechanisms underlying two poorly understood aspects of object recognition. The first experiment addressed the question of how visual features are integrated in IT. In this study, we sought to determine whether feature selectivity for shape and color is integrated by IT neurons via a conjunction-coding mechanism, or via linear summation. We demonstrate that visual responses of most IT neurons encode shape and color information in a linear manner. Our results shed light on the computational strategy that the brain employs to construct a versatile representation of the visual world.
The purpose of the second experiment was to investigate the neural mechanisms underlying repetition priming. Repetition priming is a form of rapid visual learning, whereby previous experience with an object allows for faster, more efficient perceptual processing of that object upon subsequent encounters. This behavioral process is believed to be dependent on activity reductions in single IT neurons, but this hypothesis has never been tested. Indeed, repetition priming has never been demonstrated before in monkeys. To address this issue, we adapted the experimental paradigm of repetition priming for use in primate physiology. We demonstrate that repetition priming at the level of behavior is accompanied by repetition suppression at the level of single neurons in IT. We further demonstrate that repetition suppression in IT results in a proportional scaling reduction of visual responses, and not in a sharpening of the stimulus selectivity. These findings constrain the possible mechanisms whereby visual response plasticity in IT could contribute to behavioral priming.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-12082005-181355 |
| Date | 07 July 2006 |
| Creators | McMahon, David Brian Thomas |
| Contributors | Marlene Behrmann, Carol L. Colby, Michael S. Lewicki, Rafael Malach, German Barrionuevo, Carl R. Olson |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-12082005-181355/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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