Lateral inhibition is a circuit motif found throughout the nervous system that often generates contrast enhancement and center-surround receptive fields. While widespread lateral inhibition of mitral cells (the principal output neurons of the bulb) is mediated by granule cells (inhibitory interneurons), due to the distributed representation of odorant-evoked activity it is currently unclear how this inhibition is specified or what functions it mediates.
Given the reciprocal nature of the connection between mitral and granule cells, mitral cells that are the targets of lateral inhibition (postsynaptic) are able to modulate the activity of the granule cells mediating this lateral inhibition. This led us to hypothesize that lateral inhibition could be modulated by the activity of both pre- as well as postsynaptic mitral cells. I first characterize the lateral interactions between mitral cells and show that the effectiveness of lateral inhibition between them is dependent on the activity of the postsynaptic neuron such that lateral inhibition is only able to reduce the firing rate within a specific range of postsynaptic firing rates. I call this activity-dependent lateral inhibition. I then investigated this novel form of inhibition further and provide evidence indicating that it results from cooperative activation of the inhibitory granule cells.
I investigated the mechanism and functional implications of these physiological results further using computational techniques. First, I show that integration of activity between pre- and postsynaptic mitral cells within a granule cell is sufficient to result in activity-dependent inhibition. I then used this model to show that activity-dependent inhibition is able to enhance the contrast and decorrelate initially similar input patterns to the network in a spatially independent manner. These results provide evidence for a novel form of neuronal interaction dependent on the activity of neurons within the network which could have important functional implications in olfaction as well as other brain areas.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-08062008-112521 |
| Date | 29 October 2008 |
| Creators | Arevian, Armen C |
| Contributors | Diego Restrepo, Nathaniel N. Urban, Jon Johnson, G. Bard Ermentrout, Justin Crowley, Alan Sved |
| 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-08062008-112521/ |
| 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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