| Abstract No.: | B-D2140 |
| Country: | Canada |
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| Title: | NEW INSIGHTS INTO LP-PULVINAR: SPATIOTEMPORAL PROPERTIES OF VISUAL RECEPTIVE FIELDS |
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| Authors/Affiliations: | 1 Marilyse Piché*; 1 Brian Ouellette; 1 Christian Casanova;
1 Université de Montréal, QC, Canada
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| Content: | The lateral posterior-pulvinar complex (LP-pulvinar) of the cat is divided into the lateral (LPl), medial (LPm) and pulvinar nuclei. Each sub-nucleus entertains reciprocal connections with, among other areas, area 17 and the PMLS cortex. While the receptive field (RF) properties of neurons in the LPm and LPl have been previously described, the techniques employed did not allow an in depth study of temporal dynamics nor a quantitative assessment of the spatial structure of their RFs. This is unfortunate as it is unclear how, if at all, the LP-pulvinar modifies information along cortico-thalamo-cortical loops. The goal of this study was to characterize spatiotemporal properties of the RFs of LP-pulvinar neurons using a 2D reverse correlation technique. We recorded single unit activity in the LPm, LPl, and pulvinar nuclei of anaesthetized cats. The majority of the cells in the LPl (77%, n=36) and LPm (67%, n=20) had two subregions, one that was dark-activated, the other bright-activated. Moreover, some neurons (LPl: 23%, n=11; LPm:33%, n=10) had only one contrast activated subregion, and less than 10% were activated by gratings but did not yield reproducible responses to the reverse correlation stimuli used in the present experiments. In the LPl, two-thirds of the cells had overlapping RFs, while more than the haft of the RFs in the LPm did not exhibit overlap. A suppressive subregion was present among 6 cells in the LPl. For the majority of the neurons (LPl: 61%, n=22; LPm: 63%, n=12), the peak response for both contrast were not temporally delayed. For a subset of cells (LPl: n=16, LPm: n=9), the central position displaying optimal responses underwent a translation along either the azimuth or elevation as a function of time. A subset of 8 neurons in the LPl and one neuron in the LPm had more than one clearly distinct response in the temporal domain for the dark stimulus. No reproducible data was obtained from 18 visual cells located in the pulvinar nuclei suggesting that this technique may be inappropriate for the neurons located in this nucleus. In conclusion, overlapping spatiotemporal RFs are consistent with known area 17 projections to the LPl. However, a high proportion of neurons (81%) display response dynamics that cannot easily be explained by cortico-thalamic projections. This suggests that LP-pulvinar cells receive multiple visual inputs, at different time delays, allowing a diversity and complexity in RF properties.
Supp: CIHR to CC, NSERC and FRSQ to BO.
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