| Abstract No.: | B-D2151 |
| Country: | Canada |
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| Title: | MAPPING OF LOCAL FIELD POTENTIAL OSCILLATIONS IN THE RAT CEREBELLAR CORTEX GRANULE CELL LAYER |
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| Authors/Affiliations: | 2 Ettore Zuccheroso*; 1 Maxime Levesque; 2 Richard Courtemanche;
1 CHUM, Hôpital Sainte-Justine, Montreal, QC, Canada; 2 CSBN, Concordia University, Montreal, QC, Canada
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| Content: | Objectives. Local field potential (LFP) oscillations in the granule cell layer of the cerebellar cortex could be a signal showing an underlying organizing influence on cerebellar cortex networks. Considering the regularity and homogeneity of the cerebellar cortex circuits, one important question is the relative location of these LFP oscillations across the general topography of the cerebellar cortex.
Materials and Methods. To answer this, we recorded both LFP and unit activity in continuous recording tracks across the anterior and posterior lobes of the cerebellar cortex of 3 adult male Sprague-Dawley rats. We used 3-8 multiple moveable microelectrodes simultaneously, aimed at three targets (positions) when considering the cerebellum in the transverse plane: (1) lateral caudal (2) lateral rostral (3) medial rostral. Signals were bandpass filtered for recording LFPs (1-125 Hz) and unit activity (600-6000 Hz). Recordings were made at regular 0.25 to 0.5 mm intervals, or upon a change in layers, or when capturing a single unit. The best behavior to highlight these ~7 Hz oscillations was in the rat being in a quiet, immobile state, and the oscillations disappeared on movements made by the animal. LFPs were analyzed using Fast Fourier Transforms (FFTs) to calculate the proportion of the signal within the boundaries of 5-10 Hz for consecutive time windows of 0.5 s. In each rat, recordings were made at multiple depths: for comparisons, track depth was divided in three regions. Each defined region represents 1/3 of the track depth, with region 1 being more superficial and region 3 the deepest.
Results. Microelectrodes in the same needle showed similar oscillatory activity. There was a tendency for increasing oscillatory activity with increasing depth for all rats. Mean oscillatory activity increased from region 1 to region 3 for all rats in our regional analysis. Oscillatory activity is greater in electrodes that are located more lateral, compared to the medial locations, and more caudal, compared to rostral locations. In addition, results suggest that recording sites situated in position (1) have greater oscillatory activity as compared to position (2) and (3). In all three rats there is an interaction between position and region: the best oscillatory activity would be found in lower depths of track in lateral and caudal, corresponding to Position 1, region 3 (proportion of 5-10 Hz signal ~24%).
Conclusion. These results show that oscillatory activity at ~7 Hz is located to specific subdivisions of the cerebellar cortex granule cell layer, corresponding to the Crus 2 and paramedian lobules. This specific localization could be related to the specific combinations of afferents arriving in these lobules.
Support Contributed By: NSERC and NAAR
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