Abstract
In contrast to the uniform anatomy of the cerebellar cortex, molecular and physiological studies indicate that significant differences exist between cortical regions, suggesting that the spiking activity of Purkinje cells (PCs) in different regions could also show distinct characteristics. To investigate this possibility we obtained extracellular recordings from PCs in different zebrin bands in crus IIa and vermis lobules VIII and IX in anesthetized rats in order to compare PC firing characteristics between zebrin positive (Z+) and negative (Z−) bands. In addition, we analyzed recordings from PCs in the A2 and C1 zones of several lobules in the posterior lobe, which largely contain Z+ and Z− PCs, respectively. In both datasets significant differences in simple spike (SS) activity were observed between cortical regions. Specifically, Z− and C1 PCs had higher SS firing rates than Z+ and A2 PCs, respectively. The irregularity of SS firing (as assessed by measures of interspike interval distribution) was greater in Z+ bands in both absolute and relative terms. The results regarding systematic variations in complex spike (CS) activity were less consistent, suggesting that while real differences can exist, they may be sensitive to other factors than the cortical location of the PC. However, differences in the interactions between SSs and CSs, including the post-CS pause in SSs and post-pause modulation of SSs, were also consistently observed between bands. Similar, though less strong trends were observed in the zonal recordings. These systematic variations in spontaneous firing characteristics of PCs between zebrin bands in vivo, raises the possibility that fundamental differences in information encoding exist between cerebellar cortical regions.
Highlights
The circuitry and the physiological properties of a brain region’s cellular constituents constrain its computational properties
Database This study presents results related to differences in Purkinje cells (PCs) activity between Z+ and Z2 bands using four specific datasets, the first three consist of recordings of PC activity under ketamine/xylazine anesthesia
The physiological zones and zebrin bands are not entirely congruent in the posterior lobe of the rat cerebellum, the A2 zone comprises mainly Z+ bands whereas the C1 zone comprises mainly Z2 ones [17]. Because these zones are not fully equivalent to the zebrin bands, we present the data from the zebrin and zonally-identified PCs separately for each analysis
Summary
The circuitry and the physiological properties of a brain region’s cellular constituents constrain its computational properties. The cerebellar cortex offers what appears to be perhaps a unique opportunity for deriving structure-function correlations, because, with few exceptions, it is an essentially anatomically uniform structure whose few morphologically distinct cell types are interconnected according to relatively simple geometric rules This uniformity is not absolute; for example, unipolar brush cells are limited primarily to so-called vestibulocerebellar regions [1]; the microcircuitry of most cerebellar cortical regions appears to be quite alike, suggesting that most cortical regions perform similar computations, and theories of cerebellar function have tended to be global in nature and based largely on a generic anatomical circuit diagram [2,3,4,5,6,7]. Regions in which Purkinje cells (PCs, the sole output neurons of the cerebellar cortex) express zebrin (Z+) alternate with ones that do not (Z2), subdividing much of the cerebellar cortex into longitudinally running alternating Z+ and Z2 bands [11,12,13,14,15]
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