Differential spatiotemporal development of Purkinje cell populations and cerebellum-dependent sensorimotor behaviors

Abstract

Distinct populations of Purkinje cells (PCs) with unique molecular and connectivity features are at the core of the modular organization of the cerebellum. Previously, we showed that firing activity of Purkinje cells differs between ZebrinII-positive (Z+) and -negative (Z−) cerebellar modules (Zhou et al., 2014; Wu et al., 2019). Here, we investigate the timing and extent of PC differentiation during development in mice. We found that several features of PCs, including activity levels, dendritic arborisation, axonal shape and climbing fiber input, develop differentially between nodular and anterior PC populations. Although all PCs show a particularly rapid development in the second postnatal week, anterior PCs typically have a prolonged physiological and dendritic maturation. In line herewith, younger mice exhibit attenuated anterior-dependent eyeblink conditioning, but faster nodular-dependent compensatory eye movement adaptation. Our results indicate that specific cerebellar regions have unique developmental timelines which match with their related, specific forms of cerebellum-dependent behaviors.

Activity of Cerebellar Nuclei Neurons Correlates with ZebrinII Identity of Their Purkinje Cell Afferents

“…Previous studies showed that PCs with a Z-identity on average have a higher firing frequency than Z+ PCs [22,23,40,41]. Given the inhibitory effect of PC afferents on CN neurons, we expected to observe a lower firing frequency in the Z-domain of the CN than S5 for all statistical data.…”

“…The firing frequency of Z+ and Z− PCs starts to differentiate from P12 [23], and the ZebrinII pattering in PCs is complete around P12-15 [37,38]. To determine if a similar timeline is present for CN neurons, we recorded the activity of Z+ and Z− CN neurons at different developmental stages.…”

“…The lateral, posterior interposed and caudal portion of the medial CN are mostly innervated by Z+ PCs, whereas the anterior interposed and rostral portion of the medial CN are mostly innervated by Z-PCs [21]. Recent studies in adult mice have shown that the Z+ PCs fire APs on average at lower frequencies than Z-PCs [22,23], which has been linked to various behaviors. For instance, eye blink conditioning is encoded in Z-anterior interposed nucleus, which receives innervation from the portion of the cerebellar cortex in which Purkinje cells on average fire at a higher frequency [24].…”

Maturation of Purkinje cell firing properties relies on neurogenesis of excitatory neurons

“…Both the unbiased cluster and the tSNE analysis show some cells in an intermediate state (between young and old) ( Figure 6B–C , middle cells). This suggests the existence of a transformation that occurs between younger and older cells, but the transformation does not occur at the same time for all Purkinje cells, as is expected based on previous studies showing that the heterogeneity of Purkinje cell function is an inherent property of Purkinje cells that respects and spans the timelines of anatomical and functional development of Purkinje cells ( Beekhof et al, 2021 ; McKay and Turner, 2005 ; van Welie et al, 2011 ). To further test whether there are general changes that occur at different time points or a transformation that occurs at a discrete age, we averaged the firing properties of all cells recorded in each group, allowing us to test for the relative contribution of specific firing properties in each age group, and performed an unbiased, hierarchical cluster analysis on the first two principal components of the averaged firing properties ( Figure 6D ).…”

“…Purkinje cells have a distinct firing profile characterized by spontaneously generated simple spikes and climbing fiber-induced complex spikes. In vitro recordings in rats ( Crepel, 1972 ; McKay and Turner, 2005 ) and mice ( Beekhof et al, 2021 ) show that Purkinje cell firing properties change significantly during early postnatal development (P7-P14), but it is unclear how firing patterns evolve in vivo during this dynamic period of rewiring. Therefore, we set out to answer two questions: first, how do the in vivo Purkinje cell firing patterns change during the dynamic period?…”