Role of Synchronous Activation of Cerebellar Purkinje Cell Ensembles in Multi-joint Movement Control

Abstract

SummaryIt is a longstanding question in neuroscience how elaborate multi-joint movements are coordinated coherently. Microzones of cerebellar Purkinje cells (PCs) are thought to mediate this coordination by controlling the timing of particular motor domains. However, it remains to be elucidated to what extent motor coordination deficits can be correlated with abnormalities in coherent activity within these microzones and to what extent artificially evoked synchronous activity within PC ensembles can elicit multi-joint motor behavior. To study PC ensemble correlates of limb, trunk, and tail movements, we developed a transparent disk treadmill that allows quantitative readout of locomotion and posture parameters in head-fixed mice and simultaneous cellular-resolution imaging and/or optogenetic manipulation. We show that PC ensembles in the ataxic and dystonic mouse mutant tottering have a reduced level of complex spike co-activation, which is delayed relative to movement onset and co-occurs with prolonged swing duration and reduced phase coupling of limb movements as well as with enlarged deflections of body-axis and tail movements. Using optogenetics to increase simple spike rate in PC ensembles, we find that preferred locomotion and posture patterns can be elicited or perturbed depending on the behavioral state. At rest, preferred sequences of limb movements can be elicited, whereas during locomotion, preferred gait-inhibition patterns are evoked. Our findings indicate that synchronous activation of PC ensembles can facilitate initiation and coordination of limb and trunk movements, presumably by tuning downstream systems involved in the execution of behavioral patterns.

Chronic imaging of movement-related Purkinje cell calcium activity in awake behaving mice

“…A motor rather than sensory function matches a finding in rats where cutting the trigeminal nerve had no effect on lick-related movements (Welsh et al 1995). This interpretation is also consistent with the increased PC activity reported at the initiation of locomotion (Hoogland et al 2015). Furthermore, we found slight differences in the representation of PC dendritic Ca 2ϩ events as the mice gained experience with the task.…”

“…This method produced sufficient pressure on the brain to reduce motion artifacts without causing clear signs of damage. In contrast, we found that additional pressure created by placing the coverslip inside the skull opening (Nishiyama et al 2014) or by putting agarose between the coverslip and brain (Hoogland et al 2015) caused damage to some PCs that became apparent over time (data not shown).…”

“…In the cerebellum, the cell-permeant Ca 2ϩ indicator OGB-1/AM has been used extensively to study PC activity. While OGB-1/AM has worked well in acute experiments (De Gruijl et al 2014;Hoogland et al 2015;Mukamel et al 2009;Najafi et al 2014;Ozden et al 2008Ozden et al , 2009Ozden et al , 2012Schultz et al 2009;Sullivan et al 2005;Tsutsumi et al 2015), the indicator has several drawbacks that limit its usefulness when more complex manipulations are required. OGB-1/AM is bolus loaded into the cerebellum, causing nonspecific labeling of other cell types Sullivan et al 2005).…”

“…Coherence of Ca 2ϩ activity is particularly strong in active mice (De Gruijl et al 2014;Hoogland et al 2015;Ozden et al 2012;Schultz et al 2009;Tsutsumi et al 2015). We asked whether this property also remained stable over time.…”

An optimized surgical approach for obtaining stable extracellular single-unit recordings from the cerebellum of head-fixed behaving mice

“…As an adaptation, it would be entirely feasible to instead use glass electrodes for whole-cell recordings or juxtacellular labeling (Pinault, 1996). The craniotomy opening could also serve multiple simultaneous purposes such as recording plus live imaging (Badura et al, 2014; Najafi et al, 2014) or recording plus optogenetic manipulations (Heiney et al, 2014b; Hoogland et al, 2015; Lee et al, 2015). More generally, the details that we outline for successful fixation of head plates would also apply for the successful implantation of drives that are used to collect neuronal spike data in freely moving mice.…”