bims-climfi 2021-04-18 papers

Issue of 2021–04–18
two papers selected by
Jun Maruta, Mount Sinai Health System

Nat Commun. 2021 04 12. 12(1): 2153

Autonomous Purkinje cell activation instructs bidirectional motor learning through evoked dendritic calcium signaling.

Audrey Bonnan, Matthew M J Rowan, Christopher A Baker, M McLean Bolton, Jason M Christie.

The signals in cerebellar Purkinje cells sufficient to instruct motor learning have not been systematically determined. Therefore, we applied optogenetics in mice to autonomously excite Purkinje cells and measured the effect of this activity on plasticity induction and adaptive behavior. Ex vivo, excitation of channelrhodopsin-2-expressing Purkinje cells elicits dendritic Ca2+ transients with high-intensity stimuli initiating dendritic spiking that additionally contributes to the Ca2+ response. Channelrhodopsin-2-evoked Ca2+ transients potentiate co-active parallel fiber synapses; depression occurs when Ca2+ responses were enhanced by dendritic spiking. In vivo, optogenetic Purkinje cell activation drives an adaptive decrease in vestibulo-ocular reflex gain when vestibular stimuli are paired with relatively small-magnitude Purkinje cell Ca2+ responses. In contrast, pairing with large-magnitude Ca2+ responses increases vestibulo-ocular reflex gain. Optogenetically induced plasticity and motor adaptation are dependent on endocannabinoid signaling, indicating engagement of this pathway downstream of Purkinje cell Ca2+ elevation. Our results establish a causal relationship among Purkinje cell Ca2+ signal size, opposite-polarity plasticity induction, and bidirectional motor learning.

DOI: https://doi.org/10.1038/s41467-021-22405-8

Neuron. 2021 Apr 09. pii: S0896-6273(21)00197-5. [Epub ahead of print]

Multidimensional population activity in an electrically coupled inhibitory circuit in the cerebellar cortex.

Harsha Gurnani, R Angus Silver.

Inhibitory neurons orchestrate the activity of excitatory neurons and play key roles in circuit function. Although individual interneurons have been studied extensively, little is known about their properties at the population level. Using random-access 3D two-photon microscopy, we imaged local populations of cerebellar Golgi cells (GoCs), which deliver inhibition to granule cells. We show that population activity is organized into multiple modes during spontaneous behaviors. A slow, network-wide common modulation of GoC activity correlates with the level of whisking and locomotion, while faster (<1 s) differential population activity, arising from spatially mixed heterogeneous GoC responses, encodes more precise information. A biologically detailed GoC circuit model reproduced the common population mode and the dimensionality observed experimentally, but these properties disappeared when electrical coupling was removed. Our results establish that local GoC circuits exhibit multidimensional activity patterns that could be used for inhibition-mediated adaptive gain control and spatiotemporal patterning of downstream granule cells.

Keywords: Golgi cells; cerebellar cortex; dimensionality; electrical coupling; gain control; gap junctions; inhibition; inhibitory interneurons; population codes

DOI: https://doi.org/10.1016/j.neuron.2021.03.027