Spatial pattern coding of sensory information by climbing-fiber evoked calcium signals in networks of neighboring cerebellar Purkinje cells Abbreviated Title: Spatial pattern coding in cerebellar microzones
نویسندگان
چکیده
Climbing fiber input produces complex spike synchrony across populations of cerebellar Purkinje cells oriented in the parasagittal axis. Elucidating the fine spatial structure of this synchrony is crucial for understanding its role in the encoding and processing of sensory information within the olivocerebellar cortical circuit. We investigated these issues using in vivo multineuron two-photon calcium imaging in combination with information theoretic analysis. Spontaneous dendritic calcium transients linked to climbing fiber input were observed in multiple neighboring Purkinje cells. Spontaneous synchrony of calcium transients between individual Purkinje cells falls off over approximately 200 microns mediolaterally, consistent with the presence of cerebellar microzones organized by climbing fiber input. Synchrony was increased following administration of harmaline, consistent with an olivary origin. Periodic sensory stimulation also resulted in a transient increase of synchrony following stimulus onset. To examine how synchrony affects the neural population code provided by the spatial pattern of complex spikes, we analyzed its information content. We found that spatial patterns of calcium events from small ensembles of cells provided substantially more stimulus information (59% more for 7-cell ensembles) than available by counting events across the pool without taking into account spatial origin. Information theoretic analysis indicated that, rather than contributing significantly to sensory coding via stimulus-dependence, correlational effects on sensory coding are dominated by redundancy due to the prevalent spontaneous synchrony. The olivocerebellar circuit thus uses a labelled line code to report sensory signals, leaving open a role for synchrony in flexible selection of signals for output to deep cerebellar nuclei.
منابع مشابه
Reliable coding emerges from coactivation of climbing fibers in microbands of cerebellar Purkinje neurons.
The inferior olive projects climbing fiber axons to cerebellar Purkinje neurons, where they trigger calcium-based dendritic spikes. These responses dynamically shape the immediate spike output of Purkinje cells as well as provide an instructive signal to guide long-term plasticity. Climbing fibers typically fire approximately once a second, and the instructive role is distributed over many such...
متن کاملCoding of stimulus strength via analog calcium signals in Purkinje cell dendrites of awake mice
The climbing fiber input to Purkinje cells acts as a teaching signal by triggering a massive influx of dendritic calcium that marks the occurrence of instructive stimuli during cerebellar learning. Here, we challenge the view that these calcium spikes are all-or-none and only signal whether the instructive stimulus has occurred, without providing parametric information about its features. We im...
متن کاملDendritic calcium signaling triggered by spontaneous and sensory-evoked climbing fiber input to cerebellar Purkinje cells in vivo.
Cerebellar Purkinje cells have one of the most elaborate dendritic trees in the mammalian CNS, receiving excitatory synaptic input from a single climbing fiber (CF) and from ∼200,000 parallel fibers. The dendritic Ca(2+) signals triggered by activation of these inputs are crucial for the induction of synaptic plasticity at both of these synaptic connections. We have investigated Ca(2+) signalin...
متن کاملStructural basis of cerebellar microcircuits in the rat.
The topography of the cerebellar cortex is described by at least three different maps, with the basic units of each map termed "microzones," "patches," and "bands." These are defined, respectively, by different patterns of climbing fiber input, mossy fiber input, and Purkinje cell (PC) phenotype. Based on embryological development, the "one-map" hypothesis proposes that the basic units of each ...
متن کاملTrial-By-Trial Coding Of Instructive Signals In The Cerebellum: Insights From Eyeblink Conditioning In Mice
The cerebellum is an area of the brain that plays a crucial role in the learning of motor skills. This process involves climbing fibers, which provide teaching signals to Purkinje cells in the cerebellar cortex when perturbations occur during a movement. However, controversy has arisen over climbing fibers contribution to cerebellar learning. This is because climbing-fiber signals are described...
متن کامل