![]() ![]() The organisation of the cerebellar cortex is relatively simple and is comprised of a densely packed input layer, the granule cell layer (GCL), which provides excitatory drive via parallel fibres (PFs) to Purkinje cell (PC) dendrites and molecular layer interneurons (MLIs). However, the precise role(s) performed by this structure during voluntary whisking is poorly understood and the implications for cerebellar function remain unclear. The cerebellum is strongly implicated in sensorimotor processing 11, and recent studies in the vibrissae regions of the rodent cerebellum have highlighted its functional role in the control of voluntary whisker movement 8 and in sensorimotor learning tasks 12. This behaviour has served as a well-defined paradigm to study active sensory processing and has yielded many insights into the neuronal circuit basis of sensorimotor control 3, 4, 5, 6, 7, 8, 9, 10. Such active whisking enables animals to explore, identify and discriminate objects with impressive degrees of sensitivity and capability 2. For tactile sensation, rodents rhythmically sweep their whiskers back and forth to scan the proximal surrounding. Self-motion has sensory consequences that enable the nervous system to guide and adjust future movement, with sensorimotor brain circuits constantly engaged to optimise this process 1. The exquisite sensitivity of neurons at each processing stage enables faithful propagation of kinematic representations through the cerebellum.Īnimals actively probe and interact with the world by moving to acquire sensory information. Together, GC populations provide downstream PCs with linear representations of volitional movement, while inhibitory networks invert these signals. Molecular layer interneurons exhibit bidirectional firing rate changes during whisking, similar to PCs. Although individual GCs are narrowly tuned, GC populations provide linear excitatory drive across a wide range of movement. Patch clamp recordings in GCs reveal that movement is accompanied by changes in mossy fibre input rate that drive membrane potential depolarisation and high-frequency bursting activity at preferred whisker angles. Here we examine the role of upstream inputs to PCs-excitatory granule cells (GCs) and inhibitory molecular layer interneurons-in processing of whisking signals. Psychological Science, 1(1), 46-54.Purkinje cells (PCs) in Crus 1 represent whisker movement via linear changes in firing rate, but the circuit mechanisms underlying this coding scheme are unknown. Serial vs parallel processing: Sometimes they look like Tweedledum and Tweedledee but they can (and should) be distinguished. Note on identifiability of parallel and serial processes. Memory-scanning: Mental processes revealed by reaction-time experiments. The Sciences Of The Artificial, First Edition. Townsend (1990) has gone on to argue that newer approaches are capable of distinguishing parallel from serial processing. ![]() However, it was later argued that parallel processing could generate latency curves with positive slopes, provided that parallel processing slowed down as more items were added (Townsend, 1971). ![]() For instance, in memory scanning experiments a latency curve that linearly increased with an increase in the number of items in memory would reveal parallel processing (Sternberg, 1969). In the early chronometric studies of cognitive processing, it was believed that reaction time data could be used to discover the existence of serial processing. 20) notes of computers - which are the information processors that inspired classical cognitive science - that they have "exceedingly limited capacity for simultaneous, parallel activity - they are basically one-thing-at-a-time systems." For instance, in a production system (Newell & Simon, 1972), only one production can manipulate symbols in working memory at any given time. Serial processing is characteristic of classical models in cognitive science, in which only a single rule can be executed at any one time, and a key issue to decide is which rule to execute - the problem of what to do next (Dawson, 1998). Serial processing is a kind of information processing in which only one activity can be carried out at a time. ![]()
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