Cooperative forms of granule cell and Purkinje cell activity in the frog cerebellar cortex

1. We compared the spatial pattern of shortest latency somatosensory (tactile) projections to the Purkinje cell (PC) layer and to the underlying granule cell (GC) layer in tactile areas of rat cerebellar cortex. Micro-mapping methods were used to sample single units in the PC layer and multiple units in the GC layer of both anesthetized and unanesthetized rats. Mechanical and electrical stimulation of the body surface were employed. Responsiveness of PCs to cutaneous stimulation was assessed by constructing histograms of simple spike activity and statistically comparing poststimulus activity to nonstimulated base-line PC activity. 2. We found that PCs respond to tactile stimulation with increases (7-10 ms) followed by decreases (8-15 ms) in simple spike activity. Increases in simple spike activity followed activation of the underlying GC layer by 1-4 ms, while decreases in simple spike activity were found 2-5 ms after GC layer activation. 3. PCs were found to have both excitatory and inhibitory receptive fields (RFs). Excitatory RFs were restricted to small areas of a single body part and for each PC were very similar or identical to the RFs of neurons in the immediately subjacent GC layer. Inhibitory PC RFs were larger, often containing more than one body part and for each PC, were only partially similar to the RFs of subjacent GCs. PC inhibitory RFs also often included body surfaces projecting to the nearby but not to the underlying GC layer. 4. Stimulation of a single peripheral locus resulted in small, distinct regions of PC layer excitation and inhibition. Areas of PC excitation overlie activated regions of the GC layer, while inhibited PCs overlie both activated and nonactivated GC regions. 5. We found PCs to be organized in groups or patches with respect to the specific body region that was capable of activating them (upper lip, lower lip, etc.). Adjacent patches of PCs often represented widely separated body parts. This pattern of PC layer activating RF projections was congruent with the pattern of excitatory RF projections to the underlying GC layer. 6. These results indicate that there is a vertical organization in GC-PC excitatory relations, while GC-induced PC inhibition is slightly more widely distributed. 7. Our finding that the patchlike activation of PCs is congruent with that of the underlying GC layer contrasts with the classical concept that PCs are activated by parallel fibers in a "beamlike" fashion from a patch of GCs. Thus, a reevaluation of the role of parallel fibers seems to us to be in order. 8. In conclusion, our results support the view that short-latency afferent tactile projections to both the GC and PC layers of cerebellar cortex are highly organized spatially. This specificity of body surface projections must be incorporated into modern views of the functional organization of cerebellar cortex.

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Effect of Noradrenaline on the Facial Stimulation-Evoked Mossy Fiber-Granule Cell Synaptic Transmission in Mouse Cerebellar Cortex

Frontiers in Neuroscience ◽

10.3389/fnins.2021.785995 ◽

2021 ◽

Vol 15 ◽

Author(s):

Bing-Xue Li ◽

Hua Jin ◽

Guang-Jian Zhang ◽

Li-Na Cui ◽

Chun-Ping Chu ◽

...

Keyword(s):

Synaptic Transmission ◽

Purkinje Cell ◽

Receptor Antagonist ◽

Granule Cell ◽

Adrenergic Receptor ◽

Granular Layer ◽

Mossy Fiber ◽

Cell Activity ◽

Stimulus Offset

Noradrenaline is an important neuromodulator in the cerebellum. We previously found that noradrenaline depressed cerebellar Purkinje cell activity and climbing fiber–Purkinje cell synaptic transmission in vivo in mice. In this study, we investigated the effect of noradrenaline on the facial stimulation-evoked cerebellar cortical mossy fiber–granule cell synaptic transmission in urethane-anesthetized mice. In the presence of a γ-aminobutyrateA (GABAA) receptor antagonist, air-puff stimulation of the ipsilateral whisker pad evoked mossy fiber–granule cell synaptic transmission in the cerebellar granular layer, which expressed stimulus onset response, N1 and stimulus offset response, N2. Cerebellar surface perfusion of 25 μM noradrenaline induced decreases in the amplitude and area under the curve of N1 and N2, accompanied by an increase in the N2/N1 ratio. In the presence of a GABAA receptor blocker, noradrenaline induced a concentration-dependent decrease in the amplitude of N1, with a half-maximal inhibitory concentration of 25.45 μM. The noradrenaline-induced depression of the facial stimulation-evoked mossy fiber–granule cell synaptic transmission was reversed by additional application of an alpha-adrenergic receptor antagonist or an alpha-2 adrenergic receptor antagonist, but not by a beta-adrenergic receptor antagonist or an alpha-1 adrenergic receptor antagonist. Moreover, application of an alpha-2 adrenergic receptor agonist, UK14304, significantly decreased the synaptic response and prevented the noradrenaline-induced depression. Our results indicate that noradrenaline depresses facial stimulation-evoked mossy fiber–granule cell synaptic transmission via the alpha-2 adrenergic receptor in vivo in mice, suggesting that noradrenaline regulates sensory information integration and synaptic transmission in the cerebellar cortical granular layer.

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Neural Network Model of the Cerebellum: Temporal Discrimination and the Timing of Motor Responses

Neural Computation ◽

10.1162/neco.1994.6.1.38 ◽

1994 ◽

Vol 6 (1) ◽

pp. 38-55 ◽

Cited By ~ 167

Author(s):

Dean V. Buonomano ◽

Michael D. Mauk

Keyword(s):

Neural Network ◽

Purkinje Cell ◽

Network Model ◽

Neural Network Model ◽

Granule Cell ◽

Granule Cells ◽

Cell Activity ◽

Temporal Coding ◽

Synaptic Organization ◽

Population Vector

Substantial evidence has established that the cerebellum plays an important role in the generation of movements. An important aspect of motor output is its timing in relation to external stimuli or to other components of a movement. Previous studies suggest that the cerebellum plays a role in the timing of movements. Here we describe a neural network model based on the synaptic organization of the cerebellum that can generate timed responses in the range of tens of milliseconds to seconds. In contrast to previous models, temporal coding emerges from the dynamics of the cerebellar circuitry and depends neither on conduction delays, arrays of elements with different time constants, nor populations of elements oscillating at different frequencies. Instead, time is extracted from the instantaneous granule cell population vector. The subset of active granule cells is time-varying due to the granule—Golgi—granule cell negative feedback. We demonstrate that the population vector of simulated granule cell activity exhibits dynamic, nonperiodic trajectories in response to a periodic input. With time encoded in this manner, the output of the network at a particular interval following the onset of a stimulus can be altered selectively by changing the strength of granule → Purkinje cell connections for those granule cells that are active during the target time window. The memory of the reinforcement at that interval is subsequently expressed as a change in Purkinje cell activity that is appropriately timed with respect to stimulus onset. Thus, the present model demonstrates that a network based on cerebellar circuitry can learn appropriately timed responses by encoding time as the population vector of granule cell activity.

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