Properties of Somatosensory Synaptic Integration in Cerebellar Granule Cells In Vivo

By Henrik Jörntell, Carl-Fredrik Ekerot. 2006

290 citations recorded by the source corpus.

In decerebrated, nonanesthetized cats, we made intracellular whole-cell recordings and extracellular cell-attached recordings from granule cells in the cerebellar C3 zone. Spontaneous EPSPs had large, relatively constant peak amplitudes, whereas IPSPs were small and did not appear to contribute substantially to synaptic integration at a short time scale. In many cases, the EPSPs of individual mossy fiber synapses appeared to be separable by their peak amplitudes. A substantial proportion of our granule cells had small receptive fields on the forelimb skin. Skin stimulation evoked explosive responses in which the constituent EPSPs were analyzed. In the rising phase of the response, our analyses indicated a participation of three to four different mossy fiber synapses, corresponding to the total number of mossy fiber afferents. The cutaneous receptive fields of the driven EPSPs overlapped, indicating an absence of convergence of mossy fibers activated from different receptive fields. Also in granule cells activated by joint movements did we find indications that different afferents were driven by the same type of input. Regardless of input type, the temporal patterns of granule cell spike activity, both spontaneous and evoked, appeared to primarily follow the activity in the presynaptic mossy fibers, although much of the nonsynchronized mossy fiber input was filtered out. In contrast to the prevailing theories of granule cell function, our results suggest a function of granule cells as signal-to-noise enhancing threshold elements, rather than as sparse coding pattern discriminators or temporal pattern generators.

Subfields: Cognitive Neuroscience, Neurology, Sensory Systems

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Citations in the corpus

Re-evaluating circuit mechanisms underlying pattern separation (2019, positive): “But this concept has been challenged based on the temporally dense activity of single granule cells recorded in vivo (Chadderton et al., 2004; Jörntell and Ekerot, 2006; Spanne and Jörntell, 2015; Chen et al., 2017).”
Widespread State-Dependent Shifts in Cerebellar Activity in Locomoting Mice (2012, result): “Theoretical analysis of anatomy has predicted a sparse code in which a small fraction of cells are active at any one time [62,63], consistent with later intracellular recording studies in anesthetized rats [5] and awake fish [64] (though not decerebrated cats [65]).”
Optimal degrees of synaptic connectivity (2017, unknown): “Some studies have suggested that granule-cell input is more homogeneous (Jörntell and Ekerot, 2006; Bengtsson and Jörntell, 2009) and that granule cells function as noise filters (Ekerot and Jörntell, 2008) or improve generalization (Spanne and Jörntell, 2015).”
High Frequency Burst Firing of Granule Cells Ensures Transmission at the Parallel Fiber to Purkinje Cell Synapse at the Cost of Temporal Coding (2013, background): “So far, in the scientific literature no evidence has been shown that these high-frequency bursts also exist in awake, behaving animals.”
Sensory transmission in cerebellar granule cells relies on similarly coded mossy fiber inputs (2009, background): “Although the primary afferents of both submodalities are excellent tactile event detectors, coded with bursts in the mossy fibers (7, 18), they also function as proprioceptors, and then as rate-coding estimators operating at lower firing frequencies (22, 23).”
NMDA receptors with incomplete Mg2+ block enable low-frequency transmission through the cerebellar cortex (2012, background): “The slow kinetics of these currents are well matched to the relatively slow time scale of vestibular (Arenz et al., 2008; Barmack and Yakhnitsa, 2008), joint position (van Kan et al., 1993) and proprioceptive signaling (Jörntell and Ekerot, 2006; Sawtell, 2010).”
Morphological Constraints on Cerebellar Granule Cell Combinatorial Diversity (2017, background): “We established a proxy for neuronal activity where GrCs were considered active when three of their four MFRs were synchronously active (Jörntell and Ekerot, 2006; Billings et al., 2014).”
Control of cerebellar granule cell output by sensory-evoked Golgi cell inhibition (2015, background): “Moreover, the prevalence of slow, spillovermediated IPSCs in granule cells suggests that indirect spillover activation of GABAA receptors is a major form of Golgi-cell signaling during sensory stimulation (21, 37, 48, 49).”
Synaptic Integration in Cerebellar Granule Cells (2008, methodology): “In a recent study with whole cell recordings in the C3 zone in decerebrate, unanesthetized cats, we investigated the mossy fiber input to single granule cells [6].”
Synaptic and cellular properties of the feed-forward inhibitory circuit within the input layer of the cerebellar cortex (2008, background): “Curiously, fast stimulus-locked inhibition of GrCs has rarely been observed in vivo (Chadderton et al., 2004; Jörntell and Ekerot, 2006).”