bims-climfi Biomed News
on Cerebellar cortical circuitry
Issue of 2020–05–10
two papers selected by
Jun Maruta, Mount Sinai Health System
  1. Parameter tuning differentiates granule cell subtypes enriching transmission properties at the cerebellum input stage.
  2. Synergistic excitability plasticity in cerebellar functioning.
  1. Commun Biol. 2020 May 08. 3(1): 222
    Parameter tuning differentiates granule cell subtypes enriching transmission properties at the cerebellum input stage.
    Stefano Masoli, Marialuisa Tognolina, Umberto Laforenza, Francesco Moccia, Egidio D'Angelo.
      The cerebellar granule cells (GrCs) are classically described as a homogeneous neuronal population discharging regularly without adaptation. We show that GrCs in fact generate diverse response patterns to current injection and synaptic activation, ranging from adaptation to acceleration of firing. Adaptation was predicted by parameter optimization in detailed computational models based on available knowledge on GrC ionic channels. The models also predicted that acceleration required additional mechanisms. We found that yet unrecognized TRPM4 currents specifically accounted for firing acceleration and that adapting GrCs outperformed accelerating GrCs in transmitting high-frequency mossy fiber (MF) bursts over a background discharge. This implied that GrC subtypes identified by their electroresponsiveness corresponded to specific neurotransmitter release probability values. Simulations showed that fine-tuning of pre- and post-synaptic parameters generated effective MF-GrC transmission channels, which could enrich the processing of input spike patterns and enhance spatio-temporal recoding at the cerebellar input stage.
    DOI:  https://doi.org/10.1038/s42003-020-0953-x
  2. FEBS J. 2020 May 04.
    Synergistic excitability plasticity in cerebellar functioning.
    Gen Ohtsuki, Mari Shishikura, Akitoshi Ozaki.
      The cerebellum, a universal processor for sensory acquisition and internal models, and its association with synaptic and non-synaptic plasticity have been envisioned as the biological correlates of learning, perception, and even thought. Indeed, the cerebellum is no longer considered merely as the locus of motor coordination and its learning. Here, we introduce the mechanisms underlying the induction of multiple types of plasticity in cerebellar circuit and give an overview focusing on the plasticity of non-synaptic intrinsic excitability. The discovery of long-term potentiation of synaptic responsiveness in hippocampal neurons led investigations into changes of their intrinsic excitability. This activity-dependent potentiation of neuronal excitability is distinct from that of synaptic efficacy. Systematic examination of excitability plasticity has indicated that the modulation of various types of Ca2+ - and voltage-dependent K+ -channels underlies the phenomenon, which is also triggered by immune activity. Intrinsic plasticity is expressed specifically on dendrites and modifies the integrative processing and filtering effect. In Purkinje cells, modulation of the discordance of synaptic current on soma and dendrite suggested a novel type of cellular learning mechanism. This property enables a plausible synergy between synaptic efficacy and intrinsic excitability, by amplifying electrical conductivity and influencing the polarity of bidirectional synaptic plasticity. Furthermore, the induction of intrinsic plasticity in the cerebellum correlates with motor performance and cognitive processes, through functional connections from the cerebellar nuclei to neocortex and associated regions: e.g., thalamus and midbrain. Taken together, recent advances in neuroscience have begun to shed light on the complex functioning of non-synaptic excitability and the synergy.
    Keywords:  Cerebellum; Purkinje cells; cerebellar efferent projections; cerebellar higher-order functions; dendritic excitability; intrinsic plasticity; synaptic plasticity; synergy mechanisms of multiple-plasticity
    DOI:  https://doi.org/10.1111/febs.15355
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