******** Purkinje ******** Overview ======== Adapted from: https://en.wikipedia.org/wiki/Purkinje_cell: Purkinje cells are some of the largest neurons in the human brain with an intricately elaborate dendritic arbor, characterized by a large number of dendritic spines. Purkinje cells are found within the Purkinje layer in the cerebellum. Purkinje cells are aligned like dominos stacked one in front of the other. Their large dendritic arbors form nearly two-dimensional layers through which parallel fibers from the deeper-layers pass. These parallel fibers make relatively weaker excitatory (glutamatergic) synapses to spines in the Purkinje cell dendrite, whereas climbing fibers originating from the inferior olivary nucleus in the medulla provide very powerful excitatory input to the proximal dendrites and cell soma. Parallel fibers pass orthogonally through the Purkinje neuron's dendritic arbor, with up to 200,000 parallel fibers forming a Granule-cell-Purkinje-cell synapse with a single Purkinje cell. Each Purkinje cell receives approximately 500 climbing fiber synapses, all originating from a single climbing fiber. Both basket and stellate cells (found in the cerebellar molecular layer) provide inhibitory (GABAergic) input to the Purkinje cell, with basket cells synapsing on the Purkinje cell axon initial segment and stellate cells onto the dendrites. Purkinje cells send inhibitory projections to the deep cerebellar nuclei, and constitute the sole output of all motor coordination in the cerebellar cortex. See :ref:`microcircuit` for a diagram of Purkinje cells. Quantity ======== Cat: The total number of Purkinje ceils was 1.2-1.3 million. :cite:`PalkovitsM+2-1971a`. The granule cell : Purkinje cell ratio was 1700-1800. :cite:`PalkovitsM+2-1971b` p. 29. Human: 15 million (total number both hemispheres) :cite:`TomaschJ-1968`. See Table 2 in note for :cite:`LangeW-1975` for granule cell : Purkinje cell ratio for different species. Connection to Golgi Cells ========================= Divergence ---------- Unknown :cite:`LoebnerEE-1989` Convergence ----------- Unknown :cite:`LoebnerEE-1989` Connection to Basket Cells ========================== Divergence ---------- Unknown :cite:`LoebnerEE-1989` Convergence ----------- Unknown :cite:`LoebnerEE-1989` Connection to Purkinje Cells ============================ Purkinje cells have inhibitory synaptic connections to other Purkinje cells through axon collaterals :cite:`WitterL+4-2016`. Structure --------- In mice: Collaterals were confined to a narrow sagittal plane but extended hundreds of micrometers within that plane. :cite:`WitterL+4-2016` Divergence and convergence -------------------------- In mice: 5 to 10 :cite:`WitterL+4-2016` Connection to Granule cells =========================== :cite:`GuoC+5-2016` shows that Purkinje cells directly inhibit granule cells. "... non-canonical feedback is region specific: it is most prominent in lobules that regulate eye movement and process vestibular information" Divergence and convergence -------------------------- Unknown Connection to DCN ================= Divergence ---------- In cat: 35 "one Purkinje axon may reach potentially 35 nuclear cells." :cite:`PalkovitsM+3-1977`. Also, :cite:`PalkovitsM+3-1977` Fig 2 (probably from the same source). Convergence ----------- In cat: Around 860 "the probable convergence of Purkinje axons upon nuclear cells can be deduced as being numerically somewhere around 860" :cite:`PalkovitsM+3-1977`. 700 :cite:`LoebnerEE-1989` Fig 2. .. comment: Connections: Vestibular Nuclei: Interpositus Nuclei: Fastigial Nuclei: | Lateral Nuclei: | FO,FI: 35,7x10^2 .. tbldata:: table_loebner_fig2a :id_prefix: p Source cell| Target cell | Value | Reference purkinje | Cell count | 1.3x10^6 | LoebnerEE-1989 purkinje | granule | ?,? | GuoC+5-2016 purkinje | dcn | 35,860 | PalkovitsM+3-1977 purkinje | dcn | 35,700 | LoebnerEE-1989 .. footbibliography::