Basket cells

Overview

(adapted from: http://www.scholarpedia.org/article/Cerebellum#Neuronal_types):

Basket cells are interneurons found in the lower molecular layer which are inhibitory (GABAergic) on to Purkinje cells. Their axons run in the same direction as the dendrites of the Purkinje cells, are electrically coupled, and receive both climbing fiber collaterals as well as parallel fibers originating in the granule layer.

Their axons extend along the Purkinje cell layer at right angles to the direction of the parallel fibers. They may spread over a distance equal to 20 Purkinje cell widths and 6 deep and may contact as many as 150 Purkinje cell bodies. During its course, the horizontal segment of a basket cell axon sends off groups of collaterals that descend and embrace the Purkinje cell soma and initial segment. As many as 50 different basket cells are thought to wrap their axon terminals around each Purkinje cell soma, forming a basket-like meshwork resembling that on an old Chianti bottle (Hamori & Szentagothai, 1966). Basket cell axons also ascend to contact the Purkinje cell dendritic tree. There are about six times as many basket cells as Purkinje cells.

Basket cell arrangement in cerebellar cortex. From [LlinasRR-1975].

Stimulation and inhibition of Purkinje cells. From [LlinasRR-1975].

Quantity

In Cat:

About 6x number of Purkinje cells. For cat, this is 7.5x10^6. See note for [PalkovitsM+2-1971c].

Synapse with purkinje cells:

Divergence

In cat:

[PalkovitsM+2-1971c] states that:

“Calculations of the average number of Purkinje cell baskets in which the basket axon participates gave unexpectedly low values: 8-9 baskets per axon.”

This is a “fan-out” (divergence) of about 8-9. However, the scholarpedia article (exerpt above) states up to 150 Purkinje cell bodies may be contacted. That may be for a different species, perhaps human. Some other sources of data (referenced in [DAngeloE+11-2016], Table 1 for mouse) specify a divergence of 1:30 and convergence of 7:1.

Convergence

In cat:

50 [LoebnerEE-1989].

Gap junctions and synapses between basket cells

There are also synaptic gap junctions between molecular layer interneurons which are oriented along the sagittal plane (same direction as the basket cell axons, perpendicular to the parallel fibers). Described in note for: [RieublandS+2-2014].

Data for table Cells and connections in cat

The following table has data and references for table Cells and connections in cat. Values are either a Cell count, or FO,FI where FO is fan-out (number of target cells each source cell contacts) and FI is fan-in (number of source cells going to each target cell).

Id	Source cell	Cell count or Target cell	Value	Reference
b1	basket	Cell count	7.5x10^6	[LoebnerEE-1989] 1
b2	basket	purkinje	9, 50	[LoebnerEE-1989] 1

1(1,2)

EE Loebner. Intelligent network management and functional cerebellum synthesis. In Raugh MR, editor, Cerebellar Models of Associative Memory: Three papers from IEEE COMPCON SPRING ‘89, pages 14–19. Research Institute for Advanced Computer Science, NASA Ames Research Center, 1989. PDF: LoebnerEE-1989.pdf, Notes: LoebnerEE-1989.html.