The cerebellar cortex contains approx. 50(maybe 100) billion grain cells; All with their cell bodies gathered in the deepest layer of bark: the grain cell layer. The barley cells belong to the group of cerebellar cortex nerve cell types

The grain cells are excitatory neurons and have glutamate as a transmitter substance.

The cell body of the grain cell is globular, with a diameter of 5-10 micrometers, μm, and emits 3-5 very short dendrites (10-30 micrometers in length) as well as an axon.

At the end of each grain cell dendrite is a claw-like accumulation of short thin protrusions with postsynaptic membrane sections. Here, the grain cells are contacted by the moss filament end (excitatory) and Golgi cell end end (inhibitory) giving rise to the intricate, astrocyte-encapsulated, synaptic areas called "cerebellar glomeruli". Each grain cell is contacted by 5-10 different moss filaments as well as by several Golgi cells.

The grain cell axon runs more or less straight up through the grain cell and Purkinje cell layers and out into the molecular layer. Here, at different distances from the surface, the axon divides T-shaped and forms a 5-10 mm long, 0.5-2 μm thick, so-called parallel wire. The parallel wires run transversely in the frontal plane, perpendicular to the longitudinal axis of the brain, piercing the flattened dendrite trees of the Purkinje cells. A parallel wire contacts with excitatory dendritic tagsynapses 2000-4000, successively lined up, Purkinje cells. A Purkinje cell, in turn, is contacted by approx. 300,000 (three hundred thousand) different grain cells!
The parallel wires also pass through and excite the dendrite trees of the basket, star and Golgi cells.

Under certain conditions, the signalling in a parallel thread leads to a residual strengthening of the synaptic contact in one or more of the dendritic tags of the Purkinje cells contacted. The synapse exhibits the phenomenon of LTP (Long Term Potentiation). The LTP effect lingers for anywhere from a few hours up to several days. LTP thus gives rise to a kind of memory fragment; the memory that this particular dendrite thorn synapse under special circumstances has an increased sensitivity to the influence of paralells.