Two types of granular cells in the cerebellar cortex

We recorded the activity of two types of granular cells in the rostral folia of the paramedial lobe (the projection region of the front legs) of the cerebellar cortex in cats immobilized by administration of ditiline; these cells differed in their receptive fields, the characteristics of their reaction to single stimulation of somatic nerves, and the character of their background activity. The granular cells of the first type were excited only when the nerves of the front legs were stimulated (reacting with 1–3 impulses with a latent period of 8–20 msec) and were inhibited between 20–50 and 70–180 msec after stimulation of the nerves of any leg. The cells of the second type responded with volleys of 3–6 impulses with a latent period of 20–40 msec to stimulation of the nerves of all four legs. Comparison of the reactions of the granular cells and other neurons of the cerebellar cortex showed that the cells of the first type cause excitation of the Purkinje and Golgi cells and the neurons of the molecular layer. The granular cells of the second type have an excitatory effect on the Golgi cells. The differences in the reactions of the two types of granular cells result from the fact that they are selectively innervated by the mossy fibers of different afferent pathways. Comparison with the data in the literature enables us to surmise that the fibers of the cuneocerebellar tract terminate at granular cells of the first type, while the reticular fibers terminate at cells of the second type.Institute of Problems of Information Transmission, Academy of Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 1, No. 2, pp. 167–176, September–October, 1969.     

Ectopic Purkinje cells in the cerebellar white matter of normal adult rodents: a Golgi study

In Golgi/Río-Hortega preparations of rat and rabbit cerebellar vermis we have occasionally found isolated ectopic Purkinje cells in the white matter. They were located beneath the bases of the folia and their dendritic branches extended within the confines of the white matter without penetrating into the overlying cortical layers. The general morphology of these ectopic cells was variable, particularly in the extension and shape of the dendritic trees, but all of them exhibited a lower density of dendritic branches than normal Purkinje cells. The less-developed ectopic neurons had multipolar dendritic trees with nonplanar branches irregularly studded with spines. The well-developed ones displayed a more extensive arborization of their processes and they usually preserved some morphological features of normal cortical Purkinje cells: distal dendritic branches studded with numerous spines, a pear-shaped soma, clearly defined morphological polarity and a tendency to display planar arrangement of the dendritic arbors. In semithin sections these neurons also showed cytological features of normal Purkinje cells, such as the Nissl substance forming a nuclear cap oriented toward the dendritic pole. We suggest that the abnormal location of the neurons results from a disorder of Purkinje cell migration which occurs naturally during the prenatal development of the cerebellum. The possible morphogenetic mechanisms involved in the migration and differentiation of these ectopic neurons are also discussed.     

Pattern formation in the cerebellar cortex.

The cerebellar cortex is subdivided rostrocaudally and mediolaterally into a reproducible array of zones and stripes. This makes the cerebellum a valuable model for studying pattern formation in the vertebrate central nervous system. The structure of the adult mouse cerebellar cortex and the series of embryological events that generate the topography are reviewed.     

Neurotrophic effects of PACAP in the cerebellar cortex

In the rodent cerebellum, PACAP is expressed by Purkinje neurons and PAC1 receptors are present on granule cells during both the development period and in adulthood. Treatment of granule neurons with PACAP inhibits proliferation, slows migration, promotes survival and induces differentiation. PACAP also protects cerebellar granule cells against the deleterious effects of neurotoxic agents. Most of the neurotrophic effects of PACAP are mediated through the cAMP/PKA signaling pathway and often involve the ERK MAPkinase. Caspase-3 is one of the key enzymes implicated in the neuroprotective action of PACAP but PACAP also inhibits caspase-9 activity and increases Bcl-2 expression. PACAP and functional PAC1 receptors are expressed in the monkey and human cerebellar cortex with a pattern of expression very similar to that described in rodents, suggesting that PACAP could also exert neurodevelopmental and neuroprotective functions in the cerebellum of primates including human.     

Chromatin matrix activity in Purkinje cells and granular cells of the rat cerebellar cortex during postnatal differentiation

Moore's method used for the examination of chromatin template activity in Purkinje and granule cells of 7, 14, 30 days and 3 months old rate cerebellar cortex has shown the age-dependent changes during differentiation period. The histograms for Purkinje cells have demonstrated that all neurons were distributed into 3 groups of activity according to their nuclear labelling. The cell percentage in each group varied during ontogenesis.     

The myelination of the cerebellar cortex in the cat

Summary The myelination of the cerebellar cortex of the cat was investigated in 61 cats aged from 3 hrs post partum to two and a half years. The first myelinated fibers appear at the time of birth in the central medullary ray. Before the onset of myelination, all fibers reach a critical diameter of about 1 m. About the 14th day of life the number of oligodendrocytes in the prospective white matter increases markedly. Thereafter, the oligodendrocytes invade the inner granular layer. It therefore seems that the myelination of the cerebellar cortex proceeds from the central medullary ray towards the granular layer. At the 60th day of postnatal life, most of the afferent and efferent fiber systems are myelinated. These findings are discussed in relation to the development of function and the maturation of the electrical activity of the cerebellar circuit.Dedicated to Prof. Dr. H. Leonhardt in honour of his 60th birthdaySupported by the Deutsche Forschungsgemeinschaft (La 184/3)     

High-frequency network oscillations in cerebellar cortex

Both cerebellum and neocortex receive input from the somatosensory system. Interaction between these regions has been proposed to underpin the correct selection and execution of motor commands, but it is not clear how such interactions occur. In neocortex, inputs give rise to population rhythms, providing a spatiotemporal coding strategy for inputs and consequent outputs. Here, we show that similar patterns of rhythm generation occur in cerebellum during nicotinic receptor subtype activation. Both gamma oscillations (30-80 Hz) and very fast oscillations (VFOs, 80-160 Hz) were generated by intrinsic cerebellar cortical circuitry in the absence of functional glutamatergic connections. As in neocortex, gamma rhythms were dependent on GABA(A) receptor-mediated inhibition, whereas VFOs required only nonsynaptically connected intercellular networks. The ability of cerebellar cortex to generate population rhythms within the same frequency bands as neocortex suggests that they act as a common spatiotemporal code within which corticocerebellar dialog may occur.