Multiple Purkinje Cell Recording in Rodent Cerebellar Cortex

The spatial and temporal organization of climbing fibre activation of Purkinje cells, the so‐called complex spikes, were studied in the rat cerebellar Crus II folium utilizing a multiple microeletrode recording technique. As many as 32 Purkinje cells could be simultaneously recorded by using a custom‐built electronic amplifier system and a special data storage device. Analysis of the auto‐correlation activity of complex spikes in any given group of Purkinje cells indicated that activation occurs with a particular rhythmicity having a base firing of 10 Hz. Cross‐correlation of spontaneous complex spikes demonstrated, in addition to a particular rhythmicity, an extraordinarily high degree of synchronicity within a particular spatial distribution of Purkinje cells. Thus, Purkinje cells organized in rostra‐caudal rows tend to fire within 1 ms of each other for distances as far as 800 μm (the width of a folium) from the ‘master’ neuron. By contrast, Purkinje cells located medial or lateral to the master neuron showed almost no cross‐correlation. Administration of harmaline to the animal increased the degree of auto‐ and cross‐correlation but did not change the spatial order of the distribution of the cross‐correlation. The results indicate that the olivo‐cerebellar system is organized in such a way that climbing fibre afferents may be activated in a close‐to‐synchronous and rhythmic fashion. The spatial distribution of these afferents over the cortex is such as to activate rostro‐caudal bands of Purkinje cells which tend to fire in a close‐to‐synchronous manner.