The Effect of Nucleo-Olivary Stimulation on Climbing Fiber EPSPs in Purkinje Cells

Abstract

Climbing fibers, connecting the inferior olive and Purkinje cells, form the nervous system's strongest neural connection. These fibers activate after critical events like motor errors or anticipation of rewards, leading to bursts of excitatory postsynaptic potentials (EPSPs) in Purkinje cells. The number of EPSPs is a crucial variable when the brain is learning a new motor skill. Yet, we do not know what determines the number of EPSPs. Here, we measured the effect of nucleo-olivary stimulation on periorbital elicited climbing fiber responses through in-vivo intracellular Purkinje cell recordings in decerebrated ferrets. The results show that while nucleo-olivary stimulation decreased the probability of a response occurring at all, it did not reduce the number of EPSPs. The results suggest that nucleo-olivary stimulation does not influence the number of EPSPs in climbing fiber bursts.

Keywords: EPSPs; In-vivo; Purkinje cells.

Fig. 1

Experimental setup. Illustration of the experimental setup including stimulation and recording sites within the cerebellar network. A. A sharp glass pipette was inserted into the electrophysiologically identified eyeblink region of the cerebellar cortex. B. Stimulation protocol altering between periorbital stimulation and nucleo-olivary + periorbital stimulation. C. Enlarged view on the right depicts the cerebellar network including the pathways that different stimuli take within the brain as well as the central stimulation sites

Fig. 2

Raw data traces. A. Examples of climbing fiber responses with variable numbers of EPSPs. B. Stimulation example in which nucleo-olivary stimulation is followed by periorbital stimulation

Fig. 3

Different cells have different EPSP distributions. A. Mean ± SD of EPSPs in individual cells. B. Distribution of EPSPs in cells with spontaneous climbing fiber responses

Fig. 4

Number of EPSPs in climbing fiber responses. Each row shows a different cell and columns are separate climbing fiber responses, or absence of climbing fiber responses following stimulation. The color of the pixels indicates the number of EPSPs in the climbing fiber response. A. Data including instances where stimulation did not elicit a response, for example when NO stimulation suppressed the climbing fiber response or where periorbital stimulation did not elicit a response. B. The same data but with all zeroes removed

Fig. 5

Effect of nucleo-olivary stimulation on CFR EPSP distribution. A. Comparison of EPSP counts in peri-orbitally elicited climbing fiber responses with or without preceding nucleo-olivary stimulation. B. Same as A, but with all trials in which the periorbital stimulation did not elicit a response were excluded. Both figures display probability density function (PDF), and boxplots using raincloud plots package for Matlab (see [41] for details)