Parallel fibre stimulation and the responses induced thereby in the Purkinje cells of the cerebellum

Linking Synaptic Plasticity and Spike Output at Excitatory and Inhibitory Synapses onto Cerebellar Purkinje Cells

“…Purkinje cells in vivo typically respond to brief sensory stimuli with sharp increases of spike probability followed by a more prolonged inhibition of firing (Bower and Woolston, 1983;Ebner et al, 1983;Holtzman et al, 2006). This is consistent with a feedforward excitation-inhibition sequence, as observed during direct stimulation of parallel fiber input in vivo (Eccles et al, 1966) and in vitro (Brunel et al, 2004;Mittmann et al, 2005). However, apparently pure excitatory or inhibitory responses can also sometimes be observed (Bower and Woolston, 1983;Ebner et al, 1983;Holtzman et al, 2006).…”

“…Purkinje cells are ideally suited to read out the strength of inhibitory synapses even in the absence of excitation, because they are spontaneously active (Häusser and Clark, 1997;Bean, 1997, 1999) and because inhibitory inputs have a powerful influence on Purkinje cell spiking (Midtgaard, 1992;Häusser and Clark, 1997). Moreover, PFs activate a feedforward inhibitory microcircuit, generating a precise, stereotyped excitatory-inhibitory temporal sequence (Eccles et al, 1966;Brunel et al, 2004;Mittmann et al, 2005), such that the strength of synaptic inhibition can control the timing and number of spikes activated by PFs (Mittmann et al, 2005). Thus, the efficacy of parallel fiber input depends on the "context" of inhibition provided by the feedforward inhibitory microcircuit.…”

Topography and Response Timing of Intact Cerebellum Stained With Absorbance Voltage-Sensitive Dye

“…Cb inhibitory fields were initially described electrophysiologically as two bands lateral to the excitatory parallel fiber beam (Eccles et al 1966b), which are believed to limit the natural spread of those beams (Santamaria et al 2007) and play a role in sharpening the response timing of PC responses (Mittmann et al 2005). Optical recordings of transverse inhibitory bands indicate two distinct circuits in vitro (Cohen and Yarom 2000a), whereas in vivo recordings resulted in sagittal bands (Gao et al 2006).…”

“…It has three layers overlying white matter whose sole output neurons, Purkinje cells (PCs), are excited by the ascending axons of the granule cells (Cohen and Yarom 1998;Huang et al 2006;Isope and Barbour 2002;Tolbert et al 2004), parallel fibers (Eccles et al 1966b), and climbing fibers (Eccles et al 1966a), which carry signals from the contralateral inferior olive (IO) (Dow 1942). Recent hypotheses have focused on Cb's role in behavioral timing (Kistler et al 2000;Kitazawa and Wolpert 2005;Xu et al 2006;Yarom and Cohen 2002), although controversy surrounds reports that olivocerebellar responses (Sugihara et al 1993) are synchronous (see Aggelopulos et al 1995;Baker and Edgley 2006a,b and the responses of Lang et al 2006).…”

Peripheral stimuli excite coronal beams of Golgi cells in rat cerebellar cortex

“…Reported values vary from 0.2 m/s at 28 ‡C (Cohen and Yarom, 1998) and at 32 ‡C in vitro (Vranesic et al, 1994), to 0.3^0.4 m/s in vivo (Eccles et al, 1966;Garwicz and Andersson, 1992), and even 0.3^0.7 m/s in experiments where the temperature of the agar over the exposed cerebellar surface was maintained at 35^37 ‡C (Merrill et al, 1978). These values can be partly reconciled by taking into account the temperature dependence of the speed of spike propagation.…”