Climbing fibre induced depression of both mossy fibre responsiveness and glutamate sensitivity of cerebellar Purkinje cells

Abstract

SUMMARY1. In high decerebrate rabbits, cells were sampled extracellularly from the rostral flocculus. Purkinje cells were identified by their characteristic responses to stimulation of the contralateral inferior olive. Identification of basket cells was based on the absence of olivary responses and also on their location in the molecular layer adjacent to identified Purkinje cells. Mass field potentials in the flocculus were also studied.2. Single pulse stimulation of a vestibular nerve, either ipsilateral or contralateral, at a rate of 2/sec excited Purkinje cells with a latency of 3-6 msec. This early excitation represents activation through vestibular mossy fibres, granule cells and their axons (parallel fibres). Similar early excitation also occurred in putative basket cells.3. Conjunctive stimulation of a vestibular nerve at 20/sec and the inferior olive at 4/sec, for 25 sec per trial, effectively depressed the early excitation of Purkinje cells by that nerve, without an associated change in spontaneous discharge. The depression recovered in about ten minutes. This recovery was followed by the onset of a slow depression lasting for an hour.4. Conjunctive vestibular-olivary stimulation produced no such depression in the following responses: early excitation in Purkinje cells induced from the vestibular nerve not involved in the conjunctive stimulation; early excitation in putative basket cells from either vestibular nerve; inhibition or rebound facilitation in Purkinje cells following the early excitation; vestibular-evoked field potentials in the granular layer and white matter of the flocculus. These observations lead to the conclusion that the depression occurs specifically at parallel fibre-Purkinje cell synapses involved in conjunctive stimulation.5. Ionophoretic application of glutamate to Purkinje cells in conjunction with 4/sec olivary stimulation depressed the glutamate sensitivity of Purkinje cells; aspartate sensitivity was depressed to a much lesser degree. The depression diminished in about 10 min, but this recovery was succeeded by a slow depression lasting

Pairing-specific, activity-dependent presynaptic facilitation at Aplysia sensory-motor neuron synapses in isolated cell culture

“…These types of plasticity seem excellent candidates for cellular mechanisms underlying selective synapse stabilization (Collingridge and Singer, 1990;Cline, 199 I) and associative learning (Byrne, 1987;Abrams and Kandel, 1988;Hawkins et al, 1993). A number of associative forms of synaptic plasticity have been described, all of which require neuronal activity as at least one of the associative cellular stimuli, including activitydependent enhancement of presynaptic facilitation and inhibition (Small et al, 1989) long-term potentiation (Levy and Steward, 1979;Barrionuevo and Brown, 1983;Walters and Byrne, 1985), and longterm depression (Ito et al, 1982;Stanton and Sejnowski, 1989).…”

Long-term depression of climbing fiber-evoked calcium transients in Purkinje cell dendrites

“…PF LTD can be induced by simultaneous PF and CF activation at low frequencies (18). In these models, the CF is considered invariant and provides a ''teacher signal'' that is activated when a need for adaptive learning emerges.…”

Neurometaplasticity: Glucoallostasis control of plasticity of the neural networks of error commission, detection, and correction modulates neuroplasticity to influence task precision

“…First reported in the 1970s by the physiologists Tim Bliss, Terje Lømo, and AR Gardner-Medwin [7,8], LTP is an activity dependent persistent strengthening of neurosynaptic transmission on the basis of the patterns of activity that produce a long-lasting increase in signal transmission between brain cells [9]. LTD, the opposite of LTP, was discovered around the 80s of the last century by a group of scientists [10][11][12]. LTD produces a long-lasting decrease in synaptic strength [9].…”