Disruption of classical eyelid conditioning after cerebellar lesions: damage to a memory trace system or a simple performance deficit?

Abstract

Over the past 10 years, a number of laboratories have reported that classically conditioned skeletal muscle responses, such as conditioned nictitating membrane/eyelid responses, are critically dependent on activity in the cerebellum. For example, unilateral lesions of the cerebellar interpositus nucleus have been shown to prevent acquisition and abolish retention of the conditioned eyelid response on the side ipsilateral to the lesions without affecting conditioned responding (CR) on the contralateral side. Also, recording studies involving the interpositus nucleus have consistently revealed patterns of neuronal discharge that predict execution of the CR. The lesion and recording studies have generally been cited as evidence that plasticity in the cerebellum is critically involved in the learning and memory of classically conditioned responses. This interpretation was recently challenged by Welsh and Harvey (1989a), who claimed that cerebellar lesions simply produced a performance deficit and speculated that the role of the cerebellum was not in learning and memory processes associated with the CR but only in performance of the eye blink response. Presented here are three experiments that provide additional strong evidence for a critical role of the cerebellum in the learning and memory of the Pavlovian CR. These experiments include (1) demonstrations of complete and permanent CR abolition after appropriate interpositus lesions, (2) a failure to find systematic or persisting decrements in the unconditioned response amplitude (i.e., the eye blink reflex) after appropriate interpositus lesion, and (3) observations of differential effects on the CR and unconditioned response after lesions were placed in populations of motoneurons responsible for executing the eye blink response. These data are discussed in the context of performance versus learning issues; evidence presented here rules out the possibility that interpositus lesion abolition of the eye blink CR is simply due to lesion effects on performance.

Cerebellar Modulation of Trigeminal Reflex Blinks: Interpositus Neurons

“…Although some studies report that the cerebellum is essential for eyelid conditioning but plays no role in unconditioned reflex blinks (Steinmetz et al, 1992), the majority of studies support the concept that the cerebellum modulates both conditioned and reflex blinks. For example, cerebellar cortex damage increases the amplitude of unconditioned blinks (Yeo and Hardiman, 1992;Gerwig et al, 2004), whereas a cerebellar nucleus lesion or inactivation decreases their amplitude (Welsh and Harvey, 1989;Welsh, 1992;Bracha et al, 1994;Wikgren and Korhonen, 2001;Jimenez-Diaz et al, 2002, 2004.…”

Cerebellar cortical inhibition and classical eyeblink conditioning

“…Discrete lesions of the cerebellar interpositus nucleus (electrolytically, chemically, reversibly) consistently and completely prevent the acquisition and permanently and completely abolished retention͞expression of classically conditioned eyeblink responses in rabbits, rats, and mice (20)(21)(22)(23)(24)(25)(26)(27)(28). Cortical lesions affect various aspects of learning including learning rate, asymptotic learning level, learningdependent response timing, and immediate retention, but do not completely and permanently abolish learning (refs.…”

“…The general procedures for rabbit eyeblink conditioning have been described in detail (26). In brief, 1 day after a 1-h adaptation to restraint and apparatus, rabbits were given daily training of 100 trials grouped into 10 blocks.…”

Pleistocene Palaeoart of Asia

“…Palaeoart simply defines traces or objects that would in contemporary traditions be interpreted as manifestations of art, but whose real role is much more appropriately described as external storage of memory traces, as exograms. The concept of external engrams (engrams, or memory traces in the human brain, have never been demonstrated to exist; Lashley 1950; Thompson 1967Thompson , 1986Thompson , 1990; Thompson et al 1976; Steinmetz and Thompson 1991;Steinmetz et al 1987Steinmetz et al , 1992Christian and Thompson 2005) [94,[141][142][143][144][132][133][134]58] was first applied to non-figurative cave art (Bednarik 1987) [9]. Since certain forms in which they occur are readily identifiable on the archaeological record they provide the most comprehensive indices in estimating the cognitive complexity of hominins, but they can also demonstrate the inadequacies of archaeological inferences.…”