Reverse Effects of Conditioning Produced by Two Different Unconditioned Stimuli on Thalamocortical Transmission

El Mehdi Meftah and Lucie Rispal-Padel Centre de Recherche Cerveau et Cognition, Centre National de la Recherche Scientifique, Faculté de Médecine de Toulouse Rangueil Université Paul Sabatier, 31062 Toulouse, France Meftah, El Mehdi and Lucie Rispal-Padel. Reverse effects of conditioning produced b...

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Published in:Journal of neurophysiology 1997-04, Vol.77 (4), p.1663-1678
Main Authors: Meftah, El Mehdi, Rispal-Padel, Lucie
Format: Article
Language:English
Subjects:
Animals
Association Learning - physiology
Brain Mapping
Cats
Cerebellum - physiology
Cerebral Cortex - physiology
Conditioning, Classical - physiology
Efferent Pathways - physiology
Electric Stimulation
Female
Male
Movement - physiology
Neuronal Plasticity - physiology
Red Nucleus - physiology
Synaptic Transmission - physiology
Thalamus - physiology
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Summary:El Mehdi Meftah and Lucie Rispal-Padel Centre de Recherche Cerveau et Cognition, Centre National de la Recherche Scientifique, Faculté de Médecine de Toulouse Rangueil Université Paul Sabatier, 31062 Toulouse, France Meftah, El Mehdi and Lucie Rispal-Padel. Reverse effects of conditioning produced by two different unconditioned stimuli on thalamocortical transmission. J. Neurophysiol. 77: 1663-1678, 1997. Actions of cerebellothalamocortical (CTC) networks on the musculature can be modified by associative conditioning in adult animals. During conditioning, electrical stimulation of a CTC network involved in forearm flexion movements results in either flexion or extension responses, depending on the somatosensory information given by the unconditioned stimulus (UCS). In the present work we attempt to determine what kind of neurobiological changes induced in the CTC pathways as a consequence of distinct somesthetic messages could lead to different conditioned motor responses. Two conditioning procedures in which distinct UCSs were successively applied to awake cats in chronic preparation. The conditioned stimulus (CS) was an electrical subthreshold stimulation of an interpositus nucleus (IN) site at the origin of CTC circuits controlling forelimb flexion movements. It was first paired with a UCS applied to the skin above the wrist, also producing a forearm flexion reflex, and second with a UCS applied more proximally on the forearm, producing a backward withdrawal reflex of the forelimb. The two procedures, termed "concordant" and "discordant," respectively, were carried out in a different order on the same cats, separated by 2 mo of rest. The effects of conditioning were assessed from the characteristics of the motor reponses induced by the CS and from the properties of the CTC transmission analyzed on the cortical field potentials induced by IN stimulation. The concordant procedure resulted in persistent enhancement of the amplitude and rate of occurrence of the forearm flexions induced by the CS. Concomitantly, an increase of the di- and/or trisynaptic excitatory negative component of the field potentials induced by the CS in layers III and V of the elbow motor cortical representation was observed. In contrast, during the discordant procedure, the forearm flexions initially induced by the IN stimulation were progressively abolished in favor of forearm extensions, and, in parallel, a depression of the excitatory negative component of the cortical responses
ISSN:0022-3077
1522-1598
DOI:10.1152/jn.1997.77.4.1663