Fear conditioning-related changes in cerebellar Purkinje cell activities in goldfish

Yoshida Masayuki, Kondo, Kondo Hiroki

Description

Fear conditioning-induced changes in cerebellar Purkinje cell responses to a conditioned stimulus have been reported in rabbits. It has been suggested that synaptic long-term potentiation and the resulting increases in firing rates of Purkinje cells are related to the acquisition of conditioned fear in mammals. However, Purkinje cell activities during acquisition of conditioned fear have not been analysed, and changes in Purkinje cell activities throughout the development of conditioned fear have not yet been investigated. In the present study, we tracked Purkinje cell activities throughout a fear conditioning procedure and aimed to elucidate further how cerebellar circuits function during the acquisition and expression of conditioned fear. Methods Activities of single Purkinje cells in the corpus cerebelli were tracked throughout a classical fear conditioning procedure in goldfish. A delayed conditioning paradigm was used with cardiac deceleration as the conditioned response. Conditioning-related changes of Purkinje cell responses to a conditioned stimulus and unconditioned stimulus were examined. Results The majority of Purkinje cells sampled responded to the conditioned stimulus by either increasing or decreasing their firing rates before training. Although there were various types of conditioning-related changes in Purkinje cells, more than half of the cells showed suppressed activities in response to the conditioned stimulus after acquisition of conditioned fear. Purkinje cells that showed unconditioned stimulus-coupled complex-spike firings also exhibited conditioning-related suppression of simple-spike responses to the conditioned stimulus. A small number of Purkinje cells showed increased excitatory responses in the acquisition sessions. We found that the magnitudes of changes in the firing frequencies of some Purkinje cells in response to the conditioned stimulus correlated with the magnitudes of the conditioned responses on a trial-to-trial basis. Conclusions These results demonstrate that Purkinje cells in the corpus cerebelli of goldfish show fear conditioning-related changes in response to a stimulus that had been emotionally neutral prior to conditioning. Unconditioned stimulus-induced climbing fibre inputs to the Purkinje cells may be involved in mediating these plastic changes.

Sujets

• Cerebellum
• Fear conditioning
• Goldfish
• Purkinje cell

Informations

• Publié par: biomed
• Publié le: 01 janvier 2012
• Nombre de lectures: 12
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Yoshida and KondoBehavioral and Brain Functions2012,8:52 http://www.behavioralandbrainfunctions.com/content/8/1/52

R E S E A R C H

Fear conditioningrelated changes Purkinje cell activities in goldfish * Masayuki Yoshida and Hiroki Kondo

in

Open Access

cerebellar

Abstract Background:Fear conditioninginduced changes in cerebellar Purkinje cell responses to a conditioned stimulus have been reported in rabbits. It has been suggested that synaptic longterm potentiation and the resulting increases in firing rates of Purkinje cells are related to the acquisition of conditioned fear in mammals. However, Purkinje cell activities during acquisition of conditioned fear have not been analysed, and changes in Purkinje cell activities throughout the development of conditioned fear have not yet been investigated. In the present study, we tracked Purkinje cell activities throughout a fear conditioning procedure and aimed to elucidate further how cerebellar circuits function during the acquisition and expression of conditioned fear. Methods:Activities of single Purkinje cells in the corpus cerebelli were tracked throughout a classical fear conditioning procedure in goldfish. A delayed conditioning paradigm was used with cardiac deceleration as the conditioned response. Conditioningrelated changes of Purkinje cell responses to a conditioned stimulus and unconditioned stimulus were examined. Results:The majority of Purkinje cells sampled responded to the conditioned stimulus by either increasing or decreasing their firing rates before training. Although there were various types of conditioningrelated changes in Purkinje cells, more than half of the cells showed suppressed activities in response to the conditioned stimulus after acquisition of conditioned fear. Purkinje cells that showed unconditioned stimuluscoupled complexspike firings also exhibited conditioningrelated suppression of simplespike responses to the conditioned stimulus. A small number of Purkinje cells showed increased excitatory responses in the acquisition sessions. We found that the magnitudes of changes in the firing frequencies of some Purkinje cells in response to the conditioned stimulus correlated with the magnitudes of the conditioned responses on a trialtotrial basis. Conclusions:These results demonstrate that Purkinje cells in the corpus cerebelli of goldfish show fear conditioningrelated changes in response to a stimulus that had been emotionally neutral prior to conditioning. Unconditioned stimulusinduced climbing fibre inputs to the Purkinje cells may be involved in mediating these plastic changes. Keywords:Cerebellum, Fear conditioning, Goldfish, Purkinje cell

Background The cerebellum is important for classical fear conditioning in both mammals and teleost fish. Lesions of certain parts of the cerebellum severely impair changes in heart rate that are induced by conditioned fear in various vertebrate species, including rabbits, rats, and goldfish [14]. In gold fish, reversible inactivation of neural activities in the

* Correspondence: yosidam@hiroshimau.ac.jp Graduate School of Biosphere Science, Hiroshima University, Higashihiroshima 7398528, Japan

corpus cerebella, through the usage of localized cooling and local administration of anaesthetic agents, suppress the development of classically conditioned fear responses [3,5]. The cerebella in mammals and fish share both a basic histological architecture and neural circuits [611]. In addition, it is suggested that Purkinje cells (PCs) have similar synaptic plasticity mechanisms in both mammals and fish [12]. Furthermore, PCs play key roles in cerebellar functions. Thus, investigation of PC functions during clas sical fear conditioning should further the understanding of

© 2012 Yoshida and Kondo; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.