Mecanismos neuronales del aprendizaje en los peces teleósteos

Abstract

The paper is a review of the literature specialized in identifying brain areas and neurochemical functions that underlie different learning phenomena in teleost fish. The neuroethological approach, a description of the fish brain anatomy, ontogeny and phylogeny, the evolutionary discussion of the relationships between fish and mammals, and the cumulative evidence that suggests homologies in neurobehavioral functions between fish and mammals are introduced. Two predominant approaches for studying the neurobiology of learning in fish were identified, namely brain lesions and chemical stimulation. Regarding the effect of specific brain lesions,telencephalic ablationsonly affectedhabituationlearning (sensitization and classic conditioning were not impaired). Conversely, cerebellum lesions caused impairments in classical conditioning of eye-retraction and spatial learning (similar effects in mammals suggest that the functions of the cerebellum may have evolved early in vertebrate history). Regarding emotional learning, it is argued that research on avoidance and escape learning has been narrowly oriented and that new possibilities may derive from Hineline’s (1977) parametric analysis. Medium Pallium (MP) areas were identified as critical for emotional learning in fish. Furthermore, neurobehavioral functions of MP seem to be similar to the functions of the amygdala in mammals. Concerning neurochemical processes, antagonists of the NMDA receptors affected in a dose-dependent manner the acquisition of avoidance and fear conditioning. Alternatively, Nitric Oxide (NO) and cyclic Guanosine Monophosphate (cGMP) seem to be involved in the consolidation processof emotional learning