Effects of excitotoxic lesions of the basolateral amygdala on conditional discrimination learning with primary and conditioned reinforcement

• Published in: Behavioural brain research Vol. 100; no. 1; pp. 123 - 133
• Main Authors: Burns, L.H, Everitt, B.J, Robbins, T.W
• Format: Journal Article
• Language: English
• Published: Shannon Elsevier B.V 01.04.1999; Elsevier Science
• Subjects: Amygdala; Amygdala - physiology; Anatomical correlates of behavior; Animals; Appetitive Behavior - physiology; Behavioral psychophysiology; Biological and medical sciences; Brain Mapping; Conditioned reinforcement; Conditioning, Operant - physiology; Corpus Striatum - physiology; Discrimination learning; Discrimination Learning - physiology; Dominance, Cerebral - physiology; Excitatory Amino Acids - physiology; Fundamental and applied biological sciences. Psychology; Limbic System - physiology; Male; Motivation; Neural Pathways - physiology; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Rats; Reaction Time - physiology; Amygdala; Discrimination learning; Conditioned reinforcement; Rat; Rodentia; Central nervous system; Instrumental conditioning; Male; Basal ganglion; Food reinforcement; Discrimination task; Learning; Vertebrata; Mammalia; Acquisition process; Animal; Lesion; Brain (vertebrata)
• ISSN: 0166-4328; 1872-7549
• DOI: 10.1016/S0166-4328(98)00119-3

Rats with excitotoxic lesions of the basolateral amygdala (BLA) were not impaired in the acquisition of an appetitive visuospatial conditional discrimination between stimuli varying in temporal frequency that has previously been shown to be sensitive to the effects of lesions of the striatum and cingulate cortex. After asymptotic performance was attained, discrimination was reinforced according to a fixed ratio (FR) schedule under which n presentations of sucrose were provided following n correct responses; each correct response also being reinforced immediately by a light acting as a conditioned reinforcer. Under these conditions of reinforcement when FR n=5 , BLA-lesioned rats initially showed transient impairments in several aspects of performance, but rapidly attained control levels over subsequent test sessions. No further impairments occurred when FR n=10/20 . However, in various conditions of extinction, further differences in performance were revealed between the BLA-lesioned and control groups, notably a significantly enhanced resistance to extinction when both sucrose and conditioned reinforcement were omitted. The results are discussed in terms of limbic-striatal mechanisms in the control of discrimination learning and the possible role of the amygdala in the mediation of different aspects of conditioned reinforcement.