Fornix-fimbria section and the partial reinforcement extinction effect

SummaryRats were trained to run in an alley for food reward given on every trial (continuous reinforcement, CR) or on a random 50% of trials (partial reinforcement, PR) and were then extinguished. Sham-operated controls showed the normal partial reinforcement extinction effect (PREE), in that PR-trained animals were significantly more resistant to extinction than CR-trained animals. The PREE was significantly reduced by lesions of the fornix-fimbria. The reduction was largely a consequence of a reduction in resistance to extinction in PR-trained rats with fimbria-fornix lesions. These results are discussed in the light of other experiments that have studied disconnections in the septo-hippocampal system.

[1]  P. Andersen,et al.  Organization of the hippocampal output , 1973, Experimental Brain Research.

[2]  J. Gray,et al.  Précis of The neuropsychology of anxiety: An enquiry into the functions of the septo-hippocampal system , 1982, Behavioral and Brain Sciences.

[3]  J. Rawlins,et al.  The effects of hippocampectomy and of fimbria section upon the partial reinforcement extinction effect in rats , 1980, Experimental Brain Research.

[4]  A. Siegel,et al.  Efferent connections of the hippocampal formation in the rat , 1977, Brain Research.

[5]  J. Rawlins,et al.  Resistance to extinction after schedules of partial delay or partial reinforcement in rats with hippocampal lesions , 2004, Experimental Brain Research.

[6]  P. Henke.  Persistence of runway performance after septal lesions in rats. , 1974, Journal of comparative and physiological psychology.

[7]  J. Gray,et al.  Effects of Medial and Lateral Septal Lesions on the Partial Reinforcement Extinction Effect at One Trial a Day , 1979, The Quarterly journal of experimental psychology.

[8]  O. Steward,et al.  Medial septal area lesions disrupt theta rhythm and cholinergic staining in medial entorhinal cortex and produce impaired radial arm maze behavior in rats , 1982, The Journal of neuroscience : the official journal of the Society for Neuroscience.

[9]  J. Rawlins,et al.  Hippocampal lesions do not alter the partial punishment effect , 2004, Experimental Brain Research.

[10]  J. Gray,et al.  Effects of Medial and Lateral Septal Lesions on the Partial Reinforcement Extinction Effect at Short Inter-Trial Intervals , 1979, The Quarterly journal of experimental psychology.

[11]  J. Rawlins,et al.  Septo-hippocampal connections and the hippocampal theta rhythm , 1979, Experimental Brain Research.

[12]  J. Rawlins,et al.  The role of the septo-hippocampal system and its noradrenergic afferents in behavioural responses to none-reward. , 1977, Ciba Foundation symposium.

[13]  P. Henke.  Septal lesions and aversive nonreward , 1976, Physiology & Behavior.