title: Paradoxical facilitatory effect of fornix lesions on acquisition of contextual fear conditioning in mice.
abstract: The present study examined the effect of fornix lesions on freezing behavior elicited by contextual and phasic conditioned stimuli. Male mice of the C57Bl/6 strain received electrolytic lesions of the fornix. Ten days following the lesion, they were submitted to acquisition of one-trial classical fear conditioning involving the pairing of an auditory conditioned stimulus (CS) with a footshock unconditioned stimuli (US). Analysis of conditioned fear responses showed that fornix lesions enhanced the freezing response elicited by exposure to the conditioning chamber 24 h after a single tone-shock pairing. In contrast, the two groups did not differ on their fear responses during the auditory cue test. Analysis of the time-course of freezing behavior during re-exposure to the conditioning chamber suggests, however, that the observed fornix lesion-induced facilitation of freezing to the conditioning chamber is more likely due to a facilitation of the processing of a simple (unimodal) rather than polymodal (contextual) CS-US association.
authors.affiliation: Laboratoire de Neurosciences Comportementales et Cognitives, CNRS UMR 5807, Université de Bordeaux I, Talence, France. c.laurent-demir@neurocog.u-bordeaux.fr
authors.forename: C
authors.initials: C
authors.lastname: Laurent-Demir
authors.forename: R
authors.initials: R
authors.lastname: Jaffard
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001245:Association Learning / Q000502:physiology*; D001931:Brain Mapping; D003214:Conditioning, Classical / Q000502:physiology*; D004597:Electroshock; D005239:Fear / Q000502:physiology*; D020712:Fornix, Brain / Q000502:physiology*; D008297:Male; D011939:Mental Recall / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D012931:Social Environment