Electrolytic lesions of the pedunculopontine nucleus disrupt concurrent learned aversion induced by NaCl

Bilateral electrolytic lesions in the pedunculopontine nucleus (PPN) impair acquisition of short-term, or concurrent, Taste Aversion Learning (TAL) in rats. This type of TAL is characterized by the daily presentation of two d ifferent flavor stimuli at the same time, one associated with simultaneous intragastric administration of an aversive product (hypertonic NaCl) and th e other with physiological saline. Sham-lesioned control animals learn this taste discrimination task, but both lesioned animals and control animals l earn a long-term, or delayed, TAL task in which each gustatory stimulus is presented individually every other day and the intragastric products, LiCl (0.15 M) and physiological saline, are administered after a 15-min delay. T hese results are analyzed in the context of the cerebellar circuits involve d in learning and in relation to the two TAL modalities described above. (C ) 2000 Academic Press.