Transections of stria medullaris or stria terminalis in the rat: effects on aversively controlled behavior.

Surgical transection of the stria medullaris (SM) reliably interfered with the acquisition of a one-way avoidance response but had no effect on two-way shuttle box avoidance, passive avoidance, intake of palatable fluids, or locomotor activity. Transection of the stria terminalis (ST) selectively interfered with the animals' reactions to punishment in a passive avoidance situation but had no effect on one-way or two-way active avoidance or on locomotor activity. This pattern of effects complements the results of earlier investigations from our laboratory that showed that two-way avoidance learning (but not one-way avoidance or passive aboidance behavior) was impaired after fornicotomy and after transection of the ventral connections of the septum with the lower brain stem. The latter cut, but not fornicotomy or transection of ST or SM, reproduced the effects of septal lesions on water intake, body weight, and preferential intake of palatable solutions. The results of this investigation provide support for the hypothesis that the septum exercises a number of separate functions that are mediated by different pathways.