Mammillothalamic tracts and representational memory.

The mammillothalamic tracts, which connect the mammillary bodies of the brain stem with the anterior thalamic nuclei of the forebrain, are an integral segment of Papez's circuit and have long been considered to be involved in mediation of emotional aspects of behavior. This study showed that a complete transection of these tracts substantially impairs the ability for rats to perform discriminations that depend on representational memory but not those that depend on dispositional memory. Nor were there any marked alterations in the emotional domain of behavior.