Mammillothalamic tract lesions disrupt dead reckoning in the rat

Debate surrounds the role of the limbic system structures' contribution to spatial orientation. The results from previous studies have supported a role for the mammillary bodies and their projections to the anterior thalamus in rapid encoding of relationships among environmental cues; however, this work is based on behavioral tasks in which environmental and self-movement cues could not be dissociated. The present study examines the effects of mammillothalamic tract lesions on spatial orientation in the food hoarding paradigm and the water maze. Although the food hoarding paradigm dissociates the use of environmental and self-movement cues, both sources of information are available to guide performance in the water maze. Mammillothalamic tract lesions selectively impaired performance on both tasks. These impairments are interpreted as providing further evidence for the role of limbic system structures in processing self-movement cues.