Date of Completion


Embargo Period



Etan J. Markus, John D. Salamone, Ian H. Stevenson

Field of Study

Psychological Sciences


Master of Science

Open Access

Campus Access


The hippocampus is linked to the formation and retrieval of episodic memories and spatial navigation. In rats, it is an elongated structure divided into dorsal (septal) and ventral (temporal) regions paralleling the respective divide in posterior and anterior hippocampus in humans. The dorsal hippocampus is associated with spatial processing, and the ventral to processing anxiety. Far less is known regarding the degree to which these different regions interact during information processing. The anatomical connectivity suggests a flow of information from the ventral to dorsal regions, conversely there are also commissural connections to the contra-lateral hippocampus. The current study examined the extent to which information from the ventral hippocampus impacts processing in the ipsi- and contra-lateral dorsal hippocampi. Rats were well trained on a spatial reference version of the water maze followed by muscimol (0.5 μg/μl or 1.0 μg/μl) inactivation of different hippocampal subregions in a within-animal repeated design. Various combinations of bilateral, ipsilateral, and contralateral infusions were used. Combined dorsal and ventral inactivation produced a severe impairment in spatial performance. Inactivation of only the dorsal or ventral regions resulted in intermediate impairment with performance levels falling between controls and combined inactivation. Performance was also impaired during contralateral inactivation and was almost equivalent to full hippocampus inactivation, while ipsilateral inactivation resulted in little impairment. Taken together, the data indicate that for spatial processing the hippocampus functions as a single integrated structure along the longitudinal axis, with dorsal regions highly dependent upon input from the ventral regions.

Major Advisor

Etan J. Markus