Visual discrimination in inbred mice: Strain-specific involvement of hippocampal regions

Possible differences in functionality between the dorsal and the ventral regions of the hippocampus have been investigated in C57BL/6 (C57) and DBA/2 (DBA) inbred mice differing in their hippocampal anatomy. Mice from these two strains with large ventral, small ventral, small dorsal, or sham hippocampal lesions were tested in a visual discrimination radial maze task. Results first showed no strain difference in baseline performance. Examination of the lesion effects in the former strain (C57) revealed that the three lesions produced equivalent performance impairments. In the latter (DBA), ventral lesions, regardless of the size, were found to have a more deleterious effect than had the dorsal lesion. Thus, in C57 mice, the two regions were found to exert a similar control on performance, whereas in DBA mice, there was a modest involvement of the dorsal region associated with an extensive participation of the ventral region. The fact that, in DBA mice, the ventral area appears to be extensively involved when the dorsal hippocampus is poorly functioning suggests the existence of possible compensatory mechanisms between region-related specific operations and, consequently, some form of functional plasticity within the hippocampal formation.