ARE ROSTRAL AND CAUDAL PARTS OF THE HIPPOCAMPUS OF THE LIZARD GEKKO-GECKO RELATED TO DIFFERENT TYPES OF BEHAVIOR

Spatial orientation is an important function of the hippocampus. In re ptiles the medial cortex is the equivalent of the mammalian hippocampu s. In this study we compared the structure and connections of the hipp ocampus of ground-dwelling lizards with those of gekkonid lizards whic h are able to walk on vertical walls as well as on the ceiling. This l ast type of locomotor behaviour makes high demands on spatial orientat ion. It appeared that, in contrast to the ground-dwelling lizards, in geckos the small-celled part of the medial cortex can be divided into a rostral and a caudal part. The rostral part receives visual, auditor y, vestibular and proprioceptive information from the dorsolateral tha lamic nucleus. The caudal part is connected with the the lateral corte x which is the recipient of olfactory information from the main olfact ory bulb. Also the efferent connections of the rostral and caudal part of the small-celled part of the medial cortex to the septum; and via the septum to the preoptic and hypothalamic areas remain strictly sepa rated. Since different behavioural aspects are localized in different preoptic and hypothalamic subdivisions it seems likely that the two pa rts of the hippocampus in gekkonid lizards serve different behavioural functions.