Double dissociation of function within the hippocampus: Spatial memory and hyponeophagia.

Abstract

Complete and dorsal hippocampal lesions impaired spatial performance on 2 working memory tasks: rewarded alternation on the T maze and matching to position in the water maze. In contrast, ventral hippocampal lesions had no effect on these tasks, even when task difficulty was increased by the introduction of delays. Ventral lesions did resemble complete lesions in reducing anxiety in 3 commonly used tests of anxiety (social interaction, plus-maze, and hyponeophagia). Dorsal lesions also appeared to be anxiolytic in the social interaction and plus-maze tests, but they did not affect hyponeophagia. Complete- and dorsal-lesioned rats displayed hyperactivity, whereas ventral-lesioned rats did not. These results show a double dissociation between dorsal and ventral hippocampal lesions (hyponeophagia vs. spatial memory), suggesting differentiation of function along the septotemporal axis of this structure.

Temporary inhibition of dorsal or ventral hippocampus by muscimol: Distinct effects on measures of innate anxiety on the elevated plus maze, but similar disruption of contextual fear conditioning

“…This hypothesis is consistent with the idea that the ventral hippocampus plays a more important role in unconditioned anxiety than the dorsal hippocampus, which is based on wide range of evidence Bannerman et al, 2004;Pentkowski, et al, 2006;Engin & Treit, 2007). More specifically, ventral cytotoxic lesions have been found to cause more pronounced anxiolytic effects than dorsal lesions on a variety of measures of innate anxiety, including elevated plus maze measures (Kjelstrup et al, 2002;Bannerman et al, 2002Bannerman et al, , 2004, and ventral infusion of the local anaesthetic lidocaine (a sodium channel blocker inactivating neurons and fibers of passage) significantly increased the proportion of open-arm entries on the elevated plus maze test, whereas dorsal lidocaine had no significant effect (Bertoglio et al, 2006). Moreover, ventral, but not dorsal, hippocampal muscimol reduced unconditioned fear, as assessed by the shock-probe burying test (McEown and Treit, 2010).…”

“…However, the effects of hippocampal manipulations on tests of anxiety, such as the elevated plus maze, show considerable variability across studies, depending on a variety of factors (see, for example, discussion in Bannerman et al, 2002). Two factors that may be particularly relevant concerning the present results are locomotor effects of the hippocampal manipulations and baseline anxiety levels.…”

“…Relative increases of open arm as compared to closed arm parameters are typically considered to reflect anxiolytic effects, whereas relative decreases in closed arm as compared to open arm parameters are thought to reflect anxiogenic effects (Pellow, Chopin, File, Briley, 1985;Rodgers & Dalvi, 1997; for more recent studies combining the elevated plus maze with hippocampal manipulations: Kjelstrup et al, 2002;Bannerman et al, 2002;Rezayat et al, 2005;Bertoglio et al, 2006). …”

“…Previous studies examining the effects of partial hippocampal lesions and temporary pharmacological inactivation on a range of tests of unconditioned anxiety suggested that both ventral and dorsal hippocampal inactivation may be anxiolytic, with the effects of ventral hippocampal manipulations tending to be more pronounced (Kjelstrup et al, 2002;Bannerman et al, 2002Bannerman et al, , 2004Rezayat et al, 2005;Bertoglio et al, 2006;Engin & Treit, 2007;McEown & Treit, 2010). However, the effects of hippocampal manipulations on tests of anxiety, such as the elevated plus maze, show considerable variability across studies, depending on a variety of factors (see, for example, discussion in Bannerman et al, 2002).…”

The NTSR1 gene modulates the association between hippocampal structure and working memory performance

“…Several lines of evidence have shown an important role of the hippocampus in WM. For example, lesion studies showed that rats with complete or dorsal hippocampus lesions had impaired WM (Bannerman et al, 2002). In human patients, medial temporal lobe amnesia was linked to severely impaired WM at 8 s delays, suggesting that the hippocampus per se is critical for accurate conjunction WM (Olson et al, 2006b).…”