The role of the hippocampus in passive and active spatial learning

Abstract

Rats with lesions of the hippocampus or sham lesions were required in four experiments to escape from a square swimming pool by finding a submerged platform. Experiments 1 and 2 commenced with passive training in which rats were repeatedly placed on the platform in one corner—the correct corner—of a pool with distinctive walls. A test trial then revealed a strong preference for the correct corner in the sham but not the hippocampal group. Subsequent active training of being required to swim to the platform resulted in both groups acquiring a preference for the correct corner in the two experiments. In Experiments 3 and 4, rats were required to solve a discrimination between different panels pasted to the walls of the pool, by swimming to the middle of a correct panel. Hippocampal lesions prevented a discrimination being formed between panels of different lengths (Experiment 3), but not between panels showing lines of different orientations (Experiment 4); rats with sham lesions mastered both problems. It is suggested that an intact hippocampus is necessary for the formation of stimulus-goal associations that permit successful passive spatial leaning. It is further suggested that an intact hippocampus is not necessary for the formation of stimulus-response associations, except when they involve information about length or distance. © 2014 The Authors. Hippocampus Published by Wiley Periodicals, Inc.

Perirhinal cortex lesions that impair object recognition memory spare landmark discriminations

“…Finally, the perirhinal cortex lesions appeared to be without effect when the rats were reinforced for swimming to the platform location to escape, i.e., with active training. Overall, these null results differ from those of hippocampal, retrosplenial cortex, and anterior thalamic nuclei lesions, all of which disrupt the learning of preference for the correct corner of the pool after passive training [14], [24], [25]. This dissociation further highlights differences between the perirhinal cortex and the extended hippocampal system [26].…”

“…The procedure required the rat to navigate according to the spatial disposition of a prescribed set of maze cues [12], [13]. In contrast to rats with hippocampal lesions [14], the rats with perirhinal lesions learnt a specific location that required discriminating two mirror-imaged corners (Fig. 1).…”

The response strategy and the place strategy in a plus‐maze have different sensitivities to devaluation of expected outcome

“…For instance, rats with HPC inactivation or lesions rely less on the place strategy and more on alternative strategies during a conflict probe trial (McDonald & White, ; Packard & McGaugh, ). Hippocampus‐lesioned animals also show impaired acquisition of a place‐only‐relevant version of a plus‐maze task (Chang & Gold, ; Compton, ), a place‐relevant component of a dual‐solution water maze task (Pearce, Roberts, & Good, ; Kosaki, Poulter, Austen, & McGregor, ), and a passive place learning in the water maze, which precludes the involvement of a response component (Kosaki, Lin, Horne, Pearce, & Gilroy, ). On the other hand, Corbit and Balleine (), and Corbit, Ostlund, and Balleine (), demonstrated that HPC lesions did not impair rats' sensitivity to the expected value of the outcome.…”

Dementia-related Bri2 BRICHOS is a versatile molecular chaperone that efficiently inhibits Aβ42 toxicity in Drosophila

“…The hippocampus, part of the limbic system, is a seahorse-like structure in the medial temporal lobe that is well connected to other subcortical areas and the contralateral hippocampal region. The hippocampus has a profound role in the consolidation of short-to long-term memory, cognition and spatial navigation (9)(10)(11)(12). It is among the most well studied areas of the mammalian brain and has provided a wealth of information concerning neurons and neuronal networks in health and disease.…”