Hippocampus at 25

Abstract

The journal Hippocampus has passed the milestone of 25 years of publications on the topic of a highly studied brain structure, and its closely associated brain areas. In a recent celebration of this event, a Boston memory group invited 16 speakers to address the question of progress in understanding the hippocampus that has been achieved. Here we present a summary of these talks organized as progress on four main themes: (1) Understanding the hippocampus in terms of its interactions with multiple cortical areas within the medial temporal lobe memory system, (2) understanding the relationship between memory and spatial information processing functions of the hippocampal region, (3) understanding the role of temporal organization in spatial and memory processing by the hippocampus, and (4) understanding how the hippocampus integrates related events into networks of memories.

Cholinergic modulation of spatial learning, memory and navigation

“…If we consider the general processing schemes of the strongly interconnected system of hippocampus, RSC, PPC, prefrontal cortex, BF and potentially other cortical and subcortical areas, it is clear that spatial cognition is likely only one aspect of more abstract processes they implement. Indeed, there is an ongoing stimulating debate whether hippocampal cognitive maps should be considered only in the spatial domain (Eichenbaum et al., ; Lisman et al., ). Additionally, it has been recently shown that RSC is involved in processing permanence and stability not only of spatial landmarks but also of actions and behaviour (Auger & Maguire, ).…”

“…The literature in this field is vast and multidisciplinary. Here we only provide an overview pertinent to our focus of cholinergic modulation of hippocampal function in the context of spatial learning and memory; for more extensive summaries and thought‐provoking reading please refer to (Eichenbaum et al., ; Lisman et al., ; Moser, Moser, & McNaughton, ). As stated by (O'Keefe & Nadel, ), “we shall argue that the hippocampus is the core of a neural memory system providing an objective spatial framework within which the items and events of an organism's experience are located and interrelated”.…”

Origin and role of path integration in the cognitive representations of the hippocampus: computational insights into open questions

“…More precisely, a system that evolved to rapidly bind landmarks onto a path-integration-based mapping system could subsequently evolve to perform other rapid binding tasks of diverse external sensory input onto a sequential code. This way of thinking may be the link between disparate viewpoints of the roles of hippocampus in spatial mapping in rodents and declarative memory in humans (Burgess et al, 2002;Buzsáki, 2005;Buzsáki and Moser, 2013;Eichenbaum et al, 2016Eichenbaum et al, , 1999Lisman, 1999;O'Keefe and Nadel, 1978).…”

Influence of postnatal glucocorticoids on hippocampal-dependent learning varies with elevation patterns and administration methods

“…The hippocampus is rich with glucocorticoid receptors and plays a pivotal role in regulation of the stress response by providing negative feedback to the hypothalamic-pituitary- adrenal (HPA) system. In addition, the hippocampus is a critical structure for learning and memory including short-term memory storage, the formation of new memories, and spatial working memory (Eichenbaum et al, 2016; Mahmmoud et al, 2015; Garcia, 2001). Some glucocorticoid activation is necessary for memory formation, and acute elevations can increase hippocampal LTP to promote learning (Beylin & Shors, 2003; Blank et al, 2002).…”