Hippocampus and neocortex: recognition and spatial memory

doi:10.1016/j.conb.2011.02.002

Current Opinion in Neurobiology

Volume 21, Issue 3, June 2011, Pages 440-445

https://doi.org/10.1016/j.conb.2011.02.002 Get rights and content

Recognition and spatial memory are typically associated with the perirhinal cortex and hippocampal formation, respectively. Solely focusing on these structures for these specific mnemonic functions may, however, be limiting progress in the field. The distinction between these subdivisions of memory is becoming less defined as, for example, hippocampal cells traditionally considered to encode locations also encode place–object associations. There is increasing evidence for the involvement of overlapping networks of brain structures for aspects of both spatial and recognition memory. Future models of spatial and recognition memory will have to extend beyond the hippocampus and perirhinal cortex to incorporate a wider network of cortical and subcortical structures.

Research highlights

► Recognition and spatial memory are typically associated with the perirhinal cortex and hippocampal formation, respectively. ► There is increasing evidence for the involvement of overlapping networks of brain structures for components of both spatial and recognition memory. ► Research into object–context associations has shown how hippocampal spatial representations contribute to wider aspects of memory. ► Future models of spatial and recognition memory need to extend beyond the hippocampus and perirhinal cortex.

Introduction

The neural processes that allow us to form episodic memories, that is, remember events we experience throughout our lives, are still far from fully understood. Neuropsychological studies have been pivotal in identifying those brain structures that are necessary for forming new memories but typically studies in animals are required to investigate these mnemonic processes with higher anatomical resolution. There continues to be a debate as to whether the term episodic memory can even be applied to non-humans; this is particularly relevant when considering vivid experiences where remembering can give a sense of ‘re-living’ the event in a way that has been likened to mental-time travel (see [1]). Whether or not episodic memory is directly comparable across species, there are certainly aspects of episodic memory that can be assessed in animals such as memory for objects, spatial routes and locations, and spatiotemporal context. The recent use of convergent approaches to assess the neural substrates of both recognition memory and spatial learning, including electrophysiological recordings, immediate-early gene imaging, and lesion disconnection studies, has identified an interactive network of regions that support these functions. In this review, we will discuss findings from recent studies that have shed light on aspects of object recognition, spatial memory, and how these two forms of memory are brought together. Recent findings will be put into the context of a more unified model of memory that focuses on interactions, rather than dissociations, between brain regions.

Section snippets

Recognition memory

One component of memory is recognising whether you have encountered someone or something before. This ability can be assessed non-verbally by using a preferential viewing paradigm that builds on the innate preference of animals, including humans, to look at, or explore, something novel. In rats, the spontaneous object recognition task has been used to assess the neural substrates of recognition memory [2] (see Figure 1). While there is an ongoing debate about the extent to which the hippocampus

Space, place and navigation

The hippocampus has long been implicated in spatial memory in both humans and animals [16]. Cells within the hippocampal formation contain a number of electrophysiological properties consistent with their role in forming allocentric representations of space, including head-direction, place and grid cells [17, 18]. Two recent studies have shown how these electrophysiological properties develop in very young rats from when they first explore outside of the nest [19, 20]. The authors of both

Putting things in context

While the traditional focus in animal research has been to assess either memory for objects or memory for places, a growing trend is to combine these different aspects of memory within the same task. This is arguably a more realistic approach in terms of what animals instinctively learn and also more comparable to the combined components of human episodic memory [31, 32]. Combining memory for objects and the contexts in which they occur in has also shifted the focus away from the more

Conclusions

Spatial and recognition memory have typically been considered to be distinct types of memory that are supported by separate brain regions: the hippocampal formation and perirhinal cortex, respectively. However, an overemphasis on these specific neural structures and their respective importance for spatial and recognition memory may impede progress in the field. Recent research has brought together divergent models of memory, by using behavioural tests that combine aspects of spatial and object

References and recommended reading

Papers of particular interest, published within the annual period of review, have been highlighted as:

• of special interest
•• of outstanding interest

Acknowledgements

SDV is funded by a Wellcome Trust Senior Research Fellowship in Basic Biomedical Science [WT090954AIA]; MMA is funded by a Wellcome Trust research grant [WT087855]. The authors wish to thank Andrew Nelson and John Aggleton for their extremely helpful comments on the manuscript.

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View full text

Hippocampus and neocortex: recognition and spatial memory

Research highlights

Introduction

Section snippets

Recognition memory

Space, place and navigation

Putting things in context

Conclusions

References and recommended reading

Acknowledgements

Behav Brain Res

Neuropsychologia

Neuropsychologia

Neuropsychologia

Behav Brain Res

Trends Cogn Sci

Curr Biol

J Neurosci

Cereb Cortex

Psychol Rev

Hippocampus

Nature

Episodic memory: from mind to brain

Annu Rev Psychol

Recognition memory: what are the roles of the perirhinal cortex and hippocampus?

Nat Rev Neurosci

Recognition memory: material, processes, and substrates

Hippocampus

Paradoxical false memory for objects after brain damage

Science

Perirhinal cortex resolves feature ambiguity in configural object recognition and perceptual oddity tasks

Learn Mem

New behavioral protocols to extend our knowledge of rodent object recognition memory

Learn Mem

A distributed cortical representation underlies crossmodal object recognition in rats

J Neurosci

Integrating visual and tactile information in the perirhinal cortex

Cereb Cortex

Qualitatively different modes of perirhinal-hippocampal engagement when rats explore novel vs. familiar objects as revealed by c-Fos imaging

Eur J Neurosci

Lesions of the perirhinal cortex do not impair integration of visual and geometric information in rats

Behav Neurosci

The Hippocampus as a Cognitive Map

Place cells, grid cells, and the brain's spatial representation system

Annu Rev Neurosci

Development of the hippocampal cognitive map in preweanling rats

Science

Development of the spatial representation system in the rat

Science

Hippocampal place cell instability after lesions of the head direction cell network

J Neurosci

Lesions of the mammillary body region severely disrupt the cortical head direction, but not place cell signal

Hippocampus

Transient spatial deficit associated with bilateral lesions of the lateral mammillary nuclei

Eur J Neurosci