The discovery of new cell types, such as grid and time cells, in the hippocampus has been accompanied by major anatomical and theoretical insights in the recent years. This book provides comprehensive, up-to-date information about the hippocampal formation and especially the neural basis of episodic memory, spatial location (the formation of the cognitive map) and temporal representation. The first part of the book describes the information flow from pre-hippocampal areas into the hippocampus, the second part discusses the different types of hippocampal processing and finally, the third part depicts the influence that the hippocampal processing has on other brain structures that are perhaps more closely tied to explicit cognitive or behavioral output. This book is intended for neuroscientists, especially for those who are involved in research on the hippocampus, as well as for behavioral scientists and neurologists.
Data from neuropsychological and animal research suggest that the hippocampus plays a pivotal role in two relatively different areas: active navigation, as well as episodic learning and memory. Recent studies have attempted to bridge these disparate accounts of hippocampal function by emphasizing the role that hippocampal place cells may play in processing the spatial contextual information that defines situations in which learned behaviors occur. A number of established laboratories are currently offering complementary interpretations of place fields, and this book will present the first common platform for them. Bringing together research from behavioral, genetic, physiological, computational, and neural-systems perspectives will provide a thorough understanding of the extent to which studying place-field properties has informed our understanding of the neural mechanisms of hippocampus-dependent memory. Hippocampal Place Fields: Relevance to Learning and Memory will serve as a valuable reference for everyone interested in hippocampal function.
The hippocampus has long been considered a critical substrate in the neurobiology, neuropsychology, and cognitive neuroscience of memory. Over the past few decades, a number of ground-breaking theoretical and methodological advances have radically enhanced our understanding of the structure and function of the hippocampus and revolutionized the neuroscientific study of memory. Cutting across disciplines and approaches, these advances offer novel insights into the molecular and cellular structure and physiology of the hippocampus, the role of hippocampus in the formation, (re)consolidation, enhancement, and retrieval of memory across time and development, and permit investigators to address questions about how the hippocampus interacts, functionally and anatomically, with other neural systems in service of memory. In addition, recent investigations also suggest that the mechanistic properties and functional processing features of the hippocampus permit broader contributions to cognition, beyond memory, to the domains of attention, decision-making, language, social cognition, and a variety of other capacities that are critical for flexible cognition and behavior. These advances have profound implications for the neurobiology and cognitive neuroscience of hippocampus dependent cognition and for the numerous psychiatric and neurological diseases and disorders for which hippocampal pathology is a hallmark such as Alzheimer’s disease and schizophrenia. The goal of this book is to bring together in a single source an integrated review of these advances providing state of the art treatment on the structure and function of the hippocampus. Contributors will examine the hippocampus from a variety of levels (from cells to systems) using a wide range of methods (from neurobiological approaches in non-human animals to neuroimaging and neuropsychological work in humans).
This thesis aims to explore the two dominant functional roles of the hippocampal formation, in the relational encoding of episodic memory and the neural representation of allocentric space, using a combination of pharmaceutical manipulations and single-unit recording techniques in rodents. The first part of this thesis focuses on episodic-like memory, defined by the original episodic memory triad: 'what-where-when' (Tulving 1972), which enables the behavioural aspects of episodic memory to be tested in non-human animals. Permanent neurotoxic lesions of the hippocampus and it's subregions were induced to assess their role in a putative episodic-like memory task developed by Eacott and Norman (2004). In view of the difficulties encountered in successfully demonstrating the temporal component of episodic-like memory in rats, this task tested integrated memory for 'what-where-which', where the temporal component (when) was replaced with another event specifier: context (on 'which' occasion). Disruption of the hippocampal circuitry led to a specific impairment in the integration of all three event components, whereas the associative recognition of any combination of these features in isolation was left intact. These results confirm the hippocampal dependence of this episodic-like memory task and further reveals the necessity of both CA3 and CA1, hypothetically due to the underlying autoassociative role of CA3 with CA1 functioning as the vital output pathway for this associated information and/or as a mismatch detector. There has been much debate over the inclusion of the temporal component and sceptics may argue that any such interpretations of task-dependence on episodic-like memory processing are invalid considering the requirement for temporal processing is absent. Due to the proposal that a temporal framework necessarily provides the foundation on which episodic memories are built, the second chapter focuses on the development of a suitable protocol in which integrated memory for the original 'what-where-when' episodic memory triad can be reliably tested. The other main function attributed to the hippocampus was brought to light by the fascinating revelation that it's neurons selectively fire in different regions of an environment, termed 'place cells' (O'Keefe and Dostrovsky 1971). From the numerous publications resulting from this discovery it has emerged that place cells not only respond to the spatial features of the environment but are also sensitive to a multitude of non-spatial features. These characteristics support the logical assumption that the primary firing patterns of the hippocampus should underlie it's main purported roles, leading to speculations that they reflect episodic memory processes. The second part of this thesis aims to examine the relationship between hippocampal cells and behaviour by extending the work of Ainge et al. (2007a), in which a subset of hippocampal place cells were found to encode both current and intended destination in a double Y-maze 'win-stay' task. The development of these 'goal-sensitive' cells were initially investigated during the learning phase of this task. An exciting pattern of results showed a strong positive correlation between the emergence of goal-sensitive firing and behavioural performance on the task, tempting speculations that these firing patterns may underlie spatial learning and future planning, necessary to support performance. To ensure these firing patterns were not a mere reflection of greater experience on the maze, a second study was conducted in which the task demands changed over set periods of days. A significant increase in the proportion of cells demonstrating goal-sensitive firing was revealed when the protocol shifted to incorporate the spatial memory demands of the 'win-stay' task, with all other parameters of the protocol remaining constant. These results support the theory that goal-sensitive firing patterns are specifically related to the learning and memory demands of the spatial task, not a result of increased exploration of the maze. The last of this series of studies assessed hippocampal-dependence of this task and revealed that bilateral hippocampal lesions induced an impairment in spatial 'win-stay' performance. Collectively, these experiments demonstrate that goal-sensitive firing of hippocampal cells emerge in line with behavioural performance in a hippocampal-dependent task and the emergence of these firing patterns are specific to the learning and memory demands of a spatial 'win-stay' protocol. The functional role of the hippocampus in allocentric spatial processing may thus underpin it's function in episodic memory and potentially in the imagining and planning of future events, whereby the hippocampus provides a 'space' in which retrieved information can be integrated in a coherent context to support the fluent and flexible use of information. This hippocampal function would necessarily require visual information to be accessed, concerning the arrangement of landmarks and cues within the environment, in association with information regarding internal orientation and direction and this leads to the question assessed in the final part of this thesis of where this integration occurs. Based on anatomical evidence and the current literature, the postsubiculum, an input structure to the hippocampus, emerged as a potential site for the convergence of sensory cues into the internally generated head direction cell and place cell networks to enable hippocampal-dependent spatial processing. Thus, the effects of temporary pharmacological blockade of AMPARs and NMDARs in the postsubiculum were assessed on the encoding of spatial memory in an object recognition paradigm. The impairment revealed in the ability to recognise novel object-place configurations demonstrates a key role for NMDAR-dependent plasticity within the postsubiculum itself in the formation of allocentric spatial memory. In summary, the experimental results reported in this thesis further elucidate the critical role the hippocampal formation plays in spatial and episodic memory by combining evidence from cellular physiology and neuroanatomy to the behaving animal and extends these findings to discuss a more general role for the hippocampus in imagining both past and future events, in order to successfully navigate, learn and enable past experience to influence our intended future plans and decisions.
Ever since side effects from bilateral hippocampectomy were identified in Henry Molaison (patient “HM”) during the 1950s, a critical role of the hippocampus has been recognized in the formation of declarative episodic memories. Other cognitive functions have since been proposed, such as a role in navigation, but memory has often been suggested to explain hippocampal involvement. Proving a distinct functional role in cognition is difficult, as memory can be implicated in most cognitive activities. Even when a behavior relies on memory, however, the functionality of the hippocampus extends far beyond, especially evident during activities requiring interactions between cognitive systems. Relational memory is supported by hippocampal connections with widespread regions of the cortex; these interconnections also play a fundamental role in children’s writing abilities and expertise in musical performance. Besides enhancing individual lives, such activities can play a vital role in sustaining cultural values across generations. Interactions with the environment that do not directly depend on mnemonic activity can affect plasticity in hippocampal connections, modified through natural chemicals, pharmacological drugs, and non-pharmacological behaviors. Navigational properties of the hippocampal system are not limited to memory, containing the same navigational elements as our Global Positional System (GPS). Even cognitive deficits arising from hippocampal lesions in “HM” were not limited to memory, as they included deficits in understanding cognitive relationships available in visual scenes, novel sentence contexts, and humorous situations. This book shows an expansive role of the hippocampus in cognition that goes beyond its recognized role in generating new episodic memories.
The hippocampus is one of a group of remarkable structures embedded within the brain's medial temporal lobe. Long known to be important for memory, it has been a prime focus of neuroscience research for many years. The Hippocampus Book promises to facilitate developments in the field in a major way by bringing together, for the first time, contributions by leading international scientists knowledgeable about hippocampal anatomy, physiology, and function. This authoritative volume offers the most comprehensive, up-to-date account of what the hippocampus does, how it does it, and what happens when things go wrong. At the same time, it illustrates how research focusing on this single brain structure has revealed principles of wider generality for the whole brain in relation to anatomical connectivity, synaptic plasticity, cognition and behavior, and computational algorithms. Well-organized in its presentation of both theory and experimental data, this peerless work vividly illustrates the astonishing progress that has been made in unraveling the workings of the brain. The Hippocampus Book is destined to take a central place on every neuroscientist's bookshelf.
As we move around in our environment, and interact with it, many of the most important problems we face involve the processing of spatial information. We have to be able to navigate by perceiving and remembering the locations and orientations of the objects around us relative to ourself; we have to sense and act upon these objects; and we need to move through space to position ourselves in favourable locations or to avoid dangerous ones. While this appears so simple that we don't even think about it, the difficulty of solving these problems has been shown in the repeated failure of artificial systems to perform these kinds of tasks efficiently. In contrast, humans and other animals routinely overcome these problems every single day. This book examines some of the neural substrates and mechanisms that support these remarkable abilities. The hippocampus and the parietal cortex have been implicated in various core spatial behaviours, such as the ability to localise an object and navigate to it. Damage to these areas in humans and animals leads to impairment of these spatial functions. This collection of papers, written by internationally recognized experts in the field, reviews the evidence that each area is involved in spatial cognition, examines the mechanisms underlying the generation of spatial behaviours, and considers the relative roles of the parietal and hippocampal areas, including how each interacts with the other. The papers integrate a wide range of theoretical and experimental approaches, and touch on broader issues relating to memory and imagery. As such, this book represents the state of the art of current research into the neural basis of spatial cognition. It should be of interest to anyone - researchers or graduate students - working in the areas of cognitive neuroscience, neuroanatomy, neuropsychology, and cognition generally.
In this sweeping synthesis, Neal J. Cohen and Howard Eichenbaum bring together converging findings from neuropsychology, neuroscience, and cognitive science that provide the critical clues and constraints for developing a more comprehensive understanding of memory. Specifically, they offer a cognitive neuroscience theory of memory that accounts for the nature of memory impairment exhibited in human amnesia and animal models of amnesia, that specifies the functional role played by the hippocampal system in memory, and that provides further understanding of the componential structure of memory.The authors' central thesis is that the hippocampal system mediates a capacity for declarative memory, the kind of memory that in humans supports conscious recollection and the explicit and flexible expression of memories. They argue that this capacity emerges from a representation of critical relations among items in memory, and that such a relational representation supports the ability to make inferences and generalizations from memory, and to manipulate and flexibly express memory in countless ways. In articulating such a description of the fundamental nature of declarative representation and of the mnemonic capabilities to which it gives rise, the authors' theory constitutes a major extension and elaboration of the earlier procedural-declarative account of memory.Support for this view is taken from a variety of experimental studies of amnesia in humans, nonhuman primates, and rodents. Additional support is drawn from observations concerning the neuroanatomy and neurophysiology of the hippocampal system. The data taken from divergent literatures are shown to converge on the central theme of hippocampal involvement in declarative memory across species and across behavioral paradigms.
Memory is one of the most important faculties of the mind. Memory keeps a record of our experiences which enriches our sense of self, enables us to make adaptive decisions in the present and informed plans for the future. Historically, memory research has focused on the hippocampal formation in the medial temporal lobes which is critical in the initial stages of memory formation. More recently, memory research expanded to include neocortical areas especially with regards to remote memory. An open question in neuroscience is what happens to memory representations in the brain with time. It remains unclear whether the contribution of the hippocampus to memory decreases with time in favour of the neocortex, or if both their contributions stay the same. In this dissertation, I use the non-human primate model to examine the neural mechanism underlying memory formation in the hippocampus, as well as the contribution of neocortical areas during remote memory. In the first study, I present findings that the neural mechanism underlying memory is heterogenous; varying by waking state and underlying spiking of different neuronal types. In the second study, I focus on two neocortical areas alongside the hippocampus and present findings that support a greater role for neocortical areas during remote memory. These findings support the idea that memory dependence shifts to areas outside the hippocampus with time.
The chapters in Human Spatial Memory: Remembering Where present a fascinating picture of an everyday aspect of mental life that is as intriguing to people outside of academia as it is to scientists studying human cognition and behavior. The questions are as old as the study of mind itself: How do we remember where objects are located? How do we remember where we are in relation to other places? What is the origin and developmental course of spatial memory? What neural structures are involved in remembering where? How do we come to understand scaled-down versions of places as symbolic representations of actual places? Although the questions are old, some of the answers-in-progress are new, thanks to some innovative theorizing, solid experimental work, and revealing applications of new technologies, such as virtual environments and brain imaging techniques. This volume includes a variety of theoretical, empirical, and methodological advances that invite readers to make their own novel connections between theory and research. Scholars who study spatial cognition can benefit from examining the latest from well-established experts, as well as milestone contributions from early-career researchers. This combination provides the reader with a sense of past, present, and future in terms of spatial memory research. Just as important, however, is the value of the volume as a touchstone resource for researchers who study perception, memory, or cognition but who are not concerned primarily with the spatial domain. All readers may find the fact that this volume violates the trend toward an ever-narrowing specialization refreshing. Chapters from cognitive psychologists are alongside chapters by developmentalists and neuroscientists; results from field studies are just pages away from those based on fMRI during observation of virtual displays. Thus, the book invites integrative examination across disciplines, research areas, and methodological approaches.
