Journal: Nature , vol. 297, no. 5868, pp. 681-683, 1982 Many complex spike cells in the hippocampus of the freely moving rat have as their primary correlate the animal's location in an environment (place cells). In contrast, the hippocampal electroencephalograph theta pattern of rhythmical waves (7- 12 Hz) is better correlated with a class of movements that change the rat's location in an environment. During movement through the ...
Journal: Hippocampus , vol. 3, no. 3, pp. 317-330, 1993 mV. 17. Plants were grown vertically on Petri plates contain- ing 1.5% (w/v) agar, 1 mM KCl, and 1 mM CaCl2 in continuous light for 4 to 5 days. Root protoplasts were prepared by cutting the root about 150 mm from the tip with a micromanipulator-mounted razor. The cut seedlings were infiltrated with an enzyme solution containing ...
Journal: Science , vol. 280, no. 5365, pp. 921-924, 1998 Finding one's way around an environment and remembering the events that occur within it are crucial cognitive abilities that have been linked to the hippocampus and medial temporal lobes. Our review of neuropsychological, behavioral, and neuroimaging studies of human hippocampal involvement in spatial memory concentrates on three important concepts in this field: spatial frameworks, dimensionality, and orientation and self-...
Journal: Neuron , vol. 35, no. 4, pp. 625-641, 2002 Isolated single units in rat dorsal hippocampus and fascia dentata were classified as ‘Theta’ or ‘Complex-Spike’ cells, and their firing characteristics were examined with respect to position, direction and velocity of movement during forced choice, food rewarded search behavior on a radial eight arm maze. Most spikes from CS cells ocurred when the animal was located within a particular ...
John O'Keefe
John O'Keefe, Neil Burgess THE human hippocampus has been implicated in memory1, in particular episodic2,3 or declarative4 memory. In rats, hippocampal lesions cause selective spatial deficits2,5-7, and hippocampal complex spike cells (place cells) exhibit spatially localized firing8,9, suggesting a role in spatial memory2, although broader functions have also been suggested10,11. Here we report the identification of the environmental features ...
Journal: Nature , vol. 381, no. 6581, pp. 425-428, 1996 Single unit activity was recorded from complex spike cells in the hippocampus of the rat while the animal was performing a spatial memory task. The task required the animal to choose the correct arm of a 4 arm plus-shaped maze in order to obtain reward. The location of the goal arm was varied from trial to trial and was ...
Virtual reality (VR) and event-related functional magnetic resonance imaging were used to study memory for the spatial context of controlled but lifelike events. Subjects received a set of objects from two different people in two different places within a VR environment. Memory for the objects, and for where and from whom they were received was tested by putting the ...
Journal: Neuroimage , vol. 14, no. 2, pp. 439-453, 2001 Place units in the dorsal hippocampus of the freely-moving rat signal the animal's position in an environment (place field). In the present experiments, thirty four place units were recorded in two different environments: one, a small platform where the rat had received neither training nor reward; the other, an elevated T-maze inside a set of black curtains ...
Neil Burgess, John O'keefe The firing rate maps of hippocampal place cells recorded in a freely moving rat are viewed as a set of approximate radial basis fimctions over the ( 2-D ) environment of the rat. It is proposed that these firing fields are constructed during exploration from "sensory inputs" (tuning curve responses to the distance of cues from the rat) and used by ...
Published in 1994.
The involvement of the medial temporal-lobe region in allocentric mapping of the environment has been observed in human lesion and functional imaging work. Cognitive models of environmental learning ascribe a key role to salient landmarks in representing large-scale space. In the present experiments we examined the neural substrates of the topographical memory acquisition process when environmental landmarks were ...
In the brain, hippocampal pyramidal cells use temporal as well as rate coding to signal spatial aspects of the animal's environment or behaviour. The temporal code takes the form of a phase relationship to the concurrent cycle of the hippocampal electroencephalogram theta rhythm. These two codes could each represent a different variable. However, this requires the rate and phase ...
Journal: Nature , vol. 425, no. 6960, pp. 828-832, 2003 J OKEEFE
Summary A large-scale virtual reality town was used to test the topographical and episodic memory of patients with unilateral temporal lobe damage. Seventeen right and 13 left temporal lobectomy patients were compared with 16 healthy matched control subjects. After they had explored the town, subjects' topographical memory was tested by requiring them to navigate to specific locations in the ...
Journal: Brain , vol. 124, no. 12, pp. 2476-2489, 2001 The hippocampus is widely believed to be involved in the storage or consolidation of long-term memories. Several reports have shown short-term changes in single hippocampal unit activity during memory and plasticity experiments, but there has been no experimental demonstration of long-term persistent changes in neuronal activity in any region except primary cortical areas. Here we report that, ...
Journal: Nature , vol. 416, no. 6876, pp. 90-94, 2002 Memories are thought to be attractor states of neuronal representations, with the hippocampus a likely substrate for context-dependent episodic memories. However, such states have not been directly observed. For example, the hippocampal place cell representation of location was previously found to respond continuously to changes in environmental shape alone. We report that exposure to novel square and circular environments ...
Journal: Science , vol. 308, no. 5723, pp. 873-876, 2005 ABSTRACT: ,Virtua lrealit ywa suse dt osequentiall ypresen tobjects withi na tow nsquar ean dt otes trecognitio no fobjec tlocation sfro mthe sam eviewpoin ta spresentation ,o rfro ma shifte dviewpoint .A developmenta lamnesi ccas ewit hfoca lbilatera lhippocampa lpatholog yshowed amassiv eadditiona limpairmen twhe nteste dfro mth eshifte dviewpoint compare dwit ha mild ,lis tlength-dependent ,impairmen twhe ntested ...
Journal: Hippocampus , vol. 12, no. 6, pp. 811-820, 2002 The computational role of the hippocampus in memory has been characterized as: (i) an index to dispa- rate neocortical storage sites; (ii) a time-limited store supporting neocortical long-term memory; and (iii) a content-addressable associative memory. These ideas are reviewed and related to several general aspects of episodic memory, including the di¡ erences between episodic, recognition and semantic ...
Recent research on navigation has been particularly notable for the increased understanding of the factors affecting human navigation and the neural networks supporting it. The use of virtual reality environments has made it possible to explore the effect of environment layout and content on way-finding performance, and it has shown that these effects may interact with the sex and ...
J O'Keefe
We expand upon our proposal that the oscillatory inter- ference mechanism proposed for the phase precession effect in place cells underlies the grid-like firing pattern of dorsomedial entorhinal grid cells (O'Keefe and Burgess (2005) Hippocampus 15:853-866). The origi- nal one-dimensional interference model is generalized to an appropriate two-dimensional mechanism. Specifically, dendritic subunits of layer ...
Journal: Hippocampus , vol. 17, no. 9, pp. 801-812, 2007 John O'Keefe, Neil Burgess We review the ideas and data behind the hypothesis that hippocampal pyramidal cells encode information by their phase of firing relative to the theta rhythm of the EEG. Particular focus is given to the further hypothesis that variations in firing rate can encode information independently from that encoded by firing phase. We discuss possible explanation of the phase-precession effect ...
Journal: Hippocampus , vol. 15, no. 7, pp. 853-866, 2005 A model of place-cell firing is presented that makes quan- titative predictions about specific place cells' spatial receptive fields following changes to the rat's environment. A place cell's firing rate is modeled as a function of the rat's location by the thresholded sum of the firing rates of a number of putative cortical inputs. These inputs ...
Journal: Hippocampus , vol. 10, no. 4, pp. 369-379, 2000 Neil Burgess, John O'Keefe Our model of the spatial and temporal aspects of place cell firing and their role in rat navigation is reviewed. The model provides a candidate mechanism, at the level of individual cells, by which place cell information concerning self-localization could be used to guide navigation to previously visited reward sites. The model embodies specific predic- tions regarding the formation ...
Journal: Hippocampus , vol. 6, no. 6, pp. 749-762, 1996 A virtual reality environment was used to test memory performance for simulated - `realworld" spatial and episodic information in a 22-year-old male, Jon, who has selective bilateralhippocampal pathology caused by perinatal anoxia. He was allowed to explore a large-scalevirtual reality town and then tested on his memory for spatial layout and for episodesexperienced. Topographical memory was tested by ...
Journal: Hippocampus , vol. 11, no. 6, pp. 715-725, 2001 J O'Keefe
John O'Keefe
Journal: Hippocampus , vol. 9, no. 4, pp. 352-364, 1999 In a symmetrical environment (like a square box) hippocampal place cells use a mixture of visual and idiothetic (movement) information to tell them which way the environment is oriented. The present experiment tested the hypothesis that if the visual landmarks were mobile, place cells would learn to disregard these and rely on idiothetic cues instead. Place cells were recorded in ...
J O'keefe
Published in 1991.
The leaves of woody plants at Harvard Forest in Central Massachusetts, USA, changed color during senescence; 70% (62/89) of the woody species examined anatomically contained anthocyanins during senescence. Anthocyanins were not present in summer green leaves, and appeared primarily in the vacuoles of palisade parenchyma cells. Yellow coloration was a result of the unmasking of xanthophyll pigments in senescing ...
We report the spatial and temporal properties of a class of cells termed theta-modulated place-by-direction (TPD) cells recorded from the presubicular and parasubicular cortices of the rat. The firing characteristics of TPD cells in open-field enclosures were compared with those of the following two other well characterized cell classes in the hippocampal formation: place and head-...
Journal: Pain , vol. 3, no. 1, pp. 43-56, 1977 MICHAEL A. WHITE, Beurs de K. M, KAMEL DIDAN, DAVID W. INOUYE, ANDREW D. RICHARDSON, OLAF P. JENSEN,J. Magnuson, J. O'Keefe, G. Zhang, R. R. Nemani, Leeuwen van W. J. D, J. F. Brown Shifts in the timing of spring phenology are a central feature of global change research. Long-term observations of plant phenology have been used to track vegetation responses to climate variability but are often limited to particular species and locations and may not represent synoptic patterns. Satellite remote sensing is instead used for continental to global monitoring. Although numerous methods ...
John O’Keefe, Neil Burgess John O'Keefe
Journal: Hippocampus , vol. 1, no. 3, pp. 230-235, 1991 . A computational model of the lesion and single unit data from navigation in rats is reviewed. The model uses external (visual) and internal (odometric) information from the environment to drive the firing of simulated hippocampal place cells. Constraints on the functional form of these inputs are drawn from experiments using an environment of modifiable shape. The place cell representation is ...
