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Place Fields (place + field)

Distribution by Scientific Domains

Life Sciences	100%

Selected Abstracts

A learning rule for place fields in a cortical model: Theta phase precession as a network effect

HIPPOCAMPUS, Issue 7 2005
Silvia Scarpetta
Abstract We show that a model of the hippocampus introduced recently by Scarpetta et al. (2002, Neural Computation 14(10):2371,2396) explains the theta phase precession phenomena. In our model, the theta phase precession comes out as a consequence of the associative-memory-like network dynamics, i.e., the network's ability to imprint and recall oscillatory patterns, coded both by phases and amplitudes of oscillation. The learning rule used to imprint the oscillatory states is a natural generalization of that used for static patterns in the Hopfield model, and is based on the spike-time-dependent synaptic plasticity, experimentally observed. In agreement with experimental findings, the place cells' activity appears at consistently earlier phases of subsequent cycles of the ongoing theta rhythm during a pass through the place field, while the oscillation amplitude of the place cells' firing rate increases as the animal approaches the center of the place field and decreases as the animal leaves the center. The total phase precession of the place cell is lower than 360°, in agreement with experiments. As the animal enters a receptive field, the place cells' activity comes slightly less than 180° after the phase of maximal pyramidal cell population activity, in agreement with the findings of Skaggs et al. (1996, Hippocampus 6:149,172). Our model predicts that the theta phase is much better correlated with location than with time spent in the receptive field. Finally, in agreement with the recent experimental findings of Zugaro et al. (2005, Nature Neuroscience 9(1):67,71), our model predicts that theta phase precession persists after transient intrahippocampal perturbation. © 2005 Wiley-Liss, Inc. [source]

Excitotoxic lesions of the pre- and parasubiculum disrupt the place fields of hippocampal pyramidal cells

HIPPOCAMPUS, Issue 1 2004
Ping Liu
Abstract To determine what influence the pre- and parasubiculum regions of the hippocampal formation have on neural representations within the dorsal hippocampus, single-unit recordings were made as rats with bilateral ibotenic acid lesions centered on the former regions (n = 4) or control surgeries (n = 3) foraged freely. Spatial firing specificity was measured using an information content procedure. Cells from lesioned animals (n = 57) provided significantly less spatial information than cells from control animals (n = 44). Whereas some degree of location-related activity (place fields) was observed in 98% of neurons recorded from control animals, it was observed in only 65% of the neurons from lesioned animals. The spatial resolution of the intact place fields appeared to be compromised in lesioned animals as a result of their having a higher firing rate outside the place field. These findings indicate that the pre- and parasubiculum regions have a major role in maintaining the specificity of the place field firing of hippocampal pyramidal cells. Since previous data indicate that these lesioned animals displayed delay-dependent deficits in spatial tasks, these findings also suggest that a disruption in place field activity may be a causal factor in this spatial memory deficit. © 2003 Wiley-Liss, Inc. [source]

Functional interaction between the associative parietal cortex and hippocampal place cell firing in the rat

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2005
Etienne Save
Abstract The hippocampus and associative parietal cortex (APC) both contribute to spatial memory but the nature of their functional interaction remains unknown. To address this issue, we investigated the effects of APC lesions on hippocampal place cell firing in freely moving rats. Place cells were recorded from APC-lesioned and control rats as they performed a pellet-chasing task in a circular arena containing three object cues. During successive recording sessions, cue manipulations including object rotation in the absence of the rat and object removal in the presence of the rat were made to examine the control exerted by the objects or by non-visual intramaze cues on place field location, respectively. Object rotations resulted in equivalent field rotation for all cells in control rats. In contrast, a fraction of place fields in APC-lesioned rats did not rotate but remained stable relative to the room. Object removal produced different effects in APC-lesioned and control rats. In control rats, most place fields remained stable relative to the previous object rotation session, indicating that they were anchored to olfactory and/or idiothetic cues. In APC-lesioned rats, a majority of place fields shifted back to their initial, standard location, thus suggesting that they relied on uncontrolled background cues to maintain place field stability. These results provide strong evidence that the hippocampus and the APC cooperate in the formation of spatial memory and suggest that the APC is involved in elaboration of a hippocampal map based on proximal landmarks. [source]

Lesions of the mammillary body region alter hippocampal movement signals and theta frequency: Implications for path integration models

HIPPOCAMPUS, Issue 9 2008
Patricia E. Sharp
Abstract Cells throughout the hippocampal formation are involved in processing spatial information. These same cells also show an influence of locomotor activity, and these movement signals are thought to be critical for the path integration abilities of these cells. Nuclei in the mammillary region provide ascending influences to the hippocampal formation and have been implicated in influencing both hippocampal spatial and theta signals. Here, we report the effects of mammillary lesions on movement-related signals in several hippocampal subregions. We find first, as predicted by earlier work, these lesions cause an approximately 1 Hz reduction in the frequency of theta modulation of cell firing. According to recent theoretical work, this might, in turn, be expected to influence the size of hippocampal place fields. Our data do not confirm this prediction for any of the hippocampal regions examined. Second, we report lesion effects on the relationship between firing rate and running speed for the hippocampal cells. These lesions caused a reduction in both the slope and intercept of rate-by-speed functions for cells in the hippocampus and postsubiculum. Surprisingly, cells in subiculum showed an opposite effect, so that the excitatory influence of locomotion was enhanced. Path integration theories predict that the speed at which path integration occurs is related to the strength of this movement signal. In remarkable accordance with this prediction, we report that the timing of the place cell signals is slowed following mammillary lesions for hippocampal and postsubicular cells, but, in contrast, is speeded up for subicular cells. In fact, the timing for place signals across lesion condition and brain region is predicted by a single linear function which relates timing to the strength of the running speed signal. Thus, these data provide remarkable support for some aspects of current path integration theory, while posing a challenge for other aspects of these same theories. © 2008 Wiley-Liss, Inc. [source]

Learning in a geometric model of place cell firing

HIPPOCAMPUS, Issue 9 2007
Caswell Barry
Abstract Following Hartley et al. (Hartley et al. (2000) Hippocampus 10:369,379), we present a simple feed-forward model of place cell (PC) firing predicated on neocortical information regarding the environmental geometry surrounding the animal. Incorporating the idea of boundaries with distinct sensory qualities, we show that synaptic plasticity mediated by a BCM-like rule (Bienenstock et al. (1982) J Neurosci 2:32,48) produces PCs that encode position relative to specific extended landmarks. In an unchanging environment the model is shown to undergo an initial phase of learning, resulting in the formation of stable place fields. In familiar environments, perturbation of environmental cues produces graded changes in the firing rate and position of place fields. Model simulations are compared favorably with three sets of experimental data: (1) Results published by Barry et al. (Barry et al. (2006) Rev Neurosci 17:71,97) showing the slow disappearance of duplicate place fields produced when a barrier is placed into a familiar environment. (2) Rivard et al.'s (Rivard et al. (2004) J Gen Physiol 124:9,25) study showing a graded response in PC firing such that fields near to a centrally placed object encode space relative to the object, whereas more distant fields respond to the surrounding environment. (3) Fenton et al.'s (Fenton et al. (2000a) J Gen Physiol 116:191,209) observation that inconsistent rotation of cue cards produces parametric changes in place field positions. The merits of the model are discussed in terms of its extensibility and biological plausibility. © 2007 Wiley-Liss, Inc. [source]

From grid cells to place cells: A mathematical model

HIPPOCAMPUS, Issue 12 2006
Trygve Solstad
Abstract Anatomical connectivity and recent neurophysiological results imply that grid cells in the medial entorhinal cortex are the principal cortical inputs to place cells in the hippocampus. The authors propose a model in which place fields of hippocampal pyramidal cells are formed by linear summation of appropriately weighted inputs from entorhinal grid cells. Single confined place fields could be formed by summing input from a modest number (10,50) of grid cells with relatively similar grid phases, diverse grid orientations, and a biologically plausible range of grid spacings. When the spatial phase variation in the grid-cell input was higher, multiple, and irregularly spaced firing fields were formed. These observations point to a number of possible constraints in the organization of functional connections between grid cells and place cells. © 2006 Wiley-Liss, Inc. [source]

Self-motion and the origin of differential spatial scaling along the septo-temporal axis of the hippocampus

HIPPOCAMPUS, Issue 7 2005
Andrew P. Maurer
Abstract Spatial scaling of place specific activity in the hippocampus varies systematically from the septal pole (high resolution) to the temporal pole (low resolution). Place fields get progressively larger, and the probability of observing a field in a given environment gets progressively smaller. It was previously found that decoupling movement in space from ambulation, by having the animal actively ride on a mobile platform, results in marked enlargement of the spatial scale factor in the dorsal hippocampus and a reduction in the increase in theta rhythm power with running speed, suggesting that a self-motion signal determines the spatial scale at which the hippocampal population vector updates. These results led to the hypothesis that the gain of the self-motion signal may vary systematically along the septo-temporal axis of the hippocampus. To test this hypothesis, EEG theta rhythm and ensembles of CA1 pyramidal cells and interneurons were recorded from the extreme dorsal and middle portions of the hippocampus. Pyramidal cell population vectors representing successive locations became decorrelated over substantially shorter distances in the dorsal than in the middle hippocampus. Dorsal pyramidal cells had smaller place fields, higher mean and peak firing rates, and higher intrinsic oscillation frequencies during track running than that of middle pyramidal cells. Both dorsal pyramidal cells and interneurons had more elevated mean rates during running, compared with rest, than that of the corresponding cell classes in the middle hippocampus, and both cell classes increased their rates more as a function of speed in the dorsal hippocampus. The amplitude, but not the frequency of fissure recorded theta rhythm, increased more as a function of running speed in the dorsal than in the middle hippocampus. We conclude that variation in the neuronal response to movement speed is the likely basis for the systematic variation in spatial scaling along the septo-temporal axis of the hippocampus. © 2005 Wiley-Liss, Inc. [source]

A learning rule for place fields in a cortical model: Theta phase precession as a network effect

Excitotoxic lesions of the pre- and parasubiculum disrupt the place fields of hippocampal pyramidal cells

Representation of place by monkey hippocampal neurons in real and virtual translocation

HIPPOCAMPUS, Issue 2 2003
Etsuro Hori
Abstract The hippocampal formation (HF) is hypothesized as a neuronal substrate of a cognitive map, which represents environmental spatial information by an ensemble of neural activity. However, the relationships between the hippocampal place cells and the cognitive map have not been clarified in monkeys. The present study was designed to investigate how activity patterns of place-selective neurons encode spatial relationships of various environmental stimuli; to do this, we used multidimensional scaling (MDS) for hippocampal neuronal activity in the monkey during the performance of real and virtual translocation. Of 389 neurons recorded from the monkey HF and parahippocampal gyrus (PH), 166 had place fields that displayed increased activity in a specific area of an experimental field and/or on a monitor (place-selective neurons). The MDS transformed relationships among the 16 places in the experimental field and the monitor, expressed as correlation coefficients between all possible pairs of two places based on the 166 place-selective responses, into geometric relationships in a two-dimensional MDS space. In the real translocation tasks, the 16 places were distributed throughout the MDS space, and their relative positions were well correlated to real positions in the experimental laboratory. However, the correlation between the MDS space and real arrangements was significantly smaller in virtual than real translocation tasks. The present results strongly suggest that activity patterns of the HF and PH neurons represent spatial information and might provide a neurophysiological basis for a cognitive map. Hippocampus 2003;13:190,196. © 2003 Wiley-Liss, Inc. [source]

Competitive Hebbian learning and the hippocampal place cell system: Modeling the interaction of visual and path integration cues

HIPPOCAMPUS, Issue 3 2001
Alex Guazzelli
Abstract The hippocampus has long been thought essential for implementing a cognitive map of the environment. However, almost 30 years since place cells were found in rodent hippocampal field CA1, it is still unclear how such an allocentric representation arises from an egocentrically perceived world. By means of a competitive Hebbian learning rule responsible for coding visual and path integration cues, our model is able to explain the diversity of place cell responses observed in a large set of electrophysiological experiments with a single fixed set of parameters. Experiments included changes observed in place fields due to exploration of a new environment, darkness, retrosplenial cortex inactivation, and removal, rotation, and permutation of landmarks. To code for visual cues for each landmark, we defined two perceptual schemas representing landmark bearing and distance information over a linear array of cells. The information conveyed by the perceptual schemas is further processed through a network of adaptive layers which ultimately modulate the resulting activity of our simulated place cells. In path integration terms, our system is able to dynamically remap a bump of activity coding for the displacement of the animal in relation to an environmental anchor. We hypothesize that path integration information is computed in the rodent posterior parietal cortex and conveyed to the hippocampus where, together with visual information, it modulates place cell activity. The resulting network yields a more direct treatment of partial remapping of place fields than other models. In so doing, it makes new predictions regarding the nature of the interaction between visual and path integration cues during new learning and when the system is challenged with environmental changes. Hippocampus 2001;11:216,239. © 2001 Wiley-Liss, Inc. [source]