Jeffrey Calton - Academia.edu (original) (raw)

Papers by Jeffrey Calton

Research paper thumbnail of Head Movements and Vestibular Firing Properties Anticipation in the Rodent Head Direction System Can Be Explained by an Interaction of

Research paper thumbnail of NMDA blockade inhibits experience-dependent modification of anterior thalamic head direction cells

Behavioral neuroscience, 2015

Head Direction (HD) cells of the rodent Papez circuit are thought to reflect the spatial orientat... more Head Direction (HD) cells of the rodent Papez circuit are thought to reflect the spatial orientation of the animal. Because NMDA transmission is important for spatial behavior, we sought to determine the effects of NMDA blockade on the basic directional signal carried by HD cells and on experience-dependent modification of this system. In Experiment 1, HD cells were recorded from the anterior dorsal thalamus in female Long-Evans rats while they foraged in a familiar enclosure following administration of the NMDA antagonist CPP or saline. While the drug produced a significant decrease in peak firing rates, it failed to affect the overall directional specificity and landmark control of HD cells. Experiment 2 took place over 2 days and assessed whether the NMDA antagonist would interfere with the stabilization of the HD network in a novel environment. On Day 1 the animal was administered CPP or saline and placed in a novel enclosure to allow the stabilization of the HD signal relative ...

Research paper thumbnail of Hippocampal place cell instability after lesions of the head direction cell network

The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 29, 2003

The occurrence of cells that encode spatial location (place cells) or head direction (HD cells) i... more The occurrence of cells that encode spatial location (place cells) or head direction (HD cells) in the rat limbic system suggests that these cell types are important for spatial navigation. We sought to determine whether place fields of hippocampal CA1 place cells would be altered in animals receiving lesions of brain areas containing HD cells. Rats received bilateral lesions of anterodorsal thalamic nuclei (ADN), postsubiculum (PoS), or sham lesions, before place cell recording. Although place cells from lesioned animals did not differ from controls on many place-field characteristics, such as place-field size and infield firing rate, the signal was significantly degraded with respect to measures of outfield firing rate, spatial coherence, and information content. Surprisingly, place cells from lesioned animals were more likely modulated by the directional heading of the animal. Rotation of the landmark cue showed that place fields from PoS-lesioned animals were not controlled by t...

Research paper thumbnail of Eye-hand coordination: saccades are faster when accompanied by a coordinated arm movement

Journal of neurophysiology, 2002

When primates reach for an object, they very often direct an eye movement toward the object as we... more When primates reach for an object, they very often direct an eye movement toward the object as well. This pattern of directing both eye and limb movements to the same object appears to be fundamental to eye-hand coordination. We investigated interactions between saccades and reaching movements in a rhesus monkey model system. The amplitude and peak velocity of isolated eye movements are positively correlated with one another. This relationship is called the main sequence. We now report that the main sequence relationship for saccades is changed during coordinated eye and arm movements. In particular, peak eye velocity is approximately 4% faster for the same size saccade when the saccade is accompanied by a coordinated arm movement. Saccade duration is reduced by an equivalent amount. The main sequence relationship is unperturbed when the arm moves simultaneously but in the opposite direction as the eyes, suggesting that eye and arm movements must be tightly coordinated to produce th...

Research paper thumbnail of Region-Specific Summation Patterns Inform the Role of Cortical Areas in Selecting Motor Plans

Cerebral cortex (New York, N.Y. : 1991), Jan 15, 2015

Given an instruction regarding which effector to move and what location to move to, simply adding... more Given an instruction regarding which effector to move and what location to move to, simply adding the effector and spatial signals together will not lead to movement selection. For this, a nonlinearity is required. Thresholds, for example, can be used to select a particular response and reject others. Here we consider another useful nonlinearity, a supralinear multiplicative interaction. To help select a motor plan, spatial and effector signals could multiply and thereby amplify each other. Such an amplification could constitute one step within a distributed network involved in response selection, effectively boosting one response while suppressing others. We therefore asked whether effector and spatial signals sum supralinearly for planning eye versus arm movements from the parietal reach region (PRR), the lateral intraparietal area (LIP), the frontal eye field (FEF), and a portion of area 5 (A5) lying just anterior to PRR. Unlike LIP neurons, PRR, FEF, and, to a lesser extent, A5 ...

Research paper thumbnail of Impairment of the anterior thalamic head direction cell network following administration of the NMDA antagonist MK-801

Brain research bulletin, 2014

Head direction (HD) cells, found in the rodent Papez circuit, are thought to form the neural circ... more Head direction (HD) cells, found in the rodent Papez circuit, are thought to form the neural circuitry responsible for directional orientation. Because NMDA transmission has been implicated in spatial tasks requiring directional orientation, we sought to determine if the NMDA antagonist dizocilpine (MK-801) would disrupt the directional signal carried by the HD network. Anterior thalamic HD cells were isolated in female Long-Evans rats and initially monitored for baseline directional activity while the animals foraged in a familiar enclosure. The animals were then administered MK-801 at a dose of .05 mg/kg or 0.1 mg/kg, or isotonic saline, and cells were re-examined for changes in directional specificity and landmark control. While the cells showed no changes in directional specificity and landmark control following administration of saline or the lower dose of MK-801, the higher dose of MK-801 caused a dramatic attenuation of the directional signal, characterized by decreases in pe...

Research paper thumbnail of Conditioned Inhibition Produced by Extensive Extinction of a Conditioned Stimulus

Research paper thumbnail of Preparatory Delay Activity in the Monkey Parietal Reach Region Predicts Reach Reaction Times

Journal of Neuroscience, 2006

To acquire something that we see, visual spatial information must ultimately result in the activa... more To acquire something that we see, visual spatial information must ultimately result in the activation of the appropriate set of muscles. This sensory to motor transformation requires an interaction between information coding target location and information coding which effector will be moved. Activity in the monkey parietal reach region (PRR) reflects both spatial information and the effector (arm or eye) that will be used in an upcoming reach or saccade task. To further elucidate the functional role of PRR in visually guided movement tasks and to obtain evidence that PRR signals are used to drive arm movements, we tested the hypothesis that increased neuronal activity during a preparatory delay period would lead to faster reach reaction times but would not be correlated with saccade reaction times. This proved to be the case only when the type of movement and not the spatial goal of that movement was known in advance. The correlation was strongest in cells that showed significantly more activity on arm reach compared with saccade trials. No significant correlations were found during delay periods in which spatial information was provided in advance. These data support the idea that PRR constitutes a bottleneck in the processing of spatial information for an upcoming arm reach. The lack of a correlation with saccadic reaction time also supports the idea that PRR processing is effector specific, that is, it is involved in specifying targets for arm movements but not targets for eye movements.

Research paper thumbnail of Effects of acute swim stress on LiCl-induced conditioned taste aversions

Physiology & Behavior, 1992

Research paper thumbnail of Non-spatial, motor-specific activation in posterior parietal cortex

Nature Neuroscience, 2002

Posterior parietal cortex (PPC) seems to process spatial information in a way that is strongly in... more Posterior parietal cortex (PPC) seems to process spatial information in a way that is strongly influenced by how that information will be used 1-3 . The response to a visual and auditory stimulus in a cell's receptive field is often enhanced when that stimulus is behaviorally relevant 3-9 . The enhancement is not merely all or none; activity in the lateral intraparietal area (LIP), for example, seems to be continuously modulated by the return (reward) associated with a given target 10 .

Research paper thumbnail of Nonspatial Saccade-Specific Activation in area LIP of Monkey Parietal Cortex

Journal of Neurophysiology, 2003

Research paper thumbnail of Rat Head Direction Cell Responses in Zero-Gravity Parabolic Flight

Journal of Neurophysiology, 2004

Astronauts working in zerogravity (0-G) often experience visual reorientation illusions (VRIs). F... more Astronauts working in zerogravity (0-G) often experience visual reorientation illusions (VRIs). For example, when floating upside down, they commonly misperceive the spacecraft floor as a ceiling and have a reversed sense of direction. Previous studies have identified a population of neurons in the rat's brain that discharge as a function of the rat's head direction (HD) in a gravitationally horizontal plane and is dependent on an intact vestibular system. Our goal was to characterize HD cell discharge under conditions of acute weightlessness. Seven HD cells in the anterior dorsal thalamus were monitored from rats aboard an aircraft in 0-G parabolic flight. Unrestrained rats locomoted in a clear plexiglas rectangular chamber that had wire mesh covering the floor, ceiling, and one wall. The chamber and surrounding visual environment were relatively up-down symmetrical. Each HD cell was recorded across forty 20-s episodes of 0-G. All HD cells maintained a significant direction-specific discharge when the rat was on the chamber floor during the 0-G and also during the hypergravity pull-out periods. Three of five cells also showed direction-specific responses on the wall in 1-G. In contrast, direction-specific discharge was usually not maintained when the rat locomoted on the vertical wall or ceiling in 0-G. The loss of direction-specific firing was accompanied by an overall increase in background firing. However, while the rat was on the ceiling, some cells showed occasional bursts of firing when the rat's head was oriented in directions that were flipped relative to the long axis of symmetry of the chamber compared with the cell's preferred firing direction on the floor. This finding is consistent with what might be expected if the rat had experienced a VRI. These responses indicate that rats maintain a normal allocentric frame of reference in 0-G and 1-G when on the floor, but may lose their sense of directional heading when placed on a wall or ceiling during acute exposures to 0-G.

Research paper thumbnail of Conditioned inhibition produced by extinction-mediated recovery from the relative stimulus validity effect: A test of acquisition and performance models of empirical retrospective revaluation

Journal of Experimental Psychology: Animal Behavior Processes, 2001

Research paper thumbnail of Attenuation and reacquisition of foraging behavior in a patchy environment

Behavioural Processes, 1996

The present experiment examined the attenuation and reacquisition of foraging behavior of pigeons... more The present experiment examined the attenuation and reacquisition of foraging behavior of pigeons on a restricted diet. Using the procedure of Roberts (19881, thirty-two feeders were arranged in four circular patches of eight feeders each. The feeders were baited so that each patch contained a different density of food. Pigeons learned to forage among the patches. During this initial acquisition phase, visits to the patches by the pigeons differed as a function of the food density of the patches. After this initial foraging training phase, each pigeon received one of two response elimination procedures. For half of the subjects, food was not present during the response elimination phase. For the remaining subjects, food was placed exclusively outside the patches during this phase. Foraging behavior decreased quickly and somewhat similarly for both conditions. During a final phase in which the retraining of the original foraging behavior occurred, the group given food outside the patches during response elimination provided evidence of superior foraging with respect to sensitivity to the different patch food densities. The results are discussed with regard to previously published response elimination effects.

Research paper thumbnail of Combined blockade of serotonergic and muscarinic transmission disrupts the anterior thalamic head direction signal

Behavioral Neuroscience, 2008

Head direction (HD) cells have been speculated to be part of a network mediating navigational beh... more Head direction (HD) cells have been speculated to be part of a network mediating navigational behavior. Previous work has shown that combined administration of serotonergic and muscarinic antagonists eliminates hippocampal theta activity and produces navigational deficits more severe than blockade of either neurotransmitter system alone. The authors sought to assess this effect on the directional characteristics of HD cells. HD cells were recorded from the anterior dorsal thalamus of Long-Evans rats before and after administration of the serotonergic antagonist methiothepin, the muscarinic antagonist scopolamine, both drugs, or saline. Combined drug administration produced HD cells with preferred directions that drifted within recording sessions. In addition, cells showed shifts in the preferred directions at the start of a session relative to the position of the major landmarks, suggesting that combined drug administration led to deficits in landmark control of the HD system. Single drug exposures to methiothepin or scopolamine did not noticeably affect the directional characteristics of HD cells. This finding that navigation-impairing drugs can disrupt the HD signal provides further evidence that this network plays an important role in navigational behavior.

Research paper thumbnail of Landmark control and updating of self-movement cues are largely maintained in head direction cells after lesions of the posterior parietal cortex

Behavioral Neuroscience, 2008

Head direction (HD) cells discharge as a function of the rat's directional orientation with respe... more Head direction (HD) cells discharge as a function of the rat's directional orientation with respect to its environment. Because animals with posterior parietal cortex (PPC) lesions exhibit spatial and navigational deficits, and the PPC is indirectly connected to areas containing HD cells, we determined the effects of bilateral PPC lesions on HD cells recorded in the anterodorsal thalamus. HD cells from lesioned animals had similar firing properties compared to controls and their preferred firing directions shifted a corresponding amount following rotation of the major visual landmark. Because animals were not exposed to the visual landmark until after surgical recovery, these results provide evidence that the PPC is not necessary for visual landmark control or the establishment of landmark stability. Further, cells from lesioned animals maintained a stable preferred firing direction when they foraged in the dark and were only slightly less stable than controls when they self-locomoted into a novel enclosure. These findings suggest that PPC does not play a major role in the use of landmark and self-movement cues in updating the HD cell signal, or in its generation.

Research paper thumbnail of Magnetic field polarity fails to influence the directional signal carried by the head direction cell network and the behavior of rats in a task requiring magnetic field orientation

Behavioral Neuroscience, 2012

Many different species of animals including mole rats, pigeons, and sea turtles are thought to us... more Many different species of animals including mole rats, pigeons, and sea turtles are thought to use the magnetic field of the earth for navigational guidance. While laboratory rats are commonly used for navigational research, and brain networks have been described in these animals that presumably mediate accurate spatial navigation, little has been done to determine the role of the geomagnetic field in these brain networks and in the navigational behavior of these animals. In Experiment 1, anterior thalamic head direction (HD) cells were recorded in female Long-Evans rats while they foraged in an environment subjected to an experimentally generated magnetic field of earth-strength intensity, the polarity of which could be shifted from one session to another. Despite previous work that has shown that the preferred direction of HD cells can be controlled by the position of familiar landmarks in a recording environment, the directional signal of HD cells was not influenced by the polarity of the magnetic field in the enclosure. Because this finding could be attributed to the animal being insensitive or inattentive to the magnetic field, in Experiment 2, rats were trained in a choice maze task dependent on the ability of the animals to sense the polarity of the experimentally controlled magnetic field. Over the course of 28 days of training, performance failed to improve to a level above chance, providing evidence that the spatial behavior of laboratory rats (and the associated HD network) is insensitive to the polarity of the geomagnetic field.

Research paper thumbnail of Head Movements and Vestibular Firing Properties Anticipation in the Rodent Head Direction System Can Be Explained by an Interaction of

Research paper thumbnail of NMDA blockade inhibits experience-dependent modification of anterior thalamic head direction cells

Behavioral neuroscience, 2015

Head Direction (HD) cells of the rodent Papez circuit are thought to reflect the spatial orientat... more Head Direction (HD) cells of the rodent Papez circuit are thought to reflect the spatial orientation of the animal. Because NMDA transmission is important for spatial behavior, we sought to determine the effects of NMDA blockade on the basic directional signal carried by HD cells and on experience-dependent modification of this system. In Experiment 1, HD cells were recorded from the anterior dorsal thalamus in female Long-Evans rats while they foraged in a familiar enclosure following administration of the NMDA antagonist CPP or saline. While the drug produced a significant decrease in peak firing rates, it failed to affect the overall directional specificity and landmark control of HD cells. Experiment 2 took place over 2 days and assessed whether the NMDA antagonist would interfere with the stabilization of the HD network in a novel environment. On Day 1 the animal was administered CPP or saline and placed in a novel enclosure to allow the stabilization of the HD signal relative ...

Research paper thumbnail of Hippocampal place cell instability after lesions of the head direction cell network

The Journal of neuroscience : the official journal of the Society for Neuroscience, Jan 29, 2003

The occurrence of cells that encode spatial location (place cells) or head direction (HD cells) i... more The occurrence of cells that encode spatial location (place cells) or head direction (HD cells) in the rat limbic system suggests that these cell types are important for spatial navigation. We sought to determine whether place fields of hippocampal CA1 place cells would be altered in animals receiving lesions of brain areas containing HD cells. Rats received bilateral lesions of anterodorsal thalamic nuclei (ADN), postsubiculum (PoS), or sham lesions, before place cell recording. Although place cells from lesioned animals did not differ from controls on many place-field characteristics, such as place-field size and infield firing rate, the signal was significantly degraded with respect to measures of outfield firing rate, spatial coherence, and information content. Surprisingly, place cells from lesioned animals were more likely modulated by the directional heading of the animal. Rotation of the landmark cue showed that place fields from PoS-lesioned animals were not controlled by t...

Research paper thumbnail of Eye-hand coordination: saccades are faster when accompanied by a coordinated arm movement

Journal of neurophysiology, 2002

When primates reach for an object, they very often direct an eye movement toward the object as we... more When primates reach for an object, they very often direct an eye movement toward the object as well. This pattern of directing both eye and limb movements to the same object appears to be fundamental to eye-hand coordination. We investigated interactions between saccades and reaching movements in a rhesus monkey model system. The amplitude and peak velocity of isolated eye movements are positively correlated with one another. This relationship is called the main sequence. We now report that the main sequence relationship for saccades is changed during coordinated eye and arm movements. In particular, peak eye velocity is approximately 4% faster for the same size saccade when the saccade is accompanied by a coordinated arm movement. Saccade duration is reduced by an equivalent amount. The main sequence relationship is unperturbed when the arm moves simultaneously but in the opposite direction as the eyes, suggesting that eye and arm movements must be tightly coordinated to produce th...

Research paper thumbnail of Region-Specific Summation Patterns Inform the Role of Cortical Areas in Selecting Motor Plans

Cerebral cortex (New York, N.Y. : 1991), Jan 15, 2015

Given an instruction regarding which effector to move and what location to move to, simply adding... more Given an instruction regarding which effector to move and what location to move to, simply adding the effector and spatial signals together will not lead to movement selection. For this, a nonlinearity is required. Thresholds, for example, can be used to select a particular response and reject others. Here we consider another useful nonlinearity, a supralinear multiplicative interaction. To help select a motor plan, spatial and effector signals could multiply and thereby amplify each other. Such an amplification could constitute one step within a distributed network involved in response selection, effectively boosting one response while suppressing others. We therefore asked whether effector and spatial signals sum supralinearly for planning eye versus arm movements from the parietal reach region (PRR), the lateral intraparietal area (LIP), the frontal eye field (FEF), and a portion of area 5 (A5) lying just anterior to PRR. Unlike LIP neurons, PRR, FEF, and, to a lesser extent, A5 ...

Research paper thumbnail of Impairment of the anterior thalamic head direction cell network following administration of the NMDA antagonist MK-801

Brain research bulletin, 2014

Head direction (HD) cells, found in the rodent Papez circuit, are thought to form the neural circ... more Head direction (HD) cells, found in the rodent Papez circuit, are thought to form the neural circuitry responsible for directional orientation. Because NMDA transmission has been implicated in spatial tasks requiring directional orientation, we sought to determine if the NMDA antagonist dizocilpine (MK-801) would disrupt the directional signal carried by the HD network. Anterior thalamic HD cells were isolated in female Long-Evans rats and initially monitored for baseline directional activity while the animals foraged in a familiar enclosure. The animals were then administered MK-801 at a dose of .05 mg/kg or 0.1 mg/kg, or isotonic saline, and cells were re-examined for changes in directional specificity and landmark control. While the cells showed no changes in directional specificity and landmark control following administration of saline or the lower dose of MK-801, the higher dose of MK-801 caused a dramatic attenuation of the directional signal, characterized by decreases in pe...

Research paper thumbnail of Conditioned Inhibition Produced by Extensive Extinction of a Conditioned Stimulus

Research paper thumbnail of Preparatory Delay Activity in the Monkey Parietal Reach Region Predicts Reach Reaction Times

Journal of Neuroscience, 2006

To acquire something that we see, visual spatial information must ultimately result in the activa... more To acquire something that we see, visual spatial information must ultimately result in the activation of the appropriate set of muscles. This sensory to motor transformation requires an interaction between information coding target location and information coding which effector will be moved. Activity in the monkey parietal reach region (PRR) reflects both spatial information and the effector (arm or eye) that will be used in an upcoming reach or saccade task. To further elucidate the functional role of PRR in visually guided movement tasks and to obtain evidence that PRR signals are used to drive arm movements, we tested the hypothesis that increased neuronal activity during a preparatory delay period would lead to faster reach reaction times but would not be correlated with saccade reaction times. This proved to be the case only when the type of movement and not the spatial goal of that movement was known in advance. The correlation was strongest in cells that showed significantly more activity on arm reach compared with saccade trials. No significant correlations were found during delay periods in which spatial information was provided in advance. These data support the idea that PRR constitutes a bottleneck in the processing of spatial information for an upcoming arm reach. The lack of a correlation with saccadic reaction time also supports the idea that PRR processing is effector specific, that is, it is involved in specifying targets for arm movements but not targets for eye movements.

Research paper thumbnail of Effects of acute swim stress on LiCl-induced conditioned taste aversions

Physiology & Behavior, 1992

Research paper thumbnail of Non-spatial, motor-specific activation in posterior parietal cortex

Nature Neuroscience, 2002

Posterior parietal cortex (PPC) seems to process spatial information in a way that is strongly in... more Posterior parietal cortex (PPC) seems to process spatial information in a way that is strongly influenced by how that information will be used 1-3 . The response to a visual and auditory stimulus in a cell's receptive field is often enhanced when that stimulus is behaviorally relevant 3-9 . The enhancement is not merely all or none; activity in the lateral intraparietal area (LIP), for example, seems to be continuously modulated by the return (reward) associated with a given target 10 .

Research paper thumbnail of Nonspatial Saccade-Specific Activation in area LIP of Monkey Parietal Cortex

Journal of Neurophysiology, 2003

Research paper thumbnail of Rat Head Direction Cell Responses in Zero-Gravity Parabolic Flight

Journal of Neurophysiology, 2004

Astronauts working in zerogravity (0-G) often experience visual reorientation illusions (VRIs). F... more Astronauts working in zerogravity (0-G) often experience visual reorientation illusions (VRIs). For example, when floating upside down, they commonly misperceive the spacecraft floor as a ceiling and have a reversed sense of direction. Previous studies have identified a population of neurons in the rat's brain that discharge as a function of the rat's head direction (HD) in a gravitationally horizontal plane and is dependent on an intact vestibular system. Our goal was to characterize HD cell discharge under conditions of acute weightlessness. Seven HD cells in the anterior dorsal thalamus were monitored from rats aboard an aircraft in 0-G parabolic flight. Unrestrained rats locomoted in a clear plexiglas rectangular chamber that had wire mesh covering the floor, ceiling, and one wall. The chamber and surrounding visual environment were relatively up-down symmetrical. Each HD cell was recorded across forty 20-s episodes of 0-G. All HD cells maintained a significant direction-specific discharge when the rat was on the chamber floor during the 0-G and also during the hypergravity pull-out periods. Three of five cells also showed direction-specific responses on the wall in 1-G. In contrast, direction-specific discharge was usually not maintained when the rat locomoted on the vertical wall or ceiling in 0-G. The loss of direction-specific firing was accompanied by an overall increase in background firing. However, while the rat was on the ceiling, some cells showed occasional bursts of firing when the rat's head was oriented in directions that were flipped relative to the long axis of symmetry of the chamber compared with the cell's preferred firing direction on the floor. This finding is consistent with what might be expected if the rat had experienced a VRI. These responses indicate that rats maintain a normal allocentric frame of reference in 0-G and 1-G when on the floor, but may lose their sense of directional heading when placed on a wall or ceiling during acute exposures to 0-G.

Research paper thumbnail of Conditioned inhibition produced by extinction-mediated recovery from the relative stimulus validity effect: A test of acquisition and performance models of empirical retrospective revaluation

Journal of Experimental Psychology: Animal Behavior Processes, 2001

Research paper thumbnail of Attenuation and reacquisition of foraging behavior in a patchy environment

Behavioural Processes, 1996

The present experiment examined the attenuation and reacquisition of foraging behavior of pigeons... more The present experiment examined the attenuation and reacquisition of foraging behavior of pigeons on a restricted diet. Using the procedure of Roberts (19881, thirty-two feeders were arranged in four circular patches of eight feeders each. The feeders were baited so that each patch contained a different density of food. Pigeons learned to forage among the patches. During this initial acquisition phase, visits to the patches by the pigeons differed as a function of the food density of the patches. After this initial foraging training phase, each pigeon received one of two response elimination procedures. For half of the subjects, food was not present during the response elimination phase. For the remaining subjects, food was placed exclusively outside the patches during this phase. Foraging behavior decreased quickly and somewhat similarly for both conditions. During a final phase in which the retraining of the original foraging behavior occurred, the group given food outside the patches during response elimination provided evidence of superior foraging with respect to sensitivity to the different patch food densities. The results are discussed with regard to previously published response elimination effects.

Research paper thumbnail of Combined blockade of serotonergic and muscarinic transmission disrupts the anterior thalamic head direction signal

Behavioral Neuroscience, 2008

Head direction (HD) cells have been speculated to be part of a network mediating navigational beh... more Head direction (HD) cells have been speculated to be part of a network mediating navigational behavior. Previous work has shown that combined administration of serotonergic and muscarinic antagonists eliminates hippocampal theta activity and produces navigational deficits more severe than blockade of either neurotransmitter system alone. The authors sought to assess this effect on the directional characteristics of HD cells. HD cells were recorded from the anterior dorsal thalamus of Long-Evans rats before and after administration of the serotonergic antagonist methiothepin, the muscarinic antagonist scopolamine, both drugs, or saline. Combined drug administration produced HD cells with preferred directions that drifted within recording sessions. In addition, cells showed shifts in the preferred directions at the start of a session relative to the position of the major landmarks, suggesting that combined drug administration led to deficits in landmark control of the HD system. Single drug exposures to methiothepin or scopolamine did not noticeably affect the directional characteristics of HD cells. This finding that navigation-impairing drugs can disrupt the HD signal provides further evidence that this network plays an important role in navigational behavior.

Research paper thumbnail of Landmark control and updating of self-movement cues are largely maintained in head direction cells after lesions of the posterior parietal cortex

Behavioral Neuroscience, 2008

Head direction (HD) cells discharge as a function of the rat's directional orientation with respe... more Head direction (HD) cells discharge as a function of the rat's directional orientation with respect to its environment. Because animals with posterior parietal cortex (PPC) lesions exhibit spatial and navigational deficits, and the PPC is indirectly connected to areas containing HD cells, we determined the effects of bilateral PPC lesions on HD cells recorded in the anterodorsal thalamus. HD cells from lesioned animals had similar firing properties compared to controls and their preferred firing directions shifted a corresponding amount following rotation of the major visual landmark. Because animals were not exposed to the visual landmark until after surgical recovery, these results provide evidence that the PPC is not necessary for visual landmark control or the establishment of landmark stability. Further, cells from lesioned animals maintained a stable preferred firing direction when they foraged in the dark and were only slightly less stable than controls when they self-locomoted into a novel enclosure. These findings suggest that PPC does not play a major role in the use of landmark and self-movement cues in updating the HD cell signal, or in its generation.

Research paper thumbnail of Magnetic field polarity fails to influence the directional signal carried by the head direction cell network and the behavior of rats in a task requiring magnetic field orientation

Behavioral Neuroscience, 2012

Many different species of animals including mole rats, pigeons, and sea turtles are thought to us... more Many different species of animals including mole rats, pigeons, and sea turtles are thought to use the magnetic field of the earth for navigational guidance. While laboratory rats are commonly used for navigational research, and brain networks have been described in these animals that presumably mediate accurate spatial navigation, little has been done to determine the role of the geomagnetic field in these brain networks and in the navigational behavior of these animals. In Experiment 1, anterior thalamic head direction (HD) cells were recorded in female Long-Evans rats while they foraged in an environment subjected to an experimentally generated magnetic field of earth-strength intensity, the polarity of which could be shifted from one session to another. Despite previous work that has shown that the preferred direction of HD cells can be controlled by the position of familiar landmarks in a recording environment, the directional signal of HD cells was not influenced by the polarity of the magnetic field in the enclosure. Because this finding could be attributed to the animal being insensitive or inattentive to the magnetic field, in Experiment 2, rats were trained in a choice maze task dependent on the ability of the animals to sense the polarity of the experimentally controlled magnetic field. Over the course of 28 days of training, performance failed to improve to a level above chance, providing evidence that the spatial behavior of laboratory rats (and the associated HD network) is insensitive to the polarity of the geomagnetic field.