Changing the intended direction of movement

Somesthesis and the Neurobiology of the Somatosensory Cortex - 1996-01-01Pellizzer G10.1007/978-3-0348-9016-8
The behavioral and neural correlates of processing of motor directional information are described for two different visuomotor tasks: mental rotation and context-recall. Psychological studies in human subjects suggested that these two tasks may involve different mechanisms processing directional information. Analyses of the activity of single cells and neuronal populations in the motor cortex of behaving monkeys performing in the same tasks provided direct insight into the neural mechanisms involved, and confirmed their different nature.

Assessment of
Posttraumatic Stress Disorder

Posttraumatic Stress Disorder (PTSD)

A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.
in World War II Veterans

Psychological Assessment - 1996-01-01Engdahl B, Eberly RE, Blake JD10.1037/1040-3590.8.4.445
Four
Posttraumatic Stress Disorder

Posttraumatic Stress Disorder (PTSD)

A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.
scales were compared in a community sample of 330 American former prisoners of war and combat veterans of World War II. The Mississippi Scale for Combat-Related
PTSD

Posttraumatic Stress Disorder (PTSD)

A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.
(M-
PTSD

Posttraumatic Stress Disorder (PTSD)

A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.
), the Minnesota Multiphasic Personality Inventory-2 Pk
PTSD

Posttraumatic Stress Disorder (PTSD)

A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.
scale, and the Impact of Event Scale (IES) all demonstrated moderate relationships with
PTSD

Posttraumatic Stress Disorder (PTSD)

A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.
as defined by the Structured Clinical Interview for DSM-III-R. Comparative validities were similar to those observed in Vietnam veteran samples. Confirmatory factor analysis indicated that the 3 scales loaded significantly on 1 factor. The impact of Diagnostic and Statistical Manual of Mental Disorders (4th ed.)
PTSD

Posttraumatic Stress Disorder (PTSD)

A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.
criteria changes was examined and found to be minimal. Implications for the use of the M-
PTSD

Posttraumatic Stress Disorder (PTSD)

A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.
, Pk, and IES in combat-related
PTSD

Posttraumatic Stress Disorder (PTSD)

A complex psychiatric syndrome that develops in response to trauma exposure. Individuals with PTSD experience intrusive recollections or reexperiencing of the traumatic event, avoidance of trauma reminders, emotional numbing, and hyperarousal. In addition, PTSD is associated with high rates of concomitant physical and mental health problems, increased health care use, and impairment in social and occupational functioning. Almost 7% of the general population and up to 30% of veterans meet lifetime criteria for PTSD. Indeed, PTSD is one of the most common psychiatric disorders, representing a significant and costly public health concern.
assessment are discussed.

The mental and the neural: Psychological and neural studies of mental rotation and memory scanning

In this article we review studies pertaining to psychophysical measurements and neural correlates of tasks requiring the processing of directional information in spatial motor tasks. The results of psychological studies in human subjects indicate that time-consuming processes underlie mental rotation and memory scanning. Other studies have suggested that these processes may rely on different basic mechanisms. A direct insight into their neural mechanisms was obtained analyzing the activity of single cells and neuronal populations in the brain of behaving monkeys performing the same tasks. These studies revealed the nature of the neural processes underlying mental rotation and memory scanning and confirmed their different nature.

System for projection of a three-dimensional, moving virtual target for studies of eye-hand coordination

Journal of Neuroscience Methods - 1995-11-01Schneider W, Harris TJ, Feldberg IE, Massey JT, Georgopoulos AP, Meyer RA10.1016/0165-0270(95)00068-2
Eye-hand tracking of moving visual objects in three-dimensional (3D) space is common in the behavioral repertoire of primates. However, behavioral and/or neurophysiological studies of this function are lacking mainly because devices do not exist that allow its investigation. We describe a device by which a spot of light can be presented in the immediate extrapersonal space of a subject and can be moved in various trajectories in 3D space. The target is a real image of a circular aperture produced by a system consisting of a light source, aperture, filters, several lenses and fold mirros, and a large concave mirror to focus the final real image. Rapid, computer-controlled movement of the image is obtained by tilting a gimbal-mounted guide mirror (for x and y motion) and by translating a lens (for motion in the z direction). A second configuration of the system allows movement of a 3D image in the 3D...

Current issues in directional motor control

Trends in Neurosciences - 1995-11-01Georgopoulos AP10.1016/0166-2236(95)92775-L
Many studies during the past 15 years have shown that the direction of motor output (movement or isometric force) is an important factor for neuronal activity in the motor cortex, both at the level of single cells and at the level of neuronal populations. Recent studies have investigated several new aspects of this problem including the effect of posture, the relations to time-varying movement parameters (for example, position, velocity and acceleration) and the cortical representation of memorized simple movements and complex-movement trajectories. Furthermore, the neural correlates of directional operations, such as mental rotation and memory-scanning of visuomotor directions, have also been investigated. In addition, neural networks have been used to model dynamic, time-varying, spatial motor trajectories.

Colon cancer: Personality factors predictive of onset and stage of presentation

Journal of Psychosomatic Research - 1995-11-01Kavan MG, Engdahl B, Kay S10.1016/0022-3999(95)00523-4
This study examined premorbid personality correlates of colon cancer and stage of presentation of colon cancer to health care providers. Sixty-one male veterans who completed the MMPI between 1947 and 1975 and were then diagnosed with colon cancer between 1977 and 1988 were matched with control patients. A 21-factor solution of the MMPI [1] was used to seek potential personality differences between colon cancer cases and their controls in terms of presence of colon cancer and stage of presentation for this disease. A stepwise conditional regression analysis found significant differences between the colon cancer and control groups on the Aggressive Hostility variable (p<0.018). A multivariate analysis of variance conducted across the stages of colon cancer presentation found that patients who presented later on for colon cancer had higher Phobia scores (p<0.05). Religious Fundamentalism who also related to presentation (p<0.05), but in a nonlinear manner. Discussion is related to previous findings regarding...

Motor cortical activity in a context-recall task

A monkey was trained to respond on the basis of the serial position of a test stimulus in a sequence. First, three stimuli were presented successively on a circle. Then one of them (except the last) changed color (test stimulus) and served as the go signal: The monkey was required to produce a motor response in the direction of the stimulus that followed the test stimulus. When the test stimulus was the second in the sequence, there was a change in motor cortical activity from a pattern reflecting the direction of this stimulus to the pattern associated with the direction of the motor response. This change was abrupt, occurred 100 to 150 milliseconds after the go signal, and was evident both in the activity of single cells and in the time-varying neuronal population vector. These findings identify the neural correlates of a switching process that is different from a mental rotation...

Motor cortex and cognitive processing

The Cognitive Neurosciences - 1995-01-01Georgopoulos AP
summarizes key observations and concepts concerning the involvement of the motor cortex in [the] motor cognitive processes operating on the direction of movement in space / large populations of neurons in motor cortex are engaged with reaching movements / single cells are directionally broadly tuned, but the neuronal population carries an unambiguous directional signal / the outcome of this population code can be visualized as a vector that points in the direction of the upcoming movement during the reaction time, during an instructed delay period, and during a memorized delay period / moreover, when a mental transformation is required for the generation of a reaching movement in a direction different from a reference direction, the population vector provides a direct insight into the nature of the cognitive process by which the required transformation is achieved (PsycINFO Database Record (c) 2019 APA, all rights reserved)

Image and Brain: The Resolution of the Imagery Debate

Science - 1995-01-01Georgopoulos AP
Kosslyn's Image and Brain is a tour de force in the analysis of visual perception and imagery, looked upon from all possible perspectives. It is an examination of work done during the past 15 years on visual imagery by a variety of methods, from chronometric measurements to computer models to functional brain imaging, bringing a systematic approach to bear on this multitude of data to delineate the issues of brain mechanisms underlying visual perception and imagery. The scheme adopted posits a number of systems and subsystems (for example for edge detection and for encoding motion relations) that process specific kinds of information and that together make for an apparently seamless operation of visual perception and imagery. This analytical approach is open-ended, in the sense that more processing stations can be adduced if need or evidence for them arises; it is flexible, so that rearrangements in processing order are allowed for; and...

Population activity in the control of movement

International Review of Neurobiology - 1994-12-23Georgopoulos AP
This review summarizes key observations and concepts concerning the role of neuronal populations in specification and control of the direction of movement and isometric force. Large populations of neurons in the motor cortex are engaged with reaching movements. This engagement is fairly early, starting approximately 60 msec following target onset. Single cells are directionally broadly tuned, but the neuronal population carries an unambiguous directional signal. The outcome of this population code can be visualized as a vector that points in the direction of the upcoming movement during the reaction time, during an instructed delay period, and during a memorized delay period. Moreover, when a mental transformation is required for the generation of a reaching movement in a different direction from a reference direction, the population vector provides a direct insight into the nature of the cognitive process by which the required transformation is achieved.

Behavioral neurophysiology of the motor cortex

Journal of Laboratory and Clinical Medicine - 1994-12-01Georgopoulos AP
The study of the motor cortex in behaving monkeys during the past 20 years has provided important information on the brain mechanisms underlying motor control. With respect to reaching movements in space, several aspects of motor cortical function concerning the specification of the direction of movement have now been elucidated and are reviewed in this article. The activity of single cells in the motor cortex is broadly tuned with respect to the direction of reaching, so that the discharge rate is highest with movements in a preferred direction and decreases progressively with movements made in directions more and more away from the preferred one. Thus the neural command for the direction of reaching can be regarded as an ensemble of cell vectors, with each vector pointing in the cell's preferred direction and having a length proportional to the change in cell activity. The outcome of this population code can be visualized...

Movement Parameters and Neural Activity in Motor Cortex and Area 5

The relations of ongoing single-cell activity in the arm area of the motor cortex and area 5 to parameters of evolving arm movements in two-dimensional (2D) space were investigated. A multiple linear regression model was used in which the ongoing impulse activity of cells at time t + τ was expressed as a function of the (X, Y) components of the target direction and of position, velocity, and acceleration of the hand at time t, where τ was a time shift (-200 to +200 msec). Analysis was done on 290 cells in the motor cortex and 207 cells in area 5. The time shift at which the highest coefficient of determination (R2) was observed was determined and the statistical significance of the model tested. The median R2 was 0.581 and 0.530 for motor cortex and area 5, respectively. The median shift at which the highest R2 was observed was -90 and...

Overlapping neural networks for multiple motor engrams

Proceedings of the National Academy of Sciences - 1994-08-30Lukashin A, Wilcox GL, Georgopoulos AP10.1073/pnas.91.18.8651
The hypothesis was tested that learned movement trajectories of different shapes can be stored in, and generated by, largely overlapping neural networks. Indeed, it was possible to train a massively interconnected neural network to generate different shapes of internally stored, dynamically evolving movement trajectories using a general-purpose core part, common to all networks, and a special-purpose part, specific for a particular trajectory. The weights of connections between the core units do not carry any information about trajectories. The core network alone could generate externally instructed trajectories but not internally stored ones, for which both the core and the trajectory-specific part were needed. All information about the movements is stored in the weights of connections between the core part and the specialized units and between the specialized units themselves. Due to these connections the core part reveals specific dynamical behavior for a particular trajectory and, as the result, discriminates different tasks. The...

New concepts in generation of movement

The motor cortex has long been regarded as a key node in the generation of motor output, based on observations of patients with motor seizures (Jackson 1889) as well as results from various kinds of studies employing lesions and electrical stimulation (Porter and Lemon, 1993). Evarts (1966, 1968, 1969) recorded the impulse activity of single cells in the motor cortex of behaving monkeys. He showed that cells typically changed activity before the first changes in muscle activity and that the frequency of discharge varied during movement or production of isometric force. These studies initiated research into the role of the motor cortex in the specification and control of motor output, a subject that has been hotly debated and widely speculated upon and that remains under active investigation. Simplistic notions of motor cortical function have been exemplified by the view that motor cortical cells are simply "upper motorneurons." This view is clearly...

Directional operations in the motor cortex modeled by a neural network of spiking neurons

Biological Cybernetics - 1994-05-01Lukashin A, Georgopoulos AP10.1007/BF00198913
A neural network with realistically modeled, spiking neurons is proposed to model ensemble operations of directionally tuned neurons in the motor cortex. The model reproduces well directional operations previously identified experimentally, including the prediction of the direction of an upcoming movement in reaching tasks and the rotation of the neuronal population vector in a directional transformation task.

Measuring Synaptic Interactions

Science - 1994-03-04Fetz EE, Shupe LE, Georgopoulos AP, Taira M, Lukashin A
A.P. Georgopoulos et al. present novel evidence which suggests that synaptic interactions between pairs of cortical neurons are directly related to the degree to which they fire together during directed limb movements. The cover for the issue of 2 April depicts synaptic interactions ranging form strongly excitatory (for cells with similiar direction preferences) to strongly inhibitory (for cells with opposite direcction preference). The calculation used by Georgopooulos et al. to document synaptic interaction differs from the cross correlation traditionally used to measure the effects of synaptic connections on firing probability. Instead, they "estimated the strength of presumed interaction (synaptic weight) from the i-th to the j-th neuron in a pair using an analysis based on waiting time probability density function...".

Representations of movement and representations in movement

Behavioral Brain Science - 1994-01-01Pellizzer G, Georgopoulos AP
Marc Jeannerod champions the cognitive approach to motor control from an innovative perspective. In his target article he appraises the role of mental representations in the preparation and control of movement by considering studies on mental imagery. Although this may seem odd at first, this strategy provides significant advances into the understanding of the role of mental representation in the control of movement. In recent work we applied a strategy akin to the one advocated by Jeannerod, namely, we used mental imagery paradigms to study properties of representations of movement (Pellizzer & Georgopoulos 1993a). In this commentary we would like to present some studies on mental transformations of the intended direction of movement. Moreover, we would like to show that this strategy can give information on properties of motor representations not only at a "macroscopic" level (e.g., movement time), as in the examples presented in the target article, but also at...

A Neural Network for Coding of Trajectories by Time Series of Neuronal Population Vectors

The neuronal population vector is a measure of the combined directional tendency of the ensemble of directionally tuned cells in the motor cortex. It has been found experimentally that a trajectory of limb movement can be predicted by adding together population vectors, tip-to-tail, calculated for successive instants of time to construct a neural trajectory. In the present paper we consider a model of the dynamic evolution of the population vector. The simulated annealing algorithm was used to adjust the connection strengths of a feedback neural network so that it would generate a given trajectory by a sequence of population vectors. This was repeated for different trajectories. Resulting sets of connection strengths reveal a common feature regardless of the type of trajectories generated by the network: namely, the mean connection strength was negatively correlated with the angle between the preferred directions of neuronal pair involved in the connection. The results are discussed...

Mechanisms of Eye-Hand Coordination

Defense Technical Information Center - 1993-11-29Georgopoulos AP
We studied the capacities of human subjects to localize tactile stimuli in 3D space. For that purpose, five subjects (3 women and 2 men) were asked to make a pointing movement to a visual stimulus in otherwise complete darkness. At some random time before, during or after this initial movement, a tactile probe was presented to the tip of the subject's index finger. The probe (1-mm diameter, 0.75-mm extent, 5-ms duration) was applied by a lightweight (80 g) tactile stimulator worn on the subject's hand. To complete the task, the subject was required to point to the 3D spatial location at which the probe was applied. Hand position was monitored (200 Hz) by a video-based motion analysis system. In each subject, probes presented just before or during the initial movement were systematically mislocalized in the direction of that movement so that subjects perceived the probe to be at the location occupied...

A dynamical neural network model for motor cortical activity during movement: population coding of movement trajectories

Biological Cybernetics - 1993-09-01Lukashin A, Georgopoulos AP10.1007/BF01185423
As a dynamical model for motor cortical activity during hand movement we consider an artificial neural network that consists of extensively interconnected neuron-like units and performs the neuronal population vector operations. Local geometrical parameters of a desired curve are introduced into the network as an external input. The output of the model is a time-dependent direction and length of the neuronal population vector which is calculated as a sum of the activity of directionally tuned neurons in the ensemble. The main feature of the model is that dynamical behavior of the neuronal population vector is the result of connections between directionally tuned neurons rather than being imposed externally. The dynamics is governed by a system of coupled nonlinear differential equations. Connections between neurons are assigned in the simplest and most common way so as to fulfill basic requirements stemming from experimental findings concerning the directional tuning of individual neurons and the...

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