The motor cortex and the coding of force

The relation of cellular activity in the motor cortex to the direction of two-dimensional isometric force was investigated under dynamic conditions in monkeys. A task was designed so that three force variables were dissociated: the force exerted by the subject, the net force, and the change in force. Recordings of neuronal activity in the motor cortex revealed that the activity of single cells was directionally tuned and that this tuning was invariant across different directions of a bias force. Cell activity was not related to the direction of force exerted by the subject, which changed drastically as the bias force changed. In contrast, the direction of net force, the direction of force change, and the visually instructed direction all remained quite invariant and congruent and could be the directional variables, alone or in combination, to which cell activity might relate.

Three-dimensional drawings in isometric conditions: relation between geometry and kinematics

Normal human subjects grasped a 3-D isometric handle with an otherwise unrestrained, pronated hand and exerted forces continuously to draw circles, ellipses and lemniscates (figure-eights) in specified planes in the presence or absence of a 3-D visual force-feedback cursor and a visual template. Under any of these conditions and in all subjects, a significant positive correlation was observed between the instantaneous curvature and angular velocity, and between the instantaneous radius of curvature and tangential velocity; that is, when the force trajectory was most curved, the tangential velocity was lowest. This finding is similar to that obtained by Viviani and Terzuolo (1982) for 2-D drawing arm movements and supports the notion that central constraints give rise to the relation between geometric and kinematic parameters of the trajectory.

Motor Cortex: A Changing Perspective

The study of the motor cortex in the full-blown behavioral context of voluntary movement was introduced by Evarts (1966, 1968, 1969). INdeed, this is the only appropriate way to study the initiaition of voluntary movement. The possibility of studying single cell activity in the behaving animal (Ricci et al. 1957) ahs opened new avenues and has changed the way in which we look at the neural bases of motor behavior, especially since motor mechanisms can be studied not only within narrowly defined motor conditions but also within a wide variety of behavioral contexts. Some of the changes that have gradually occurred during the past 25 years or so are outlined and briefly discussed below.
Authors: Georgopoulos APExperimental Brain Research Supplement - 1992-01-01

Cortical control of motor behavior at the cellular level

The studies reviewed in this paper describe the relations of single-cell activity in central motor structures to complex visuomotor tasks and document the fact that various cortical areas process visuomotor information in parallel. Moreover, the studies provide clear evidence that the map in the motor cortex is modifiable and dynamically maintained.

Biomedical program research: The primate motor system

The the Johns Hopkins University Applied Physics Laboratory-Medical School Collaborative Biomedical Program was begun in the mid-1960s, one of the major facets was to engage the technical expertise of the engineers and physical scientists at the Laboratory to apply state-of-the-art technology to the solution of extant biological problems. A major accomplishment of this program has been the design and fabrication of unique instruments and systems that allow the exploration of specific research protocols designed to delineate the role of individual behavioral and physiological variables in studies of primate motor performance. The specific instruments provided through this collaborative program are summarized, as are the research results produced by their use over the past twenty years. The principal result of this research has been to delineate the role of the primate motor cortex in specifying and/or controlling upper-limb movements controlled by the proximal joints.
Authors: Georgopoulos AP, Massey JTJohns Hopkins APL Technical Digest - 1991-12-01

Prevalence and Correlates of Depressive Symptoms among Former Prisoners of War

Studies of former prisoners of war (POWs) provide valuable insights into posttraumatic adaptation because they gather information from a large population who survived the traumatic experiences of military captivity. Previous studies of POWs have shown elevated rates of psychiatric symptoms and disorders. This report presents evidence from a longitudinal study of three large, representative, national samples of former POWs. The study finds that depressive symptomatology, as measured by the Center for Epidemiologic Studies Depression Scale, is elevated in World War II POWs from the Pacific and European theaters and in Korean conflict POWs. Decades later, depressive symptomatology is found to be strongly associated with prior treatment in captivity. Differences in depressive symptomatology among the three POW groups can be attributed to captivity-related factors and to buffering factors, such as age at capture and education.
Authors: Page WF, Engdahl B, Eberly REJournal of Nervous and Mental Disease - 1991-11-01

Prevalence of Somatic and Psychiatric Disorders Among Former Prisoners of War

American former prisoners of war (POWs) are an aging group who seek health care with increasing frequency. To examine the prevalence of long-term physical and emotional consequences of captivity in this population, the authors analyzed medical and psychiatric examination data for 426 former POWs. Detailed psychiatric diagnostic criteria were used to assess the POWs' mental health. Compared with general population groups, POWs had moderately elevated lifetime prevalence rates of depressive disorders and greatly elevated rates of posttraumatic stress disorder (Post-traumatic Stress DisorderPost-traumatic 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.), although their rates of hypertension, diabetes, myocardial infarction, bipolar disorder, schizophrenia, and alcoholism were not elevated. POWs who lost more than 35 percent of their body weight during captivity had higher rates of anxiety disorder, depressive disorders, PTSDPost-traumatic 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., and schizophrenia, compared with other POWs.
Authors: Eberly RE, Engdahl BHospital and Community Psychiatry - 1991-08-01

An adaptational view of trauma response as illustrated by the prisoner of war experience

We propose a model of PTSDPost-traumatic 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. symptoms in which they have positive evolutionary adaptational value in traumatic environments. The persistence of PTSDPost-traumatic 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. symptoms following return to more benign environments may result from biological changes within the organism, reflected by a primary response of increased levels of underlying traits such as Negative Affectivity. Secondary symptoms such as social withdrawal and substance abuse are conceptualized as subsequent coping with the primary trauma response. This model was tested using data on 413 former World War II Prisoners of War (POWs). The results were consistent with the model, indicating an enduring high level of Negative Affectivity as measured by scales on the MMPI. Captivity severity scores, developed using a factor analysis of POW experience variables, were related to lifetime and current diagnoses of PTSDPost-traumatic 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., generalized anxiety disorder, and major or minor depression. They were not related to schizophrenia, alcohol abuse/dependence, bipolar I...
Authors: Eberly RE, Harkness AR, Engdahl BJournal of Traumatic Stree - 1991-07-01

Comorbidity of psychiatric disorders and personality profiles of American World War II prisoners of war

Examined the psychiatric comorbidity and personality characteristics of 62 World War II prisoners of war (POWs). This study extends the previous findings of N. Speed et al (see record 1989-26181-001). Each former POW completed the Schedule for Affective Disorders and Schizophrenia-Lifetime Version (SADS-L), a posttraumatic stress disorder (PTSDPost-traumatic 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.) symptom severity scale based on criteria from the Diagnostic and Statistical Manual of Mental Disorders (DSM-III) and the Minnesota Multiphasic Personality Inventory (MMPI). The Ss displayed a remarkable frequency of comorbid psychiatric disorders and a current adjustment characterized by traits of depression, anxiety, and somatization. Only 19% were free from all SADS-L lifetime psychiatric diagnoses, and only 9 had MMPI profiles within "normal limits." The amount of comorbidity of PTSDPost-traumatic 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. and depression 40 yrs after captivity was also remarkable. Findings support the hypothesis that depression is a late manifestation of being chronically ill with PTSDPost-traumatic 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..
Authors: Engdahl B, Speed N, Eberly RE, Schwartz JJournal of Nervous and Mental Disease - 1991-04-01

Age, education, maltreatment, and social support as predictors of chronic depression in former prisoners of war

This study examined the relationships of prisoner of war captivity trauma variables and individual protective variables to current depressive symptoms as indexed by the CES-D and its components. The sample consisted of 989 U.S. former POWs of World War II and the Korean War, who have been followed since the mid 1950s. Depressive symptoms persisted over 40 years later. Age, education, medical symptoms during captivity, and level of social support were related to later levels of adjustment. Theoretical and methodological implications of the findings were discussed.
Authors: Engdahl B, Page WF, Miller TWSocial Psychiatry and Psychiatric Epidemiology - 1991-03-01
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