Three-dimensional drawings in isometric conditions: planar segmentation of force trajectory
permalinkExperimental Brain Research - 1992-12-01Pellizzer G, Massey JT, Lurito JT, Georgopoulos AP10.1007/BF00227975
Normal human subjects grasped an isometric handle with an unrestrained, pronated hand. They were asked to exert forces continuously to draw lemniscates (figure eights) in specified or self-chosen planes and in the presence or absence of a three-dimensional visual feedback cursor and a visual template. In every condition, the mean plane orientation in the force space differed appreciably between the two loops of the figure, as described previously by Soechting and Terzuolo (1987a) for free drawing arm movements. These findings suggest that the planar segmentation of the motor trajectory is not a consequence of joint motion but arises from central constraints related to the production of motor trajectory in space.
Motor cortical activity in a memorized delay task
permalinkExperimental Brain Research - 1992-12-01Smyrnis N, Taira M, Ashe J, Georgopoulos AP10.1007/BF00230390
Two rhesus monkeys were trained to move a handle on a two-dimensional (2D) working surface in directions specified by a light at the plane. They first captured with the handle a light on the center of the plane and then moved the handle in the direction indicated by a peripheral light (cue signal). The signal to move (go signal) was given by turning off the center light. The following tasks were used: (a) In the non-delay task the peripheral light was turned on at the same time as the center light went off. (b) In the memorized delay task the peripheral light stayed on for 300 ms and the center light was turned off 450-750 ms later. Finally, (c) in the non-memorized delay task the peripheral light stayed on continuously whereas the center light went off 750-1050 ms after the peripheral light came on. Recordings in the arm area of the...read more
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.
Teaching Job Interview Skills to Alcoholics: Implications for Future Employment Rates
permalinkJournal of employment Counseling - 1992-03-01Dunn GE, Thomas AH, Engdahl B10.1002/j.2161-1920.1992.tb00147.x
Twenty-three inpatient alcoholics participated in a job-finding skills workshop. They demonstrated better job interview skills and a higher employment rate compared with a control group.
Three-dimensional drawings in isometric conditions: relation between geometry and kinematics
permalinkExperimental Brain Research - 1992-01-01Massey JT, Lurito JT, Pellizzer G, Georgopoulos AP10.1007/BF00228198
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
permalinkExperimental Brain Research Supplement - 1992-01-01Georgopoulos AP
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.
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
permalinkJohns Hopkins APL Technical Digest - 1991-12-01Georgopoulos AP, Massey JT
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.
Prevalence and Correlates of Depressive Symptoms among Former Prisoners of War
permalinkJournal of Nervous and Mental Disease - 1991-11-01Page WF, Engdahl B, Eberly RE10.1097/00005053-199111000-00004
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.
Prevalence of Somatic and Psychiatric Disorders Among Former Prisoners of War
permalinkHospital and Community Psychiatry - 1991-08-01Eberly RE, Engdahl B10.1176/ps.42.8.807
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
, 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,
, and schizophrenia, compared with other POWs.
An adaptational view of trauma response as illustrated by the prisoner of war experience
permalinkJournal of Traumatic Stree - 1991-07-01Eberly RE, Harkness AR, Engdahl B10.1002/jts.2490040305
We propose a model of Post-Traumatic Stress Disorder (
) symptoms in which they have positive evolutionary adaptational value in traumatic environments. The persistence of
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
, generalized anxiety disorder, and major or minor depression. They were not related to schizophrenia, alcohol abuse/dependence, bipolar I...read more
Comorbidity of psychiatric disorders and personality profiles of American World War II prisoners of war
permalinkJournal of Nervous and Mental Disease - 1991-04-01Engdahl B, Speed N, Eberly RE, Schwartz J10.1097/00005053-199104000-00001
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
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
and depression 40 yrs after captivity was also remarkable. Findings support the hypothesis that depression is a late manifestation of being chronically ill with
Age, education, maltreatment, and social support as predictors of chronic depression in former prisoners of war
permalinkSocial Psychiatry and Psychiatric Epidemiology - 1991-03-01Engdahl B, Page WF, Miller TW10.1007/BF00791528
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.