Polysomnographic sleep is not clinically impaired in vietnam combat veterans with chronic Posttraumatic Stress Disorder
permalinkBiological Psychiatry - 1998-11-15Hurwitz TD, Mahowald MW, Kuskowski MA, Engdahl B10.1016/S0006-3223(98)00089-4Background: Because sleep is typically disturbed in
Posttraumatic Stress Disorder, this study was undertaken to evaluate a group of Vietnam combat veterans with the disorder using clinical polysomnographic techniques.Methods: Eighteen Vietnam combat veterans with
PTSDand 10 healthy non-combat-exposed Vietnam era veterans participated in 2 nights of polysomnographic study and a multiple sleep latency test.Results: No significant differences between subjects and controls were noted except for greater sleep onset latency to stage 2 (p < .03), and lower arousals/hour from stages 3 & 4 (p < .04) on night 2, and lower subjectively estimated total sleep time on night 1 (p < .005) in the case of
PTSDsubjects. Otherwise, results from the second night served to replicate those from the first, and no significant differences appeared on 2 successive nights for any polysomnographic variable. No daytime hypersomnolence was detected.Conclusions: Polysomnographically recorded sleep was notably better than expected in the...
Interview with Apostolos P. Georgopoulos
Matching Patterns of Activity in Primate Prefrontal Area 8a and Parietal Area 7ip Neurons During a Spatial Working MemoryTask
Variability and Correlated Noise in the Discharge of Neurons in Motor and Parietal Areas of the Primate Cortex
permalinkJournal of Neuroscience - 1998-02-01Lee D, Port NL, Kruse W, Georgopoulos AP10.1523/JNEUROSCI.18-03-01161.1998We analyzed the magnitude and interneuronal correlation of the variability in the activity of single neurons that were recorded simultaneously using a multielectrode array in the primary motor cortex and parietal areas 2/5 in rhesus monkeys. The animals were trained to move their arms in one of eight directions as instructed by a visual target. The relationship between variability (SD) and mean of the discharge rate was described by a power function with a similar exponent (∼0.57), regardless of the cortical area or the behavioral condition. We examined whether the deviation from mean activity between target onset and the end of the movement was correlated on a trial-by-trial basis with variability in activity during the hold period before target onset. In both cortical areas, for about a quarter of the neurons, the neuronal noise of these two periods was positively correlated, whereas significant negative correlations were seldom observed. Overall, neurons with...
Online visual control of the arm
Neuronal Population Coding: Multielectrode Recordings in Primate Cerebral Cortex
permalinkStrategies in teh Study of Biological Neural Networks - 1998-01-01Lee D, Port NL, Kruse W, Georgopoulos APThe central nervous system can be described in terms of its ability to detect and categorize various spatiotemporal patterns in the sensory receptor arrays and to produce coordinated behavior by providing appropriate control signals to the individual effectors. This task is achieved by a vast network of neurons, and, therefore, it may be difficult to fully understand the functional significance of the activity of individual neurons outside the context of the network. Direct information concerning the role of individual neurons in a network can be obtained by simultaneously recording the activity of several neurons. For that purpose, we have been using a seven-electrode system to examine neuronal activity in the primate cortex while the animal performs various behavioral tasks. This chapter first describes our recording system and software/hardware for spike isolation and then reports some results from our analysis on the activity of neurons recorded simultaneously during a simple visuomotor task....
Functional Magnetic Resonance Imaging of mental rotation and memory scanning: a multidimensional scaling analysis of brain activation patterns
permalinkBrain Research Reviews - 1998-01-01Tagaris GA, Richter W, Kim SG, Pellizzer G, Andersen P, Ugurbil K, Georgopoulos APMental rotation and memory scanning are typical examples of cognitive operations presumably involved in various tasks. The original tasks involved judgements to be indicated by key presses or verbal responses, whereas recent variants required directed movements as responses. The cardinal sign of both mental rotation and memory scanning tasks is the increase of the response time with task demands, namely the angle of rotation or of the number of items in the list scanned. The rates of processing information in these two kinds of tasks are uncorrelated, which suggests that different brain mechanisms may be involved. In contrast, the rates of rotation of a figure or a movement direction are positively correlated, which suggests that common aspects of brain mechanisms may be involved in widely different cases of mental rotation. The overall brain mechanisms underlying mental rotation and memory scanning are largely unknown. With respect to mental rotation, a consistent finding...
Time-resolved Functional Magnetic Resonance Imaging of mental rotation
Functional Magnetic Resonance Imagingseeks to elucidate neuronal activity during a single execution of a mental task, which corresponds typically to a timescale of seconds. However, this is also the timescale of the hemodynamic response, which delays and blurs the signal in time. In order to distinguish the temporal characteristics of the neuronal activity from that of the hemodynamic response, which is often vaguely known, we recorded a set of
fMRItime courses under conditions of a varying behavioral parameter, and correlated this parameter to the width of the
fMRIresponse. For the task under investigation, the mental rotation of three-dimensional objects, we found that the activation in the parietal lobe is related to an aspect of the task that is described by the reaction time (for example, the very act of mental rotation), and not only to aspects of the task that are constant from trial to trial, such as the visual...
Transformation of the intended direction of movement during continuous motor trajectories
Manual interception of moving targets II. On-line control of overlapping submovements
Manual interception of moving targets I. Performance and movement initiation
permalinkExperimental Brain Research - 1997-10-01Port NL, Lee D, Dassonville P, Georgopoulos AP10.1007/PL00005769We investigated the capacities of human subjects to intercept moving targets in a two-dimensional (2D) space. Subjects were instructed to intercept moving targets on a computer screen using a cursor controlled by an articulated 2D manipulandum. A target was presented in 1 of 18 combinations of three acceleration types (constant acceleration, constant deceleration, and constant velocity) and six target motion times, from 0.5 to 2.0 s. First, subjects held the cursor in a start zone located at the bottom of the screen along the vertical meridian. After a pseudorandom hold period, the target appeared in the lower left or right corner of the screen and traveled at 45° toward an interception zone located on the vertical meridian 12.5 cm above the start zone. For a trial to be considered successful, the subject's cursor had to enter the interception zone within 100 ms of the target's arrival at the center of the...
Neural Modeling of Motor Cortex and Spinal Cord
Mental Rotation Studied by Functional Magnetic Resonance Imaging at High Field (4 Tesla): Performance and Cortical Activation
permalinkJournal of Cognitive Neuroscience - 1997-07-01Tagaris GA, Kim SG, Strupp JP, Andersen P, Ugurbil K, Georgopoulos AP10.1162/jocn.19184.108.40.2069We studied the performance and cortical activation patterns during a mental rotation task (Shepard & Metzler, 1971) using
fMRI(fMlU) at high field (4 Tesla). Twenty-four human subjects were imaged (
fMRIgroup), whereas six additional subjects performed the task without being imaged (control group). All subjects were shown pairs of perspective drawings of 31, objects and asked to judge whether they were the same or mirror images. The measures of performance examined included (1) the percentage of errors, (2) the speed of performance, calculated as the inverse of the average response time, and (3) the rate of rotation for those object pairs correctly identified as "same." We found the following: (1) Subjects in the
fMRIgroup performed well outside and inside the magnet, and, in the latter case, before and during data acquisition. Moreover, performance over time improved in the same manner as in the control group. These...
Voluntary Movement: Computational Principles and Neural Mechanisms
Sequential activity in human motor areas during a delayed cued finger movement task studied by time-resolved Functional Magnetic Resonance Imaging
fMRI. Activity during movement preparation can be resolved from activity during movement execution in a single trial. All three areas were active during both movement preparation and movement execution. Activity in the primary motor cortex was considerably weaker during movement preparation than during movement execution; in the premotor cortex and the supplementary motor area, activity was of similar intensity during both periods. These observations are consistent with results from single neuronal recording studies in primates.
Box-Jenkins intervention analysis of Functional Magnetic Resonance Imaging data
permalinkNeuroscience Research - 1997-03-01Tagaris GA, Richter W, Kim SG, Georgopoulos AP10.1016/S0168-0102(97)01154-1Data obtained in
fMRItypically form a time series of MRI signal collected over a period of time at constant intervals. These data are potentially autocorrelated and may contain time trends. Therefore, any assessment of significant changes in the MRI signal over a certain period of time requires the use of specific statistical techniques. For that purpose we used the Box-Jenkins intervention time series analysis to determine brain activation during task performance. We found that for a substantial number of pixels there was significant autocorrelation and, occasionally, time trends. In these cases, use of the classical t-test would not be appropriate. In contrast, Box-Jenkins intervention analysis, by detrending the series and by explicitly taking into account the correlation structure, provides a more appropriate method to determine the presence of significant activation during the task period in
Neural Networks and Motor Control
Motor Cortex: Neural and Computational Studies
Mental transformations in the motor cortex
Arm movements in monkeys: behavior and neurophysiology