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M R DeLong

Publications and source records attributed to M R DeLong.

At least 91 records · Page 5Linked to original sources
PubMed1985

Primate globus pallidus and subthalamic nucleus: functional organization.

Neuronal relations to active movements of individual body parts and neuronal responses to somatosensory stimulation were studied in the external (GPe) and internal (GPi) segments of the globus pallidus (GP) and the subthalamic nucleus (STN) of awake monkeys. In GPe (n = 249), GPi (n = 151), and STN (n = 153), 47, 29, and 28% of the cells, respectively, discharged in relation to active arm movements, 10, 11, and 15% to leg movements, and 22, 22, and 18% to orofacial movements. Of the neurons whose activity was related to arm movements, 26, 16, and 21% in GPe, GPi, and STN, respectively, discharged in relation to movements of distal parts of the limb. Of cells whose discharge was related to active limb movements, 37, 22, and 20% in GPe, GPi, and STN, respectively, also responded to passive joint rotation, which was usually specific in terms of joint and direction of movement. Only a small percentage of cells responded to muscle or joint palpation, tendon taps, or cutaneous stimulation. Short-latency, direction-specific neuronal responses to load perturbations confirmed the existence of proprioceptive driving. In both GPe and GPi, leg movement-related neurons were centrally located in the rostrocaudal and dorsoventral dimensions. In contrast, arm movement-related cells were found throughout the entire rostrocaudal extent of both segments, although in greater numbers caudally. In the central portions they were situated largely inferior and lateral to leg movement-related neurons. Neurons related to orofacial movements were largely confined to the caudal halves of both segments, where they were located largely ventral to arm movement-related cells. The STN cells whose activity was related to leg movements were observed largely in the central portions of the nucleus in the rostrocaudal and mediolateral dimensions. Cells whose activity was related to arm movements were found throughout the rostrocaudal extent of the nucleus, but were most numerous at the rostral and caudal poles. Neurons related to movements of the facial musculature and to licking and chewing movements were distributed over the entire rostrocaudal extent of the nucleus, where they generally occupied the ventrolateral regions. In all three nuclei, neurons with similar functional properties were sometimes clustered together. Within the arm and leg areas, however, there was no clear evidence for a simple organization of clusters related to different parts of the limb. These studies provide further evidence for a role of the basal ganglia in the control of limb movements.(ABSTRACT TRUNCATED AT 400 WORDS)

Action Potentials↗
PubMed1985

Microstimulation of the primate neostriatum. I. Physiological properties of striatal microexcitable zones.

Microstimulation was carried out at over 1,250 sites in the putamen in four unanesthetized rhesus monkeys. At numerous sites, microstimulation resulted in movements of individual body parts including leg, arm, and face. Microstimulation-evoked limb movements were invariably contralateral to the stimulating electrode. In nearly all instances, the response at threshold was restricted to or maximal about a single joint. A small percentage of stimulation-evoked axial and orofacial movements were bilateral. The same motor response was frequently evoked over distances of up to 1,200 micron along a single penetration, suggesting that a relatively homogeneous motor-response zone underlies the observed micro-stimulation effects. We have designated these presumptive functional units striatal microexcitable zones (SMZ). The boundaries of adjacent SMZ involved in different movements frequently appeared to overlap. Amplitude, velocity, and acceleration of microstimulation-evoked elbow movements were assessed quantitatively. With increasing stimulus current, each of these parameters increased monotonically until saturation occurred. The spread of intrastriatal microstimulation currents was found to be comparable to that reported for motor cortex. The effective radius of 40-microA putamen microstimulation currents was estimated to be approximately 150 micron. This effectively rules out the possibility of current spread to the internal capsule. Microstimulation effects were abolished by fiber-sparing lesions produced by microinjections of the neurotoxin ibotenic acid. Moreover, chronaxie measurements in putamen (327 +/- 47 microseconds) were significantly higher than for capsular stimulation (150 +/- 32 microseconds). These observations are consistent with the proposal that movements evoked by putamen microstimulation resulted from activation of putamen output neurons. On the other hand, a possible contribution from the antidromic activation of corticostriate afferent terminals or axons cannot be excluded.

Animals↗
PubMed1985

Microstimulation of the primate neostriatum. II. Somatotopic organization of striatal microexcitable zones and their relation to neuronal response properties.

Sensorimotor response properties of neostriatal neurons were characterized in conjunction with assessments of the motor effects of intrastriatal microstimulation in unanesthetized rhesus monkeys. Neuronal activity and microexcitability were assessed at 250- to 500-micron intervals and, in some cases, at 25- to 100-micron intervals. The results are based on the functional characterization of 878 putamen and 224 caudate neurons and analysis of the effects of microstimulation at each of these recording sites. Recording/stimulation sites were located between stereotaxic planes A6 and A22 in 81 microelectrode tracks from three monkeys. A total of 443 (50.4%) putamen neurons showed discrete responses to the sensorimotor examination. Of neurons with sensorimotor responses, 232 (52.4%) showed increased rates of discharge in relation to both active and passive movements of specific body parts. An additional 193 (43.6%) cells increased their rates of discharge only during the monkey's active movements of specific body parts. The remaining 18 (4.0%) cells appeared to respond exclusively to passive somatosensory stimulation. The sensorimotor response areas of putamen neurons ranged in size from an entire limb to a single joint. Putamen neurons were somatotopically organized throughout the rostrocaudal extent of the nucleus. Neurons with sensorimotor response areas involving the leg were located in the dorsolateral putamen, those with orofacial representations were located ventromedially, and those with arm representations were located in an intermediate position. Microstimulation evoked discrete movements of individual body parts at 21.6% of the 878 putamen sites. Over 95% (181/190) of the effective sites were located within the central half of the rostrocaudal extent of the putamen, between stereotaxic planes A10 and A17. The pattern of somatotopic organization revealed by microstimulation was the same as that derived from sensorimotor response properties of putamen neurons. Moreover, a close correspondence was observed between the movements evoked from a given SMZ and the functional properties of local neurons. In contrast to the results obtained in the putamen, none of the 224 stimulation sites in the caudate nucleus was microexcitable, and only 17 (7.6%) of the caudate neurons had definable sensorimotor response properties. This is consistent with the view that the primate putamen, by virtue of its anatomic connections with the sensorimotor and premotor cortical fields, is more directly involved in motor functions, whereas the caudate nucleus, by virtue of its connections with cortical "association" areas, is involved in more complex behavioral functions.

Animals↗
PubMed1984

Single cell studies of the primate putamen. I. Functional organization.

In order to clarify the functional organization of the putamen and the nature of sensory inputs to this structure we studied the relation of single cell activity to active movements and somatosensory stimulation in the awake primate. Neurons (N = 707) were categorized on the basis of their relation to active movements or responses to sensory stimulation of individual body parts. 38% of neurons studied were related to the arm, 9% to the leg, 11% to the mouth or face, and 3% to axial portions of the body. The remaining neurons exhibited non-specific activation which could not be confidently localized to an individual body part (12%) or did not respond during the examination (26%). The high proportion of arm neurons was due to the focus of this study on cells related to arm movements. A large proportion (41%; N = 270) of the "arm" neurons was responsive to somatosensory stimulation. For these neurons the most effective stimulus (82%) was passive joint rotation. Six (5%) of the arm neurons responded to cutaneous stimulation. The putamen was found to be somatotopically organized. Neurons related to different body parts (leg, arm, and face) were segregated, and each body part was represented over a long anteroposterior extent of the nucleus. Clusters of 2-5 neurons with similar relations to active movements or responsive to passive movements of a single joint were often encountered over a 100-500 mu distance. Clusters of neurons with sensory driving were organized by joints. Rather than a single elbow or shoulder area, multiple clusters of neurons related to each joint were widely distributed over a long anteroposterior extent of the nucleus and were adjacent to clusters of neurons related to other joints of the arm. These clusters of neurons with similar functional properties may correspond to the subunits of the striatum which have been revealed by anatomic and morphologic studies. We propose that these clusters of neurons with similar functional properties represent the basic functional units of the striatum in a manner analogous to the functional columns of the neocortex.

Animals↗
PubMed1984

Single cell studies of the primate putamen. II. Relations to direction of movement and pattern of muscular activity.

The major goal of this study was to determine whether the activity of single cells in the primate putamen was better related to the direction of limb movement or to the underlying pattern of muscular activity. In addition, the neural responses to load application were studied in order to determine whether the same neurons were also responsive to somatosensory stimuli. Two rhesus monkeys were trained to perform a visuomotor arm tracking task which required elbow flexion/extension movements with assisting and opposing loads in order to dissociate the direction of elbow movement from the pattern of muscular activity required for the movement. Neurons in the putamen were selected for study only if they were related both to the task and to arm movements outside the task. Most (96%) of the cells studied responded to load application: 36% of these showed short-latency (less than 50 ms), "sensory" responses. Forty-four percent of neurons had significant relations to the level of static load as the animal held the arm stationary against the steady loads: in general, static load effects were relatively weak. During the elbow flexion/extension movements in the task, 76% of cells had significant relations to the direction of movement, and 52% of neurons had significant dynamic relations to the level of load. Half of all neurons studied were primarily related to the direction of movement independent of the load. Only thirteen percent of cells in the putamen had a pattern of activity similar to that of muscles. These results indicate that neuronal activity in the putamen is predominantly related to the direction of limb movement rather than to the activity of particular muscles and that the basal ganglia may play a role in the specification of parameters of movement independent of the activity of specific muscles. These results also indicate that the basal ganglia receive proprioceptive input which may be used in the control of ongoing movement.

Animals↗
PubMed1984

Role of basal ganglia in limb movements.

Recent anatomic and physiologic studies have shed new light on the functional organization of the basal ganglia and their role in movement. The basal ganglia receive topographically organized input from the entire neocortex. Influences from sensorimotor and "association" cortices appear to remain segregated in the basal ganglia. The concept of segregated parallel subcortical loops subserving "motor" and "complex" functions is discussed. Recent neurophysiologic studies in behaving primates suggest that basal ganglia output plays a role in controlling the direction and amplitude of movement but is not primarily involved in the initiation of limb movement or selection of specific muscles. These studies are generally consistent with data from patients with Parkinson's disease, which likewise indicates a deficit in the programming of movement amplitude in step-tracking tasks, with little or no change in reaction-time or pattern of muscular activity.

Animals↗
PubMed1983

Alzheimer's disease: a disorder of cortical cholinergic innervation.

Great emphasis is being placed on identification of neurotransmitter systems involved in the symptomatic manifestations of neurological and psychiatric disorders. In the case of Alzheimer's disease, which now seems to be one of the most common causes of mental deterioration in the elderly, compelling evidence has been developed that acetylcholine-releasing neurons, whose cell bodies lie in the basal forebrain, selectively degenerate. These cholinergic neurons provide widespread innervation of the cerebral cortex and related structures and appear to play an important role in cognitive functions, especially memory. These advances reflect a close interaction between experimental and clinical neuroscientists in which information derived from basic neurobiology is rapidly utilized to analyze disorders of the human brain.

Alzheimer Disease↗
PubMed1983

Relations between parameters of step-tracking movements and single cell discharge in the globus pallidus and subthalamic nucleus of the behaving monkey.

We describe the relations between the direction, amplitude, and velocity of step-tracking arm movements and the frequency of single cell discharge in the external (GPe) and internal (GPi) segments of the globus pallidus and the subthalamic nucleus (STN) of the behaving monkey. Statistically significant relations to the direction, amplitude, and peak velocity of the movement were found in all structures studied predominantly during the movement but also during the reaction time. For movements in a particular direction, the discharge rate was frequently a linear function of the movement amplitude and/or peak velocity. The slopes of this relation differed for different cells and comprised both positive and negative values. STN differed from both GPe and GPi in that (a) a larger proportion of neurons in STN showed significant relations to the direction of movement and (b) the onset times of changes in neural activity related to movement occurred earlier in STN than in GPe or GPi. The results of these studies suggest that cells in GPe, GPi, and STN may be involved in the control of movement parameters. Loss of the basal ganglia output related to the amplitude or velocity of movement might account for the impairments of step movements observed in Parkinsonian patients. On the other hand, deranged or excessive output related to amplitude or velocity control might result in the excesses of movement observed in other disorders, such as chorea and hemiballismus. These studies also provide direct evidence that the STN exerts a specific influence on basal ganglia output related to the control of movement parameters.

Animals↗
PubMed1981

Alzheimer disease: evidence for selective loss of cholinergic neurons in the nucleus basalis.

The nucleus basalis of Meynert provides diffuse cholinergic input to the neocortex. When compared with an age- and sex-matched control, the nucleus basalis from a patient with Alzheimer disease demonstrated substantial reduction of neurons. Loss of this neuronal population may represent an anatomical correlate of the well-documented cholinergic derangement in Alzheimer disease.

Aged↗
PubMed1978

Dimensions of visual perceptions of clothing.

The relation of two descriptive properties of clothing, "complexity" and "fashionability," with evaluative preference responses of "like" and "would-like-to-own" was explored for two selected groups of untrained females who differed in age. The students agreed more than the older women on the judged "fashionability" of 10 photographs of clothing and also were influenced more by "fashionability" in their responses of "like" and "would-like-to-own." For both groups "complexity" was judged consistently but was not highly related to preferences.

Adult↗
PubMed1978

Possible involvement of central pacemakers in clinical disorders of movement.

This review considers the evidence for possible involvement of central nervous system pacemaker neurons in several clinical disorders of movement. Two basic types of tremor are discussed from this point of view, i.e., 4--7/sec parkinsonian tremor, of possible thalamocortical origin, and 7--11/sec essential tremor of possible olivo-cerebellar origin. The importance of motor programs and abnormalities in their utilization are considered with reference to the loss of motor function in parkinsonism (? loss of motor programs), and the inappropriate release of such programs as a possible basis for the involuntary movements seen in other movement disorders, such as chorea, athetosis, dystonia, and hemiballismus. The possible role of pacemaker neurons controlling such programs is considered. Finally, the subject of locomotion and the pacemaker model of the spinal locomotor pattern generator for stepping are considered in relation to clinical disorders of gait. While critical evidence is lacking for pacemaker inovlvement in any of these disorders, their possible role is emphasized.

Feedback↗
PubMed1973

Putamen: activity of single units during slow and rapid arm movements.

The activity of putamen neurons was studied in a monkey during the performance of both slow and rapid arm movements. More than half of all movement-related units discharged preferentially in relation to slow movements and less than 10 percent in relation to rapid movements. These findings indicate that at least a portion of the basal ganglia (the putamen) is primarily involved in the control of slow movements and are consistent with the hypothesis of Kornhuber that the primary motor function of the basal ganglia is to generate slow ("ramp") rather than rapid ("ballistic") movements.

Action Potentials↗