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Biomedical subjects

S Hocherman

Publications and source records attributed to S Hocherman.

At least 37 records · Page 2Linked to original sources
PubMed1988

The contribution of vision and of sidedness to responses of the ankle musculature to continuous movement of the base of support.

Eight healthy women were subjected to continuous sinusoidal movements of the base of the platform on which they stood. Each subject was tested once in the anterior-posterior (AP) and once in the lateral movement direction. In the first 30 s of each test, subjects' eyes were open while during the following 30 s their eyes were closed. Bilateral EMG recordings from the Medical Gastrocnemius (MG) and the Tibialis Anterior (TA) muscles were continuously taken from the moment subjects became used to the imposed movement. Results revealed that during AP movements the MG and TA muscles were reciprocally activated and deactivated, thereby continuously stabilizing the ankle joint in advance of the imposed anterior or posterior perturbation. Similarly, during lateral movements each MG muscle was activated in the homologous side of the movement trajectory. These basic postural sets were neither affected by elimination of vision nor by sidedness. However, absence of vision caused decrease of the ratio between the IEMG of the MG muscle to that of the TA muscle during AP movements. This decrease resulted from decrease in the activity of the MG muscles and/or from increased activity of the TA muscles while vision was eliminated. The latter phenomenon occurred to a greater extent in the right leg.

Adult↗
PubMed1987

Auditory- and movement-related neural activity interact in the pulvinar of the behaving rhesus monkey.

We recorded the activity of 101 pulvinar nucleus neurons in a rhesus monkey performing an auditory discrimination task. The monkey was trained to push a lever to the left after hearing a noise burst and to the right after hearing a tone. When the stimulus was presented every 3 s the auditory evoked potentials (AEPs) habituated very rapidly to about 10% of initial height. With a stimulation rate of 1 every 15 s, however, the AEPs maintained full amplitude. A movement-related increase in firing rate was recorded in 81 units (80%) and could usually be detected 100-200 ms before onset of arm EMG. A stimulus-related firing was detected in 70 units (69%). Most of the stimulus-driven units (65/70) were also movement-driven. No responses correlated to the movement or to the sound stimuli were seen during passive conditions, i.e. when the monkey was not engaged in task performance. The occurrence of both stimulus- and movement-related activity in single pulvinar units suggests sensory-motor interaction possibly related to the decision to perform a certain movement.

Animals↗
PubMed1986

Stroke rehabilitation. Three exercise therapy approaches.

The purpose of this study was to compare the therapeutic efficacy of three exercise therapy approaches. Three groups of adult stroke patients (N = 131) participated in the study. The first group received conventional treatment that consisted of traditional exercises and functional activities. The treatment of the second group was based on proprioceptive neuromuscular facilitation techniques. The third group was treated using the Bobath approach. The improvement of each patient was evaluated after six weeks of treatment in terms of functional gains in activities of daily living as measured using the Barthel index, changes in the muscle tone of the involved limbs as measured using a five-point ordinal scale, changes in the isolated motor control of the ankle and wrist as measured by tests of muscle strength and range of motion, and changes in the patients' ambulatory status as measured using a nominal scale of four categories. The therapeutic effects of exercise according to each of the three approaches were compared using descriptive and nonparametric statistical methods. No substantial advantage could be attributed to any one of the three therapeutic approaches.

Activities of Daily Living↗
PubMed1984

Platform training and postural stability in hemiplegia.

Thirteen hemiplegic patients who had a cerebrovascular accident (CVA) in the anterior cerebral circulation were subjected to training on a moving platform. Each session consisted of a 5 min stance on the platform while they moved along an anteroposterior axis, and a 5min stance during transverse movement. Movement amplitude of the platform was adjusted once every three training sessions to the largest that the patients could sustain without using their hands for support. An electromyogram (EMG) was recorded from the tibialis anterior (TA) muscles of each patient during training and at stance on the floor. In addition, the distribution of body weight on the feet was measured in each case before the training program began and at its termination after three weeks (15 training sessions). A matched group of 11 hemiplegic patients served as controls. The maximal movement amplitude that each patient in the control group could sustain was determined twice, once at the beginning of the study and again after three weeks. Ten patients in the experimental group showed more than a two-fold increase in the maximal movement amplitude (MMA) that they could sustain. The patients most impaired initially showed the greatest increase in MMA--five- to seven-fold. In the control group, only one patient had an MMA increase greater than two-fold. A significant improvement in weight distribution on the feet during stance on the floor was found in the experimental patients, but not in the controls. EMG records indicated that improvement in stance did not result from increased TA activation in the hindered leg.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1983

Induction of semichronic epileptic foci using cobalt oxide.

This paper describes a new method for production of semichronic epileptic foci in the cerebral cortex of cats. Cortical lesions that turned into epileptic foci were induced by extradural application of cobalt oxide powder. These lesions extended through the entire depth of the gray matter, but did not cause gross macroscopic damage. The cobalt oxide powder was removed from the dura mater 7 days after its application, at which time the lesion already showed epileptic activity; this activity did not diminish 7, 14, or 21 days later. Testing of epilepsy was done with a special procedure that allowed work with anesthetized animals. Before treatment with cobalt oxide began, the maximal dose of convulsant drug that would not cause an epileptic electrocorticogram response was determined for each animal (the "trigger dose"). Subsequent testing of potential epileptic foci consisted of monitoring the electrocorticographic responses to rapid intravenous injections of the trigger convulsant dose. The success of the present method in production of epileptic foci is evaluated by several criteria and is compared with other methods.

Animals↗
PubMed1983

Surgical control of semichronic epileptic foci in the cat's sensorimotor cortex.

The present work was undertaken in order to find out whether delicate subpial incisions can be used to stop the epileptic activity of cortical lesions induced by cobalt oxide. Epileptic foci were produced in cats by epidural application of cobalt oxide powder. The presence of epilepsy was demonstrated a week later in anesthetized cats by injections of a "trigger dose" of pentamethylenetetrazole. Performance of subpial incisions through the focus area immediately abolished all ongoing epileptic activity. Such activity could not be evoked again by subsequent injection of pentamethylenetetrazole trigger doses throughout a 2-week period. The practical implications of this result are discussed. Some theoretical consequences of the similarity between the response of penicillin foci and that of cobalt oxide foci to the application of subpial incisions were evaluated. Finally, an attempt is made to explain the differences between our results and those produced by other investigators who also attempted to inactivate cobalt lesions in the cortex.

Animals↗
PubMed1981

The response of single units in the auditory cortex of rhesus monkeys to predicted and to unpredicted sound stimuli.

Rhesus monkeys were trained to predict the nature of short auditory signals of two different types, to which they responded differentially. Prediction was based on visual signals that preceded the auditory ones. The monkey's use of the visual signals as predictors was assessed through two behavioural criteria. (1) performance in trials in which the visual signals was followed by the correct auditory signal (true conditioning) vs performance in trials in which the visual signal was followed by the wrong auditory signal (false conditioning). (2) Reaction time in trials with different types of conditioning. The response of single auditory cortex units to correctly and to incorrectly predicted auditory signals was recorded. The unconditioned response of every unit to each type of auditory stimulus was also obtained. Of 92 units that were analysed in detail, the response of about half was affected by the predictability of the stimulus. Units were affected in two different ways. One involved facilitation of the response to correctly predicted signals and inhibition of the response to incorrectly predicted signals. The other involved facilitation of the response to incorrectly predicted signals and base line response to correctly predicted signals. These findings were discussed in terms of neural mechanisms that relate to prediction.

Animals↗
PubMed1981

A ball-joint manipulator for microelectrode recording.

The conventional technique for single unit recording involves insertion of microelectrodes into the brain along an axis which is perpendicular to the cross-sectional plan of a recording chamber. Thus, only tissue that lies within the projection of the recording chamber can be reached. This limitation is overcome by use of a ball-joint manipulator which enables insertion of electrodes into the brain at a wide range of tilt angles. Construction of the ball-joint manipulator and the method by which the stereotactic location of the electrode recording tip is determined are described in the present note.

Animals↗
PubMed1980

The surgical control of acute epileptic foci in the cat's cerebral cortex.

Topectomy is the treatment of choice for patients suffering from intractable focal epilepsy not responding to pharmacological treatment. A disadvantage of this method is the neurological deficit produced by excision of functional neurons. For this reason the excision of epileptic foci in vital cortical regions is avoided. Thus patients suffering from intractable focal epilepsy in the motor area do not, as yet, have a satisfactory medical or surgical solution to their problem. The purpose of this work is to suggest a different surgical approach on the basis of new data regarding vertical neural connections in the cortex that are vital to the maintenance of the epileptic foci. This possibility has been investigated so far only in acute animal experiments with the intention of applying this method next in chronic animal experiments and then, if successful, in human beings.

Animals↗
PubMed1979

A critical epileptic area in the cat's cortex and its relation to the cortical columns.

The critical size of active penicillin foci in cat's parietal cortex was determined in two different ways: (a) by gradually enlarging the area of drug application from 0.78 mm2 to 3.14 mm2; (b) by reducing the area of the active penicillin focus, using subpial incisions. Results indicate that a critical area of 0.7 mm2 is necessary. The possibility that in the parietal cortex a single functional column may be the basic generator unit for inter-ictal spikes is discussed. It is concluded that: (a) the size of the critical area is related to the cross-sectional area of a single functional column. This column is not yet determined by parallel anatomical findings; (b) inactivation of a given epileptic focus in the cat's cortex may be achieved by cutting layer III of the focus.

Animals↗
PubMed1979

Modality-specific effects on discrimination of short empty time intervals.

The ability of human subjects to judge the duration of short empty time intervals was studied in relation to the modality composition of the marker signals. At each trial, a pair of empty intervals was presented by a series of three successive stimuli, and the subject was asked to point out the longer interval of the two. Tone pips and flashes of light were used as the bounding signals. All the possible combinations of auditory and visual stimuli were used, in random order, to delimit pairs of intervals. Performance was found modality-independent when the first two stimuli were of the same modality. Strong response biases were introduced by varying the modality of the first or the second stimulus. Analysis of these biases indicates that memorization of the empty time intervals is affected by the modality of the binding signals.

Adult↗
PubMed1976

Evoked unit activity in auditory cortex of monkeys performing a selective attention task.

Single-unit responses were recorded from the auditory cortex of rhesus monkeys performing a selective atteintion task which used combined light and sound stimuli. The animals were first trained to push a lever to the left for a noise burst and to the right for a tone burst, and then trained to push left for a left light and right for a right light. Subsequently, one of the four possible light and sound stimulus combinations (Noise + Left Light, Noise + Right Light, Tone + Left Light, Tone + Right Light) was randomly presented on each trial. In blocks of 100 trials only one part of the combined stimulus (either the light or the sound) determined the direction of lever push that would be reinforced. Responses of single units to identical sound stimuli were compared for blocks in which sound was the relevant cue and blocks in which light was the relevant cue. Typically, differences were in response strength without alteration of response pattern. Even the earliest response components (15-20 msec latency) could show changes. Two-thirds of the response comparisons showed differences in strength depending upon whether sound or light was the relevant cue, with about as many responses stronger for light relevant as for sound relevant. Independent of which modality was relevant, unit responses for trials in which both parts of the combined light and sound stimulus indicated the same direction of lever push were generally stronger than unit responses for trials in which the two parts of the combined stimulus signalled opposite directions of lever pushes.

Animals↗