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Biomedical subjects

E M Schmidt

Publications and source records attributed to E M Schmidt.

At least 19 recordsLinked to original sources
PubMed1992

The effects of cooling supplementary motor area and midline cerebral cortex on neuronal responses in area 4 of monkeys.

It has been postulated that the supplementary motor area (SMA) is involved in the initiation of movement and in gating of afferent input to motor cortex (MI) from peripheral receptors. We studied the responses of 119 neurons in MI to imposed disturbances of wrist-movement performance generated by the introduction of torque pulses before, during and after localized cooling of the SMA in conscious monkeys. The cooling of SMA did not prevent monkeys from making these simple movements. Eighty-two neurons responded to the wrist perturbations. Only 7 of these neurons changed their responsiveness with unilateral or bilateral cooling of SMA. From the data we have obtained on MI neuronal firing patterns, the SMA does not appear to modulate the long-latency trans-cortical stretch reflex during the periods in a task that we have investigated. Nor does it prevent animals from performing these simple movements to a visual target.

Animals↗
PubMed1990

Microstimulation mapping of precentral cortex during trained movements.

1. The precentral cortex of three Macaca mulatta monkeys were mapped with intracortical microstimulation (ICMS) while the monkeys performed alternating wrist flexion and extension movements. A forearm cocontraction task was also employed with one monkey. Electromyogram (EMG) recordings from forearm muscles were used to evaluate the results of ICMS. 2. We have found that the results of ICMS can be misleading if EMG activity is not recorded from the responding muscle. Inhibition can be interpreted as excitation if muscle palpation or joint movement are the only response criteria. 3. Movement of the stimulating electrode by as little as 200 microns in a single radial column sometimes changed EMG responses from inhibition to excitation or vice versa, indicating that cortical inhibitory areas for a muscle can be located very close to excitatory zones. 4. Both excitation and inhibition of muscles could be produced with ICMS of precentral cortex when the animal was performing a task involving the muscles being mapped. EMG responses to ICMS were stable, provided that the stimulation was applied at the same time during a repetitive task such that the motoneurons were at a given level of excitability. 5. Zones where ICMS produced inhibition of a particular forearm muscle were interspersed among zones that produced excitation for that muscle. 6. Regions exist in precentral cortex where ICMS activates antagonistic wrist muscles producing cocontraction. 7. The extensive cortical region from which any individual muscle can be activated or suppressed with ICMS and the various combinations of muscles that are activated from within this region suggest that different types of movements involving a single muscle are represented at different locations within this region. 8. At a few locations in precentral cortex, the EMG responses to ICMS were not just a function of the level of excitation of the motoneuron pool at the time of stimulation but were also dependent on the specific task the monkey was performing at the time of stimulation.

Animals↗
PubMed1990

HIV infected hospital patients in New York State. The development of longitudinal information from a hospital discharge data system.

Abstracted records of all patients discharged from New York State acute care hospitals from January 1, 1983, through October 1, 1987, containing a diagnosis of HIV infection (N = 36,664) were linked into a longitudinal file of 20,005 patient-specific case histories. A validation study utilizing Medicaid patient-specific discharge information for calendar year 1985 showed that, on the average, each case history of the longitudinal file contained 85% (+/- 5%) of the expected discharges. The number of patients present in the longitudinal file was 10% (+/- 4%)--too large a percentage, due to a failure to link all the discharges to the appropriate case histories. The number of patients with a diagnosis of Pneumocystis carinii pneumonia (PCP) found in the longitudinal file was found to be consistent with the number reported to the New York State AIDS Registry. The longitudinal file appears to be sufficiently accurate and complete to use in evaluating HIV-related acute care in hospitals.

Adolescent↗
PubMed1977

Intracellular recording from pulsating cerebral cortex.

An instrument has been developed for recording intracellulary from cortical neurons in an exposed pulsating brain. The electrode moves with the brain pulsations maintaining the electrode within the impaled cell. Stable recordings have been obtained for up to 20 min.

Animals↗