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Biomedical subjects

D S Goodin

Publications and source records attributed to D S Goodin.

At least 73 records · Page 4Linked to original sources
PubMed1990

Evidence that the long-latency stretch responses of the human wrist extensor muscle involve a transcerebral pathway.

Ballistic wrist extensor movements were interrupted by a sudden perturbing force in two conditions, and subjects were asked either to compensate for ('oppose') the perturbation or to cease the extensor movement ('let-go') when the interruption occurred. In the first condition, the interruption occurred unexpectedly in some of the trials, whereas in the second it occurred on every trial. Responses were recorded from the flexor and extensor carpi radialis muscles, and from the scalp and cervical spine. Unexpected perturbing forces were associated with an early extensor EMG response (M1) and longer latency EMG responses in both flexor and extensor muscles. When the interruptions occurred in every trial, both the late EMG activity and the cerebral responses were markedly attenuated. The relation between expectation of perturbation and the occurrence or size of the late EMG activity indicates that this response is under supraspinal control. The potentials recorded over the cervical spine and scalp were, like the late EMG activity, influenced by the expectancy of interruption. These potentials persisted even when the potentials related to the mechanically elicited SEP were removed by subtraction of responses to anticipated interruptions from those to unanticipated interruptions. The earliest of these potentials preceded the late EMG activity by 30-50 ms. They were present when the late responses were present, absent when the late responses were absent, and became progressively smaller when the late responses became smaller, suggesting a tight coupling between these events and the late EMG events. These results indicate that cerebral activity, unrelated merely to mechanical stimulation, consistently precedes the late EMG activity, and thereby directly suggests that the long-latency response has a cerebral (possible cortical) pathway.

Adult↗
PubMed1990

Organization of sensory discrimination and response selection in choice and nonchoice conditions: a study using cerebral evoked potentials in normal humans.

1. It has been suggested that the long-latency "event-related" cerebral evoked potentials (ERPs) reflect certain aspects of the neural processing underlying sensory discrimination in a two-choice reaction time task. The present paper examines the hypothesis that the coupling of these ERPs to sensory discrimination is variable and that the discrimination process is completed at different points during the course of cerebral processing, depending on the actual requirements of the task. 2. We recorded the cerebral evoked potentials and electromyogram (EMG) of the responding muscle in five different reaction time tasks, each requiring sensory discrimination and response selection of varying complexity. In the Choice condition two stimuli were presented, and two separate responses were required. In the two Go-No Go conditions two stimuli were presented, but a response was required to only one or the other of the stimuli. In the two Simple conditions only one stimulus was presented, and one response was required. 3. Under both Choice and Go-No Go conditions, the frequency histogram of the onset latency of the compound muscle action potential for the response to the frequent tone showed a bimodal distribution without overlap, suggesting that there were two distinct types of responder: fast and slow. The comparable histograms for the onset latency of the response to the rare tone also showed a bimodal distribution, but the mean onset latency was prolonged relative to the response to the frequent tone, and the mean separation was less so that the two distributions overlapped each other. 4. Despite the marked difference in response latencies between the fast and slow responders, there was no appreciable difference in cerebral evoked responses between the two groups. Moreover, in response to the frequent tone, all slow responders and, likewise, all fast responders had similar onset latencies of the averaged EMG activity regardless of condition. Nonetheless, fast or slow responders to the frequent tone on one block of trials were also fast or slow responders, respectively, to the rare tone on the same block of trials. 5. These results suggest that two separate sensory discrimination processes are occurring; the first relating to the presence or absence of the frequent (expected) stimulus, and the second relating to the presence or absence of the rare stimulus. The response to each tone can either be generated immediately after that tone is positively identified or, when accuracy is required, can be delayed until both stimuli have been successfully discriminated by the subject.

Acoustic Stimulation↗
PubMed1989

Effects of different sensory inputs on the median-derived somatosensory evoked potential.

We studied the effect of a variety of "interfering" stimuli on the median-derived somatosensory evoked potentials recorded over Erb's point, cervical spine, and scalp. We found that the amplitude of N20 and P27 recorded over the scalp was attenuated by active movement, vibration, and tactile stimulation of the ipsilateral hand but not by passive movement. Cervical and peripheral responses were unaffected. The pathophysiologic basis and clinical significance of these findings are discussed.

Adult↗
PubMed1988

Magnetic resonance imaging in amyotrophic lateral sclerosis.

Magnetic resonance imaging (MRI) was used in 5 patients with clinically definite amyotrophic lateral sclerosis to determine the frequency of central white matter abnormalities. Two patients had symmetrical areas of increased signal intensity seen on MRI extending from the cortex, through the corona radiata, posterior limb of the internal capsule, and cerebral peduncles into the pons. These MRI abnormalities presumably relate to the pathological changes observed by others in the central white matter of patients with amyotrophic lateral sclerosis.

Adult↗
PubMed1988

Recovery of peripheral and central responses to median nerve stimulation.

We recorded the responses to paired stimuli delivered to the median nerve at the wrist in 8 healthy adult volunteers, in order to characterize the recovery of function after a single conditioning stimulus. Responses were recorded over the nerve at the ipsilateral elbow and in the Erb's point region, over the second cervical spinous process, and over the contralateral 'hand area' of the scalp. The data from 1 subject were discarded because of possible artifactual contamination. In the others, the peripheral responses recovered both in latency and amplitude over a time period that accorded with previously published studies. We found, however, that the recovery periods for latency and amplitude of the responses recorded over the spine and scalp were prolonged compared with the corresponding values for the peripheral responses. Except for the responses recorded over the scalp, the recovery of amplitude either preceded or occurred at the same time as latency. By contrast, for the responses recorded over the scalp, there was a delay in the recovery of amplitude compared with latency. The differences in recovery period that we found at different levels of the nervous system are presumably related to structural and electrophysiological differences in afferent pathways, the presence of interposed synapses, and the intrinsic refractory properties of central neuronal populations.

Adult↗
PubMed1988

Visual evoked potentials in the investigation of "blindsight".

We recorded long-latency visual evoked potentials in four patients with homonymous hemianopias, one of whom had clinical evidence of "blindsight." Stimuli consisted of different words that appeared randomly and at a constant angle to either side of the center of a TV screen, and subjects responded to one previously specified word (the "target") by finger extension. Target stimuli in the intact hemifield elicited a well-formed P3 response in all subjects, whereas stimuli in the blind field produced no such response except in the subject with blindsight. In addition, the earlier potentials in this subject were larger with stimulation of the blind hemifield than the intact field. By contrast, a P100 response was present only with stimulation of the intact field in this subject. These results indicate that cognitive processing of visual stimuli can occur even when subjective awareness of such stimuli is absent, and suggest that such processing occurs independently of the geniculostriate pathway.

Adult↗
PubMed1988

PD and ciladopa.

Explore the source record for details and available documents.

Antiparkinson Agents↗
PubMed1988

Ambulatory EEG recordings in epileptic and nonepileptic children.

We examined the cassette-recorded 24-hour ambulatory EEG findings in children who had either clinically definite seizures or episodic behavioral disturbances not regarded as epileptic on clinical grounds. Among 40 epileptic patients, 22 had one or more attacks during the 24-hour recording session. In 15 of these patients all clinical attacks had appropriate ictal electrographic accompaniments; in another 6 some (but not all) attacks did so. Among 55 children with nonepileptic spells clinically, the 24-hour recording was uninterpretable for technical reasons in one, and in 30 it provided no relevant information because there were no recorded clinical or electrographic attacks. In the remaining 24 patients, one or more clinical attacks were captured, and in no instance was there any accompanying electrographic change. Our findings indicate that the absence of ictal EEG changes during attacks cannot be used in isolation to make a diagnosis of pseudoseizures, but support such a diagnosis made on clinical grounds. The more important role of the ambulatory EEG is to exclude a diagnosis of nonepileptic attacks by demonstrating electrographic seizure activity accompanying typical clinical attacks. Whether the technique will have a useful role in the evaluation of patients when the nature of an episodic disturbance of cerebral function is unclear clinically remains to be established, but will require long-term follow-up to validate any conclusions reached by the electrophysiologic technique.

Adolescent↗
PubMed1987

Electrophysiological differences between demented and nondemented patients with Parkinson's disease.

Long-latency auditory evoked potentials were studied in demented and nondemented patients with Parkinson's disease who were matched for age, stage of disease, duration of illness, and amount and nature of antiparkinsonian medication. We found clear electrophysiological differences between the two groups of patients in that the N1, N2, and P3 peak latencies were prolonged in the demented group compared both to the nondemented group and to normal controls. Moreover, the N1 latency but not the N2 and P3 latency prolongation distinguished the demented parkinsonian patients from demented patients with Alzheimer's disease. These results provide strong evidence for the existence of different subtypes of dementia and suggest that electrophysiological recordings may be helpful in establishing the underlying pathogenesis of a dementia syndrome when there is clinical uncertainty.

Alzheimer Disease↗
PubMed1987

Sensory discrimination and its relationship to the cerebral processing of infrequent stimuli.

We recorded cerebral evoked potentials, back and forward averaged from the EMG onset of the responding muscle, in three reaction time tasks, each requiring an identical motor response to an identical stimulus but differing in the nature of the sensory discrimination required. Two types of stimuli were presented: a rare one to which the subject responded with finger-extension, and a frequent one to which no response was required. We found a close but variable relationship between the cerebral events associated with performance of a task and the timing of the motor response. As completion of the discrimination process was delayed relative to stimulus occurrence, EMG activity began later relative to the cerebral potentials. Moreover, we were able to record these cerebral events only from the response to the rare (unexpected) stimulus and not when subjects were required to respond to the frequent stimulus, suggesting that the sensory discrimination, in these experiments, is an event that occurred only in the processing of the unexpected stimulus.

Adult↗
PubMed1986

Acute syphilitic meningitis. Its occurrence after clinical and serologic cure of secondary syphilis with penicillin G.

Acute syphilitic meningitis developed in a 36-year-old man three months after apparently successful treatment of secondary syphilis with doses of penicillin G benzathine recommended by the current Centers for Disease Control guidelines. He was then treated with high-dose intravenous penicillin G sodium, with resolution of symptoms and cerebrospinal fluid abnormalities. Although other instances of neurosyphilis following adequate therapy for early syphilis have been reported, in most cases reinfection cannot be convincingly excluded. We believe this patient represents a particularly well-documented example of progression to neurosyphilis, despite recommended therapy with penicillin. A review of recently reported cases suggests that progression of syphilis, despite "appropriate" therapy, is not an isolated event.

Acute Disease↗
PubMed1986

Subclasses of event-related potentials: response-locked and stimulus-locked components.

The manner in which information processing proceeds and the relationship of the components of the cerebral "event-related" evoked potential (ERP) to the presumed stages of such processing are uncertain. We studied these relationships by recording long-latency evoked potentials from the scalp in conjunction with electromyographic (EMG) recording in experiments in which subjects were required to make a motor response to one of two auditory stimuli. The cerebral response was averaged from the tone onset (stimulus-synchronized average) and the EMG onset (response-synchronized average). We found that N2 was quite distinct from the other ERP components (P165 and P3) in its lack of a close relationship to the motor response required in a sensory discrimination task. This suggests that, contrary to general belief, the P165-N2-P3 components of the ERP are not generated in an orderly sequence, but rather are generated separately and are possibly related to different cognitive processes.

Adult↗