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Biomedical subjects

D S Goodin

Publications and source records attributed to D S Goodin.

87 records · Page 5Linked to original sources
PubMed1986

Electrophysiological differences between subtypes of dementia.

The distinction between subtypes of dementia, in particular between 'cortical' and 'subcortical' dementias, is controversial. In order to study this we recorded the long latency auditory evoked potential in demented patients with clinically definite Huntington's disease, Parkinson's disease, and Alzheimer's disease. We compared the peak latencies of the components of this response both between these groups and with normal subjects, controlling for the effects of age. We found highly significant electrophysiological differences not only between the subcortical group (combined patients with Huntington's and Parkinson's disease) and the cortical group (patients with Alzheimer's disease), but also within the subcortical group itself. Using the pattern of electrophysiological response alone, we were able to classify correctly most of our patients using a logistic regression model. These results support the notion that there are distinguishable subtypes of dementia.

Adult↗
PubMed1985

Dermatomal somatosensory evoked potentials in unilateral lumbosacral radiculopathy.

We examined scalp-recorded somatosensory evoked potentials (SSEPs) to electrical stimulation of the peroneal nerves and to stimulation in the L5 and S1 dermatomes in 19 patients with unilateral radiculopathies involving these segments. For the dermatomal studies at least two trials of 512 responses were recorded from the vertex with reference to both the midfrontal and contralateral parietal electrodes, using an averaging technique. Findings on the symptomatic and asymptomatic sides were compared in each patient. We found that peroneal SSEPs were normal in all patients. Dermatomal SSEPs correctly identified the lesion in 5 patients. In 1 patient dermatomal SSEPs lateralized the lesion correctly but localized it to the adjacent root. In 10 cases dermatomal SSEPs gave misleading information, indicating an abnormality on the asymptomatic side in 1 patient and no abnormality in 9. In the remaining 3 patients, both SSEPs and radiological contrast studies failed to identify any lesion, although the radiculopathy was confirmed by electromyography. These findings raise doubt about the ultimate utility of these evoked potential techniques in the evaluation of patients with suspected radiculopathies.

Adult↗
PubMed1985

Electrophysiologic evaluation of lumbosacral radiculopathies: electromyography, late responses, and somatosensory evoked potentials.

We compared the diagnostic utility of EMG, F wave and H-reflex studies, and peroneal and dermatomal SEPs in evaluating 28 patients with clinically unequivocal L-5 or S-1 compressive root lesions. The single most useful electrophysiologic technique was EMG, which often provided evidence of denervation in a myotomal pattern when other electrophysiologic findings were normal. We found abnormal late responses in 14 patients, but always in association with EMG abnormalities. Peroneal-derived SEPs were always normal. Dermatomal SEPs confirmed the diagnosis in seven patients, including two in whom other electrophysiologic studies were normal.

Adolescent↗
PubMed1985

Task-dependent hemisphere asymmetries of the visual evoked potential.

Stimulus-related and event-related components of the visual evoked potential were recorded in three separate tasks that required language comprehension or spatial discrimination. Task-dependent asymmetries in the evoked potential were found for both the language task and one of the tasks involving spatial discrimination. Moreover, an identical stimulus presented in two different contexts elicited potentials with a significantly different distribution over the two sides of the head. These asymmetries were largely confined to the event-related components and presumably reflect task-dependent differences in neural processing. Reaction-time studies for these tasks, however, indicated that these asymmetries occurred too late to arise from neural structures responsible for language comprehension or spatial discrimination per se, and must therefore reflect subsequent neural events.

Adult↗
PubMed1985

Electrophysiologic evaluation of dementia.

Several electrophysiologic techniques including routine electroencephalography, frequency analysis, and evoked potentials have been used in the evaluation of demented patients. The clinical utility of these tests, both in diagnosis and establishing prognosis, is considered.

Adult↗
PubMed1984

The relationship between the evoked potential and brain events in sensory discrimination and motor response.

The relationship between the various components of the cerebral evoked potential, sensory discrimination and the initiation of motor responses is controversial. In order to study this relationship, we recorded long-latency evoked potentials from the scalp together with the EMG in a reaction time experiment where the subject was required to make a motor response to one of two auditory stimuli. The peak latencies of event-related components were all found to correlate with EMG response times. Similar results have been reported by others and have led to suggestions that one or another of these components reflects electrical activity in neural structures that are responsible for sensory discrimination. In our experiments, however, the EMG response generally preceded all these components. This observation, whether it relates to the simplicity of our task, the use of EMG to measure reaction time, or to some combination of these factors, implies these these event-related potentials cannot reflect cortical events involved in either sensory discrimination or the initiation of a motor response. Presumably these components must reflect subsequent neural events in the processing of infrequent target tones.

Adult↗
PubMed1983

Variations in early and late event-related components of the auditory evoked potential with task difficulty.

A variation in the difficulty of an auditory discrimination was used to investigate the relationship between the event-related P165, N2 and P3 components of the auditory evoked potential. Equivalent increases in the latencies of all 3 components were found with increased task difficulty. The P165 component, however, could be differentiated from the two later components since it increased in amplitude with increased task demands while the N2 and P3 amplitudes remained constant. It is suggested that the P165, N2 and P3 components comprise a functional sequence in the processing of rare events and possibly involved in a subject's preparations for the future.

Adult↗
PubMed1983

Sequential changes in the P3 component of the auditory evoked potential in confusional states and dementing illnesses.

The P3 component of the auditory evoked potential has been shown to reflect "endogenous" processes related to cognition. This component was measured serially in seven patients who had confusional states or dementing illnesses that fluctuated in severity over time. The latency of P3 component reflected the clinical impression of changes in mental function for each of the patients. These results suggest that the P3 component of the auditory evoked potential provides an objective serial measure of cognitive state that may be useful in following patients with dementing illnesses and in evaluating the effectiveness of any specific therapy.

Adult↗
PubMed1978

Age-related variations in evoked potentials to auditory stimuli in normal human subjects.

Auditory evoked potentials were recorded from 47 subjects ranging in age from 6 to 76 years in order to assess the effects of maturation and aging on the evoked (N1 and P2) and event-related (N2 and P3) components. Because of clear differences in the effects of age on the event-related components between children (less than 15 years of age) and adults the subjects were divided into two populations for analysis. For adults there was a systematic increase in the latency and decrease in amplitude of each component with age. Also the rate of the age-related increase in latency was proportional to the latency of the component. The scalp distributions of both the stimulus-evoked and event-related components were found to vary with age yielding a more nearly equipotential distribution for older subjects. For children the latencies of the event-related components decreased with age. The stimulus-evoked components had latencies which were not significantly different from those predicted from the adult data. In contrast to the adult data, age affected the scalp distributions of the stimulus-evoked components differently than the event-related components. These results suggest an aging process is relfected in the auditory evoked potential which is not the simple inverse of maturational processes.

Acoustic Stimulation↗
PubMed1978

Long latency event-related components of the auditory evoked potential in dementia.

Long-latency auditory evoked potentials were recorded from two groups of patients, with and without dementia, and were compared with those from a population of normal subjects ranging in age from 15 to 76 years. A sequence of tones of two different frequencies (1000 Hz and 2000 Hz) was presented and each patient was asked to count the occurrences of the rare (P = 0.15) tones in the sequence. Evoked potential waveforms were averaged separately for the rare and frequent tone. Of the various evoked potential components elicited by the tones, the P3 component (latency 300-500 ms) was found to be the most sensitive to aging in normal subjects. It was also the only component which could be used to differentiate between the demented patients and the normal subjects or non-demented patients. The non-demented patients did not differ from normal in any waveform measure. The magnitude of the latency change of the P3 component in dementia relative to normal was sufficiently large that it may provide a practical and objective measure of dementia in a clinical setting.

Acoustic Stimulation↗
PubMedDate not supplied

Effect of reference point on visual evoked potentials: clinical relevance.

For clinical purposes the VEP is generally recorded from the mid-occipital region referenced to the vertex or mid-frontal region. This may lead to interpretive errors that can be avoided if a relatively inactive reference point, such as linked mastoids, is used simultaneously. The additional recording derivation may also be helpful in clarifying aberrant or ambiguous wave forms. The diagnostic yield from the two montages is similar, although the linked-mastoid reference provides a greater number of technically inadequate recordings due to smaller size of P100 and increased contamination by muscle artifact.

Adolescent↗