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Biomedical subjects

D S Goodin

Publications and source records attributed to D S Goodin.

At least 19 recordsLinked to original sources
PubMed1995

The frontal N30 component of the median-derived SEP in patients with predominantly unilateral Parkinson's disease.

There are conflicting reports concerning attenuation of the frontal N30 component of the median-derived somatosensory evoked potential in patients with Parkinson's disease (PD). We found that the mean N30 latency (28.03 +/- 2.50 msec) and amplitude (2.30 +/- 1.58 microV) obtained with stimulation of the affected arm of 10 patients with predominantly unilateral PD were not significantly different from those obtained from the unaffected arm (mean latency, 28.14 +/- 2.47 msec; mean amplitude, 2.43 +/- 1.65 microV) or from 10 age-matched controls (mean latency, 29.01 +/- 1.88 msec; mean amplitude, 1.92 +/- 0.64 microV). Three patients had an N30 of abnormal amplitude; in two, responses were absent with stimulation of either side, and in one there was a response asymmetry exceeding the normal range, with the smaller response elicited from the affected arm. Thus, only one of 10 patients had a diminished N30 consistent with the clinical findings. We conclude that the N30 is unlikely to be clinically useful in the assessment of patients with PD.

Aged↗
PubMed1994

Late electromyographic activity following stretch in human forearm muscles: physiological role.

We have previously found that the late reflex electromyographic (EMG) responses to muscle stretch are simultaneously present in both the stretched muscle and its antagonist, suggesting that it may be involved in the control of limb stiffness rather than in a servo-mechanism that returns the limb to an initial or intended position. Nevertheless, in these earlier experiments the size of the late EMG activity was always greater in the stretched muscle than its antagonist, suggesting also a possible servo-role for these responses. To clarify this, we have now recorded the late EMG activity simultaneously from both the right extensor and flexor carpi radialis muscles in ten subjects under four experimental conditions. These conditions differed in which muscle was activated voluntarily prior to the stretch stimulus and in which muscle was stretched by the perturbing force. In all cases subjects were asked to maintain the limb in a fixed position and oppose any displacement that occurred. The amount of integrated EMG activity for both the M2 and M3 components of the late response was greater in the agonist muscle (i.e., the muscle actually stretched by the perturbing force) than the antagonist. The ratio of agonist to antagonist activity, however, was significantly larger for the M2 than for the M3 component. These results suggest that both the M2 and M3 components of the late EMG response have a dual functional role, being involved both in a servo-mechanism and in the control of limb stiffness. Each component, however, seems to have a distinctive role.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

Biochemical alterations in multiple sclerosis lesions and normal-appearing white matter detected by in vivo 31P and 1H spectroscopic imaging.

The goals of the current study were threefold: first, to confirm previous single volume proton (1H) magnetic resonance spectroscopy results of reduced N-acetyl aspartate (NAA, a putative marker of neurons) in multiple sclerosis (MS) white matter lesions using multiple volume 1H magnetic resonance spectroscopic imaging (MRSI); second, to measure the phospholipid metabolites phosphomonoesters and phosphodiesters in such lesions using phosphorus (31P) MRSI; and third, to test the hypothesis that biochemical changes occur in the normal-appearing (on spin echo T2-weighted magnetic resonance images) white matter in patients with MS. Thirteen subjects with clinically definite MS were studied with both 1H and 31P MRSI, and 19 controls were studied with either 1H MRSI, 31P MRSI, or both. MS lesion, MS normal-appearing white matter, and region-matched control spectra from the centrum semiovale were analyzed. The major findings of this study were that in both white matter lesions and normal-appearing white matter in patients with MS, the metabolite ratio NAA/creatine and the total 31P peak integrals were significantly reduced compared with controls. In addition, in MS lesions NAA/choline and phosphodiesters/total 31P were significantly reduced compared with controls, and in MS normal-appearing white matter there was a trend for NAA/choline to be reduced compared with controls. In normal-appearing white matter in patients with MS, total creatine and phosphocreatine were significantly increased compared to controls, as detected with both 1H (total creatine peak integrals) and 31P (phosphocreatine/total 31P) MRSI techniques. These results suggest reduced neuronal density and altered phospholipid metabolites in white matter lesions in patients with MS.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1994

In vivo detection of myelin phospholipids in multiple sclerosis with phosphorus magnetic resonance spectroscopic imaging.

The goal of this study was to investigate myelin phospholipids in vivo in multiple sclerosis lesions and normal-appearing white matter by evaluating the spectral broad component from phosphorus 31 magnetic resonance spectroscopic imaging data. The phospholipid broad component was reduced nearly 35% (p < 0.001) in both lesions and in normal-appearing white matter in multiple sclerosis subjects compared to control subjects, suggesting reduced myelin phospholipid concentration or altered relaxation times.

Adult↗
PubMed1994

Visual evoked potentials.

The recording of visual evoked potentials (VEPs) is an important means of obtaining reproducible, quantitative data on the function of the anterior visual pathways. In this review, the technical aspects of recording VEPs are briefly discussed, components of the VEPs are described, and the clinical uses of VEPs are considered. It is concluded that VEPs are useful in providing information concerning the functional integrity of the anterior visual pathways. They are especially useful in evaluating patients with visual symptoms but no objective findings on examination and in patients without visual symptoms but with diseases that are known to involve the visual pathways commonly and subclinically. Lastly, the utility and limitations of VEPs in various neurological disorders are summarized, bearing in mind the widespread availability of advanced neuroimaging techniques.

Acoustic Stimulation↗
PubMed1993

Neural processing in a three-choice reaction-time task: a study using cerebral evoked-potentials and single-trial analysis in normal humans.

1. Previous studies have shown that the long latency event-related potentials (ERPs) reflect certain aspects of the sensory discrimination process, although the coupling of these ERPs to the actual discrimination is variable. Indeed, we have previously shown that during a two-choice reaction time task the discrimination is accomplished as a two-stage process, with the more frequently occurring stimulus discriminated at an earlier point than the rarer stimulus. The present paper examines the hypothesis that, in a three-choice reaction time task, the discrimination is similarly organized, i.e., is accomplished with the use of a three-stage process. 2. In the present experiments, we continuously recorded the electrocerebral activity (EEG) from the scalp and the electromyogram (EMG) from the responding muscles in a three-choice reaction time task in 10 strictly right-handed subjects. EEG and EMG responses were subsequently analyzed off-line by aligning them by the onset of either the stimulus (stimulus-synchronized) or the response (response-synchronized) for both correct and incorrect responses. 3. Subjects could be classified as "fast" or "slow" responders based on the mean response-latency to the most frequently occurring of the three tones (Frequent tone). Fast responders to the Frequent tone were also fast responders to the more frequent of the rare tones (the Rare-1 tone). By contrast, the response latency to the Frequent tone did not predict the speed of response to the most rare tone (the Rare-2 tone). 4. In the response-synchronized averages well-formed premovement potentials were present for the correct responses to all three tones. In the case of the Frequent tone, these potentials were symmetrical over the two cerebral hemispheres (as expected because both hands responded to this tone). They began > or = 200 ms before the average onset of the stimulus, suggesting that the preparation to respond preceded the stimulus. In the case of the two rare tones, the amplitudes of these premovement potentials were asymmetrical over the two hemispheres. For the Rare-1 tone, these potentials were lateralized to the hemisphere contralateral to the hand moved. For the Rare-2 tone, however, these premovement potentials were initially lateralized to the ipsilateral hemisphere, indicating that, even when subjects were able to respond rapidly and correctly to this tone, they were anticipating a need to respond with the incorrect hand (in anticipation of the more frequent Rare-1 tone).(ABSTRACT TRUNCATED AT 400 WORDS)

Adult↗
PubMed1993

Expectancy and response strategy to sensory stimuli.

We investigated the relationship between sensory discrimination and the selection of appropriate responses in subjects performing two different reaction-time tasks, in which three auditory stimuli were presented in random order and with a different likelihood of occurrence. Subjects anticipated the need to make different responses based on the likelihood that a particular stimulus would occur on a particular trial. This was determined by the occurrence and distribution of premovement potentials prior to the stimulus, which were consistent with preparation to respond to the most frequently occurring stimulus. These anticipatory cerebral events, however, could be altered after recognition that this frequent stimulus had not occurred. Thus, after the occurrence of a stimulus other than the anticipated frequent tone, the scalp distribution of cerebral potentials changed in a manner suggesting that the next most frequently occurring stimulus was anticipated. Nonetheless, subjects were able to respond to the least probable stimulus both accurately and rapidly despite a failure to anticipate it correctly, as judged by the cerebral "lateralized readiness potential." These results indicate that stimulus evaluation and response selection are integrated and dynamic cerebral processes, and raise doubt about the functional significance of the so-called premovement readiness potential.

Acoustic Stimulation↗
PubMed1992

The basis and functional role of the late EMG activity in human forearm muscles following wrist displacement.

The present paper examines the hypothesis that the long latency EMG activity produced by muscle stretch is the result of long loop reflex pathways involved in the control of limb stiffness. We recorded the cerebral responses and late EMG activity in agonist and antagonist muscles following sudden stretch of the wrist extensor muscles under 4 experimental conditions in 11 subjects. In each experiment subjects held their right wrist extended isometrically against a constant force of 2.3 N and a trial was begun with a step increase in the force from 2.3 N to 18.4 N, to stretch the extensor muscle. In the first and second experiments the force change occurred unpredictably and subjects had to either oppose the perturbation (Unpredictable Oppose) or relax the forearm muscles once the increase in force was detected (Unpredictable Let-Go). In the third and fourth experiments the force change occurred predictably when subjects pressed a thumb switch with the left hand to cause it. As before, subjects were instructed to either oppose the perturbation (Predictable Oppose) or relax the forearm muscles (Predictable Let-Go). Responses were recorded from the flexor and extensor carpi radialis muscles and from the scalp. When the perturbing force occurred unpredictably, early latency EMG activity (the MI response) was seen in the stretched extensor muscle, and longer latency EMG activity was seen simultaneously in both extensor and flexor muscles. When the force change occurred predictably the late EMG activity was considerably attenuated, especially in the Predictable Let-Go condition. Cerebral responses similarly depended upon the predictability of the perturbation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Effect of different high-pass filters on the long-latency event-related auditory evoked potentials in normal human subjects and individuals infected with the human immunodeficiency virus.

The effect of different high-pass filters on long-latency auditory evoked potentials was investigated in 25 subjects, 15 of whom were asymptomatic individuals seropositive for the human immunodeficiency virus (HIV) and 10 of whom were normal control subjects without known risk factors for HIV infection. High-pass filtering was done simultaneously at 0.25 Hz and 1.0 Hz, and cerebral responses to rare (2,000 Hz) and frequent (1,000 Hz) tones were recorded from Fpz, Cz, and Pz electrode placements and averaged separately. Using either filter, well-formed and reproducible responses were obtained, although the latencies of the N1, P2, N2, and P3 components of the response were slightly shorter when a 1.0 Hz filter was used. In addition, the appearance of the late response was modified in a manner suggesting that components of the ERP considerably slower than P3 were being attenuated by a 1.0-Hz filter. Although it could be argued that this makes the use of a 1.0-Hz filter setting preferable in the clinical setting, the variability and reproducibility of the ERP were comparable when either high-pass filter was used, and both resulted in similar findings in the HIV-infected individuals compared to normals.

Adult↗
PubMed1992

Evaluation of dementia by event-related potentials.

Event-related potentials depend on the context of the target stimulus and relate to the cognitive aspects of discriminating target from nontarget stimuli. For clinical purposes, they are elicited most commonly by auditory stimuli. They are influenced by advancing age and by alterations in mental function. They have been used to distinguish dementia from pseudodementia. More specifically, the P3 component of these potentials has a high sensitivity and specificity to dementia, and a prolongation in P3 latency is therefore helpful in establishing the diagnosis of dementia with confidence. Serial studies can provide a means of following changes in cognitive function over time. It may also be possible to distinguish between different types of dementia by the pattern of electrophysiologic abnormalities and in particular by which components of the event-related potentials are delayed.

Brain↗
PubMed1991

The nature of suprasegmental influences on the late reflex activity in human forearm muscles.

The earliest component of the late EMG response (M2) to sudden stretch of an isometrically contracting muscle is influenced by suprasegmental mechanism, but whether these are tonic, phasic, or both, is uncertain. We have therefore investigated the nature of these mechanisms by varying the predictability of the direction of perturbation of forearm muscles held isometrically against a constant flexor or extensor force of 2.3 N. We found that the M2 response did not change appreciably regardless of whether the direction of perturbation was known in advance or which hand was used by the subject. These findings suggest that any tonic supraspinal influence of the M2 response is of little significance compared to the importance of phasic mechanisms and provide support for the existence of a cerebral arc subserving this reflex component.

Adult↗
PubMed1990

Detection of epileptiform activity by different noninvasive EEG methods in complex partial epilepsy.

The diagnostic utility of different noninvasive electrode placements for deriving the electroencephalogram and detecting interictal epileptiform discharges was compared. Anterior temporal and nasopharyngeal electrodes in combination with routine scalp electrodes detected over 97% of the spikes, whereas recording from only standard electrode placements detected 58%. Minisphenoidal and surface sphenoidal electrodes were generally not helpful. In some circumstances, however, the use of surface sphenoidal electrodes provided important confirmatory information. In no case did the minisphenoidal electrodes provide unique information, and their use seems unjustified, although the inclusion of other nonstandard electrodes in the recording montage is important to increase the yield.

Adolescent↗
PubMed1990

Long latency event-related potentials in patients infected with human immunodeficiency virus.

Long latency auditory evoked potentials were recorded in 55 homosexual men infected with human immunodeficiency virus (HIV). Forty-one of these patients were asymptomatic from the infection and 14 had clinical signs of illness. Nine of the symptomatic patients were demented and 8 (6 of whom were demented) met other diagnostic criteria for acquired immunodeficiency syndrome (AIDS). Cerebral responses were recorded from Fz, Cz, and Pz electrode placements referred to linked mastoids and averaged separately to rare (2,000 Hz) and frequent (1,000 Hz) tones presented in a pseudorandom sequence. Electroencephalography (EEG) was performed in 54 of the patients and magnetic resonance imaging (MRI) or computed tomography (CT) was done in 14 (13 of whom were symptomatic from the infection). The latency of N1, P2, N2, and P3 components was delayed in HIV-positive patients compared to normal and this was particularly so for the N1, N2, and P3 components. These changes were more marked in those patients who were symptomatic from their infection, especially in those who were demented. They were, however, present to a lesser degree even in asymptomatic (Class II) patients. Thus, 78% of the demented patients and 28% of nondemented patients had a delay in latency of at least one of the evoked potential components beyond the upper limit of our normal population. By contrast, the EEG was normal in all patients with asymptomatic HIV infection and most symptomatic patients, although 5 patients in this latter group had mild generalized slowing. MRI and CT findings were similarly nonspecific, particularly in the nondemented group.(ABSTRACT TRUNCATED AT 250 WORDS)

Acoustic Stimulation↗
PubMed1990

A comparison of magnetic and electrical stimulation of peripheral nerves.

We compared magnetic stimulation using different coil designs (2 rounded coils and a butterfly-prototype coil) with electrical stimulation of the median and ulnar nerves in 5 normal subjects. Using magnetic stimulation we were able to record technically satisfactory maximal sensory and motor responses only with the butterfly coil. Submaximal electrical stimuli preferentially activated sensory rather than motor axons, but submaximal magnetic stimuli did not. The onset latency, amplitude, area and duration of responses elicited electrically or magnetically with the butterfly coil during routine sensory and motor nerve conduction studies were similar, and motor and sensory conduction velocities were comparable when studied over long segments of nerve. However, the motor conduction velocities with magnetic and electrical stimulation differed by as much as 18 m/sec in the across-elbow segment of ulnar nerve. Thus, recent developments in magnetic stimulator design have improved the focality of the stimulus, but the present butterfly coil design cannot replace electrical stimulation for the detection of focal changes in nerve conduction velocity at common entrapment sites, such as in the across-elbow segment of the ulnar nerve.

Action Potentials↗