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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
PubMed1998

Cerebral accompaniments to simple and choice reaction tasks in Parkinson's disease.

In order to clarify the nature and basis of the delayed reaction time that occurs in Parkinson's disease, we measured reaction times and cerebral responses in six parkinsonian patients and six normal age-matched control subjects. Each participated in one simple reaction task and three choice reaction tasks of different complexity. The reaction times were delayed in the parkinsonian patients in all conditions but especially in the more difficult choice tasks. In addition, the cerebral responses showed delayed latencies of the N1, N2, and P3 components of the event-related cerebral potential. These findings are similar to the changes that we observed previously in patients with both Parkinson's disease and dementia, and suggest that bradyphrenia may account, in part, for the slowing of response time in Parkinson's disease.

Adult↗
PubMed1998

Event-related potentials in the study of sensory discrimination and motor response in simple and choice reaction tasks.

The central organization of the so-called stages of information processing and, in particular, whether such processes proceed serially or in parallel is controversial. Many investigators have considered such organization is substantially serial, although new evidence implies the existence of parallel overlapping processes in which the boundaries between the different stages of information processing are quite blurred. Such evidence derives in part from computer-assisted analysis of the brain's electrical activity.

Brain↗
PubMed1997

Changes of forearm EMG and cerebral evoked potentials following sudden muscle stretch during isometric contractions in patients with Parkinson's disease.

Various investigators have reported that the late reflex EMG activity following muscle stretch is increased in patients with Parkinson's disease. To explore the basis of this increased activity, we have now recorded the late EMG responses together with associated cerebral responses following muscle stretch in parkinsonian patients. Nine patients and eight controls participated in two sets of experiments in which they grasped a handle attached to a torque motor and maintained the wrist isometrically against a constant flexor force. The force was changed unpredictably (first set) or predictably (second set of experiments), causing a stretch of wrist extensors or flexors. Cerebral responses and muscle responses from the forearm were recorded and averaged separately depending upon condition. The late muscle responses to unpredictable muscle stretch were enhanced in parkinsonian patients while the cerebral responses were attenuated when compared to controls. The alteration of the electrocerebral response began approx. 25 ms prior to the late M2 muscle response. Both controls and patients showed a markedly attenuated cerebral response when the muscle stretch was predictable. These results indicate that the electrocerebral response to muscle stretch is altered prior to the onset of M2 in patients with Parkinson's disease, and suggest that these cerebral events reflect components of a long-latency transcerebral reflex pathway that is affected in this disorder.

Brain↗
PubMed1997

The decision to make a movement: neurophysiological insights.

It is unclear how the brain enables a subject to discriminate between two or more sensory stimuli and to respond appropriately to them. This process must include the ability to detect and identify the stimuli, and to select and initiate an appropriate motor response. With the advent of improved computer technology, this behavior can now be studied in the laboratory, not only by monitoring the input to (stimulus) and output from the brain (response), but also by measuring the associated electrical activity of the brain in order to gain an understanding of how this task is accomplished. In this paper we discuss our work in this area and its relevance to understanding the neural organization of the decision to make a movement in response to a sensory stimulus.

Animals↗
PubMed1996

Response times and handedness in simple reaction-time tasks.

The anticipatory (preparatory) cerebral events in simple reaction-time tasks may depend on the ability of a subject to predict accurately the time of occurrence of the stimulus requiring a particular response. In order to examine this hypothesis, we recorded cerebral and muscle responses in two different conditions, each involving three simple reaction-time tasks. Auditory tones were presented either regularly (i.e., predictably) or irregularly and subjects were required to respond to each tone with left hand, right hand or both hands in different runs. Responses were simultaneously averaged both backward and forward from the response (response-synchronized) and forward from the stimulus (stimulus-synchronized). Response-synchronized cerebral potentials to the regular tones were characterized by a slow negative shift, the bereitschaftspotential (BP), that began prior to stimulus onset and whose terminal phase was characterized by a small, higher frequency, negative shift (HFNS). By contrast, response-synchronized cerebral potentials to the irregular tones for both groups did not contain a BP, but a more conspicuous HFNS that began after stimulus onset. Both the response time and the latency of the N1 sensory-related component of the cerebral evoked potential recorded in the stimulus-synchronized averages (which aligns with HFNS) were delayed in the irregular condition. These findings suggest that, for both right- and left-handed subjects, the BP is not required for voluntary movement, and that anticipatory cerebral activity, as reflected by the BP, represents not only a preparation to make a particular response but also a preparation to process the stimulus.

Adult↗
PubMed1996

Comparison of late components in simultaneously recorded event-related electrical potentials and event-related magnetic fields.

We have attempted to define the late components of the event-related magnetic field (ERF) and to relate them to the late components of the event-related electrical potential (ERP). Simultaneous multichannel electroencephalogram (EEG) and magnetoencephalogram (MEG) were recorded in 13 subjects during an auditory oddball paradigm in two series of experiments. EEG responses to frequent tones consisted of the N1 and P2 components of the auditory vertex potential. Responses to rare tones consisted of N1, apparent P2, N2 and P3 components. All EEG components were best seen in the midline and were highly reproducible for all subjects. MEG responses to frequent tones consisted of N1m and P2m components that were highly reproducible only when recorded over the temporal region. By contrast, the ERF to rare tones was less well defined and only the N1m component could be identified satisfactorily. There was little consistent activity in the MEG at the time of occurrence of the N2 and P3 components of the ERP.

Acoustic Stimulation↗
PubMed1996

Response compatibility and the relationship between event-related potentials and the timing of a motor response.

1. Earlier studies have shown that changes in the difficulty of sensory discrimination in a choice reaction time task result in a prolongation of the peak latency for several components of the long-latency event-related potential (ERP). With the use of the technique of response-locked averaging, we have previously shown that manipulation of the difficulty of sensory discrimination also affects response execution as assessed by the interval between the ERP and onset of the response. In the present paper we examine the hypothesis that changing the compatibility of the responses may also affect the difficulty of the discrimination, as well as the execution of the response, as assessed by the interval between stimulus onset and the ERP. Such an effect of response compatibility would provide further evidence for the close integration of motor and sensory processes in the performance of choice reaction time tasks. 2. We continuously recorded the electroencephalogram (EEG) from the scalp and the electromyogram (EMG) from the responding muscles in both compatible and noncompatible visual choice reaction time tasks. In the compatible task subjects responded to a lateralized visual stimulus with the hand ipsilateral to the stimulus, whereas in the noncompatible task they responded with the contralateral hand. EEG and EMG responses were analyzed and averaged off-line, aligning the waveforms by either stimulus onset (stimulus-synchronized averages) or response onset (response-synchronized averages), and averaged separately for both correct and incorrect response outcomes. 3. Response times were significantly faster for frequent stimuli than rare stimuli and were significantly faster to rare stimuli in the compatible than the noncompatible condition. In responses to the frequent stimuli (where both hands were required to respond), the right hand was slightly but consistently faster than the left hand. The right hand also accounted for 83% of the errors made. 4. Stimulus-synchronized and response-synchronized ERPs to either frequent or rare stimuli had a similar appearance for correct responses in both the compatible and noncompatible conditions. The coupling of the response to the ERP for the rare stimuli, however, was different for the two conditions: the response occurred later relative to the ERP components in the response-synchronized average in the noncompatible condition compared with the compatible condition. By contrast, the coupling of the ERPs to the onset of the stimulus was the same in the two conditions. 5. Stimulus-synchronized averages for error responses in which the rare tone was mistaken for a frequent tone showed early sensory processing (as judged by the ERPs) that was similar to that of correct responses to the rare stimuli. After the apparent positive (P2) component of the cerebral response, however, the processing differed, with a superimposed broad negativity possibly reflecting awareness by the subject that a mistake had been made. By contrast, the response-synchronized averages for these error trials appeared like those to frequent stimuli, with the response being coupled to the P2 component of the cerebral response. 6. These results suggest that response compatibility affects response selection processes but does not alter sensory discrimination. However, despite the similarly tight coupling of the response to the ERP in both the compatible and noncompatible conditions, the response occurred later relative to the ERPs in the noncompatible condition. This suggests that different components of the ERP are responsible for triggering the response in different circumstances. Our observations on the error trials suggests that the decision to respond (on these trials) is based on the occurrence of cerebral events that are evoked by either rare or frequent stimuli, whereas this decision (on correct response trials) is based on cerebral events elicited only by the rare stimuli.

Adult↗
PubMed1996

Side effect profile of interferon beta-1b in MS: results of an open label trial.

To determine which patients are prone to side effects from interferon beta-1b and which side effects are most troublesome, we studied 72 patients with clinically definite MS who were started on interferon beta-1b after its release and found that the side effects significantly associated with treatment included skin reactions, flu-like symptoms, fatigue, leukopenia, new or worsened depression, and new or worsened headache. Of these, only fatigue and depression were significantly associated with discontinuance of therapy. Moreover, the course of disease before initiation of treatment also had a significant impact on the likelihood of discontinuing medication. Thus, despite an apparently similar therapeutic benefit (as judged by the similarly reduced attack rate in each group), patients with a secondary chronic progressive course were more likely to discontinue treatment (63%) than patients with either a relapsing/progressive course (18%) or a remitting/relapsing course (7%). Indeed, in the final regression equation, the only factors significantly related (r = 0.875) to the discontinuance of therapy were fatigue (p < 0.0001), a fatigue-depression interaction (p < 0.0001), and a chronic progressive course of disease (p<0.0001). Thus, if future clinical trials are to provide useful information on the value of interferon beta-1b in progressive MS, the side effects of fatigue and depression will need to be ameliorated to limit the drop-out rate from such trials.

Analysis of Variance↗
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↗