Search PubMed⌕ Search

Biomedical subjects

D S Goodin

Publications and source records attributed to D S Goodin.

At least 37 records · Page 2Linked to original sources
PubMed1999

Simple and choice reaction time in Parkinson's disease.

Reaction-times were evaluated in 6 parkinsonian patients and 6 normal control subjects using a simple reaction task and 3 choice reaction tasks of differing complexity. Reaction-times were measured as the time from stimulus onset to the onset of electromyographic activity in the responding muscle. Reaction-time was significantly delayed in patients compared to controls in all tasks, but to a greater extent in the more difficult tasks. The relative magnitude of the change, however, was only 4% in the simple reaction task and 8% in the more difficult choice tasks. These results suggest that the deficit in Parkinson's disease is unlikely to represent a defect in preprogramming as suggested by some investigators. Instead, our results indicate a disturbance in the cerebral processing of the auditory stimuli after their occurrence and prior to the initiation of motor activity.

Acoustic Stimulation↗
PubMed1999

Order effects in response times of parkinsonian patients and normal controls.

Response latencies were measured in 6 parkinsonian patients and 6 normal subjects in a choice reaction task requiring the discrimination of two different tones with different probabilities of occurrence (frequent and rare). Response latency was measured from stimulus onset to onset of electromyographic activity in the responding muscle. Rare-tone responses were separated on the basis of the number of frequent tones intervening between the rare tone of interest and the immediately preceding rare tone (defined as rare-tone position). Frequent-tone responses were separated by the number of consecutive frequent tones occurring either before or after a rare tone (defined as frequent-tone position). Rare- and frequent-tone position had a significant impact on response latency. Both patients and controls had the shortest response latencies to rare tones when four frequent tones (the median interval for these experiments) intervened. Similarly, the response latency to frequent tones increased at approximately this same median interval after a rare event for both patients and controls. These findings suggest that normal controls utilize probability information about both global probabilities and their immediate past experience in order to modify upcoming responses. Our findings also indicate that patients with Parkinson's disease do not differ from normal subjects in this regard, and thus that even subtle attributes of preprogramming are not affected in Parkinson's disease, despite suggestions by others to the contrary.

Acoustic Stimulation↗
PubMed1999

Changes of forearm EMG and cerebral evoked potentials following sudden muscle stretch in patients with Huntington's disease.

Various investigators have reported that the late-reflex electromyographic (EMG) activity following muscle stretch is decreased in Huntington's disease. To explore the basis of this decreased activity, we recorded the late EMG responses together with associated cerebral responses following muscle stretch in patients with Huntington's disease. Five patients and seven controls voluntarily 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 of 2.3 newtons (N). The force was changed unpredictably (first set of experiments) or predictably (second set) to 10.4 N, causing a stretch of wrist extensors or flexors. Rectified surface EMG from the extensor and flexor carpi radialis muscles was integrated for the M2 and M3 components of the late responses. Cerebral responses were recorded from F3, F4, C3, C4, and Cz and averaged separately depending upon condition. The late muscle responses to unpredictable muscle stretch were decreased or absent in patients with Huntington's disease. The cerebral responses recorded at Cz differed markedly between patients and controls, beginning approximately 15 ms prior to the onset of the late M2 muscle response. Although the initial positivity was similar in amplitude, all other cerebral components were markedly reduced in the patient group. Both controls and patients showed a markedly attenuated cerebral response when the muscle stretch was predictable. The electrocerebral response to muscle stretch is thus altered prior to the onset of M2 in patients with Huntington's disease, suggesting that the long-latency reflex involves transcerebral pathways that are affected in this disease.

Adult↗
PubMed1999

Perils and pitfalls in the interpretation of clinical trials: a reflection on the recent experience in multiple sclerosis.

Therapeutic trials in multiple sclerosis, in part because of the marked intra- and inter-individual variability of its clinical course, are prone to serious flaws in both design and interpretation. As a consequence, it has been a common historical pattern that treatment regimens, which are enthusiastically recommended at one point in time, are later proven to be ineffective by more definitive studies. This review considers several recently published therapeutic trials in order to exemplify some of the difficulties that commonly arise in this area of clinical research.

Cladribine↗
PubMed1999

Survey of multiple sclerosis in northern California. Northern California MS Study Group.

A random sample of 493 multiple sclerosis (MS) patients registered with the Northern California Chapter of the National MS Society was surveyed by mail and subsequently interviewed with regard to their MS, life style, diet, medical treatment, family history, and insurance coverage. Of this sample, 168 patients (34%) returned completed questionnaires. The answers on the questionnaire were entered into a database and scores on the extended disability status scale (EDSS), the neurologic rating scale (NRS), the ambulation index (AI), and the mean disability scale (MDS) were determined from the patient's answers to a portion of the questionnaire using a previously validated conversion program. This survey population of 168 patients seemed to represent well both the random sample and the frame population from which it was drawn. Patients commonly experienced symptoms for which there are medical treatments currently available such as bladder symptoms, fatigue, spasticity, pain, and depression. Surprisingly, however, with the exception of spasticity, patients were only infrequently treated for these complaints. In addition, despite the recent approval of the beta-interferons and copolymer I in the treatment of MS, only 74% of the appropriate candidates for such treatment had these options discussed with them and only 45% ever actually received such treatment. Certain clinical features and dietary habits were strongly associated with both EDSS scores and total disability. Not unexpectedly, either a progressive disease course or the presence of neurological dysfunction in any one of a number of functional areas (e.g. bladder, vision, cognitive change, etc.) correlated with higher EDSS scores and greater total disability. Fatigue was also strongly correlated with disability. Indeed, fatigue accounted (in whole or in part) for 65% of the disability experienced by patients; an observation which only underscores the fact that fewer than one third of the patients who experience fatigue have ever been tried on medications. Interestingly, the only factors associated with lower EDSS scores and less total disability were exercise and alcohol consumption. Such associations from a single survey, however, do not establish causation. It is the purpose of this study to establish a baseline level of function within this survey population so that future surveys in the same set of individuals can allow a prospective assessment of how health outcome has influenced different aspects of the patient's medical care, lifestyle, and insurance coverage.

Adult↗
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↗
PubMed1998

A questionnaire to assess neurological impairment in multiple sclerosis.

This study assessed the feasibility of using a self-report questionnaire to measure neurological impairment in multiple sclerosis (MS). Thirty patients aged 21-67 years participated. Each patient was examined and scored on three commonly used impairment scales; the extended disability status scale (EDSS), the neurologic rating scale (NRS) and the ambulation index (A1). Two other scales were also determined; the sum of the EDSS functional scores (SFS), and a five point scale rating functional status (FS). The physician also filled out a copy of the questionnaire based on interview and examination of the patient. All of these scores were determined and the physical questionnaire filled out blind to the patient's answers on their self-report questionnaire. The first 15 consecutive patients served as the pilot group to develop a computer program to convert answers on the questionnaire into predicted scores on each of the five scales. The second 15 patients served as the independent test group to assess the validity of the computer program. Using this program, both patient and physician questionnaires accurately predicted (r > 0.87) the scores on each of the five scales measured manually. In addition, the scores on all five scales were highly cross-correlated (r > 0.85) suggesting that, in fact, each measured a similar attribute of MS (i.e., impairment). Therefore, the five scales were combined into a single measure, the mean disability score (MDS), which showed the highest correlations (r > 0.95) of any scale between the predicted scores and the actual scores determined by examination. The results of this study indicate that the self-report questionnaire is a valid measure of neurological impairment in MS and, thus, that it can be used to survey this health outcome in an MS population. Moreover, this questionnaire can be filled out by a physician (based directly on the neurological examination) and, together with the computer program for scoring each patient, can be used to provide consistent scoring in clinical trials.

Adult↗
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↗