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Biomedical subjects

J G Van Dijk

Publications and source records attributed to J G Van Dijk.

14 recordsLinked to original sources
PubMed1998

Compound muscle action potential cartography of an accessory peroneal nerve.

In daily practice, accessory peroneal nerves (APNs) are detected in less than the 18-25% of legs, as revealed by systematic searches. In one APN case, compound muscle action potential cartography showed that the APN was only apparent when the recording electrode was placed over a small lateral region of the extensor digitorum brevis muscle. Effects of recording site can explain why many APNs go unrecognized.

Action Potentials↗
PubMed1995

Residual cognitive dysfunctioning at 6 months following coronary artery bypass graft surgery.

Neuropsychological testing is a sensitive method for quantitative assessment of cognitive dysfunctioning following cardiopulmonary bypass (CPB). However, the methodological problems associated with this method, such as learning effects due to repeated testing and the effects of distress on test performance, have often been underestimated. In this study, these confounding effects were controlled for by including the spouses of patients, exposed to the same potential stress effects associated with the operation, as a nonsurgical control group. The experimental group consisted of 63 patients (40-75 years) undergoing elective coronary artery bypass graft (CABG) surgery. A battery of standardized neuropsychological tests was administered to both groups 2 weeks preoperatively and 1 week, 1 month, and 6 months postoperatively. Statistical testing of inter-group differences in preoperative to postoperative changes in test performance revealed the following results: (1) For immediate memory and learning, in general test scores showed the same time course for both groups. (2) For recent memory, patients' scores showed a significant deterioration at 1 month after CABG surgery compared with the scores of spouses. This effect had not completely disappeared at 6 months postoperatively. (3) For attention and psychomotor speed as well as verbal fluency, patients' scores had deteriorated significantly at 1 week after surgery, with incomplete recovery at 6 months. These negative cognitive effects were not related to the patients' ages or CPB parameters (duration of CPB, aortic cross-clamp time, mean flow and arterial pressure during CPB and aortic cross-clamping, and minimum nasopharyngeal temperature). No differences in self-ratings of mood over time were found between the patients and spouses. The results indicate that, when adequately controlling for the effects of learning and distress, some cognitive functions are still impaired at 6 months after CABG surgery.

Adult↗
PubMed1994

Auditory information processing in sleep: late cortical potentials in an oddball paradigm.

Information processing of auditory stimuli in sleeping healthy volunteers is studied by means of an oddball paradigm. Latencies of the early (N1P2) complex are affected by NREM sleep depth and show a progressive slowing. The amplitude of the early N1 component depends on stimulus type and probability and is increased following deviant stimuli. In strict comparison with waking, late responses (N2-P3) complex only follows deviant stimuli. Both latencies and amplitude increase more in NREM than in REM sleep. Thus the early response is mainly affected by vigilance, the late response mainly depends on stimulus type. Results are discussed in terms of comparison processing, context updating and orienting response patterning hypotheses put forward in cognitive psychophysiology.

Adult↗
PubMed1993

A comparison of the concentration-effect relationships of midazolam for EEG-derived parameters and saccadic peak velocity.

1. Concentration-effect relationships of midazolam were assessed in an open study in six healthy volunteers. Saccadic eye movements and EEG parameters derived by fast Fourier transform (FFT) and aperiodic analysis (AP) were used to quantify drug effects. 2. Midazolam was infused at a rate of 0.6 mg kg-1 h-1 for a maximum of 15 min. Hypnotic effects were avoided by terminating infusions when subjects could no longer perform the eye movement test properly. 3. Wake-sleep transitions could be recognized through frequent observation of eye movements. The dose needed to reach maximum conscious sedation averaged 0.10 mg kg-1, ranging from 0.06 to 0.13 mg kg-1. 4. Sigmoidal concentration-effect relationships were found for EEG beta-amplitudes in five of six subjects, with average EC50 values (+/- s.d.) of 120 +/- 54 ng ml-1 for FFT and 104 +/- 40 ng ml-1 for AP. For the 'total number of waves' in the beta frequency range (AP) an average (n = 6) EC50 of 63 +/- 37 ng ml-1 was found. Changes in EEG alpha-amplitudes were found in three subjects, resulting in an average EC50 value of 55 +/- 32 ng ml-1. 5. For saccadic peak velocity (PV) concentration-effect relationships were linear in five subjects and sigmoidal in one. The maximal measured decrease in PV averaged -44 +/- 9%. 6. The differences in concentration-effect relationships for various effect parameters call for further studies with emphasis on the external validity and reproducibility of data. In such studies the dose needed to reach wake-sleep transition may be used as a relevant clinical end-point.

Adult↗
PubMed1992

Background EEG reactivity in auditory event-related potentials.

Mental activity has influences on auditory event-related potentials (AERP) as well as on some EEG rhythms, notably the alpha rhythm. In this study, background reactivity (BR) of the EEG was investigated in the context of AERPs. Single responses of 14 healthy subjects were analysed in 3 reaction time AERP experiments of increasing difficulty: the first involved one type of tone delivered at random intervals, the second offered two types of tone (an "oddball" design), and the third offered 3 types of tone. Averages were formed and subtracted from the separate responses to reduce their contribution to the EEG. The 1526 msec EEG epoch was divided in 9 overlapping periods, and averaged power spectra were calculated for these periods. Changes in area of the delta, theta, alpha and beta bands in the course of the epoch were calculated. Background alpha and beta activity decreased following infrequent but not following frequent tones. The decrease was larger for more difficult tasks and reached a maximum in the period in which the AERP P3 and N3 peaks fell. Delta and theta powers showed increases rather than decreases; these could be attributed to the contribution of AERP activity to total EEG power. No clear relationships were found between the amount of background reactivity and peak latencies or reaction times. The occurrence of background reactivity, not apparent in an average, shows that the averaged AERP reveals only part of the EEG changes related to mental activity. Background reactivity proved to be more sensitive to task difficulty than P300 latency. The results are discussed in the context of the additive model of evoked potentials.

Acoustic Stimulation↗
PubMed1992

Altered postural reflexes in Parkinson's disease: a reverse hypothesis.

In subjects standing on a movable platform, sudden dorsiflexion of the ankle joint elicits a set of reflexes in leg muscles. These responses include a short latency (SL) and medium latency (ML) stretch reflex in the gastrocnemius muscle and a distal to proximal innervation sequence of long latency (LL) reflexes in the shortened tibialis anterior and vastus lateralis muscles. Because of their role in maintaining upright stance these responses have been termed postural reflexes. In patients with Parkinson's disease (PD), the following abnormalities have been described: 1) enhanced ML-amplitudes; 2) a reversed LL innervation sequence; and 3) delayed onset latencies. These abnormalities are thought to be due to defective motor programming and disturbed control of spinal and supraspinal reflex centers by basal ganglia circuits. The altered reflexes have been held responsible for some of the clinical features of PD, including balance impairment and rigidity. In this paper, we argue the reverse hypothesis that postural reflexes are essentially normal in PD, and that the observed alterations are at least in part consequence rather than cause of balance impairment, the stooped parkinsonian posture and rigidity of PD patients.

Humans↗
PubMed1992

Korsakoff minus Wernicke syndrome.

It is commonly believed that Korsakoff's amnesic state in alcoholics is characteristically the sequel to Wernicke's disease. However, in a study of 44 Korsakoff patients it was found that 33 had developed serious memory impairment without having had alarming neurological symptoms. This insidious nature of the onset of the disease indicates that all alcohol-dependent patients should be treated with vitamin B.

Alcohol Amnestic Disorder↗
PubMed1991

Long-term EEG monitoring in the early premature: developmental and chronobiological aspects.

Long-term cassette EEG monitoring in the neonatal intensive care unit has established prognostic criteria regarding the developmental outcome by quantifying seizure activity. The clinical significance of the organization of continuous and discontinuous EEG patterns in the early premature is still an open question. This report presents quantified EEG data from repeated 24 h records during the first week of life in premature infants (conceptional age less than 32 weeks) with and without ultrasound evidence of intracerebral hemorrhage. The repartition and evolution of EEG background activity is not a reliable parameter regarding pathology. The continuity index is rather a maturational variable and its ultradian fluctuation is an early expression of the "basic rest activity cycle" (BRAC) rhythm.

Aging↗
PubMed1991

Long latency postural responses are functionally modified by cognitive set.

We examined how cognitive set influences the long latency components of normal postural responses in the legs. We disturbed the postural stability of standing human subjects with sudden toe-up ankle rotations. To influence the subjects' cognitive set, we varied the rotation amplitude either predictably (serial 4 degrees versus serial 10 degrees) or unpredictably (random mixture of 4 degrees and 10 degrees). The subjects' responses to these ankle rotations were assessed from the EMG activity of the tibialis anterior, the medial gastrocnemius, and the vastus lateralis muscles of the left leg. The results indicate that, when the rotation amplitude is predictable, only the amplitude of the long latency (LL) response in tibialis anterior and vastus lateralis varied directly with perturbation size. Furthermore, when the rotation amplitude is unpredictable, the central nervous system selects a default amplitude for the LL response in the tibialis anterior. When normal subjects are exposed to 2 perturbation amplitudes which include the potential risk of falling, the default LL response in tibialis anterior appropriately anticipates the larger amplitude perturbation rather than the smaller or an intermediate one.

Adult↗
PubMed1990

Habituation of K-complexes or event-related potentials during sleep.

We examined habituation and dishabituation of evoked K-complexes (equivalent to auditory event-related potentials) during sleep. Habituation is investigated by presenting trains of stimuli with a 5 sec inter-stimulus interval and a 4 min inter-train interval. Habituation is complete by the third identical stimulus in a train and dishabituation occurs after deviant stimuli and after the inter-train interval. Although there are morphological differences between K-complexes in sleep and auditory event-related potentials in wakefulness, they share the phenomenon of habituation to repetitive events.

Acoustic Stimulation↗
PubMed1990

Trigeminal neuralgia-like pain in an aged woman with fibrous dysplasia of the skull base.

A 72 year old woman with attacks of severe lancinating pain in the right frontotemporal region of her face had, on CT scan of the skull base, fibrous dysplasia of the right sphenoid bone, involving the areas traversed by the trigeminal nerve. Her pain ceased following treatment with methysergide. In patients with hemifacial pain but no evident facial or skull deformities, CT scan of the skull base may be helpful in elucidating the diagnosis.

Aged↗
PubMed1988

Respiration during sleep in Huntington's chorea.

In view of recent reports on lower brainstem dysfunction in Huntington's chorea, we studied respiration during sleep in 12 patients with Huntington's chorea (HC) and in controls. There were no statistically significant differences between patients and controls with respect to apnea periods, respiratory frequency and time elapsed between minimal and maximal value of the respiratory curve. No statistically significant differences in respiratory variability were observed between patients and controls. In the present study, no indication was found for dysfunction of lower brainstem structures involved in respiration in HC.

Adult↗