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Biomedical subjects

M M Schugens

Publications and source records attributed to M M Schugens.

At least 19 recordsLinked to original sources
PubMed1999

Long-term retention of classical eyeblink conditioning in amnesia.

The retention of classical eyeblink conditioning was investigated in amnesic patients 10 days and 2 months after original learning. During reacquisition, the first CR occurred earlier and the CR frequencies during the first 10 trials were higher than in the baseline session. The overall CR rates increased significantly across sessions during both acquisition and extinction. The amnesics did not differ from matched controls on any of these effects, although they did not recall previous conditioning sessions and did not become fully aware of CS-US contingencies. The smaller number of electrodermal responses to the CS tone during extinction in the amnesics may relate to their lack of insight into the change in the reinforcement schedule.

Amnesia↗
PubMed1999

Learned maintenance of pain: muscle tension reduces central nervous system processing of painful stimulation in chronic and subchronic pain patients.

The effect of level of muscle tension on the perception of painful stimuli was assessed in 13 chronic back pain patients, 14 subjects at high risk for chronic back pain, and 14 matched healthy controls. Subjects received painful intracutaneous electric stimuli to the forearm or the lower back while they produced either high or low muscle tension levels. Visual analog scale (VAS) ratings of acute pain were obtained after each trial. Electroencephalograms, electromyograms, skin conductance levels, and blood pressure were measured during the trials. Although subjective pain ratings were not significantly affected by muscle tension levels, the chronic pain patients displayed elevated N150 and N150/P260 amplitudes of the somatosensory-evoked potentials in the low as compared to the high muscle tension condition. The high risk group showed a trend toward higher N150 amplitudes in the low as compared to the high tension condition. The results of this study partially support the hypothesis that increases in muscle tension might serve as a pain-reducing mechanism in chronic pain patients and those at risk for chronicity, thus leading to a vicious pain-tension cycle.

Adult↗
PubMed1998

The non-competitive N-methyl-D-aspartate-antagonist memantine does not affect segmental mono- and polysynaptic reflexes in man.

Studies in rats have shown that the polysynaptic flexor reflex (FR) but not the monosynaptic reflexes are affected by N-methyl-D-aspartate (NMDA) receptor antagonists. Theoretically, the suppression of FR might be caused by an alteration of the spinal nociceptive neurons. To investigate, whether the non-competitive NMDA receptor antagonist memantine interferes with nociception in man, we studied both its effect on pain perception and on FR. In a double-blind study 14 male subjects were randomly assigned to either placebo or memantine (30 mg p.o.) treatment. H-reflex (HR) and FR as well as pain and tolerance threshold were determined prior to and 6 h after drug intake. Contrary to expectations, there were no differential treatment effects either on FR threshold and magnitude or on pain and tolerance thresholds or the HR amplitude.

Adult↗
PubMed1997

The NMDA antagonist memantine impairs classical eyeblink conditioning in humans.

The present study investigated the effects of a single oral dose (30 mg) of the non-competitive N-methyl-D-aspartate (NMDA) receptor antagonist memantine on memory and learning in human subjects. Sixteen male healthy volunteers participated in a double blind placebo controlled study. There were no significant effects of memantine on mood, attention or immediate and delayed verbal and visuospatial memory. Memantine did, however, delay the acquisition of classical eyeblink conditioning and reduced the overall frequency of conditioned responses without affecting reflex or spontaneous eyeblinks. These findings are compatible with the higher affinity of memantine to cerebellar as compared to forebrain tissue and demonstrate the dissociability of different memory systems by pharmacological tools.

Adult↗
PubMed1996

Memory dysfunction of the frontal type in normal ageing.

In this study healthy subjects divided into five consecutive age groups (20-60 years of age) completed a series of memory tasks which had previously been shown to reveal impairments in patients with frontal lobe lesions. Significant age differences were found for free recall, retention rates for material which required effortful encoding, memory for temporal order and prospective memory. In the tests addressing these memory functions, subjects of more than 60 years of age performed more poorly than the youngest group, and they also showed evidence of false recognition (increased false alarm rates and confabulatory responses). The general pattern suggests that inefficient frontal functioning might contribute to age-related memory problems.

Adult↗
PubMed1996

Classical eyeblink conditioning in Parkinson's disease.

Patients with Parkinson's disease (PD) show impairments of a range of motor learning tasks, including tracking or serial reaction time task learning. Our study investigated whether such deficits would also be seen on a simple type of motor learning, classic conditioning of the eyeblink response. Medicated and unmediated patients with PD showed intact unconditioned eyeblink responses and significant learning across acquisition; the learning rates did not differ from those of healthy control subjects. The overall frequency of conditioned responses was significantly higher in the medicated patients with PD relative to control subjects, and there was also some evidence of facilitation in the unmedicated patients with PD. Conditioning of electrodermal and electrocortical responses was comparable in all groups. The findings are discussed in terms of enhanced excitability of brainstem pathways in PD and of the involvement of different neuronal circuits in different types of motor learning.

Adult↗
PubMed1996

Impaired procedural learning after damage to the left supplementary motor area (SMA).

Two paradigms of procedural learning, serial reaction time and tracking tasks, were given to a patient with damage to the supplementary motor area (SMA) of the left mesiofrontal cortex. This patient exhibited impaired procedural learning during the serial reaction time test and mirror reversed tracking. Unreversed tracking performance was normal. Therefore the SMA--as well as the cerebellum and the striatum--participate in the development of skills requiring internal elaboration of motor behaviour.

Adult↗
PubMed1995

Pain-related cerebral potentials in patients with frontal or parietal lobe lesions.

The present study investigated the processing of painful electrical stimuli in patients with unilateral frontal or parietal lobe damage and matched control subjects. Patients with frontal lesions showed increased pain thresholds when the stimuli were administered contralateral to the lesion. While the peak-to-peak amplitudes of the N150/P250 components of the somatosensory potentials increased linearly with stimulus intensity in the control subjects, the responses in the frontal group did not change significantly between stimulation at pain and tolerance threshold. There was no evidence for altered pain processing in patients with parietal lobe lesions. The findings of the present study support the hypothesis of an involvement of the frontal cortex in pain perception in humans.

Adult↗
PubMed1995

Memory and skill acquisition in Parkinson's disease and frontal lobe dysfunction.

Animal experiments and human neuropsychological studies have provided evidence for the hypothesis that skill acquisition may be regulated by the basal ganglia. In the present studies, perceptual and cognitive skill acquisition as well as a number of explicit verbal memory functions were investigated in patients in early and more advanced stages of Parkinson's disease (PD) and in patients with frontal lobe lesions. Patients in more advanced stages of PD were impaired at cognitive skill acquisition as well as during recall conditions that involved active semantic organisation of the stimulus material. Similar explicit memory deficits were present in frontally lesioned patients. PD patients with unilateral symptoms showed a selective impairment in acquiring a cognitive skill. Perceptual skill acquisition was preserved in all groups. The overall pattern of memory impairment in PD is largely consistent with dysfunction of fronto-striatal circuitry.

Corpus Striatum↗
PubMed1993

Proximal and distal reaction times (RTs) are not differentially affected in Parkinson's disease.

The hypothesis was tested that proximal and distal reaction times (RTs) might be differentially affected in Parkinson's disease (PD). Twelve patients with PD were compared with 12 age-matched healthy controls on tests of finger-, hand-, leg-, and torso-RTs. Patients were significantly slower in initiating all movements and were slower in executing all movements except for the leg (stepping) task. Choice- versus simple-RTs were also not differentially affected in the PD group. In the healthy subjects, age was significantly positively correlated with response initiation times (RITs) but not with movement times (MTs).

Aged↗
PubMed1993

The cerebellum and cognitive functions in humans.

Recent neuropsychological studies have given rise to the hypothesis that the cerebellum is involved in nonmotor cognitive functions. The interpretation of these findings is, however, restricted by methodological problems, such as heterogenous patient samples. The present study compared patients with pathology confined to the cerebellum and patients with combined cerebellar and brainstem lesions to matched normal controls on a range of memory and learning tasks. Two procedural learning tasks were also conducted, involving perceptual (mirror reading) and conceptual skill acquisition (the Tower of Hanoi task). Patients with damage to both cerebellum and brainstem, but not patients with cerebellar pathology alone, showed impairments on memory and visuoconstructive tasks and evidence of frontal lobe dysfunction. Cerebellar damage had no effect on skill acquisition. These results do not support the hypothesis of cerebellar involvement in procedural learning per se.

Adult↗
PubMed1993

Classical conditioning after cerebellar lesions in humans.

We explored classical conditioning in human subjects who had lesions in their cerebellar circuitry. Seven patients with damage to cerebellar structures and matched control subjects underwent simple delay tone-airpuff conditioning. Eyelid conditioned response (CR) acquisition was severely disrupted in the patient group, whereas autonomic CRs and slow cortical potentials developing between conditioned stimulus (CS) and the unconditioned stimulus (UCS) were unaffected. Results are consistent with animal studies and earlier case reports indicating that intact cerebellar structures are necessary for the acquisition of classically conditioned motor responses.

Adult↗
PubMed1992

Discrimination of muscle tension in chronic pain patients and healthy controls.

The purpose of this study was to assess the perception of muscle tension in chronic pain patients and healthy controls. Twenty chronic back pain patients, 20 patients who suffered from temporomandibular pain and dysfunction, and 20 healthy controls were instructed to produce eight different levels of muscle contraction in either the m. masseter or the m. erector spinae. Each level was produced three times; trials were presented in random order. Analyses of the accuracy and the sensitivity of discrimination of muscle tension levels revealed that the patients were less able to perceive muscle contraction levels correctly and that they underestimated their actual levels of muscle tension. Patients and controls did not differ in the extent to which they contracted muscles not involved in the task. Patients suffering from musculoskeletal disorders seem to display a genuine deficit in discrimination of muscle tension that is related to neither local physiological changes at the site of pain, lack of motivation, in-attention, nor fatigue.

Adult↗
PubMed1992

Symptom-specific psychophysiological responses in chronic pain patients.

Symptom-specific psychophysiological responding was assessed in 20 chronic back pain patients, 20 patients suffering from temporomandibular pain and dysfunction, and 20 matched healthy controls. Surface EMG from the lower and upper back, the masseter, and the biceps muscles, and heart rate and skin conductance level were continuously recorded during adaptation, resting baseline, and stressful and neutral imagery phases. Univariate and multivariate analyses of variance were performed on raw data as well as data corrected for autocorrelation. The results showed significantly higher EMG reactivity which was lateralized to the left side at the patients' site of pain but not distal sites. This hyperreactivity was observed only during stressful imagery. The healthy controls displayed a significantly higher response in heart rate, but skin conductance level was not significantly different. The results are interpreted as indicative of idiosyncratic muscular response patterns to personally relevant situations at the site of pain in patients suffering from chronic muscular pain.

Adult↗
PubMed1991

T-maze discrimination and reversal learning after unilateral temporal or frontal lobe lesions in man.

The interpretation of conditional discrimination and reversal learning as acquisition of declarative knowledge suggests that subjects with temporal lobe/hippocampal lesions are likely to be impaired on such tasks. Patients with unilateral left or right temporal lobectomy (and small hippocampal excisions) and patients with unilateral frontal lobe resections were compared with healthy controls on a discrimination reversal task, embedded in a computer game modelled on T-maze tasks traditionally used in animal experiments. The right temporal group showed a deficit in acquiring an initial conditional discrimination, and the frontal group tended to display a marginal impairment in discrimination reversal. These findings are compared with results from animal studies in terms of the mechanisms underlying reversal learning.

Adult↗
PubMed1990

Nicotine-induced catecholamine synthesis after lesions to the dorsal or ventral noradrenergic bundle.

The role of projections from coerulear (A6) and lateral tegmental (A1-A5) noradrenergic cell groups in the induced catecholamine response to (-)-nicotine was studied following lesions to the dorsal (DNAB) or ventral (VNAB) noradrenergic bundle by 6-hydroxydopamine. The lesions produced large reductions in basal noradrenaline levels in hippocampus (after DNAB lesions) and hypothalamus (after VNAB lesions), while not affecting basal levels of dopamine or 5-hydroxytryptamine. Vehicle and sham operated controls showed a significant increase in DOPA accumulation in response to (-)-nicotine (0.8 mg/kg s.c.) following inhibition of amino acid decarboxylase. In DNAB lesioned rats, the response induced by (-)-nicotine in both the hippocampus and hypothalamus was significantly attenuated, whereas in VNAB lesioned rats the induced response was still evident. The effect of (-)-nicotine was also studied in the nucleus accumbens and was found not to be affected by either lesion. These data suggest that increases in catecholamine synthesis in the hippocampus and hypothalamus reflect increased noradrenaline synthesis, and that this effect occurs specifically in noradrenergic projections originating in the locus coeruleus.

Animals↗
PubMed1990

Lateralisation of language functioning by the Wada procedure and divided visual field presentation of a verbal task.

In cases of intractable epilepsy, language and memory functioning in the hemisphere contralateral to the lesion is determined prior to unilateral temporal surgery. Patients with unilateral temporal lobe lesions were assessed using the intracarotid sodium amytal (Wada) procedure to determine the lateralisation of language and memory functioning. They also performed a divided visual field task in which letters were presented in pairs for brief durations on a computer screen in a phonemic matching task. The results showed only moderate agreement between the two methods with regard to identification of the speech-dominant hemisphere, indicating the divided visual field matching paradigm to be unsuitable as a basis for surgical decision-making.

Adolescent↗