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Biomedical subjects

H Flor

Publications and source records attributed to H Flor.

At least 37 records · Page 2Linked to original sources
PubMed2001

Alcohol-associated stimuli activate the ventral striatum in abstinent alcoholics.

Alcohol-associated cues may act as conditioned stimuli that activate the brain reward system and motivate alcohol intake in alcoholics. Alcohol-associated visual stimuli were presented during functional magnetic resonance imaging. An activation of the ventral putamen was observed in alcoholics but not in control subjects. Patients with a strong activation of the ventral putamen relapsed during the next three months. This observation supports the hypothesis that alcohol use affects areas involved in brain reward circuits and that their stimulus-induced activation may be associated with an increased risk for relapse.

Adult↗
PubMed2001

The relationship of perceptual phenomena and cortical reorganization in upper extremity amputees.

In this study 16 unilateral upper extremity amputees participated in a comprehensive psychophysiological examination that included the assessment of painful and non-painful phantom and stump sensations, thermal and electric perception as well as two-point discrimination thresholds, the detailed analysis of referred sensation and the measurement of reorganizational changes in primary somatosensory cortex using neuroelectric source imaging. Reorganization of the primary somatosensory cortex was associated with increased habitual phantom limb pain, telescoping, non-painful stump sensations and painful referred sensation induced by painful stimulation. It was unrelated to non-painful phantom sensations, non-painful referred sensation elicited by painful or non-painful stimulation, painful referred sensation elicited by non-painful stimulation, perception thresholds and stump pain. These data substantiate the hypothesis that painful and non-painful phantom phenomena are mediated by different neural substrates.

Adaptation, Physiological↗
PubMed2001

Phantom movements and pain. An fMRI study in upper limb amputees.

Using functional MRI, we investigated 14 upper limb amputees and seven healthy controls during the execution of hand and lip movements and imagined movements of the phantom limb or left hand. Only patients with phantom limb pain showed a shift of the lip representation into the deafferented primary motor and somatosensory hand areas during lip movements. Displacement of the lip representation in the primary motor and somatosensory cortex was positively correlated to the amount of phantom limb pain. Thalamic activation was only present during executed movements in the healthy controls. The cerebellum showed no evidence of reorganizational changes. In amputees, movement of the intact hand showed a level of activation similar to movement of the right dominant hand in the healthy controls. During imagination of moving the phantom hand, all patients showed significantly higher activation in the contralateral primary motor and somatosensory cortices compared with imagination of hand movements in the controls. In the patients with phantom limb pain but not the pain-free amputees, imagined movement of the phantom hand activated the neighbouring face area. These data suggest selective coactivation of the cortical hand and mouth areas in patients with phantom limb pain. This reorganizational change may be the neural correlate of phantom limb pain.

Adult↗
PubMed2000

A neural substrate for nonpainful phantom limb phenomena.

Activity in the cerebral cortex associated with non-painful phantom limb sensation was studied in 14 upper extremity amputees. In four subjects, repetitive tactile stimulation of the digits or the lower corner of the mouth elicited non-painful phantom sensation in the amputated limb, in the remaining 10 patients no sensation could be evoked. Neuroelectric source imaging revealed significantly elevated activity in SI and posterior parietal cortex, and significantly decreased activity in ipsilateral SII cortex when referred sensations were present. However, nonpainful referred phantom sensations were not associated with a shift of the cortical representation of the mouth into the hand region, as previously suggested. Nonpainful phantom limb experiences seem to have widely distributed neural networks in multiple cortical regions.

Adult↗
PubMed2000

fMRI evaluation of somatotopic representation in human primary motor cortex.

We used fMRI to map foot, elbow, fist, thumb, index finger, and lip movements in 30 healthy subjects. For each movement type confidence intervals of representational sites in the primary motor cortex (M1) were evaluated. In order to improve the precision of their anatomical localization and to optimize the mapping of cortical activation sites, we used both the assessment of locations in the conventional 3D system and a 2D projection method. In addition to the computation of activation maxima of activation clusters within the precentral gyrus, centers of gravity were determined. Both methods showed a high overlap of their representational confidence intervals. The 2D-projection method revealed statistically significant distinct intralimb locations, e.g., elbow versus index finger movements and index finger versus thumb movements. Increased degree of complexity of finger movements resulted in a spread of the somatotopic location toward the arm representation. The 2D-projection method-based fMRI evaluation of limb movements showed high precision and was able to reveal differences in intralimb movement comparisons. fMRI activation revealed a clear somatotopic order of movement representation in M1 and also reflected different degrees of complexity of movement.

Adult↗
PubMed2000

Pavlovian aversive and appetitive odor conditioning in humans: subjective, peripheral, and electrocortical changes.

Differential Pavlovian conditioning of aversive and appetitive odors was examined in 30 male healthy subjects. The appetitive conditioning group (n=15) received a pleasant odor (vanilla), the aversive conditioning group (n=15) an unpleasant odor (fermented yeast) as unconditioned stimulus. Slides of two different neutral faces that were easy to discriminate served as conditioned stimuli (CS). An EEG was recorded from nine electrodes. Electromyographic activity was measured bilaterally from the m. corrugator supercilii and m. zygomaticus. The startle response was obtained from the m. orbicularis oculi. Finally, heart rate and skin conductance response were assessed. The subjective data and the skin conductance response revealed successful differential aversive conditioning. By contrast, the pleasant odor failed to produce appetitive odor conditioning. The conditioned and unconditioned response of the corrugator muscles confirm previous reports on the m. corrugator being strongly involved in the expression of negative affect. Contrary to previous findings, magnitude of the startle reflex was not found to be modulated depending on the valence of the CS. Central psychophysiological parameters showed little change during differential conditioning. The presence of subjective-evaluative conditioning and contingency awareness without significant changes in cortical and cardiovascular correlates might be due to extremely localized cortical processing of conditioned olfactory cues or primarily subcortical processing. The latter interpretation is strengthened by the presence of differential conditioning in non-voluntary responses such as the corrugator muscles.

Adolescent↗
PubMed2000

Standardized stimuli to assess drug craving and drug memory in addicts.

Due to conditioning processes, originally neutral stimuli become drug-associated cues and can initiate drug craving. Standardized stimuli are required to assess stimulus-induced activation of drug memory and craving in brain imaging and neurophysiology studies. We developed substance-specific visual and olfactory stimuli for alcohol, tobacco, opiate and cannabis abuse and tested them in subjects with the respective addiction and in healthy volunteers. Stimulus-related drug craving differed significantly between the diagnostic groups and indicated that the stimuli are suitable for craving studies.

Adult↗
PubMed2000

Steady-state movement-related potentials evoked by fast repetitive movements.

We investigated steady-state movement-related cortical potentials elicited by fast repetitive movements (1/sec) with 50-channel EEG. The experimental design comprised a comparison (a) between unilateral movements of the digits and the toes and (b) between metronome-paced and self-paced initiation of the movements. A distinct biphasic pattern of electrical activity following movement onset was observed, namely a frontal negative peak at a latency of 90 ms (post-MP100) anda frontal positive peak at a latency of 310ms (post-MP300). Pacing exerted its effects mainly on the amplitude and on the latency of the post-MP300. Source analysis revealed that both peaks could be modelled by a single source. The source locations were highly reproducible across the metronome-paced and self-paced conditions, and, they followed the expected somatotopic organisation.

Adult↗
PubMed2000

Phantom limb pain: cortical plasticity and novel therapeutic approaches.

Phantom limb pain is still a very frequent consequence of peripheral deafferentation or amputation of a limb. Recent findings from animal and neuroimaging studies suggest that phantom limb pain might be a central phenomenon, related to changes in the cortical, thalamic and spinal representation of the painful limb, and might be a type of somatosensory pain memory. Based on these assumptions, new treatment approaches focus on sensory discrimination training or motor cortex stimulation in an effort to influence cortical reorganization. Prevention of perpetuation of a somatosensory pain memory might also be possible through pharmacological agents such as N-methyl-D-aspartate antagonists and gamma-aminobutyric acid agonists, substances that have been shown to influence and prevent cortical reorganization.

Journal Article↗
PubMed2000

The thought translation device (TTD) for completely paralyzed patients.

The thought translation device trains locked-in patients to self-regulate slow cortical potentials (SCP's) of their electroencephalogram (EEG). After operant learning of SCP self-control, patients select letters, words or pictograms in a computerized language support program. Results of five respirated, locked-in-patients are described, demonstrating the usefulness of the thought translation device as an alternative communication channel in motivated totally paralyzed patients with amyotrophic lateral sclerosis.

Biofeedback, Psychology↗
PubMed1999

Plasticity in the motor system related to therapy-induced improvement of movement after stroke.

Neuroplasticity might play a beneficial role in the recovery of function after stroke but empirical evidence for this is lacking thus far. Constraint-induced (CI) therapy was used to increase the use of a paretic upper extremity in four hemiparetic stroke patients. Dipole modeling of steady-state movement-related cortical potentials was applied before and after training and 3 months later. The source locations associated with affected hand movement were unusual at follow-up because activation of the ipsilateral hemisphere was found in the absence of mirror movements of the unaffected hand. This long-term change may be considered as an initial demonstration of large-scale neuroplasticity associated with increased use of the paretic limb after application of CI therapy.

Aged↗
PubMed1999

Constraint-induced movement therapy for motor recovery in chronic stroke patients.

OBJECTIVE: Assessment of the effectiveness of constraint-induced (CI) movement therapy and quantitative evaluation of the effects of CI therapy. DESIGN: Intervention study; case series; pretreatment to posttreatment measures and follow-up 3 months after intervention. SETTING: An outpatient department. PATIENTS: Five chronic stroke patients with moderate motor deficit; convenience sample. INTERVENTIONS: CI therapy consisting of restraint of the unaffected upper extremity in a sling for 14 days combined with 6 hours of training per weekday of the affected upper extremity. MAIN OUTCOME MEASURES: Actual Amount of Use Test (AAUT), Motor Activity Log (MAL), Wolf Motor Function Test (WMFT), and Arm Motor Ability Test (AMAT) RESULTS: There was a substantial improvement in the performance times of the laboratory tests (AMAT, WMFT, p < or = .039) and in the quality of movement (AMAT, WMFT, p < or = .049; MAL, p = .049), particularly in the use of the extremity in "real world" environments (AAUT, p = .020), supported by results of quantitative evaluation. The effect sizes were large and comparable to those found in previous studies of CI therapy. CONCLUSIONS: CI therapy is an efficacious treatment for chronic stroke patients, especially in terms of real world outcome.

Aged↗
PubMed1999

Localization of somatosensory evoked potentials in primary somatosensory cortex: a comparison between PCA and MUSIC.

The aim of this study was to test source modeling strategies for EEG-data from a clinical group of amputees. The experimental conditions (measuring time, age and condition of the patients) resulted in low quality EEG-data. Noise reduction was achieved by a principal component analysis (PCA) and a multiple signal classification (MUSIC). A comparison of the results of these two methods with traditional signal handling yielded superior results for the MUSIC algorithm.

Aged↗
PubMed1999

Applied psychophysiology and learned physiological regulation.

This commentary emphasizes the importance of including animal research and basic human research, contrasts the present state of affairs for biofeedback in the United States versus Europe, and proposes an alternative, more expanded definition of applied psychophysiology, which includes research, diagnostics, and education, as well as interventions.

Animals↗
PubMed1999

Deficient discrimination of EMG levels and overestimation of perceived tension in chronic pain patients.

Twenty chronic low back pain patients (CBP), twenty tension headache (THA) patients, and twenty healthy controls (HC) participated in a tension production task where subjects had to attain four levels (4, 8, 12, 16 microV) of muscle tension at the m. frontalis and the m. erector spinae. Ratings of perceived tension, pain, and aversiveness as well as EMG, heart rate, and skin conductance levels were recorded. Signal detection and correlational methods revealed that the patients were deficient in muscle tension discrimination at high tension levels in both muscles. They generally overestimated low and underestimated high levels of muscle tension, especially in the CBP group. At low muscle tension levels, both healthy controls and patients showed deficient discrimination ability. Perceived muscle tension, aversiveness, and pain ratings during the tasks were higher in the patient groups. These data confirm and clarify previous reports of deficient tension perception and show concurrent overestimation of bodily symptoms in chronic musculoskeletal pain patients.

Adult↗