Biomedical subjects

W H Miltner

Publications and source records attributed to W H Miltner.

13 recordsLinked to original sources

PubMed2001

Dipole analysis of ultralate (C-fibres) evoked potentials after laser stimulation of tiny cutaneous surface areas in humans.

Ultralate (C-fibres) laser evoked potentials (LEP) can be obtained by stimulation of a tiny skin surface area (0.23 mm(2)). Since their generators are unknown up to now, we performed brain source analyses of ultralate LEPs using high resolution electroencephalography (64 channels) and a realistic head model that was based on individual magnetic resonance images. Ultralate LEPs were characterized by a negative-positive complex with a large positive component maximal at the vertex. Source analysis revealed that ultralate LEPs could be explained by two dipole sources in the upper bank of the contralateral and ipsilateral Sylvian fissure (SII) and one dipole in the median region corresponding to the anterior cingulate gyrus.

Adult↗

PubMed2000

The influence of semantic priming on event-related potentials to painful laser-heat stimuli in humans.

In this study we investigated the effects of different semantic primes on the processing of painful stimuli. For prime stimuli, descriptors of three categories were used: somatosensory pain-related, affective pain-related, and neutral adjectives. While subjects (n=10) processed these primes, a painful laser-heat stimulus was applied. Laser-evoked potentials (LEPs) were recorded and pain intensity ratings were obtained after each single laser stimulus. Painful stimuli applied while subjects processed pain-related primes (affective and somatosensory adjectives) resulted in larger LEP amplitudes at 370 ms post laser stimulus compared to amplitudes of laser-evoked activities while subjects processed neutral primes (F((2,18))=3.90, P=0.05). It is suggested that pain-related semantic primes might preactivate neural networks subserving pain memory and pain processing. The processing of pain-related primes seems to preactivate cortical cell-assemblies involved in the processing of the succeeding painful laser stimuli.

Acoustic Stimulation↗

PubMed2000

Rapid functional plasticity of the somatosensory cortex after finger amputation.

Recent research indicates that areas of the primary somatosensory (SI) and primary motor cortex show massive cortical reorganization after amputation of the upper arm, forearm or fingers. Most of these studies were carried out months or several years after amputation. In the present study, we describe cortical reorganization of areas in the SI of a patient who underwent amputation of the traumatized middle and ring fingers of his right hand 10 days before cortical magnetic source imaging data were obtained. Somatosensory-evoked magnetic fields (SEF) to mechanical stimuli to the finger tips were recorded and single moving dipoles were calculated using a realistic volume conductor model. Results reveal that the dipoles representing the second and fifth fingers of the affected hand were closer together than the comparable dipoles of the unaffected hand. Our findings demonstrate that neural cell assemblies in SI which formerly represented the right middle and ring fingers of this amputee became reorganized and invaded by neighbouring cell assemblies of the index and little finger of the same hand. These results indicate that functional plasticity occurs within a period of 10 days after amputation.

Afferent Pathways↗

PubMed2000

Objective measurement of functional upper-extremity movement using accelerometer recordings transformed with a threshold filter.

BACKGROUND AND PURPOSE: The consensus is that the most important outcome for rehabilitation is functional activity in the life situation. Constraint-Induced Movement Therapy, a new treatment that transfers in-clinic gains to the life situation, demands objective measurement of real-world movement. However, direct, objective, and accurate measures of arm use in the real world are not available. Previous attempts to use accelerometry to measure extremity movement have failed because of unacceptable variability. This problem has been addressed here by use of a threshold filter. METHODS: Nine stroke patients and 1 healthy individual wearing accelerometers were videotaped while they carried out their usual activities at home or in the clinic; the duration of their arm, torso, and ambulatory movements was judged by 2 observation teams. In addition, 11 college students performed 5 standardized activities of daily living for varying durations in the laboratory. The accelerometer data were transformed; the raw value recorded for a given epoch was set to a constant if it exceeded a low threshold. RESULTS: The threshold-filtered recordings measured the duration of movement accurately and with very little variability. Correlations between the threshold-filtered recordings and the observer ratings of the duration of arm, torso, and ambulatory movements were 0.93, 0.93 and 0.99, respectively; the corresponding correlations for the raw values were -0.17, 0.34, and 0.85. CONCLUSIONS: These results present initial evidence for the validity of threshold-filtered accelerometer recordings for objectively measuring the amount of real-world upper-extremity movement as an index of treatment outcome for rehabilitation patients.

Adult↗

PubMed2000

Treatment-induced cortical reorganization after stroke in humans.

BACKGROUND AND PURPOSE: Injury-induced cortical reorganization is a widely recognized phenomenon. In contrast, there is almost no information on treatment-induced plastic changes in the human brain. The aim of the present study was to evaluate reorganization in the motor cortex of stroke patients that was induced with an efficacious rehabilitation treatment. METHODS: We used focal transcranial magnetic stimulation to map the cortical motor output area of a hand muscle on both sides in 13 stroke patients in the chronic stage of their illness before and after a 12-day-period of constraint-induced movement therapy. RESULTS: Before treatment, the cortical representation area of the affected hand muscle was significantly smaller than the contralateral side. After treatment, the muscle output area size in the affected hemisphere was significantly enlarged, corresponding to a greatly improved motor performance of the paretic limb. Shifts of the center of the output map in the affected hemisphere suggested the recruitment of adjacent brain areas. In follow-up examinations up to 6 months after treatment, motor performance remained at a high level, whereas the cortical area sizes in the 2 hemispheres became almost identical, representing a return of the balance of excitability between the 2 hemispheres toward a normal condition. CONCLUSIONS: This is the first demonstration in humans of a long-term alteration in brain function associated with a therapy-induced improvement in the rehabilitation of movement after neurological injury.

Adult↗

PubMed1999

Decrease in phantom limb pain associated with prosthesis-induced increased use of an amputation stump in humans.

The experience of phantom limb pain, non-painful phantom limb sensation and telescoping was ascertained by questionnaire in a group of upper extremity amputees wearing a functionally effective Sauerbruch prosthesis which permits extensive use of the affected limb and in a group of patients wearing a cosmetic prosthesis that did little to increase the utilization of the amputation stump. The Sauerbruch prosthesis group exhibited a significant and large decrease in amount of phantom limb pain while the cosmetic prosthesis group showed no change. Neither group experienced a decrease in non-painful phantom limb sensation or telescoping. The amount of phantom limb pain has been found to be highly correlated with the amount of injury-related, afferent-decrease cortical reorganization. It is possible that the increased use of the amputation stump induced by wearing a Sauerbruch prosthesis produced a countervailing use-dependent, afferent-increase type of cortical reorganization that reversed the phantom limb pain. These preliminary results require replication. Their therapeutic implications are discussed.

Adult↗

PubMed1999

Coherence of gamma-band EEG activity as a basis for associative learning.

Different regions of the brain must communicate with each other to provide the basis for the integration of sensory information, sensory-motor coordination and many other functions that are critical for learning, memory, information processing, perception and the behaviour of organisms. Hebb suggested that this is accomplished by the formation of assemblies of cells whose synaptic linkages are strengthened whenever the cells are activated or 'ignited' synchronously. Hebb's seminal concept has intrigued investigators since its formulation, but the technology to demonstrate its existence had been lacking until the past decade. Previous studies have shown that very fast electroencephalographic activity in the gamma band (20-70 Hz) increases during, and may be involved in, the formation of percepts and memory, linguistic processing, and other behavioural and perceptual functions. We show here that increased gamma-band activity is also involved in associative learning. In addition, we find that another measure, gamma-band coherence, increases between regions of the brain that receive the two classes of stimuli involved in an associative-learning procedure in humans. An increase in coherence could fulfil the criteria required for the formation of hebbian cell assemblies, binding together parts of the brain that must communicate with one another in order for associative learning to take place. In this way, coherence may be a signature for this and other types of learning.

Adult↗

PubMed1999

Effects of constraint-induced movement therapy on patients with chronic motor deficits after stroke: a replication.

BACKGROUND AND PURPOSE: Constraint-induced movement therapy (CI therapy) has previously been shown to produce large improvements in actual amount of use of a more affected upper extremity in the "real-world" environment in patients with chronic stroke (ie, >1 year after the event). This work was carried out in an American laboratory. Our aim was to determine whether these results could be replicated in another laboratory located in Germany, operating within the context of a healthcare system in which administration of conventional types of physical therapy is generally more extensive than in the United States. METHODS: Fifteen chronic stroke patients were given CI therapy, involving restriction of movement of the intact upper extremity by placing it in a sling for 90% of waking hours for 12 days and training (by shaping) of the more affected extremity for 7 hours on the 8 weekdays during that period. RESULTS: Patients showed a significant and very large degree of improvement from before to after treatment on a laboratory motor test and on a test assessing amount of use of the affected extremity in activities of daily living in the life setting (effect sizes, 0.9 and 2.2, respectively), with no decrement in performance at 6-month follow-up. During a pretreatment control test-retest interval, there were no significant changes on these tests. CONCLUSIONS: Results replicate in Germany the findings with CI therapy in an American laboratory, suggesting that the intervention has general applicability.

Adult↗

PubMed1998

Motor cortex plasticity during constraint-induced movement therapy in stroke patients.

Stroke patients in the chronic phase received constraint-induced (CI) movement therapy. The motor cortex was spatially mapped using focal transcranial magnetic stimulation (TMS) before and after 2 weeks of treatment. Motor-output areas of the abductor pollicis brevis muscle, motor evoked potential (MEP) amplitudes and location of centre of gravity (CoG) of motor cortex output were studied. After CI therapy, motor performance improved substantially in all patients. There was also an increase of motor output area size and MEP amplitudes, indicating enhanced neuronal excitability in the damaged hemisphere for the target muscles. The mean centre of gravity of the motor output maps was shifted considerably after the rehabilitation, indicating the recruitment of motor areas adjacent to the original location. Thus, even in chronic stroke patients, reduced motor cortex representations of an affected body part can be enlarged and increased in level of excitability by an effective rehabilitation procedure. The data therefore demonstrate a CNS correlate of therapy-induced recovery of function after nervous system damage in humans.

Brain Mapping↗

PubMed1998

Reorganization of the somatosensory cortex after amputation of the index finger.

Cortical reorganization occurs within the primary somatosensory and the primary motor cortex after amputation of the arm or forearm. Here we report on a patient showing cortical reorganization after amputation of his right index finger. Our findings indicate that the neural networks within the area of the amputated finger in the somatosensory cortex (SI) were invaded by neighbouring structures, i.e. of neural cell assemblies that subserve the thumb and middle finger of his right hand.

Amputation, Traumatic↗

PubMed1998

Brain electrical correlates of pain processing.

Pain is the result of complex neuronal activities within the brain and not simply the result of peripheral activities of the nociceptive system. Pain results from an interaction of many neuronal modules located in different brain areas. This interaction is modified by anticipation, learning, and perception. Electrophysiological phenomena allow the characterization of the information processing associated with pain. This characterization is important for theoretical purposes and for the evaluation of different therapeutic strategies. Furthermore, electrophysiological phenomena support the investigation of functional plasticity in the brain as one of the consequences of chronic pain processing. It is expected that new methods of cortical source analysis will contribute considerably to our understanding of different aspects of pain processing and of the management of pain.

Animals↗

PubMed1998

Adaptive AR modeling of nonstationary time series by means of Kalman filtering.

An adaptive on-line procedure is presented for autoregressive (AR) modeling of nonstationary multivariate time series by means of Kalman filtering. The parameters of the estimated time-varying model can be used to calculate instantaneous measures of linear dependence. The usefulness of the procedures in the analysis of physiological signals is discussed in two examples: First, in the analysis of respiratory movement, heart rate fluctuation, and blood pressure, and second, in the analysis of multichannel electroencephalogram (EEG) signals. It was shown for the first time that in intact animals the transition from a normoxic to a hypoxic state requires tremendous short-term readjustment of the autonomic cardiac-respiratory control. An application with experimental EEG data supported observations that the development of coherences among cell assemblies of the brain is a basic element of associative learning or conditioning.

Adaptation, Physiological↗

PubMed1997

A bioadaptive approach for experimental pain research in humans using laser-evoked brain potentials.

In order to find an experimental approach counteracting habituation in experimental pain research using short infrared laser stimulation in humans we developed a bioadaptive method based on subject's report on painfulness of stimulation (pain report; PR). After determination of the initial relationship between the energy of the laser stimulus and the corresponding PRs, the approach continuously adjusts the intensity of noxious stimuli so that PR is kept constant across time. Each difference between the PR evoked by the actual laser stimulus and the desired PR leads to an increase or decrease of the laser output energy value for the next stimulation with the desired PR proportional to the PR difference as well as to the slope of the initial correlation function between laser energy and corresponding PRs. This method has been applied in a study with nine volunteers. Results show that the approach leads to a constant PR by increasing the laser output energy by 0.01 mJ/s per mm2 on the average. Furthermore, an analysis of the laser-evoked brain potentials (LEPs) recorded from Cz was performed for the first and second half of stimuli. However, no significant changes in latencies or amplitudes of the main LEP components recorded at 210 ms (N210) and 350 ms (P350) were found. The method seems to be useful for different approaches in experimental and clinical pain research.

Adult↗