Cortical reorganization in human amputees and mislocalization of painful stimuli to the phantom limb.

In human arm amputees, a significant relationship was found between the amount of reorganization in the primary somato-sensory cortex, and the amount of body surface from which painful stimuli evoked sensations that were perceived to be emanating from the now missing extremity, i.e. the phantom limb.

Simultaneous recording of slow brain potentials and transcranial magnetic stimulation of hand area in human motor cortex.

Recording of slow brain potentials (SPs) and transcranial magnetic stimulation (TCMS) of the human motor cortex were combined to probe the relationship between SP level and excitability of cortical neurons. In experiment 1, TCMS was applied during and shortly after the warning interval in a forewarned reaction time task. Electromyographic (EMG) responses to TCMS increased only slightly during the warning interval and were significantly elevated 150 ms after the imperative stimulus.

Reduced emotional response of schizophrenic patients in remission during social interaction.

Inappropriate emotional response during social interaction is a prominent feature of schizophrenia during the acute stage of illness. This study evaluates the course of reduced facial activity in schizophrenic patients in remission and compares it with healthy controls. The experimental conditions included watching two films, one inducing happy and the other sad emotional states.

Spectral responses in the gamma-band: physiological signs of higher cognitive processes?

It has recently been proposed that brain responses in the gamma-range (> 20 Hz) include information about specific cognitive processes in the human brain. Empirical data substantiating this assumption come from EEG and MEG recordings during visual and language processing. For example, 30 Hz activity has been found to be stronger during processing of words than during processing of meaningless but pronounceable pseudo-words.

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.

Evoked potentials distinguish between nouns and verbs.

Electrocortical correlates of the processing of nouns and verbs were recorded in 32 healthy individuals performing lexical decisions. Analyses of EEG data recorded through 29 channels revealed different topographies of cortical activity evoked by nouns and verbs. Differences were most pronounced at recording sites over the frontal lobes.

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.

Phantom-limb pain as a perceptual correlate of cortical reorganization following arm amputation.

Although phantom-limb pain is a frequent consequence of the amputation of an extremity, little is known about its origin. On the basis of the demonstration of substantial plasticity of the somatosensory cortex after amputation or somatosensory deafferentation in adult monkeys, it has been suggested that cortical reorganization could account for some non-painful phantom-limb phenomena in amputees and that cortical reorganization has an adaptive (that is, pain-preventing) function. Theoretical and empirical work on chronic back pain has revealed a positive relationship between the amount of cortical alteration and the magnitude of pain, so we predicted that cortical reorganization and phantom-limb pain should be positively related.

Electrocortical distinction of vocabulary types.

Psycholinguistic theories propose that words of the 2 major vocabulary classes, content (open-class) and function (closed-class) words, are computationally distinct and have different neuronal generators. This predicts distinct EEG patterns elicited by words of these 2 classes. To test this prediction, content and function words, together with matched pseudowords, were presented in a lexical decision task (where subjects had to decide whether stimuli were meaningful words or not).

Motor programming in both hemispheres: an EEG study of the human brain.

Differential hemispheric involvement in controlling simple and complex motor movements was investigated in humans using EEG spectral responses. Analysis of spectral power in the alpha band revealed the following. While during a simple motor task (tapping) signs of unilateral cortical activation were present, more complex sequential motor behaviour (Luria finger apposition task) led to symmetrical bihemispheric activation.

Baroreceptor cortical effects, emotions and pain.

The specificity of baroreceptor-dependent inhibition of pain reactions to electrical stimuli was investigated during induction of different emotional states in 27 subjects. Baroreceptors were stimulated through the PRES (Phase Related External Suction) technique, while emotions were induced by means of pleasant, neutral and unpleasant slides. The dependent variables were pain ratings, somatic evoked potentials (N150 and P260) recorded from Fz, Cz and Pz, and skin conductance response (SCR), while heart rate was recorded as a PRES requirement.

Visual stimulation alters local 40-Hz responses in humans: an EEG-study.

Irregular changing visual patterns and coherently moving bars were presented either in the upper or lower half of the visual field of 12 human subjects. EEG responses recorded over the occipital lobe showed an increase of 40 Hz spectral power when a regular pattern of moving bars appeared. This enhancement of 40-Hz activity varied as a function of visual field presentation.

Extensive reorganization of the somatosensory cortex in adult humans after nervous system injury.

Magnetic source imaging revealed that the topographic representation in the somatosensory cortex of the face area in upper extremity amputees was shifted an average of 1.5 cm toward the area that would normally receive input from the now absent nerves supplying the hand and fingers. Observed alterations provide evidence for extensive plastic reorganization in the adult human cortex following nervous system injury, but they are not a sufficient cause of the phantom phenomenon termed 'facial remapping'.

Category-specific semantic impairment in Alzheimer's disease and temporal lobe dysfunction: a comparative study.

In this paper we report an in-depth case study of a patient suffering from Alzheimer's disease who presented with a category-specific disorder relating to processing of knowledge about animate objects in the presence of spared knowledge of inanimate objects. Impairments appeared not only in a confrontation naming task but also on a range of visual knowledge tasks, such as drawing from memory or part-whole matching. The pattern of impairment was compared to that shown by a post-encephalitic patient who manifested a well-documented category-specific deficit for animate objects.

Effects of PRES baroreceptor stimulation on thermal and mechanical pain threshold in borderline hypertensives and normotensives.

Prior studies have noted a pain relieving effect of baroreceptor stimulation and of higher tonic blood pressure in animals and humans. The present study used a new technique for the controlled, noninvasive stimulation of human carotid baroreceptors (PRES). PRES baroreceptor manipulation was delivered to both normotensive subjects (n = 11) and medication-free labile hypertensive subjects (n = 10) during both thermal and mechanical pain.

Neurophysiological differences between perception and imagery.

The present study was designed to examine brain activity underlying mental imagery is conceptualized as behavior guided by internal representation only, the activity of the prefrontal lobes was assumed to be a measure of differentiation of imagery from perception. Twenty-one subjects were requested to observe and imagine a swinging pendulum and to touch and imagine a coshball in separate trials. The EEG was recorded from 15 standard electrode sites and analyzed with (1) traditional alpha power and (2) an estimation of dimensional complexity (a measure derived from nonlinear dynamics).

Behavioral treatment of scoliosis and kyphosis.

A behavioral treatment of scoliosis and kyphosis was tested with 27 adolescent patients (19 scoliosis, eight kyphosis patients) to determine in which cases the conspicuous and restraining brace treatment could be replaced. In 22 compliant patients, posture biofeedback (PB) was highly effective compared to five non-compliant patients. Biologically more mature scoliosis patients (menarche at the beginning of treatment) seemed to profit more from PB.

Words and pseudowords elicit distinct patterns of 30-Hz EEG responses in humans.

Meaningful words, such as moon, and physically similar but meaningless pseudowords, such as noom, were presented visually in a lexical decision task. The EEG was recorded from 17 scalp electrodes. Significant differences between both stimulus classes were observed in evoked spectral responses of the 'gamma-band' approximately 30 Hz.

Central effects of baroreceptor activation in humans: attenuation of skeletal reflexes and pain perception.

Activating the arterial baroreceptors blunts pain sensation and produces other forms of central nervous system inhibition in animals. These effects may be important to blood pressure regulation but have not been rigorously verified in humans. We describe (i) a noninvasive behaviorally unbiased method for baroreceptor stimulation and (ii) the application of this method to measurement of baroreceptor-mediated attenuation of pain perception and of the Achilles tendon reflex.

Brain potentials during mental arithmetic: effects of extensive practice and problem difficulty.

Recent behavioral investigations indicate that the processes underlying mental arithmetic change systematically with practice from deliberate, conscious calculation to automatic, direct retrieval of answers from memory [Bourne, L.E.Jr.

Slow cortical potential biofeedback and the startle reflex.

The negativity of slow cortical potentials (SCP) of the surface EEG is a measure of brain excitability, correlating with motor and cognitive preparation. Self-control of SCP positivity has been shown to reduce seizure activity. Following SCP biofeedback from a central EEG electrode position, subjects gained bidirectional control over their SCP.

Positive shifts of event-related potentials: a state of cortical disfacilitation as reflected by the startle reflex probe.

Cortical positivity as measured by slow event-related potentials is assumed to represent a decreased excitability of cortical networks and suppression of their behavioral-cognitive output. The blink reflex probe is a commonly used defensive electromyographic response whose amplitude was shown to be modulated by emotional and attentional orientation. It was used here as an indicator of cortico-subcortical excitation.

Sensory effects of baroreceptor activation and perceived stress together predict long-term blood pressure elevations.

Activating the arterial baroreceptors in animals has been shown to blunt pain sensation and provide other forms of central nervous system inhibition. This study tested the hypothesis that, among human subjects, a tonic increase in blood pressure (BP) could be a learned response to environmental stressors among subjects in whom the baroreceptor inhibitory mechanism is active. In a sample of 96 healthy, normotensive men and women, amount of pain-reduction produced by baroreceptor stimulation predicted an increase in resting BP 20 months later: the increase was proportional to self-assessed daily life stress.