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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. The findings are relevant to basic mechanisms of blood pressure stabilization and cardiovascular reactivity and may also have implications for noncompliance with antihypertensive medications and for the pathophysiology of essential hypertension.

Movement-preceding and stimulus-preceding negativities were recorded when a movement was followed by one of three informative visual stimuli. The meaning of the visual stimulus alternated between (a) conveying a task-relevant instruction about a subsequent time production task and (b) providing feedback (knowledge of results) about performance on the current time production task. In a control condition, premovement and postmovement scalp potentials were recorded when subjects made the same movements but in a voluntary, self-paced manner. Under all conditions, movements were preceded by a movement-preceding negativity, and neither the amplitude nor the lateral asymmetry of this negativity was affected by the subsequent presentation of either kind of informative stimulus. When the movement was followed by a stimulus conveying knowledge of results, the negativity in the postmovement epoch was enhanced, but this enhancement was not evident in epochs preceding instruction stimuli. We conclude that not all task relevant stimuli elicit a stimulus-preceding negativity, and we provide a functional interpretation of this negativity in terms of emotional anticipation and the contingency of the stimulus on a previous event.

Readiness potentials (RP) have been recorded in 9 subjects who performed voluntary unilateral plantar flexions with the right or left foot. These show a paradoxical ipsilateral dominance. Spatio-temporal dipole models were obtained for these data, by iterative parameter estimation. The non-uniqueness of the inverse problem leads to several models which describe the data almost equally well, and which all pass orthogonality tests for the individual residuals and source waves. In these dipole models the ipsilateral preponderance is attributed to generators in the contralateral hemisphere, which agrees with results from MEG recording. According to these models the main generators of the RP are in the primary motor cortex, one bilaterally in its posterior wall and the other in the contralateral crown. This agrees with earlier results for finger RPs. However, for foot RPs, it was difficult to distinguish individual sub-components in both the observed scalp potentials and the estimated temporal activation patterns of the dipoles. Some of the presented models include a fronto-central dipole which possibly represents activity of the supplementary motor area. It is concluded that this finding is at best suggestive and needs further investigation.

Ten subjects performed a time production task, in which they were instructed to press a button four seconds after the presentation of an auditory stimulus. Two seconds after the button press they received either auditory or visual feedback on the temporal accuracy of their response. In such a paradigm negative slow brain potentials can be recorded preceding the response (Movement Preceding Negativity, MPN) as well as preceding the feedback stimulus (Stimulus Preceding Negativity, SPN). Spatiotemporal dipole modelling is used to gain insight in the possible generators of MPN and SPN. From the models it follows that the MPN can be described by one contralateral radial dipole and a bilateral pair of tangential dipoles. All three dipoles are located near central electrode positions, so the generators of the MPN probably reside within the motor cortex. The SPN is modelled by a bilateral frontotemporal pair of dipoles, hypothetically representing activation of the Insulae Reili. The insular cortex is involved in the processing of affective-motivational input, such as carried by the feedback in the present paradigm. However, processing of the information content of the feedback stimulus might by itself also activate the frontal cortex. Both the response and the feedback stimulus are followed by a positive peak, which can be described by the same deep posterior dipole. Both peaks probably represent a P3, which is related to context updating.

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. Among the subjects reporting the greatest amount of stress, the pain inhibition effect accounted for more than 80% of the BP variance. These results support the hypothesis that the reduction in perceived stress produced by baroreceptor stimulation may reward learned increases in BP.

To study the contribution of the Stimulus-Preceding Negativity (SPN) to the late wave of the Contingent Negative Variation (CNV), negativity was recorded preceding an instruction stimulus (S1), an instruction stimulus to which a motor response was required (S2) and a stimulus that transmitted Knowledge of Results (KR). All recorded negativities showed a centro-parietal maximum. The pre-instruction negativities tended to be larger over the left hemisphere, while a right hemisphere preponderance was found for the pre-KR negativity. Unlike the pre-S1 negativity, the pre-KR negativity may depend on affective-motivational processes. The pre-S1 negativity was small and influenced by factors other than the instruction at S1. It is concluded that the SPN contributes to the late CNV, but that this contribution was relatively small.

The project "Brass-board integration of a reformer/fuel cell/battery/electric motor system for electric traction" contributes to the development of a new and environmentally friendly power source for electrically driven cars. This research is carried out by Loughborough university of rechnology (united Kingdom), TECNARS s.r.l. (Iraly), ECN, HOLEC and TNO (The Netherlands), " The project concerns the deveiopment of an integrated system (brass-board) for a hybrid delivery van for urban use. A SPFC fuel cell stack is used to supply the average power the "model van" needs for its drive pattern. A battery system is needed for acceleration and high speed. The selection and testing of the batteries is performed by TNO. From the specifications of the model van on acceleration, range and speed it becomes clear that the batteries should exhibit both a high specific power and a high specific energy. In order to select the most suited battery for the brass-board system specific technical information on the possible battery types have been gathered. The performance goals of the battery have been set and the availability, delivery time and cost have been considered. Using this set of information a NilCd battery was selected. The selection criteria show that not only the technical aspects are important but also the availability on a full scale and the cost. Next to the selection criteria used also preliminary results of the battery tests will be presented in the paper.

Parkinson's disease is characterized not only by tremor, akinesia and rigidity, but also by frontal cognitive dysfunction, that can be understood as a disturbance in the 'Supervisory Attentional System' (SAS). This concept refers to a system, located in the frontal cortex, that regulates attentional processes under novel, non-routine conditions. The hypothesis that cognitive dysfunction in Parkinson's disease results from a disturbance in the SAS was investigated by recording 'processing negativity' in 33 parkinsonian patients and 17 controls. Processing negativity is an event-related potential that reflects neuronal activity during selective attention. The contribution of the frontal cortex to selective attention can be studied directly using processing negativity. Parkinsonian patients were also scored for clinical symptoms and subjected to a neuropsychological test battery. Processing negativity was clearly disturbed in the parkinsonian patients. Moreover, parkinsonian patients with the lowest scores on 'frontal' neuropsychological tests such as Stroop, Trail Making and Word Fluency, also had the lowest processing negativity. Our results support the hypothesis that cognitive dysfunction in Parkinson's disease might be understood as a disturbance in the frontal regulation of attentional processes. Degeneration of the dopaminergic mesocortical innervation of the frontal cortex in Parkinson's disease is a possible neurochemical substrate of these frontal attentional disturbances.

Many researchers have used off-line techniques for the automatic detection of electromyogram (EMG) onset. However, very little is known about the accuracy of these methods. In the present study, five such methods are evaluated and their accuracy is reported. Five subjects were asked to produce fast (ballistic) and slow (ramp) contractions with thumb and index finger of the right hand in a simple reaction time task. EMG was recorded from the first dorsal interosseus muscle, and onsets were visually determined in the raw EMG. These onsets were compared with the onsets produced by the automated methods on the rectified and low-pass filtered EMG. Four of the automated methods produced very reliable estimates of the visually determined onsets, at least when additional constraints upon the initial estimates were made. Studies using automated methods for EMG onset detection should report findings about their accuracy.

The answer to the question “under what circumstances is stimulus anticipation accompanied by a slow wave?” can help us to understand the processes underlying anticipatory behaviour. The classic task used in the electrophysiology research of anticipation is the forewarned reaction time (RT) task in which a warning stimulus (WS) announces the future presentation of an imperative stimulus (RS) to which a response has to be made. The late wave of the Contingent Negative Variation (CNV) that is recorded under these circumstances reflects at least two different processes: anticipation of the RS and preparation for the movement. Both are irrevocably confounded in this task and their contribution to the negativity recorded prior to RS is not equal. Rohrbaugh and Gaillard (1983) have presented evidence for the similarity of the late wave and the readiness potential (RP) which can be recorded preceding unsignalled movements. The largest part of the late wave is certainly an RP, related to motor preparation. This statement should not make us forget that the RP itself reflects, apart from strictly motoric aspects (Barrett et al., 1986; Kutas and Donchin, 1977), cognitive processes which are related to the uncertainty about the force needed (Hink et al., 1983), to the timing of the movement (Libet et al., 1982), its motivational consequences (McAdam and Seales, 1969) and the information that becomes available following the movement (Freude et al., 1988; Hink et al., 1982). It is reasonable to suppose that the anticipation of the RS is also accompanied by a negative wave although a crucial experiment to demonstrate its existence is difficult to perform.

Ten normal human subjects performed isometric contractions up to a fixed force level, which had to be attained at two different speeds, in a choice reaction time task. Force production speed was indicated by an instruction stimulus, which was either inserted at the warning stimulus (Precue condition) or at the response stimulus (No-Precue condition). These conditions were used to test the hypothesis that the late wave of the CNV consists of movement- and stimulus-preceding negativities. The latter condition was expected to produce larger CNV late wave amplitudes because of the anticipation of the additional informative stimulus. The results were in agreement with this prediction. Two components, one centrally dominant and the other frontally dominant, were distinguished in the CNV. The central component is suggested to be identical to the Readiness Potential and the frontal component is discussed in terms of stimulus anticipation and task demands.

The present study was designed to investigate the effect of baroreceptors on a spinal reflex. The Achilles tendon reflex (T reflex), a monosynaptic spinal reflex, was chosen as an indicator of descending influences of central activation. The baroreceptors are stretch receptors which respond to extensions of the arterial wall. Carotid sinus baroreceptors can be manipulated non-invasively by means of a cuff around the neck. In this study, the phase-related external suction (PRES) neck cuff technique was used. PRES applies short changes in cuff pressure as a function of heart cycle phase, controlling for non-specific effects found in other baroreceptor manipulation methods. The T reflex was reduced when elicited during the highest levels of baroreceptor activation. Reflex amplitude was largest when elicited during the lowest levels of baroreceptor activation. These results are consistent with previous findings that baroreceptor activation reduces CNS excitability.

A slow negative shift called “stimulus-preceding negativity” (SPN) has been observed preceding feedback. The aim of the present study is to investigate whether the SPN is related to perceptual or conceptual anticipation. Event-related potentials (ERPs) were recorded in an S1–S2–S3 sequence with intervals of 3 s. S1 was an auditory warning signal; the task stimulus presented at S2 consisted of two digits on which subjects (n=8) performed an arithmetic task. They had to match their solution with a probe stimulus presented at S3. Perceptual anticipation was manipulated by varying the discriminability of S2 (intact vs. degraded). Conceptual anticipation was manipulated by varying the amount of information processing required at S2 (easy vs. difficult arithmetic). Motor preparation was varied by requiring a speeded versus a delayed response. No negativity was found before the task stimulus (S2), whereas the probe stimulus (S3) was always preceded by a negative shift. The amplitude of this negative shift was larger under the speed than under the delayed instruction. Its amplitude showed a left-hemisphere preponderance and was larger for the difficult than for the easy condition. ERPs preceding task stimuli seem to reflect functionally different processes from ERPs preceding probe and feedback stimuli. The difference is explained in terms of motivational factors that come into play with feedback and probably play a role in the anticipation of the probe stimulus.

The Contingent Negative Variation (CNV) is an event-related slow potential. It was recorded in healthy volunteers (n = 8) and in patients suffering from migraine without (n = 12) or with (n = 5) aura, during one (CNV1) and three second (CNV3) foreperiods in a forewarned reaction time task. CNV1 was recorded at the vertex while CNV3 was recorded at multiple electrode sites to assess topographical differences. Seven out of twelve migraine patients without aura had increased CNV1 amplitudes. CNV3 amplitudes were increased as well, but only at electrode positions C3 and C4 and not at Fz. CNV3, which allows for analysis of both an early and a late CNV component, could improve the discrimination of migraine without aura beyond that of CNV1. In migraine with aura all CNV parameters were at control levels, confirming previous results. The data obtained are discussed in terms of arousal, activation and stress and the "biobehavioral model of migraine" (Welch, 1986).

The aim of the present study was to specify the involvement of the basal ganglia in motor response selection and response inhibition. Two samples were studied. The first sample consisted of patients diagnosed with Parkinson's disease (PD) who received deep-brain stimulation (DBS) of the subthalamic nucleus (STN). The second sample consisted of patients who received DBS for the treatment of PD or essential tremor (ET) in the ventral intermediate nucleus of the thalamus (Vim). Stop-signal task and go/no-go task performances were studied in both groups. Both groups performed these tasks with (on stimulation) and without (off stimulation) DBS to address the question of whether stimulation is effective in improving choice reaction time (RT) and stop-signal RT. The results show that DBS of the STN was associated with significantly enhanced inhibitory control, as indicated by shorter stop-signal RTs. An additional finding is that DBS of the STN led to significantly shorter choice RT. The effects of DBS on responding and response inhibition were functionally independent. Although DBS of the Vim did not systematically affect task performance in patients with ET, a subgroup of Vim-stimulated PD patients showed enhanced stop-signal RTs in on stimulation versus off stimulation. This result suggests that the change in performance to stop signals may not be directly related to STN function, but rather results from a change in PD function due to DBS in general. The findings are discussed in terms of current functional and neurobiological models that relate basal ganglia function to the selection and inhibition of motor responses.