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PubMed1994

Acute effects of levodopa on wrist movement in Parkinson's disease. Kinematics, volitional EMG modulation and reflex amplitude modulation.

Acute changes in motor performance due to levodopa were evaluated by a series of four motor tests unified by their focus on wrist flexion-extension movements. Subjects with idiopathic Parkinson's disease were evaluated with this battery of tests before (OFF) and after their usual morning dose of levodopa (ON). The test battery consisted of (i) repetitive self-paced movement in which velocity was to be maximized; (ii) visually guided tracking of a sinusoid and a square wave; and (iii) an assay of stretch reflex modulation during volitional sinusoidal tracking. The maximal wrist joint velocity of self-paced reciprocating flexion and extension movements increased after levodopa (ON), without significant changes in the movement period or amplitude. In the two tracking tasks, some subjects improved as evident by a lower root mean square (rms) error, but in similar numbers of subjects the rms error increased. Overall, the rms error, peak velocity or peak movement amplitude did not change after levodopa in either tracking task. Significant and consistent changes did occur after levodopa in an assay of reflex modulation during error-constrained tracking (Johnson et al., Brain 1991; 114: 443-60). The amplitude of volitional EMG increased after levodopa, with a concurrent reduction in reflex EMG. These changes are consistent with the noted increase in movement velocity. These results show that the effects of levodopa on movement velocity were not consistently translated into increased accuracy. The changes in the long latency reflex gain argue for a central control of this reflex, mediated by structures sensitive to levodopa. Finally, the results show that the quantitative evaluation of levodopa therapy cannot be unidimensional, but requires a battery of motor tests as undertaken in this study.

Aged↗
PubMed2000

Motor cortex brain activity induced by 1-Hz transcranial magnetic stimulation is similar in location and level to that for volitional movement.

RATIONALE AND OBJECTIVES: The relatively high temporal and spatial resolution of functional MR imaging was used to compare the blood oxygenation level dependent (BOLD) response associated with movement induced by transcranial magnetic stimulation (TMS) with that for a similar movement executed volitionally (VOL). METHODS: Seven healthy adults were studied in a 1.5-T MR scanner. One hertz TMS at 110% of motor threshold was applied over the motor cortex for the thumb in 21-pulse trains in alternation with VOL every 63 seconds and interleaved with functional MR imaging. RESULTS: BOLD increases in motor cortex associated with TMS and VOL movement were similar (2%-3%). Mean separation of their centers of activity was 3.7 + 1.9 mm (mean displacement: left/right = 0.3 +/- 4.1 mm; superior/inferior = 0.7 +/- 1.9 mm). There was no indication of supraphysiological brain activity. CONCLUSIONS: Motor cortex BOLD response associated with thumb movement induced by 1-Hz TMS at 110% motor threshold is similar in both location and level to that caused by a similar movement executed volitionally.

Adult↗
PubMed1997

Functional neuromuscular stimulation controlled by surface electromyographic signals produced by volitional activation of the same muscle: adaptive removal of the muscle response from the recorded EMG-signal.

In order to use the volitional electromyography (EMG) as a control signal for the stimulation of the same muscle, it is necessary to eliminate the stimulation artifacts and the muscle responses caused by the stimulation. The stimulation artifacts, caused by the electric field in skin and tissue generated by the stimulation current, are relatively easy to eliminate by shutting down the EMG-amplifier at the onset of the stimulation pulses. The muscle response is a nonstationary signal, therefore, an adaptive linear prediction filter is proposed. The filter is implemented and for three filter lengths tested on both simulated and real data. The filter performance is compared with a conventional fixed comb filter. The simulations indicate that the adaptive filter is relatively insensitive to variations in amplitude of the muscle responses, and for all filter lengths produces a good filtering. For variations in shape of the muscle responses and for real data, an increased filter performance can be achieved by increasing the filter length. Using a filter length of up to seven stimulation periods, it is possible to reduce real muscle responses to a level comparable with the background noise. Using the shut-down circuit and the adaptive filter both the stimulation artifacts and the muscle responses can be effectively eliminated from the EMG signal from a stimulated muscle. It is therefore possible to extract the volitional EMG from a partly paralyzed muscle and use it for controlling the stimulation of the same muscle.

Artifacts↗
PubMed2006

Volitional hyperventilation during ramp exercise to exhaustion.

The purpose of this study was to determine whether volitional hyperventilation at 20 L x min(-1) above normal exercise values affected exercise duration while performing ramp exercise to exhaustion. Nine healthy subjects performed a ramp exercise test to exhaustion. On a subsequent test they hyperventilated, with the aid of visual and audio feedback, at 20 L x min(-1) greater than their initial test. Ramp exercise time to exhaustion was substantially reduced from 771.6 +/- 85.2 s to 726.6 +/- 86.6 s (p < 0.002) with the additional hyperventilation. Subjects underwent 2 more ramp exercise tests and performed a 5 s maximum voluntary ventilation or a forced vital capacity test at work rates corresponding to rest, below lactate threshold (LT), above LT, immediately after exercise, and 3 min recovery. Generally, the flow rates were not affected by exercise below LT and were enhanced during above-LT exercise, exhaustion, and recovery. This indicated a change in pulmonary function that is dependent on exercise intensity. In spite of this increased ability to generate high flow rates, exercise performance was diminished when respiratory muscle work was increased volitionally by 20 L x min(-1), indicating a strong coupling between respiratory muscle work and fatigue during ramp exercise in normal subjects.

Adult↗
PubMed2000

Modulation of laryngeal responses to superior laryngeal nerve stimulation by volitional swallowing in awake humans.

Laryngeal sensori-motor closure reflexes are important for the protection of the airway and prevent the entry of foreign substances into the trachea and lungs. The purpose of this study was to determine how such reflexes might be modulated during volitional swallowing in awake humans, when persons are at risk of entry of food or liquids into the airway. The frequency and the amplitude of laryngeal adductor responses evoked by electrical stimulation of the internal branch of the superior laryngeal nerve (ISLN) were studied during different phases of volitional swallowing. Subjects swallowed water on command while electrical stimuli were presented to the ISLN at various intervals from 500 ms to 5 s following the command. Laryngeal adductor responses to unilateral ISLN stimulation were recorded bilaterally in the thyroarytenoid muscles using hooked wire electrodes. Early ipsilateral R1 responses occurred at 17 ms, and later bilateral R2 began around 65 ms. The muscle responses to stimuli occurring during expiration without swallowing were quantified as control trials. Responses to stimulation presented before swallowing, during the swallow, within 3 s after swallowing, and between 3 and 5 s after a swallow were measured. The frequency and amplitude of three responses (ipsilateral R1 and bilateral R2) relative to the control responses were compared across the different phases relative to the occurrence of swallowing. Results demonstrated that a reduction occurred in both the frequency and amplitude of the later bilateral R2 laryngeal responses to electrical stimulation for up to 3 s after swallowing (P = 0.005). The amplitude and frequency of ipsilateral R1 laryngeal responses, however, did not show a significant main effect following the swallow (P = 0.28), although there was a significant time by measure interaction (P = 0.006) related to reduced R1 response amplitude up to 3 s after swallowing (P = 0.021). Therefore, the more rapid and shorter unilateral R1 responses continued to provide some, albeit reduced, laryngeal protective functions after swallowing, whereas the later bilateral R2 responses were suppressed both in occurrence and amplitude for up to 3 s after swallowing. The results suggest that R2 laryngeal adductor responses are suppressed following swallowing when residues may remain in the laryngeal vestibule putting persons at increased risk for the entry of foreign substances into the airway.

Adult↗
PubMed1997

Motor control physiology below spinal cord injury: residual volitional control of motor units in paretic and paralyzed muscles.

We have described motor control in people with different degrees of SCI by using surface polyelectromyographic recordings during single- and multijoint volitional motor tasks. We have shown that neurobiologic conditions of the injured spinal cord can be expressed in two main categories: "new anatomy" and "reduced anatomy". The evidence for a variety of definite features of motor control elicited by volitional effort for the performance of a present or even clinically absent motor task suggests that we can benefit from animal experimental neurobiologic studies while we are progressing toward the application of this new knowledge for the restoration of impaired spinal cord function in humans. Reports on the successfully enhanced regenerating capabilities of the axons and improved connectivity within neuronal circuits after SCI encourage us to intensify our efforts in parallel with studies on the recovery processes found in experimentally induced lesions in animals, as well as in accidentally induced SCI in humans.

Adolescent↗
PubMed1998

Modulation of volitional ethanol intake in the rat by central delta-opioid receptors.

The acute effect of opioid antagonists on volitional ethanol intake was studied in unselected Sprague-Dawley rats using a two-bottle, free-choice model. The total daily intake of ethanol during saline treatment was 1.79 +/- 0.4 g/kg/day (n = 136). The rats were deprived of fluids for the last 4 hr of the light period. Saline or drug was given intraperitoneally 20 to 30 min before the onset of dark, and the ethanol and water intakes were measured during the following hour. The ethanol intake during this hour was 0.75 +/- 0.06 g/kg (n = 136). Naltrexone significantly reduced ethanol intake. There was also a significant reduction in ethanol intake following administration of ICI-174,864. Naloxonazine and naloxone methiodide lacked effect. None of the treatments had any effect on the water or food intake. The results suggest that central delta-opioid receptors modulate volitional ethanol intake in the rat.

Alcohol Drinking↗
PubMed2003

Surface electromyographic recording of volitional activity: a technique to detect partial motor conduction block.

Partial motor conduction block, an electrophysiological hallmark of demyelination, helps to identify acquired demyelinating neuropathies but its electrophysiological detection can be difficult. We report a technique that may be helpful in this regard. Twenty-five patients with partial motor conduction block secondary to acquired demyelinating polyneuropathy (ADP), 7 with amyotrophic lateral sclerosis (ALS), 7 with stroke, and 11 control subjects, were studied. Amplitude of compound muscle action potentials was recorded after distal electrical (E) stimulation and for volitionally (V) induced responses in 82 muscles. Mean +/- SD V/E ratio was 12.3 +/- 6.6 for ADP patients, 58.1 +/- 17 for ALS patients, 11.4 +/- 9 for stroke patients, and 55.4 +/- 12.3 for controls. The V/E ratios for patients with partial motor conduction block and stroke were significantly reduced compared with ALS patients and healthy controls (P < 0.05). Surface electromyographic (EMG) recording for determination of the V/E ratio may be a useful technique for detection of a proximal conduction block if a central lesion or poor effort can be excluded. Further study of this novel technique is necessary.

Action Potentials↗
PubMed2002

Volitional control of autonomic arousal: a functional magnetic resonance study.

Electrodermal activity reflects autonomic sympathetic innervation of dermal sweat glands providing an index of emotion-related bodily states of arousal. Relaxation techniques, which are facilitated by external (bio)feedback of electrodermal activity, can be used by trained subjects to actively control bodily and emotional arousal. Biofeedback relaxation provides an experimental model to explore neural mechanisms contributing to emotional representations and intentional autonomic control. We used functional magnetic resonance imaging (fMRI) to explore neural mechanisms contributing to integration of volitional intent, self-representation, and autonomic states of arousal, embodied within performance of a biofeedback relaxation exercise. Data were obtained from 17 subjects to assess brain activity during relaxation in which a visual index of electrodermal arousal was modulated by accuracy (addition of random "noise") or sensitivity (by scalar adjustments of feedback). A central matrix of cortical, subcortical and brainstem autonomic centres was activated during biofeedback relaxation, as well as regions that mediate visual and somatesthetic representations and executive control. Anterior cingulate, amygdala, and insula activity was modulated by task manipulations that increased demand on processing interoceptive representations, while variation in anterior insula activity reflected an interaction between accuracy and sensitivity of feedback. These findings identify neural substrates that support integration of perceptual processing, interoception, and intentional modulation of bodily states of arousal.

Adult↗
PubMed2002

On the role of monoamine oxidase-A for the maintenance of the volitional consumption of ethanol in two different rat models.

It is hypothesized that although the overall metabolism of ethanol in the brain is very limited, a very small percentage of the brain tissue may carry out that little amount of metabolism. Specifically, hydrogen peroxide may be used as a co-substrate for the metabolism of ethanol to acetaldehyde by catalase and the action of monoamine oxidase in the monoaminergic neurons would supply the hydrogen peroxide. This production of acetaldehyde may result in the formation of novel metabolites that provide the rewarding stimulus for the consumption of ethanol. To test this hypothesis, a reversible inhibitor of the A-isoform of monoamine oxidase, BW A616U, was compared to irreversible inhibitors of one or both MAO-A and B isoenzymes. Doses of 12.5-75 mg/kg p.o. BW A616U reduced the behavioral effects, ptosis and catalepsy, due to monoamine depletion by 2.5 mg/kg reserpine, but these signs of monoamine depletion were evident 24 h after injection. In the cyanamide-induced drinking rat, 50 mg/kg BW A616U reduced consumption of ethanol by 37%. Phenylzine, an irreversible MAO-A and B inhibitor, reduced consumption of ethanol by 67%, but also food consumption; however, the intake of both increased during the post-treatment period. The MAO-B inhibitor, R(-)-deprenyl, was without effect. Both BW A616U, 50 mg/kg and 75 mg/kg, and 2.0 mg/kg i.p. clorgyline reduced the consumption of ethanol in the genetic drinking Myers high-ethanol preferring (mHEP) rat and reduced the proportion of ethanol consumed to total fluids by over 50%. Again, R(-)-deprenyl was without effect. Clorgyline also markedly reduced the intake of food during the 3-day treatment period, only. However, the consumption of ethanol remained depressed during the 4 days after either 75 mg/kg BW A616U or clorgyline. These data demonstrate that inhibition of MAO-A, but not MAO-B, reduces the volitional consumption of ethanol probably by preventing the formation of both biogenic aldehydes and acetaldehyde so that rewarding alkaloidal products cannot be formed.

Alcohol Drinking↗
PubMed2003

Activation of cerebellum and basal ganglia on volitional swallowing detected by functional magnetic resonance imaging.

Although regions of the sensorimotor cortex, insula, and anterior cingulate gyrus are reported to be activated during swallowing, findings concerning contributions of the cerebellum and basal ganglia have been contradictory. We investigated cerebellar and basal ganglionic activation using functional magnetic resonance imaging (fMRI). In 11 subjects, single-shot gradient-echo echoplanar image volumes sensitive to BOLD contrast were acquired in block design fashion using an oblique orientation covering both cerebrum and cerebellum. Using statistical parametric mapping, regional activation upon swallowing was observed in the sensorimotor cortex, insula, cerebellum, putamen, globus pallidus, thalamus, anterior cingulate gyrus, supplementary motor area, superior temporal gyrus, and substancia nigra. The cerebellum was activated bilaterally, especially on the left; activation of the putamen and globus pallidus was also found bilaterally. Thus, volitional swallowing involves the cerebellum and basal ganglia as well as cortical structures. The method used was well tolerated by normal subjects and should also be applicable to patients with dysphagia.

Adult↗
PubMed1990

Changes in the discharge patterns of motor cortical neurones associated with volitional changes in stepping in the cat.

Extracellular recordings have been obtained from motor cortical neurones of cats walking along a horizontal ladder. We present responses obtained when the animal produced defined volitional changes in limb trajectory, and during different conditions of locomotion. Our results show substantial changes in discharge pattern of some cells under these different conditions. Encounters with displaced rungs produce marked changes in discharge pattern including some which precede foot contact and others graded to the magnitude and direction of displacement.

Animals↗
PubMed1981

Volitional problems in carrying through a difficult decision: the case of drug addiction.

Attempts by young drug addicts to decrease or quit drug consumption were studied by means of a series of interviews. Interest was focused on volitional problems arising due to difficulties in living up to commitments in the face of temptations and various types of emotional stress. It was found that relapses occurred mostly under the influence of emotional stress and that they were preceded by various forms of twisted reasoning, a finding similar to those for other types of addictive behaviors such as smoking and alcoholism. The techniques used by the drug addicts to fight temptations were similar to those reported by other patients. Knowledge of techniques seemed to be rather scarce. There was a correlation between knowledge of technique and success in quitting drug habits. Strong stimulus pull factors were evident in some cases and were apparently counteracted by more or less successful attempts by the patients to escape the tempting situation.

Adolescent↗
PubMed2004

Effects of NMDA glutamate receptor antagonist drugs on the volitional consumption of ethanol by a genetic drinking rat.

The ability of drugs that reduce NMDA receptor activity on the volitional consumption of ethanol in the genetic drinking rat, mHEP line, was investigated. After the consumption of ethanol solutions and water by each male or female mHEP rat had stabilized on its preferred concentration, different doses of LY 274614, a competitive NMDA antagonist, MK 801, a non-competitive NMDA antagonist, (+)-HA-966 or ACPC (1-aminocyclopropane-1-carboxylic acid), antagonists of the glycine site were administered daily for three days. The dose of 3.0 mg/kg i.p. LY 274614 reduced the consumption of ethanol by 64% compared to the pre-treatment baseline, while 0.3 mg/kg of MK 801 reduced consumption by 44%, 20 mg/kg (+)-HA-966 reduced consumption by 47% and 300 mg/kg of ACPC reduced consumption by 30%. These doses of LY 274614 and MK 801 reduced the ability of Sprague-Dawley rats to walk on a rotorod. Effects of these drugs on food intake were small except for the 20 mg/kg dose of (+)-HA-966. Therefore, the drugs did not have an anti-caloric effect and manipulations of the glutamatergic system through NMDA receptors may modify the consumption of ethanol. This interaction should be explored further for its therapeutic potential and to better understand the control by central neuronal systems of the consumption of ethanol.

Alcohol Drinking↗
PubMed2001

Volitional selection of direction in the generation of anticipatory ocular smooth pursuit in humans.

Anticipatory smooth pursuit eye movements cannot normally be generated in the absence of a moving target. However, repeated presentation of identical target motion stimuli, preceded by warning cues, leads to the build up of anticipatory smooth pursuit prior to target onset. These anticipatory responses arguably depend more on motor habit than cognitive expectations. Here, we show that directional cues, concomitant with a timing cue, may be used to initiate predictive (velocity scaled) movements in response to target stimuli of random direction. Furthermore, we show stored velocity and timing information may be directionally transferred, thus allowing predictive movements in a novel direction. This demonstrates the internal origin of these movements and their volitional as opposed to reflexive nature.

Brain↗
PubMedDate not supplied

Volition and alcohol-risk reduction: the role of action orientation in the reduction of alcohol-related harm among college student drinkers.

The present study examined the role of action orientation in health behavior change. Eighty-six binge drinking college students completed measures of alcohol use, alcohol-related consequences (e.g., driving drunk), motivation to change drinking, and action orientation. Alcohol use and consequences were reassessed 1 month later. Results showed that, although there was no significant change in alcohol quantity per occasion, students reported a significant decline in alcohol-related problems over time. Hierarchical regression analyses were conducted to examine whether action orientation was associated with changes in alcohol involvement. Controlling for alcohol problems and motivation to change at Time 1, those with higher dispositional action orientation showed fewer alcohol-related consequences at Time 2. These results suggest that those who are low in action orientation may have more difficulty enacting intentions to modify harmful health behaviors. The findings underscore the importance of volitional skills in interventions to promote change in health behavior.

Adolescent↗
PubMed2003

The volitional inhibition of anticipatory ocular pursuit using a stop signal.

Unlike limb movements, smooth pursuit eye movements cannot normally be performed in the absence of a target. However, when subjects have a high expectancy of an imminent target appearance, the situation changes, and anticipatory smooth pursuit (ASP) tends to precede target onset by several hundred milliseconds. The velocity of this ASP is scaled predictively according to expected target velocity. And when an upcoming target is unexpectedly altered, or fails to appear, ASP continues regardless for approximately 150-200 ms before modification by visual feedback begins [J. Neurophysiol., 84 (2000) 2340]. These and other observations led to the earlier suggestion that ASP might be ballistic, being pre-programmed from start to finish. Two experiments with different timing parameters were therefore performed to test this hypothesis using a version of Logan's [Psychol. Rev., 91 (1984) 295] stop signal task. The aim was to test whether ASP could be stopped at will, and if so, whether the time taken to stop varied as a function of the time since ASP onset. Results showed that in response to a stop signal, ASP can be inhibited at any point in its trajectory, and for the majority of subjects in experiment 1, and all the subjects in experiment 2, with a latency that does not change significantly with target speed or time since ASP onset. These results provide the first demonstration that anticipatory movements can be stopped volitionally in response to a stop signal. Possible cognitive and neurophysiological mechanisms underlying this process are discussed.

Adult↗
PubMed1997

Pallidotomy in Parkinson's disease increases supplementary motor area and prefrontal activation during performance of volitional movements an H2(15)O PET study.

Supplementary motor area and right dorsal prefrontal cortex activation in Parkinson's disease is selectively impaired during volitional limb movements. Since posteroventral pallidotomy improves motor performance in Parkinson's disease patients 'off' medication (i.e. off medication for 9-12 h), we hypothesized that it would also concomitantly increase supplementary motor area and dorsal prefrontal cortex activation. Six Parkinson's disease patients with a median total motor Unified Parkinson's Disease Rating Scale (UPDRS) of 52.5 (range 34-66) 'off' medication underwent unilateral right posteroventral pallidotomy. The patients had H2(15)O PET when 'off' medication before and 3-4 months after surgery. Each PET study comprised four to six measurements of regional cerebral blood flow either at rest or while performing regularly paced joystick movements in freely selected directions (forward, backward, left or right) using the left hand. Pre- and postoperative scans were performed in an identical manner and the associated levels of activation were compared using statistical parametric mapping. After pallidotomy, the median total motor UPDRS score 'off' medication decreased by 34.7% (P = 0.03) and mean response times of joystick movements following the pacing tones improved by 13.8% (P = 0.08). Relative increases in activation of the supplementary motor area and right dorsal prefrontal cortex were observed during joystick movements (P < 0.001). Decreased activation was seen in the region of the right pallidum (P = 0.001). We conclude that pallidotomy reduces pallidal inhibition of thalamocortical circuits and reverses, at least partially, the impairment of supplementary motor area and dorsal prefrontal cortex activation associated with Parkinson's disease.

Adult↗