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At least 199 records · Page 11Linked to original sources
PubMed2007

Volitional control of attention and brain activation in dual task performance.

This study used functional MRI (fMRI) to examine the neural effects of willfully allocating one's attention to one of two ongoing tasks. In a dual task paradigm, participants were instructed to focus either on auditory sentence comprehension, mental rotation, or both. One of the major findings is that the distribution of brain activation was amenable to strategic control, such that the amount of activation per task was systematically related to the attention-dividing instructions. The activation in language processing regions was lower when attending to mental rotation than when attending to the sentences, and the activation in visuospatial processing regions was lower when attending to sentences than when attending to mental rotations. Additionally, the activation was found to be underadditive, with the dual-task condition eliciting less activation than the sum of the attend sentence and attend rotation conditions. We also observed a laterality shift across conditions within language-processing regions, with the attend sentence condition showing bilateral activation, while the dual task condition showed a left hemispheric dominance. This shift suggests multiple language-processing modes and may explain the underadditivity in activation observed in the current and previous studies.

Acoustic Stimulation↗
PubMed1989

Volitional control of involuntary movements.

Voluntary suppressibility of abnormal movements is helpful in the classification of movement disorders because this ability appears to be a common component of tics. However, there has been no systematic study of voluntary suppressibility in other movement disorders. We have therefore assessed 146 patients with tremors and dyskinetic disorders as to their ability to suppress movements by mental concentration. Patients were videotaped while trying to stop their movements, and the length of time they could suppress their abnormal movements was recorded. One hundred percent (10 of 10) of patients with tics could suppress movements for an average of 2.5 min. Two percent (1 of 50) of essential tremor patients could suppress the tremor, and the tremor of 24% (12 of 50) was made worse by mental concentration. Eighty percent (4 of 5) of neuroleptic-induced tremor could be improved mentally. Seventy percent (35 of 50) of patients with parkinsonian tremor could voluntarily diminish their tremor for an average of 48 s. Fifty percent (8 of 16) of chorea (tardive dyskinesia, Huntington's disease, postencephalitic) was reduced. Dystonia was suppressible in 20% (3 of 15). It is concluded that movement disorders besides tics can be voluntarily suppressed and that suppressibility should not be used to classify movement disorders. Tics, however, are easier to suppress and can be suppressed for a longer time.

Adult↗
PubMed1984

Mandibular postural tremor during relaxation and during volitional innervation of the jaw muscles.

Jaw tremor was recorded as the changes in the vertical distance between mandible and maxilla. Two states of motor performance of the jaw muscles were chosen: relaxed and actively positioning of the mandible close to toothcontact, referred to as respectively rest- and activity tremor. Rest tremor contained a strong ballistocardiac component (bc power = 50%) and was of small amplitude (9.4 micron rms). Activity tremor revealed increased amplitudes (19.2 micron rms) with a predominant neuromuscular component (nm power = 75%). Bc tremor patterns differed significantly from nm tremor patterns. A negative linear relationship, which apparently was similar for rest and for activity tremor (P greater than 0.10), existed between the estimated bc contribution and tremor amplitude. As tremor amplitude increased neuromuscular activity appeared increasingly time locked to bc activity, which should be attributed to synchronization of spindle activity, either through the stretch reflex or through vascular pulsation. The average bc contribution to tremor amplitude remained of almost constant magnitude (7.0 micron rms), with no differences between rest and activity for the group as a whole. During resting conditions, complete relaxation of the jaw muscles was not attained by the majority of the subjects. The latter revealed a heart rate arrhythmia that was strongly correlated with motor (nm) activity (P less than 0.001). During activity conditions no such correlation was present. The present results demonstrate that for the understanding and the interpretation of the underlying mechanisms of jaw tremor genesis, both the recording technique, i.e., differential jaw displacements, and the signal analysis procedure, i.e., autocorrelograms and power spectra over extended record length, were of crucial importance.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Automatic and strategic volitional saccadic eye movements in psychotic patients.

Drug-free schizophrenics were compared with depressive psychotics and normal controls on two saccade initiation tasks which differed with respect to the type of stimulus that initiated a saccadic response. Strategic initiation (SIS) appears to use a route different from that in automatic initiation (AIS). The SIS task revealed slowed responding in psychiatrically ill patients if their cognition was impaired, but all groups responded similarly on the AIS task. Schizophrenics could be separated from depressed psychotics by their inability to utilize temporal redundancy to speed up saccade initiation on the SIS task. Neurophysiological evidence implicates specific impairments in the frontal eye field (FEF) and/or basal ganglia.

Depressive Disorder↗
PubMed2002

Vocal cord closure pressure during volitional swallow and other voluntary tasks.

Our goal was to determine and compare vocal cord (VC) closure pressure and its associated intratracheal pressure during several physiological events such as swallowing, coughing, straining, and phonation. We studied 11 healthy subjects (age 41 +/- 2 years) with no current or previous history of laryngeal or pulmonary diseases. VC closure pressure during the above-mentioned tasks was studied using a concurrent manometric and endoscopic technique. VC closure pressure during dry swallows averaged 298 +/- 23 mm Hg, while intratracheal pressures exhibited a biphasic pattern ranging from -4 +/- 0.5 to +6 +/- 0.8 mm Hg. Average VC closure pressure during cough was 280 +/- 20 mm Hg, during straining/valsalva maneuver it averaged 330 +/- 45 mm Hg, during phonation it produced an initial rapidly rising spike like pressure (222 +/- 25 mm Hg) followed by a sustained minimally positive pressure during continued phonation of two tested vowel sounds (15-25 mm Hg). Between-group comparison showed that for all studied tasks, the in-' tercordal pressures were significantly higher than those of respective intratracheal pressures (p < 0.05). The vocal cords generate closure pressures that vary depending on the performed function.

Adult↗