Activation timing of postural muscles during bilateral arm flexion in self-timing, oddball and simple-reaction tasks.

BACKGROUND: We investigated the effect of time constraint on activation timing of postural muscles during bilateral arm flexion in self-timing, oddball and simple-reaction tasks. METHODS: Thirteen healthy adults flexed their arms from a suspended position with maximum speed and stopped at the shoulder level. For erector spinae-longissimus (ES), biceps femoris (BF), and gastrocnemius (GcM), onset timing of burst activation with respect to the anterior deltoid (AD), and the displacement of the center of pressure in the anteroposterior direction (CoPy) were analyzed. RESULTS: AD reaction time was significantly shorter in the simple-reaction task than oddball task, suggesting that time constraint would be lower in the task order noted above and affected the state of postural preparation. The following properties were found in the onset timing of postural muscle: (1) the onset timing of BF and GcM were earlier in the task order noted above, and (2) the earliest activated distal muscle in the self-timing task was activated later in the simple-reaction task. CoPy displacement was smaller in the same task order as the onset timing. CONCLUSIONS: It appears that with sufficient postural preparation, the focus of postural control is on the reduction of postural disturbance and earlier lower leg muscle activation.

Anticipatory postural control associated with bilateral arm flexion and event-related potential in a Kanji Stroop-like task.

OBJECTIVE: We investigated anticipatory postural control during arm flexion and event-related potential (ERP) in a Kanji Stroop-like task. METHODS: The Kanji for RED or BLUE colored in red, blue, or black was randomly presented on a screen for 100 ms. Subjects flexed their arms in response to target stimuli colored black (control condition) or which were congruent or incongruent with the meaning of Kanji characters. P300 of ERPs elicited by the target stimuli and onset timing of electromyographic activity in arm and postural muscles were measured. RESULTS: Reaction time of the anterior deltoid (AD) was shorter and P300 amplitude larger in the order of control, congruent, and incongruent conditions. A distinct P515 component was recognized in ERPs under congruent and incongruent conditions. No significant difference among conditions was observed in onset timing of erector spinae, biceps femoris, or gastrocnemius activity with respect to AD. CONCLUSIONS: Changes in cognitive processing and allocation of attentional resources according to task demands influence the onset timing of arm movement, but not that of anticipatory postural control, suggesting the presence of fixed synergy of arm movement and postural control. SIGNIFICANCE: These findings are important for understanding the effects of cognitive function on anticipatory postural control.

P300 and response time from the colored Kanji Stroop task.

The P300 component of the event-related brain potential during the colored Kanji Stroop task was used in conjunction with response time to identify the locus of interference. Participants were instructed to respond to the colored Kanji characters as quickly as possible in the respective stimulus conditions. Response time varied with the congruence and incongruence stimulus conditions. However, the P300 latency remained stable during the stimulus-related processes. P300 amplitude decreased from the parietal, central to the frontal electrode sites in order in each stimulus condition. The findings provide further evidence that response-related processes are the primary source of Stroop interference.

Sex differences in perceptual processing: performance on the color-Kanji stroop task of visual stimuli.

During color, colored Kanji characters and Stroop task of the visual stimuli, the P300 component of the event-related brain potential (ERPs) was used in conjunction with response time to identify sex differences in perceptual processing. Participants were instructed to respond to the display colors and name colored Kanji characters as quickly as possible in the respective stimulus conditions. Response time varied in all stimulus conditions, the males took longer than females. The P300 latency of males was longer and amplitude was smaller than females. The results suggest that cognitive strategy of males is different from females.