Bilateral deficit and symmetry in finger force production during two-hand multifinger tasks

A comprehensive study of patterns of finger forces during one-hand and two-hand multifinger maximal force production trials was performed with particular emphasis on differences between tasks involving symmetrical and asymmetrical finger groups (symmetrical and asymmetrical tasks). Twelve healthy right-handed subjects performed maximal voluntary force production tasks with different finger combinations. Force deficit (FD) for a finger group within a hand was defined as a drop in peak force in a multifinger task as compared to the sum of individual finger peak forces in single-finger tasks. FD showed a dependence on both the number of fingers within the hand and the number of fingers in the other hand. An additional drop in peak finger forces was seen in two-hand tests (bilateral deficit, BD). BD summed over two hands was independent of the number of fingers involved in the two-hand tasks, but dependent on the distribution of fingers between the two hands. BD for a hand was larger for tasks involving fewer fingers within the hand and more fingers in the other hand. It was higher for asymmetrical tasks than for symmetrical tasks. The difference between asymmetrical and symmetrical tasks was due to the different behavior of asymmetrically involved fingers. FD was larger for asymmetrical master (explicitly involved) fingers, while forces produced involuntarily by asymmetrical slave (explicitly non-involved) fingers were larger. These differences brought down the total moment produced by both hands in the frontal plane. FD and BD are phenomena of different origin whose effects sum up. The observations have led to further development of a previously proposed double-representation, mirror-image (DoReMi) hypothesis and refinement of the neural network underlying the two-hand finger interaction.     

Effects of symmetry groups on complexity and goodness in visual pattern

Two experiments were performed to investigate stimulus determinants of pattern complexity and pattern goodness. Two hundred and ninety-six undergraduates rated complexity and goodness of two-dimensional patterns, which consisted of solid and/or open circles. The patterns were invariant under transformations of reflection or rotation, and they formed cyclic groups or dihedral ones. The results were summarized as follows. (1) Goodness of patterns increased with the order of cyclic and dihedral groups with different weights. (2) Complexity of patterns having line-segments decreased with the order of cyclic and dihedral groups with equal weights, whereas that of patterns having no line-segments was medium regardless of the order. (3) Simplicity and goodness of patterns with a vertical axis of reflection were higher than those with the other orientation axes. (4) Patterns consisting of solid circles were rated more complex than those of open ones. (5) Complexity increased as a positively accelerated function of the number of circles, whereas goodness increased as a negatively accelerated function. It was concluded that complexity and goodness were determined by compound factors, which are processed at different stages of human visual system.     

Changes in the symmetry of rapid movements Effects of velocity and viscosity

Investigations of pain using functional imaging techniques have revealed an extensive central network associated with nociception. This network includes the thalamus, insula, prefrontal cortex and anterior cingulate cortex (ACC) as well as the somatosensory cortices. Positron emission tomography (PET) of regional cerebral blood flow (rCBF) has demonstrated activation of the ACC during cognitively challenging tasks such as the Stroop interference task and divided attention. One interpretation of this research is that ACC is involved in the general features of attention and that it does not play a specific role in pain processing per se. Three-dimensional PET imaging provides a method for assessments of rCBF in a single individual during multiple tasks. In addition, coregistration of PET and magnetic resonance (MR) images allows for better localisation of the PET signals so that differences in cortical activation sites can be more accurately determined. This approach was used to assess rCBF during the experience of pain by subtracting images collected during heat from those during noxious heat stimulation. Two regions of the ACC had elevated rCBF, one in the perigenual region and one in the mid-rostrocaudal region (i.e. midcingulate cortex). During the execution of the Stroop task, the group result showed the midcingulate region overlapping with the site seen during the experience of pain. This group result, however, was not confirmed in the individual subject analysis, which revealed widespread and independent areas of ACC response to pain and Stroop. It is concluded that the ACC contributes to multiple cognitive procedures. It is inadequate to describe the primary contribution of ACC to pain processing as “attention” because it is unlikely that the multiple small and independent activation sites produced by pain and Stroop subserve attentive processing throughout the brain. Received: 22 July 1996 / Accepted: 28 May 1997     

Effects of gender-typed tasks and gender roles on cardiovascular reactivity

This study explored the effects of gender-typing of a task on cardiovascular reactivity among 60 men and 58 women, who were preselected on the basis of their “masculinity” and “femininity” scores on the Personal Attribute Questionnaire (PAQ; Spence &; Helmreich, 1978). Both gender-role orientation and gender-typing of (he task (but not sex of participant) accounted for a significant amount of variance in systolic blood pressure (SBP) and heart rate (HR) reactivity. Femininity scores predicted increases in SBP responses to the task in the entire sample. HR responses were determined by a significant interaction of sex of participant, a “feminine” gender-role orientation, and gender-typing of the task. Among men, gender-typing of task interacted with gender-role orientation: men whose personality did not fit the situation (e.g., men scoring high on “femininity” who worked on a male-typed task) exhibited elevated MR reactivity. There were no significant effects for HR reactivity among women. These findings underscore the role of psychosocial factors as determinants of SBP and HR responses, especially among men.     

Effects of mental tasks on the cardiorespiratory synchronization

The cardiovascular and respiratory systems are functionally related to each other, but it is unclear if the cerebral cortex can affect their interaction. The effect of a mental task on the synchronization between cardiovascular and respiratory systems was investigated in the article. Electroencephalogram (EEG), electrocardiogram (ECG) and respiratory signal (RES) were collected from 29 healthy male subjects during the mental arithmetic (MA) task and the synchrogram was used to estimate the strength of cardiorespiratory synchronization. Our results showed that MA task significantly increased the breath rate, the heart rate and the EEG power spectral energy in theta band at FC3, FC4 and C4 electrodes (p < 0.01), decreased the duration of cardiorespiratory synchronization epochs (p < 0.05). Moreover the duration of cardiorespiratory synchronization epochs during MA task was negatively correlated with the EEG power spectral energy in theta band at FC3, FC4 and C4 electrodes and the sympathetic activity (p < 0.05). The results demonstrated that ANS and cerebral cortex are implicated in the changes of cardiorespiratory synchronization during MA task.     

Effects of anxiety-reducing hypnotic training on learning and reading-comprehension tasks

The effect of anxiety-reducing hypnotic training on learning and reading-comprehension tasks was examined. Fifteen college students who reported having test-taking anxiety were randomly assigned to an experimental or a control group. The experimental group received hypnotic training to reduce anxiety prior to taking a learning and reading-comprehension test. No significant difference was found between the experimental and the control group on the simple-recall task. However, on the reading-comprehension test the experimental group scored significantly higher than the control group. Further examination of the total score revealed that the experimental group difference was due to superior performance on the inference items. There was no difference between groups on items that required the recall of information from the passage. These findings support the notion that hypnotic training may be useful to reduce anxiety and improve test performance.     

Effects of task attentiveness on task-irrelevant activity and boredom in the signal detection tasks

It has been reported that subsidiary behavior, including body movements, and irrelevant thoughts occur spontaneously during a vigilance situation. These activities are called task-irrelevant activity. To examine the effects of task attentiveness on task-irrelevant activity and on the subjective feeling of boredom, 31 subjects were asked to engage in two types of signal detection tasks. The body movements were measured by recording the rotating angle of a swivel chair that the subject sat on. More task-irrelevant thoughts and subsidiary behavior occurred accompanied by higher subjective feeling of boredom in the low attentive task than in the high attentive task. These findings indicate the possibility of the task-irrelevant activity as an index of subjective boredom.     

ERP repetition effects in indirect and direct tasks: Effects of age and interitem lag

Event-related potentials (ERPs) were recorded for visually presented words in young and older participants while they performed two tasks. In the indirect task, participants responded to occasional target words. Some of the nontarget words were repeated after a single intervening trial, and others were repeated after a mean of 10 trials. In the direct task participants responded to every item, discriminating between words presented for the first and the second times. Compared with ERPs to unrepeated words, those to words repeated in the indirect task after either lag were more positive in both participant groups. For the short lag, this effect was larger among the older participants. In the direct task, words repeated after either lag elicited a positive shift in the ERPs of the young participants. In the older participants, short lag repeats elicited a repetition effect, but smaller than the equivalent effect among the young participants. Long lag repeats failed to elicit a repetition effect in the direct task in the older participants. The findings show that word repetition in these tasks reflects the modulation of two ERP components, which differ in their sensitivity to age-related changes in memory function.     

Differences in coordination of elbow flexor muscles in force tasks and in movement tasks

Summary Motor-unit activity in m. biceps brachii, m. brachialis and m. brachioradialis during isometric contractions has been compared with motor-unit activity during slow voluntary (extension and flexion) movements made against external loads. During these slow movements the recruitment threshold of m. biceps motor units is considerably lower than it is during isometric contractions but the recruitment threshold of both m. brachialis and m. brachioradialis motor units is considerably higher. For all three elbow flexor muscles the motor-unit firing frequency seems to depend on the direction of movement: the firing frequency is higher during flexion movements (3 deg/s) and lower during extension movements (−3 deg/s) than during isometric contractions. The relative contribution of the biceps to the total exerted flexion torque during slow voluntary movements is estimated to increase from 36% to about 48% and that of the brachialis/brachioradialis is estimated to decrease from 57% to about 45% compared to the relative contribution of these muscles during isometric contractions. This difference in the relative contribution of the three major elbow flexor muscles is shown to be caused by differences in the central activation in force tasks and movement tasks.     

Detection and enumeration of immunoglobulin secreting cells

A method is described in which sheep red blood cells (SRBC) are coated with anti-immunoglobulin (Ig) antibodies (Ab) for use in reverse hemolytic plaque assays (RHPA) as follows. The non-complement fixing F(ab')2 fragments of rabbit anti-mouse Ig Ab are derivatized with the N-hydroxysuccinimide ester of palmitate. The hydrophobic palmitate tails spontaneously insert into the SRBC membranes, thus coating the cells with anti-Ig F(ab')2 molecules. The SRBC are lysed by successive additions of mouse Ig, rabbit anti-mouse Ig and complement. When this procedure is carried out in agar gel, Ig-secreting mouse cells produce localized hemolytic areas (plaques). The procedure is more reproducible and more sensitive than RHPA performed with protein A-coated SRBC. In principle, this procedure should be adaptable to the detection of cells secreting any molecule for which specific antibodies are available.     

Automated enumeration of immature granulocytes

The performance characteristics of the XE-2100 (Sysmex, Kobe, Japan) automated immature granulocyte (IG) count were studied. The automated IG count was compared with the manual morphology count and with a proposed reference flow cytometric count. The comparison data were analyzed by both least-squares and Passing-Bablok regression analysis. Long-term imprecision using preserved blood quality control specimens at different levels showed a range from 2.59% to 3.57% coefficient of variation (CV) for within-run imprecision and 3.57% to 6.85% CV for total imprecision. The within-run reproducibility performed using fresh blood on 3 different specimens showed a range from 5.55% to 8.24% CV. The counts were stable at both room temperature and after refrigeration for 24 hours.Passing-Bablok regression analysis showed excellent agreement between the proposed reference flow cytometric IG count and the XE-2100 IG count, while there was less agreement with the manual morphology count. Our results indicate that the automated IG count can replace the manual morphology count for IG counting in the clinical laboratory. The results also confirm that the flow cytometric IG count is superior to and can replace the manual morphology count as a reference method for IG counting.     

Differences in central control of m. biceps brachii in movement tasks and force tasks

Summary Motor-unit activity in m. biceps brachii during isometric flexion contractions has been compared with motor-unit activity during a slow voluntary movements against constant or increasing preloads and b flexion contractions while movements were imposed by a torque motor. Recruitment levels and firing frequency behaviour of the motor units were found to be very similar when torques were generated during isometric contractions and during the imposed movements. However, these characteristics of the biceps motor units were quite different during the slow voluntary movements. It is suggested that the central activation of the and/or motoneurone pools of m. biceps brachii is different for force tasks and slow movement tasks, even if the same torques are exerted and/or movements are made.     

Effects of amygdaloid lesions on the performance of rats in four passive avoidance tasks

The effects of amygdaloid lesions on shock punished step-down and rearing responses, quinine punished drinking, and ice water punished step-through responses were investigated in 4 experiments. Amygdaloid lesions impaired the suppression of step-down, rearing, and step-through responses but had no effect on the suppression of quinine consumption. Various interpretations of the response disinhibitory effects of amygdaloid damage are considered. It is concluded that no unitary explanation adequately explains this phenomenon. More extensive investigations of the conditions producing response disinhibition and their anatomical organization are suggested.     

Effects of visual and verbal presentation on cognitive load in vigilance,memory, and arithmetic tasks

Degree of pupil dilation has been shown to be a valid and reliable measure of cognitive load, but the effect of aural versus visual task presentation on pupil dilation is unknown. To evaluate effects of presentation mode, pupil dilation was measured in three tasks spanning a range of cognitive activities: mental multiplication, digit sequence recall, and vigilance. Stimuli were presented both aurally and visually, controlling for all known visual influences on pupil diameter. The patterns of dilation were similar for both aural and visual presentation for all three tasks, but the magnitudes of pupil response were greater for aural presentation. Accuracy was higher for visual presentation for mental arithmetic and digit recall. The findings can be accounted for in terms of dual codes in working memory and suggest that cognitive load is lower for visual than for aural presentation.     

Effects of aging on the novelty P3 during attend and ignore oddball tasks

The effects of attention were assessed on novelty P3 amplitude and scalp distribution elicited by environmental sounds in young and elderly volunteers who participated in either actively attended or ignored oddball conditions. For the young, novelty P3 amplitude decreased with time on task during both attend and ignore sequences. Amplitude decrements were greatest at frontal sites during the attend condition, but at all sites during the ignore condition. A reliable amplitude decrement was not observed for the elderly in either the attend or ignore oddball series. The data suggest that attention differentially activates multiple generators that contribute to scalp-recorded novelty P3 activity. The lack of novelty P3 habituation seen in the elderly is consistent with changes in frontal lobe function as age increases.     

Effects of working memory demands on frontal slow waves in time-interval reproduction tasks in humans

Very few studies have examined the event-related potentials associated with the retention of temporal information for later use. In the present experiment, event-related potentials were recorded during two duration reproduction tasks in which a delay was introduced between the encoding and the reproduction phases. Furthermore, working memory demands were varied during the delay (number of durations to be memorized and degree of manipulation of the durations). These variables had no significant effect on the amplitude of the contingent negative variation observed during duration encoding. By contrast, the amplitude of the slow wave recorded over middle frontal regions during the delay increased with working memory demands, which confirms the key role played by these frontal regions in the cognitive processes engaged during the retention of duration in working memory.     

Brain DC potential changes of computerized tasks and paper/pencil tasks

Analysis of slow cortical potentials and their topography is currently discussed as an indication of cortical activity associated with cognitive operations/performance. In this paper, changes of the EEG DC potential were analyzed in two computerized tasks (correcting typing errors, performing Excel) and two paper/pencil tasks (correcting typing errors, a cognitive test) to assess mental load related to ergonomical and task characteristics. DC recordings were analyzed for the mean values of baseline and the first and the second 4 min of each task from 24 persons. A 2 (computer usage experience low vs. high)×4 (Task)×3 (Time: baseline, first half of task, second half)×6 (Lead) MANOVA of DC potential changes (DCPCs) showed at F3, F4 and C3 positive DCPCs for paper/pencil tasks and negative DCPCs for computerized tasks. Ratings of task difficulty were related to high vs. low task demands, whereas DCPCs were related to task medium, time on task and lead. Highly experienced persons showed a pronounced left–right difference at parietal locations and at frontal and central locations related to task medium by trend. Results were interpreted as higher cortical activation associated with mental load caused by additional attentional/controlling demands of computerized tasks.