A study of the effects of cranial electrical stimulation on attention and concentration

There have been several anecdotal accounts that cranial electrical stimulation (CES) enhances attention and the ability to learn new tasks in a normal population, but only one published investigation confirms that CES improves attention using the Alpha Stim CES (Madden and Kirsch, 1987). The purpose of this study was to corroborate the findings of Madden and Kirsch, using more precise measures of attention, such as a Continuous Performance Test (CPT). A pretest and posttest CPT was given to two groups using the LISS CES device. The control group consisted of twenty-one subjects who received the placebo treatment. The experimental group of thirty-one subjects received twenty minutes of CES. Four measures of the CPT show significant gains in attention: Number of Hits,p=.010 Hit RT ISI Change,p=.016, Risk Taking,p=.055; and Attentiveness,p=.054. Based on subjects who demonstrated improvement by one standard deviation on two different measures of the CPT, thirty-one percent of the experimental group improved versus four percent of the control group. The use of CES as a method of increasing attention is a promising are that requires further investigation.     

Perception of different frequencies of cranial transcutaneous electrical nerve stimulation in normal and HIV-positive individuals.

Sine-wave transcutaneous electrical nerve stimulation (TENS) of varying frequencies applied across the cranium (ear to ear) has been demonstrated to evoke three different noncutaneous sensations in three discrete, nonoverlapping frequency bands in normal, healthy subjects. This report describes two studies which evaluate perception of these cranial TENS-evoked, frequency-dependent sensations in normal and HIV-positive individuals. In Exp. I, all of 50 normal, healthy subjects reported perceiving the same three noncutaneous sensations in the same three nonoverlapping frequency bands as long as stimulated and over repeated trials. In Exp. II, 34 HIV-positive individuals (14 asymptomatic, 9 ARC, 11 AIDS) who were free of neurological symptoms differed significantly from 10 normal, healthy controls, and from the norms observed in Exp. I, on perception of the three different TENS-evoked sensations. Also, inability to maintain perception of the stimulus over repeated trials, observed only in the HIV-positive individuals, increased significantly with severity of HIV infection.     

Emotions in sport: Perceived effects on attention,concentration, and performance

This study explored attentional patterns associated with positive and negative emotions during sport competition, and athletes' perceptions of the consequences of these attentional changes for concentration and performance. Sixty‐nine athletes completed the Sport Emotion Questionnaire following a national softball competition. They also retrospectively reported their perceptions of how emotions influenced their attention, concentration, and sport performance. Excitement and happiness were more closely associated with concentration than anxiety, dejection, and anger. Although excitement demanded more attention than the negative emotions, the positive emotions were perceived as more likely to lead to a performance‐relevant focus and automatic physical movements, both of which were beneficial for concentration and performance. Emotional intensity increased these effects.     

Chronic effects of electrical stimulation of muscle on the fractionated components of audio response time

Six male volunteer subjects underwent five weeks (15 sessions) of electrical stimulation (ES) of the triceps brachii muscle (medial head), participated in a pretest, and five weekly post-treatment performance tests of an elbow extension task. Response time (RSP) was electronically fractionated into the two components of reaction time (RT): premotor reaction time (PMT) and motor reaction time (MT): and movement time (MVT) for 45 degrees of elbow extension. Acceleration characteristics of the movement were quantified via a piezoelectric accelerometer mounted on a specially-built mechanism that allowed the desired motion in a transverse plane. Statistical analysis did not indicate significant treatment effects on the criterion measures, however, a significant linear trend for MT and significant linear and quadratic trends for MVT were indicated. Neuromuscular adaptation to the passage of electric current through nerve and muscle tissue was indicated by a significant quadratic trend and significant differences between all weekly accumulative (treatment) voltages. An unexpected significant negative correlation between PMT and MT was considered cause for further study. The particular technique of ES administration, although it produced consistant changes in RSP components (Ward and Grabiner 1981) was not as effective as methods described by other investigators for increased human performance.     

The effects of attention on speech perception: an fMRI study

Focusing of attention to a specific speech source plays an important role in everyday speech perception. However, little is known of the neuronal substrates of focused attention in speech perception. Thus, the present study investigated the effects on neuronal activation of directed attention to auditory stimuli that differed in semantic content. Using an event-related fMRI protocol, single vowels, three-phoneme pseudowords and three- and four-phoneme real nouns and words were randomly presented to the subjects during four different instructional conditions. One condition was passive listening without any specific instructions of focusing of attention. The other conditions were attention focused on either the vowels, the pseudowords or the words. Thus, the acoustic stimulation was constant across conditions. The subjects were 13 healthy adults. Functional MRI was performed with a 1.5 T scanner, using an event-related design. During passive listening, there were significant activations bilaterally in the superior temporal gyrus. Instruction to attend to the pseudowords caused activation in middle temporal lobe areas, extending more anterior compared to the activations seen during passive listening. Instruction to attend to the vowel sounds caused an increase in activation in the superior/medial temporal lobe, with a leftward asymmetry. Instruction to attend to the words caused a leftward asymmetry, particularly in the middle and superior temporal gyri. It is concluded that attention plays a modulatory role in neuronal activation to speech sounds, producing specific activations to specific stimulus categories that may act to facilitate speech perception.     

The effects of fine motor movement and tactile stimulation on the math problem solving of students with attention problems

This study evaluated the effectiveness of fine motor physical activity with tactile stimulation during two conditions of math problem solving, visual and auditory. Eight 4th and 5th grade students with attention problems participated. Using an alternating treatments design, students solved as many math story problems as they could, presented on worksheets or verbally during two conditions, with and without tactile stimulation during 20 min. Motor behavior, recorded from videotape, and number of correctly completed word problems were measured. Results suggest that fine motor manipulation of a tactile stimulation object reduced excessive motor movement and increased task completion of students with attention problems.     

Influence of functional electrical stimulation training on premotor and motor reaction time.

This study was designed to investigate the influence of functional electrical stimulation on the improvement of reaction time and its fractionated components during learning an horizontal arm-sweep task. 62 subjects participated and were divided into control, stimulation, and trail/stimulation groups. Functional electrical stimulation was an effective method of improving total reaction time and its central component, premotor time.     

Effects of attention state on electrodermal activity during auditory stimulation of children.

During passive and active listening tasks electrodermal activity of 49 healthy school children was studied. The procedure included baseline recording, a passive listening task, instructions, and simple and discriminative active-listening tasks. On the passive task from Trials 1 to 10, habituation of the amplitude of the skin conductance response (SCR) occurred. Habituation of SCR amplitude did not occur during the active tasks. The children seemed to pay more attention during the active tasks than during the passive task, since the need to press the key is apt to require and may even increase general attention. As for temporal variables of SCR, the frequency of spontaneous SCRs showed a significant negative correlation with SCR latency and rise time. Reaction time exhibited a significant negative correlation with age. An increase in reaction time was found during the discriminative active-listening task over that for the simple active-listening task during the course of 10 trials. The younger children (6-8 yr.) seemed to require longer to pay attention than the older ones (10-12 yr.). Children seemed to pay more attention during the discriminative than during the simple active-listening task, since the need to press the key for discrimination should require and is likely to increase general attention.     

Grouping effects on spatial attention in visual search.

In visual search tasks, spatial attention selects the locations containing a target or a distractor with one of the target's features, implying that spatial attention is driven by target features (M.-S. Kim & K. R. Cave, 1995). The authors measured the effects of location-based grouping processes in visual search. In searches for a color-shape combination (conjunction search), spatial probes indicated that a cluster of same-color or same-shape elements surrounding the target were grouped and selected together. However, in searches for a shape target (feature search), evidence for grouping by an irrelevant feature dimension was weaker or nonexistent. Grouping processes aided search for a visual target by selecting groups of locations that shared a common feature, although there was little or no grouping by an irrelevant feature when the target was defined by a unique salient feature.     

Ageing effects on the attention demands of walking

Attention demands of walking were determined in six male and six female young adults (mean 26.3 yr) and 12 gender-matched healthy, active older adults (mean 71.1 yr) using a dual task procedure with a reaction time (RT) secondary task. In three conditions an auditory stimulus, a visual stimulus and both stimuli (auditory/visual) were presented. Relative to no-walking baselines, increased RT was found in all conditions revealing an attentional cost of normal walking. When participants traversed the laboratory walkway and also positioned one of their feet within a target area on the ground, attention demands were greater than in unconstrained walking. In the targeting task, RTs to the visual stimulus were longer than for the auditory stimulus due to the interference associated with viewing both the stimulus monitor and the foot-target. Older participants' RTs in the visual and auditory/visual conditions, but not in the auditory condition, were significantly longer than for the young group in both walking tasks but RTs for young and older adults were not different in no-walking baseline trials. Inspection of mean RT functions at time intervals following gait initiation (0-3000 ms from the first step) suggested a fluctuating attentional cost of walking with increased demands associated with contingencies requiring step length regulation. The findings have applied significance in demonstrating the possibility of increased falls and pedestrian accident risk in older individuals in dual task situations such as road crossing.     

Task- and location-switching effects on visual attention

In two experiments, we examined the effects of task and location switching on the accuracy of reporting target characters in an attentional blink (AB) paradigm. Single-character streams were presented at a rate of 100 msec per character in Experiment 1, and successive pairs of characters on either side of fixation were presented in Experiment 2. On each trial, two targets appeared that were either white letters or black digits embedded in a stream of black letter distractors, and they were separated by between zero and five items in the stream (lags 1-6). Experiment 1 showed that report of the first target was least accurate if it immediately preceded the second target and if the two targets were either both letters or both digits (task repetition cost). Report of the second target was least accurate if one or two distractors intervened between the two targets (the U-shaped AB lag effect) and if one target was a letter and the other a digit (task switch cost). Experiment 2 added location uncertainty as a factor and showed similar effects as Experiment 1, with one exception. Lag 1 sparing (the preserved accuracy in reporting the second of two targets if the second immediately follows the first) was completely eliminated when the task required attention switching across locations. Two-way additive effects were found between task switching and location switching in the AB paradigm. These results suggests separate loci for their attentional effects. It is likely that the AB deficit is due mainly to central memory limitations, whereas location-switching costs occur at early visual levels. Task-switching costs occur at an intermediate visual level, since the present task switch involved encoding differences without changes in stimulus-response mapping rules (i.e., the task was character identification for both letters and digits).     

Method of stimulation, mouth movements, concentration, and viscosity: effects on the degree of taste adaptation

Although sensory adaptation, the gradual loss of sensation during prolonged stimulation, has been demonstrated in laboratory taste experiments, a comparable loss of taste intensity is not experienced in real-life eating situations. This discrepancy may be due to differences in the proximal stimuli or to differences in the ways the taste receptors are stimulated. In two experiments, the effects of four potentially relevant variables were investigated: stimulus intensity, stimulus viscosity, mouth movements, and presentation method. During the initial seconds of stimulation, adaptation to the weakest of the two solutions was faster. Although more viscous stimuli were less sweet, viscosity as such did not affect adaptation rate, nor did mouth movements. Among the three presentation methods, a sucrose-soaked filter paper on the tongue produced more adaptation than either sipping the solution or flowing it over the tongue. This suggests that even mouth movements far more subtle than those still present in the no-movement condition of a sip-and-spit experiment can disrupt the adaptation process.     

Aversive and attractive properties of electrical stimulation for Paramecium caudatum.

Although there are data to show that mild electrical stimulation from a cathode source can serve as positive or attractive stimulus for paramecia, the properties of anode stimulation have not been clear. This research gives evidence to support the previously reported positive properties of cathode stimulation but showed that anode stimulation has opposite (negative or aversive) properties.     

Detection by the guinea pig of acoustic stimulation and of electrical stimulation of the brain

A threshold procedure using operant behavioral techniques with positive reinforcement was developed after initial efforts with avoidance behavioral procedures proved unsatisfactory. In the first of three experiments the operant threshold procedure was tested by determining masked auditory thresholds for trains of clicks. In a second experiment, similar techniques were used to measure thresholds for electrical stimulation of the brain. The last experiment, again an auditory problem, involved a determination of the absolute thresholds for trains of short noise bursts as a function of the time between bursts. Middle ear malfunction proved to be a more severe problem than had been anticipated on the basis of reports in the literature. The threshold procedure, however, seems to be adequate for determination of absolute or masked thresholds with auditory or electrical stimuli.