Whole-body vibration improves cognitive functions of an adult with ADHD

Abstract

Adult attention deficit hyperactivity disorder (ADHD) is associated with a variety of cognitive impairments, which were shown to affect academic achievement and quality of life. Current treatment strategies, such as stimulant drug treatment, were demonstrated to effectively improve cognitive functions of patients with ADHD. However, most treatment strategies are associated with a number of disadvantages in a considerable proportion of patients, such as unsatisfactory effects, adverse clinical side effects or high financial costs. In order to address limitations of current treatment strategies, whole-body vibration (WBV) might represent a novel approach to treat cognitive dysfunctions of patients with ADHD. WBV refers to the exposure of the whole body of an individual to vibration and was found to affect physiology and cognition. In the present study, WBV was applied on 10 consecutive days to an adult diagnosed with ADHD. Neuropsychological assessments were performed repeatedly at three different times, i.e., the day before the start of the treatment, on the day following completion of treatment and 14 days after the treatment have been completed (follow-up). An improved neuropsychological test performance following WBV treatment points to the high clinical value of WBV in treating patients with neuropsychological impairments such as ADHD.

Appendix

Alertness

In the task for tonic alertness (Zimmermann and Fimm 2002), participants were asked to respond as quickly as possible by pressing a button when a visual stimulus (a cross of about 1.2 by 1.8 cm) appeared on a computer screen. A total of 40 stimuli were undertaken. The mean reaction time and the variability of reaction time were calculated as measures of tonic alertness.

Distractibility

In the distractibility task (Incompatibility; Zimmermann and Fimm 2002), arrows pointing to the left or right were presented briefly on the left or right side of the fixation point in the center of the computer screen. The participants were requested to press a response button as quickly as possible on the side indicated by the direction of the arrow, independent of the position of the arrow. The number of errors (omission plus commission) was calculated as a measure of distractibility as the capacity to reject irrelevant information.

Divided attention

The divided attention task (Zimmermann and Fimm 2002) required participants to concentrate simultaneously on a visual and an acoustic task presented by a computer. In the visual task, a series of matrices [consisting of a regular array of 16 dots and crosses (4 × 4)] was presented in the center of the computer screen. The participants were asked to press the response button as quickly as possible whenever the crosses form the corners of a square. In the acoustic task, the participants had to listen to a continuous sequence of alternating high and low sounds. The participants were requested to press the response button as quickly as possible when irregularities of the sequence occurred. The number of errors (omission plus commission) was calculated as a measure of divided attention.

Vigilance

In the task for vigilance (Zimmermann and Fimm 2002), a horizontal bar was presented at the center of a computer screen. The horizontal bar continuously moved upwards and downwards from the center for irregular distances. A target stimulus was defined if the distance for which the horizontal bar moved upwards was considerably larger than in the majority of other movements. The participants were requested to press a response button as quickly as possible when a target event occurred. A total of 2,800 stimuli (movements of the bar) were presented. The target rate was about one target stimulus per minute for a total of about 36 targets. The time intervals between target stimuli were irregular. The number of errors (omission plus commission) was calculated as a measure of vigilance. The task measured vigilance by requiring the participant to remain alert and ready to react to infrequently occurring target stimuli over a relatively long and unbroken period of time.

Flexibility

In the flexibility task (Zimmermann and Fimm 2002), participants were required to place each hand on a separate response button while viewing a computer screen, on which a letter and a digit number (of about 12 by 16 mm) were displayed simultaneously. The distance between the letter and the digit number was 5 cm. The participant was instructed to respond by alternately pressing the button that was on the same side of the screen as the letter and then pressing the button that was on the same side of the screen as the number (i.e., letter–number–letter–number). After each response, a new letter and number appeared, randomly assigned to either side of the screen. A total of 100 trials were presented. The number of errors (omission plus commission) was calculated as a measure of flexibility.

Working memory

The Digit Span Backward task, a subtest of the Wechsler Memory Scale (Wechsler 1987), was applied as measure of working memory. Series of numbers were read to the participants who were required to repeat the digits in the reversed order. The number of correctly repeated sequences was registered.

Divergent thinking

Divergent thinking was measured with a test for letter fluency [based on the Controlled Oral Word Association Test (Benton et al. 1989; Schmand et al. 2008)]. In this test, participants were asked to produce, within 1 min, as many different words as possible beginning with the same letter. This task was performed three times (three trials), each time with another letter for which words had to be produced. The total number of correctly produced words in all three trials was registered as a measure of letter fluency. Parallel versions of the test differed in the letters, which have been used (K–O–M; D–A–T; P–G–R).

Inhibition

Inhibition was measured with the Stroop Color-Word Interference task (Houx et al. 1993; Stroop 1935). The Stroop Color-Word Interference task consisted of two conditions. First, in the Color-Block condition, colored rectangles (rectangles printed in yellow, green, blue and red) were presented on a card, and the participants were required to name the color of the rectangles as fast as possible. Second, in the Color-Word Interference condition, color words (yellow, green, blue and red) were presented and printed in mismatching ink (e.g., red printed in blue ink). The participants were required to name the color of the words as fast as possible and to ignore the meaning of the printed word. Each condition consisted of the same number of stimuli. The time in seconds to complete each condition was registered.

Self-rated impairment of attention

The participants’ experienced problems of attention in the academic setting (i.e., studying and attending lectures) were measured with a sample of items taken from the Attention Questionnaire (Schepers 2007). Participants were presented with eleven statements describing problems of attention (e.g., “Thoughts interfere with my concentration when attending a lecture”) and were asked to indicate how often these problems currently occurred compared with a normal (“average”) state. The scale ranged from 1 (far less often than normal) to 5 (far more often than normal). The sum score of all items was calculated as a measure of self-rated impairment of attention.