Takamichi Taniguchi

Individual classification of ADHD children by right prefrontal hemodynamic responses during a go/no-go task as assessed by fNIRS

While a growing body of neurocognitive research has explored the neural substrates associated with attention deficit hyperactive disorder (ADHD), an objective biomarker for diagnosis has not been established. The advent of functional near-infrared spectroscopy (fNIRS), which is a noninvasive and unrestrictive method of functional neuroimaging, raised the possibility of introducing functional neuroimaging diagnosis in young ADHD children. Previously, our fNIRS-based measurements successfully visualized the hypoactivation pattern in the right prefrontal cortex during a go/no-go task in ADHD children compared with typically developing control children at a group level. The current study aimed to explore a method of individual differentiation between ADHD and typically developing control children using multichannel fNIRS, emphasizing how spatial distribution and amplitude of hemodynamic response are associated with inhibition-related right prefrontal dysfunction. Thirty ADHD and thirty typically developing control children underwent a go/no-go task, and their cortical hemodynamics were assessed using fNIRS. We explored specific regions of interest (ROIs) and cut-off amplitudes for cortical activation to distinguish ADHD children from control children. The ROI located on the border of inferior and middle frontal gyri yielded the most accurate discrimination. Furthermore, we adapted well-formed formulae for the constituent channels of the optimized ROI, leading to improved classification accuracy with an area under the curve value of 85% and with 90% sensitivity. Thus, the right prefrontal hypoactivation assessed by fNIRS would serve as a potentially effective biomarker for classifying ADHD children at the individual level.

Acute neuropharmacological effects of atomoxetine on inhibitory control in ADHD children: A fNIRS study

The object of the current study is to explore the neural substrate for effects of atomoxetine (ATX) on inhibitory control in school-aged children with attention deficit hyperactivity disorder (ADHD) using functional near-infrared spectroscopy (fNIRS). We monitored the oxy-hemoglobin signal changes of sixteen ADHD children (6–14 years old) performing a go/no-go task before and 1.5 h after ATX or placebo administration, in a randomized, double-blind, placebo-controlled, crossover design. Sixteen age- and gender-matched normal controls without ATX administration were also monitored. In the control subjects, the go/no-go task recruited the right inferior and middle prefrontal gyri (IFG/MFG), and this activation was absent in pre-medicated ADHD children. The reduction of right IFG/MFG activation was acutely normalized after ATX administration but not placebo administration in ADHD children. These results are reminiscent of the neuropharmacological effects of methylphenidate to up-regulate reduced right IFG/MFG function in ADHD children during inhibitory tasks. As with methylphenidate, activation in the IFG/MFG could serve as an objective neuro-functional biomarker to indicate the effects of ATX on inhibitory control in ADHD children. This promising technique will enhance early clinical diagnosis and treatment of ADHD in children, especially in those with a hyperactivity/impulsivity phenotype.

Neuropharmacological effect of atomoxetine on attention network in children with attention deficit hyperactivity disorder during oddball paradigms as assessed using functional near-infrared spectroscopy.

Abstract. The current study aimed to explore the neural substrate for atomoxetine effects on attentional control in school-aged children with attention deficit hyperactivity disorder (ADHD) using functional near-infrared spectroscopy (fNIRS), which can be applied to young children with ADHD more easily than conventional neuroimaging modalities. Using fNIRS, we monitored the oxy-hemoglobin signal changes of 15 ADHD children (6 to 14 years old) performing an oddball task before and 1.5 h after atomoxetine or placebo administration, in a randomized, double-blind, placebo-controlled, crossover design. Fifteen age-, gender-, and intelligence quotient-matched normal controls without atomoxetine administration were also monitored. In the control subjects, the oddball task recruited the right prefrontal and inferior parietal cortices. The right prefrontal and parietal activation was normalized after atomoxetine administration in ADHD children. This was in contrast to our previous study using a similar protocol showing methylphenidate-induced normalization of only the right prefrontal function. fNIRS allows the detection of differential neuropharmacological profiles of both substances in the attentional network: the neuropharmacological effects of atomoxetine to upregulate the noradrenergic system reflected in the right prefrontal and inferior parietal activations and those of methylphenidate to upregulate the dopamine system reflected in the prefrontal cortex activation.

Reduction in Cortical Activation in the Sensorimotor Cortex during Motor Skill Learning of a Pursuit Rotor Task: A Functional Near-Infrared Spectroscopy Study

To investigate the cerebral mechanisms underlying learning of motor skills, we assessed serial changes of brain activation patterns during a pursuit rotor (PR) task in 12 right-handed healthy subjects using functional near-infrared spectroscopy (fNIRS). The subjects performed the task with their right hand for 15-s, alternated with a 30-s rest period, for 18 repetitions (cycles 1 to 18). Gains in motor skill were evaluated by recording the time for which the stylus remained on the target. Performance improved with repetition of the task. Task-related increases of oxygenated hemoglobin (oxy-Hb) were observed around the predicted location of the sensorimotor cortices on both hemispheres. The increased oxy-Hb levels appeared to reduce with repetition of the task in the channels covering the left sensorimotor area. Furthermore, there was a significant correlation between PR task performance gain and the oxy-Hb signal in the left and right sensorimotor areas. Our results suggest that cortical activation in the sensorimotor cortex reflects changes in a number of factors including sensory feedback processing, correct motor commands, and perceptual or cognitive function during learning of a PR task. Therefore, changes in contralateral sensorimotor cortical activation may serve as a motor sequence learning biomarker for rehabilitation purposes or the prediction of recovery.

Cholecystokinin and prostaglandins inhibit responses of vagal afferent activity to systemic administration of nicotine in anesthetized rats

Systemic administration of nicotine suppresses food intake. Since gastric vagal afferents convey satiation signals to the hypothalamus in response to cholecystokinin, we investigated the possibility that nicotine increases afferent activity of the gastric vagal nerves by stimulating release of cholecystokinin. Furthermore, involvement of prostaglandins in the responses of gastric vagal afferents to nicotine was also investigated because prostaglandins stimulate gastric vagal afferent activity. Experiments were performed in urethane-anesthetized rats. Intravenous administration of 300 microg/kg but not 3 or 30 microg/kg nicotine produced biphasic increases in afferent activity. The maximum of the first increase was reached within 1 min, while that of the second increase was reached 10-15 min after nicotine injection. Pretreatment with MK-329, a type A cholecystokinin receptor antagonist, significantly reduced the first increase, without influencing the second increase. Pretreatment with indomethacin, a cyclooxygenase inhibitor, further reduced the first increase and abolished the second increase. These results suggest that nicotine can exert its anorexic effect via an increase in gastric vagal afferent activity which is caused by enhanced release of both cholecystokinin and prostaglandins.

The effects of tool holding during motor imagery: A mental chronometry study

Motor imagery is useful for motor rehabilitation. Using mental chronometry (MC), this study assessed the effectiveness of tool holding on imagination/execution (I/E) time ratios during motor imagery tasks. Forty-eight healthy right-handed adults performed two tasks: holding a pen and not holding a pen while imagining the movement involved in writing the letters of the alphabet from A through J. When using their preferred right hands, the I/E time ratios were significantly lower when imagining writing while actually holding the pen than when not. The I/E time ratios were similar between the two conditions when the participants used their non-preferred left hands. These results suggest that the use of a tool can impact brain function. Further, tool use may affect the rehabilitation process, as tools are incorporated into the body schema during motor imagery of an automated tool-use task. This kind of test does not require strict motion restriction as do more cumbersome methodologies, such as brain imaging. As a result, MC can be used with patients in a sitting position in a great variety of environments where rehabilitation is widely practiced. Correspondence to: Tsubasa Oikawa, RPT, MS, Nishinasuno Marronnier Visiting Nursing Station, 537-3 Iguchi, Nasushiobara, Tochigi 329-2763, Japan, Tel: +81-287-37-6322; Fax: +81-287-39-3305; E-mail: t.oikawa@iuhw.ac.jp

Variation factors of stereotypical hand movements in subjects with Rett syndrome

ABSTRACT Background: Stereotypical hand movements have been observed in most individuals diagnosed with Rett syndrome. Objectives: To investigate factors that increase or decrease hand stereotypies in individuals with Rett syndrome. Methods: A questionnaire regarding hand stereotypies or purposeful hand behaviours was sent to 1016 schools for special needs education and 204 facilities in Japan. Results: Information was acquired from 216 cases (3–53 years old) with Rett syndrome; 81.9% and 87.6% of individuals had factors that increased and decreased stereotypical hand movements, respectively. Stereotypies were mainly increased by displeasure (63.8%) or pleasure (48.5%), and decreased by somnolence (43.5%), pleasure (30.0%), or food (24.1%). Conclusion: Emotion was the main factor increasing stereotypical hand movements, whereas there were a large number of factors that decreased these movements. The factors that decrease stereotypies could be useful to prevent the skin problems or joint contracture observed in patients with Rett syndrome.

The effects of tool holding on body schema during motor imagery: a near-infrared spectroscopy study

[Purpose] The purpose of this study is to assess the influence of tool holding on brain activities during motor imagery in two tasks: imagining the movement of writing the alphabet while holding a pen and without holding the pen. [Subjects and Methods] Eleven healthy right-handed adults performed two tasks, holding a pen and not holding the pen during imagining the movement of writing the alphabet using a pen. Regions of targets were Brodmann areas 6 which were a motor-related region, 44/45 and 39/40 which taken on the role of forming the body schema. Change of the oxygenation state of hemoglobin associated with brain activity were acquired using a near-infrared spectroscopy. [Results] When using their dominant right hands, task-related increases in oxy-Hb were prominent in Brodmann areas 44/45 and 39/40 when imagining writing while actually holding the pen than when not. When using the non-dominant left hands, there were no significant differences between the two conditions in the same areas. [Conclusion] These results suggest that the tool held can be incorporated into the body schema in the motor imagery of an automated tool use task. Therefore, tool holding during motor imagery might be more effectively influence during rehabilitation.

Comparison of cortical activation in an upper limb added-purpose task versus a single-purpose task: a near-infrared spectroscopy study.

[Purpose] The purpose of this study was to compare prefrontal activations during an added-purpose task with those during a single-purpose task using functional near-infrared spectroscopy. [Subjects] Six healthy right-handed adults were included in this study. [Methods] The participants were instructed to complete both added-purpose and single-purpose activities separately with each hand. The near-infrared spectroscopy probes were placed on the scalp overlying the prefrontal cortex, according to the International 10–20 system (Fz). Changes in the oxygenated hemoglobin and deoxygenated hemoglobin concentrations in the prefrontal cortex were measured during performance of the activities. We then compared the number of activation channels with significant increase in oxygenated hemoglobin, during added-purpose activity to single-purpose activity using both hands separately. [Results] A greater number of widespread activations were observed in the prefrontal cortex during the added-purpose task than during the single-purpose task. These results were noted with both right and left hands. [Conclusion] According to our findings, added-purpose activity can bring about more activation in the prefrontal cortex, which may provide occupational therapists with effective guides in therapeutic practice.

Fixation Duration Changes in Rett Syndrome after Habilitation Intervention

The purpose of the present study was to examine the effect of longitudinal habilitation intervention by care staff upon fixation duration in an individual with Rett syndrome using an eye-tracking system. The participant was a 22- year-old woman suffering from Rett syndrome. She could watch television but could not communicate verbally or execute purposeful upper extremity movements. We evaluated whether she could change the pattern of an eye gaze target by learning with the intervention of care staff. Fixation duration to the experimental targets was significantly changed after intervention for 3 weeks compared with before intervention. We consider that this improvement occurred because the patient learned the experimental tasks. Our findings suggest that individuals with Rett syndrome can acquire various abilities using eye gaze. Eye-tracking was shown to be a feasible method for visualizing the learning abilities of individuals with Rett syndrome and judging the outcome of habilitation intervention.