Hiroshi Maeoka

Influence of transcranial direct current stimulation of the dorsolateral prefrontal cortex on pain related emotions: a study using electroencephalographic power spectrum analysis.

Pain is a multidimensional experience with sensory-discriminative, cognitive-evaluative and affective-motivational components. Emotional factors such as unpleasantness or anxiety are known to have influence on pain in humans. The aim of this single-blinded, cross over study was to evaluate the effects of transcranial direct current stimulation (tDCS) on emotional aspects of pain in pain alleviation. Fifteen subjects (5 females, 10 males) volunteered to participate in this study. In an oddball paradigm, three categories of 20 pictures (unpleasant, neutral, and pleasant) served as rare target pictures from the International Affective Picture System (IAPS). The power of the delta (1-4 Hz), theta (4-8 Hz), alpha (8-12 Hz), beta (12-25 Hz), and gamma (30-40 Hz) frequency bands in the three categories were measured using electroencephalography during an oddball paradigm at pre- and post-anodal or sham tDCS above the left dorsolateral prefrontal cortex (DLPFC). Results showed that the beta band power was significantly increased, and the alpha band power was significantly decreased during unpleasant pictures after anodal tDCS compared with sham tDCS. Furthermore, regarding unpleasant pictures, subjective reports of Self Assessment Manikin (SAM) for emotional valence after anodal tDCS showed a significant decrease of unpleasantness. Therefore, emotional aspects of pain may be effectively alleviated by tDCS of the left DLPFC as was shown not only by subjective evaluation, but also by objective observation of cerebral neural activity. This processing may be mediated by facilitation of the descending pain inhibitory system through enhancing neural activity of the left DLPFC.

Enhancement of precise hand movement by transcranial direct current stimulation.

The effect of transcranial direct current stimulation (tDCS) on the precise nondominant hand movement was investigated by applying anodal stimulation over the right primary motor cortex. We recruited 14 healthy participants for this single-blind, sham-controlled crossover trial. A circle-drawing task was performed before, immediately after, and at 30 min after 20 min of 1 mA anodal or sham tDCS. Anodal tDCS, compared with sham stimulation, significantly improved the circle-drawing task compared with sham stimulation. The deviation area and path length of the task were significantly decreased after anodal tDCS application and were further enhanced at 30 min after stimulation. These results suggest that anodal tDCS over the primary motor cortex enhances the precise movement of the nondominant hand for 30 min in healthy participants.

Effects of plantar perception training on standing posture balance in the old old and the very old living in nursing facilities: a randomized controlled trial

Objective: To determine whether plantar perception training using a hardness discrimination task efficiently improves stabilization of standing posture balance in the old old as well as the very old. Design: A randomized two-group parallel controlled trial. Setting: Nursing homes. Participants: Forty-six elderly persons 75 years of age or older living in nursing facilities were randomly assigned evenly to either an intervention or a control group. Intervention: The intervention group was given a task to discriminate hardness differences while standing on foam rubber of different levels of hardness, while the control group was given the task to simply remain standing on foam rubber. The tasks were imposed for 10 successive days. Outcome measures: Outcome assessment was made by determinations of centre-of-gravity sway in the standing position and the Functional Reach Test. Results: Planter perception was significantly improved and centre-of-gravity sway in the standing position was also significantly reduced in the intervention group after the intervention. In the control group, however, there were no significant changes in perception or in sway (P < 0.01) There was a significant difference in the Functional Reach Test values between the two groups: an increment of 12.3 ± 10.1 cm in the intervention group vs. 2.3 ± 5.8 cm in the control group (P < 0.001). Conclusion: These results suggested that plantar perception exercises might efficiently stabilize standing postural balance in the old old as well as the very old.

The influence of repeated pain stimulation on the emotional aspect of pain: a preliminary study in healthy volunteers

Purpose Pain is a multidimensional experience with sensory-discriminative, cognitive-evaluative, and affective-motivational components. Emotional factors, such as unpleasantness or anxiety, are known to have influence on pain in humans. Repeated painful stimulation has been reported to reduce subjective pain intensity. Nevertheless, there is little evidence of the influence of such stimulation on the emotional factors of pain. The aim of this study was to evaluate the influence of repeated painful stimulation on the experience of unpleasantness and anxiety. Materials and methods Eight subjects (six females, two males) volunteered to participate in this study. Subjects received repeated painful stimulation for 3 consecutive days each instance lasting 6 seconds, 60 times per day, on the medial side of the forearm of the nondominant hand. We examined the following items to evaluate changes of responses to painful stimulation: pain thresholds, pain tolerance levels, pain intensities, unpleasantness, and anxiety. Furthermore, pain thresholds and pain tolerance levels were compared between different sites on the ipsilateral and contralateral forearms. Results No immediate or chronological changes in pain thresholds or pain tolerance levels were observed. Pain intensities were reduced significantly over the 3-day experimental period (P<0.05). On the other hand, there was no great change in unpleasantness during the 3-day period. Anxiety was increased significantly after the painful stimulation compared with that without the painful stimulation and before day 1 of the stimulation (P<0.05). Conclusion These results suggest that repeated painful stimulation may result in habituation to pain intensities but not habituation to emotional factors.

Incongruence between Verbal and Non-Verbal Information Enhances the Late Positive Potential.

Smooth social communication consists of both verbal and non-verbal information. However, when presented with incongruence between verbal information and nonverbal information, the relationship between an individual judging trustworthiness in those who present the verbal-nonverbal incongruence and the brain activities observed during judgment for trustworthiness are not clear. In the present study, we attempted to identify the impact of incongruencies between verbal information and facial expression on the value of trustworthiness and brain activity using event-related potentials (ERP). Combinations of verbal information [positive/negative] and facial expressions [smile/angry] expressions were presented randomly on a computer screen to 17 healthy volunteers. The value of trustworthiness of the presented facial expression was evaluated by the amount of donation offered by the observer to the person depicted on the computer screen. In addition, the time required to judge the value of trustworthiness was recorded for each trial. Using electroencephalography, ERP were obtained by averaging the wave patterns recorded while the participants judged the value of trustworthiness. The amount of donation offered was significantly lower when the verbal information and facial expression were incongruent, particularly for [negative × smile]. The amplitude of the early posterior negativity (EPN) at the temporal lobe showed no significant difference between all conditions. However, the amplitude of the late positive potential (LPP) at the parietal electrodes for the incongruent condition [negative × smile] was higher than that for the congruent condition [positive × smile]. These results suggest that the LPP amplitude observed from the parietal cortex is involved in the processing of incongruence between verbal information and facial expression.

Neurorehabilitation of Chronic Pain: Relationships among Pain, Motion, and Perception

Chronic pain emerges not only because of the injury of peripheral organs or a plastic change in spinal nerves, but also because of plasticity in the brain [1]. Therefore, the development of interventions dedicated to the rehabilitation of pain must occur via approaches that cause changes in the brain, instead of approaches that treat only peripheral organs. In particular, pain is composed of three facets, including a sensory aspect, a cognitive aspect, and an emotional aspect [2]. Thus, the rehabilitation of the brain represents an approach to that will address the cognitive and emotional aspects in particular.