Biomedical subjects

Hideki Ohira

Publications and source records attributed to Hideki Ohira.

At least 19 recordsLinked to original sources

PubMed2007

An ERP study on self-relevant object recognition.

We performed an event-related potential study to investigate the self-relevance effect in object recognition. Three stimulus categories were prepared: SELF (participant's own objects), FAMILIAR (disposable and public objects, defined as objects with less-self-relevant familiarity), and UNFAMILIAR (others' objects). The participants' task was to watch the stimuli passively. Results showed that left-lateralized N250 activity differentiated SELF and FAMILIAR from UNFAMILIAR, but SELF and FAMILIAR were not differentiated. In the later time-course, SELF was dissociated from FAMILIAR, indicating the self-relevance effect in object recognition at this stage. This activity did not show consistent lateralization, in contrast to previous studies reporting right lateralization in self-relevant face and name recognition. We concluded that in object recognition, self-relevance was processed by higher-order cognitive functions later than 300ms after stimulus onset.

Adult↗

PubMed2006

An electrophysiological comparison of recollection for emotional words using an exclusion recognition paradigm.

The positive-going shift of event-related potential (ERP) components that occur when recognizing emotional words has been thought to be due to valence effects on either recollection or familiarity. This study investigated the independent contributions of recollection and familiarity on recognition of emotional words in order to examine which is thus responsible for the greater magnitude of ERP components seen in response to recognition of emotional, as opposed to neutral words. ERPs were measured while participants completed an exclusion recognition task. In the test phase, participants were required to respond "old" only to target items, which were included in one of two lists that were presented in the study phase. They were also asked to respond "new" to distracters and non-target items that were in the other previously presented list. "Old" responses to targets and non-targets were contrasted with an ERP analysis. Results suggested that the late positivity reflected recollection. The magnitude of this positivity, elicited around the left parietal area, was greater for negative stimuli compared to neutral and positive stimuli. The findings of the present study suggested that enhanced recollection of negative words may contribute to increased magnitudes of components such as the LPC. The emotional valence of words may have separate behavioral and electrophysiological effects on recollection and familiarity.

Adult↗

PubMed2006

L-Theanine reduces psychological and physiological stress responses.

L-Theanine is an amino acid contained in green tea leaves which is known to block the binding of L-glutamic acid to glutamate receptors in the brain. Because the characteristics of L-Theanine suggest that it may influence psychological and physiological states under stress, the present study examined these possible effects in a laboratory setting using a mental arithmetic task as an acute stressor. Twelve participants underwent four separate trials: one in which they took L-Theanine at the start of an experimental procedure, one in which they took L-Theanine midway, and two control trials in which they either took a placebo or nothing. The experimental sessions were performed by double-blind, and the order of them was counterbalanced. The results showed that L-Theanine intake resulted in a reduction in the heart rate (HR) and salivary immunoglobulin A (s-IgA) responses to an acute stress task relative to the placebo control condition. Moreover, analyses of heart rate variability indicated that the reductions in HR and s-IgA were likely attributable to an attenuation of sympathetic nervous activation. Thus, it was suggested that the oral intake of L-Theanine could cause anti-stress effects via the inhibition of cortical neuron excitation.

Acute Disease↗

PubMed2006

Gamma band activity and its synchronization reflect the dysfunctional emotional processing in alexithymic persons.

In the present study, we investigated the gamma band response and its phase synchrony between electrodes in alexithymia, which is characterized by a disability in identifying and describing feelings. Individuals with high and low alexithymia scores were selected according to the scores on the 20-item Toronto Alexithymia Scale. EEG was recorded from alexithymic and nonalexithymic persons viewing emotionally negative or neutral stimuli. Nonalexithymic persons exhibited increased gamma band power and phase synchronization at the 400-450-ms time window when processing emotionally negative stimuli. Neither enhanced gamma band power nor phase synchronization was observed in alexithymic persons in the negative emotion condition. These results suggest that gamma band activity reflects emotional processing, and alexithymic persons may have a deficit in communication between brain regions or in the utilization of memory or emotional information during the processing of emotional stimuli.

Adult↗

PubMed2005

Association of neural and physiological responses during voluntary emotion suppression.

Recent neuroimaging studies have shown that several prefrontal regions play critical roles in inhibiting activation of limbic regions during voluntary emotion regulation. The present study aimed to confirm prior findings and to extend them by identifying the frontal neural circuitry associated with regulation of peripheral physiological responses during voluntary emotion suppression. Ten healthy female subjects were presented with affectively positive, neutral, and negative pictures in each of an Attending and Suppression task. Regional cerebral blood-flow changes were measured using 15O-water positron emission tomography, and autonomic (heart rate: HR, skin conductance response: SCR) and endocrine (adrenocorticotropic hormone: ACTH) indices were measured during both tasks. The left amygdala and the right anterior temporal pole were activated during the Attending task, whereas activation was observed in the left lateral prefrontal cortex (LPFC), including the adjacent medial prefrontal cortex (MPFC), and medial orbitofrontal cortex (MOFC) during the Suppression task. In the Attending task, activation in the amygdala and MOFC positively correlated with magnitudes of the SCR and ACTH responses. Emotion suppression elicited enhancement of SCR and the strength of the effect positively correlated with activation in the MOFC. These results suggest that the MOFC plays a pivotal role in top-down regulation of peripheral physiological responses accompanying emotional experiences.

Adrenocorticotropic Hormone↗

PubMed2005

Immune, endocrine and cardiovascular responses to controllable and uncontrollable acute stress.

This study, using a triadic-yoked design, clarified the effects of controllability of acute stress on responses of immune, cardiovascular (heart rate and blood pressure), and cortisol activities. Forty-three women in their follicular phase completed a mental arithmetic task as a stressor in which controllability was manipulated by correct or yoked-bogus feedback. The task decreased proportions of CD3+ T cells, CD4+ T cells, and CD19+ B cells, whereas it increased the numbers of white blood cells, lymphocytes, natural killer (NK) cells, and NK cell activity (NKCA). Our main hypothesis that greater immune and cardiovascular responses to the task would be obtained under the uncontrollable condition than under the controllable condition was not supported. However, the uncontrollable stress condition, but not the controllable situation, led to higher correlations between heart rate or blood pressure, and various immune parameters. On the other hand, parameters of heart rate variability reflecting sympathetic and parasympathetic activities showed significant correlations only with NKCA. These results suggest that immune responses were most directly associated with cardiovascular activities under the uncontrollable condition.

Acute Disease↗

PubMed2005

Neural evidence of effects of emotional valence on word recognition.

There are no clear reports of electrophysiological evidence of the facilitating effect of negative valence on word recognition. However, behavioral psychological studies have suggested that negative words can be recognized more accurately than positive and neutral words. This study aimed to examine whether, and if so how, the valence of words could influence accuracy and event-related potentials (ERPs) in a recognition task. ERPs were recorded from 20 healthy subjects during performance of a word recognition task. We found a behavioral advantage in discriminability between old and new items for negative words. As for ERPs, the positive-going shift was evident for correct responses to targets in late latency at midline and left centro-parietal sites. Additionally, the magnitude of this component was greatest for negative targets, next for positive targets, and least for neutral targets. The findings offer support for the idea that negative content greatly accelerates recognition memory compared to positive and neutral words.

Adolescent↗

PubMed2005

Effects of value and reward magnitude on feedback negativity and P300.

Feedback negativity is a negative component of the event-related brain potential observed 250-300 ms after feedback stimuli. The present study investigated the effects of value (correct or incorrect) and reward magnitude (no, small or large) on feedback negativity and P300. Feedback negativity was larger after incorrect feedback than after correct feedback, irrespective of reward magnitude. In contrast, P300 amplitude increased with reward magnitude, irrespective of value. The amplitude of feedback negativity was correlated with a trait score of negative affect and not positive affect, whereas P300 amplitude was correlated with positive affect and not negative affect. These results suggest that value and reward magnitude are processed separately in the brain.

Adult↗

PubMed2005

Dissociation of conscious and unconscious repetition priming effect on event-related potentials.

Although the neural basis of the unconscious priming effect has previously been investigated, the results of these studies have possibly been contaminated by a conscious priming effect. The aim of the present study was to dissociate the effects of conscious and unconscious priming on event-related potential (ERP) by using the process-dissociation procedure. A prime word was presented briefly, followed by a word-stem, in each trial. Under the inclusion condition, subjects were instructed to complete the word-stem using the prime word, while under the exclusion condition subjects were asked to complete the word-stem with a word not seen as prime. The behavioral priming effect was obtained under both conditions, indicating that the prime words were processed unconsciously and influenced the word-stem completion task. We found that two ERP components were affected by repetition priming. First, the N400 amplitude was decreased by word repetition under the inclusion condition, but not under the exclusion condition. This result suggests that N400 would reflect conscious lexical processing, but not unconscious lexical activation. Second, the negativity at left front lateral region was enhanced by word repetition under the exclusion condition. We discuss this finding herein in relation to the activity of the left inferior prefrontal cortex with regard to word semantic processing.

Adolescent↗

PubMed2005

Temporal variation of acute stress responses in sympathetic nervous and immune systems.

Sympathetic nervous activity plays a prominent role in acute stress responses in the immune system, enhancement of innate immunity and suppression of specific immunity. The present study was conducted to examine the temporal characteristics of such immune responses to acute stress and to determine their association with sympathetic activity in detail. For this purpose, 15 female undergraduates engaged in a continuous mental arithmetic task for 14 min, and we collected their blood samples for immune indices (CD3+ T cells, CD4+ T cells, NK cells) each 3 min during the task and saliva samples before and after the task. Our results showed that the proportion of Natural Killer cells (NK cells) increased even 2 min after initiation of the task, whereas proportions of CD3+ and CD4+ lymphocytes decreased 8 min after initiation of the task. Moreover, we found significant correlations between cardiovascular activity and the variations of immune indices.

Adult↗

PubMed2004

Functional association of the amygdala and ventral prefrontal cortex during cognitive evaluation of facial expressions primed by masked angry faces: an event-related fMRI study.

The present study examined the functional association of the amygdala and right ventral prefrontal cortex (PFC) during cognitive evaluation of facial expressions. A situation was created where emotional valence of the stimuli was unconsciously manipulated by using subliminal affective priming. Twelve healthy volunteers were asked to evaluate the facial expressions of a target face (500-ms duration) such as "anger", "neutral", or "happy". All target faces expressed relatively weak anger. Just before the presentation of the target face, a prime of three conditions of 35-ms duration, angry face, neutral face, and white blank was presented. The subjects could not consciously identify the primes in this procedure. Activity in the right amygdala was greater with subliminal presentation of the angry prime compared with subliminal presentation of a neutral face or white-blank stimuli. Most importantly, the degree of activation of the right amygdala was negatively correlated with that of the right ventral PFC only with the anger prime. Furthermore, activation of the amygdala was positively correlated with rate of judgment when the subjects recognized anger in the target faces. These results are discussed in terms of the functional association between the right PFC and the amygdala and its influence on cognitive processing.

Adult↗

PubMed2004

Reactivity of immune, endocrine and cardiovascular parameters to active and passive acute stress.

This study clarified associations among immune, autonomic, and endocrine activities during mental arithmetic and cold pressor stress tasks in 26 women in the follicular phase. Both tasks decreased CD3+ T cells, CD4+ T cells, and CD19+ B cells, whereas they increased lymphocytes, granulocytes, NK cells, and NK cell activity (NKCA). The mental arithmetic task had a greater impact than the cold pressor task on changes in CD3+ T cells and in NK cells. Cardiovascular reactivity to active stress was associated with increased NK cells and decreased CD3+ T cells. Reduced cortisol levels during passive stress were associated with decreased CD19+ B cells and with increased NK cells. The merits of this study are that it controlled the following factors. Perceived stress during the two tasks was matched; both tasks lasted long enough to elicit high-magnitude responses; and the length of the intervening rest period minimized probable carryover effects between tasks.

Adult↗

PubMed2004

Eyeblink activity as an index of cognitive processing: temporal distribution of eyeblinks as an indicator of expectancy in semantic priming.

Eyeblink activity was examined as a psychophysiological index of cognitive processing during a typical semantic priming task. To examine the expectancy-induced effects, the proportion of semantically related pairs was controlled. 8 undergraduates engaged in a lexical decision task for target words. Each condition differed in target type (Semantically Related with prime vs Unrelated vs Nonword) and proporion of Semantically Related pairs (High vs Low). As a result, the temporal distribution of blinks was clearly influenced by the semantic priming effect. The peak of blink bursts, which is correlated with the end of cognitive processing, occurred the fastest in the semantically Related and High proportion condition. While blink latency showed larger individual differences, the temporal distribution of blinks was suggested as a more efficient index of cognitive processing.

Adult↗

PubMed2004

Effects of expression and inhibition of negative emotions on health, mood states, and salivary secretory immunoglobulin A in Japanese mildly depressed undergraduates.

Previous studies have indicated that expression of negative emotions facilitates mental and physical health and inhibition of negative emotions increases susceptibility to illness. This study was conducted to examine whether those findings can be expanded to populations with non-Western cultural backgrounds. Specifically, we explored effects of expression and inhibition of negative emotions on health, mood states, and mucosal immune function in mildly depressed Japanese individuals. 16 depressed and 16 nondepressed female undergraduates were required either to write about their unpleasant experiences and superficial topics or to suppress any emotional responses and thoughts about them. Secretory immunoglobulin A (s-IgA) in saliva and psychological indices were measured at an experimental session and at a follow-up 1 wk. later. Beneficial effects of expression of emotions on subjective health were indicated in the nondepressed group, whereas harmful effects of inhibition on subjective health were shown in the depressed group. Emotional expression by writing improved mood states both in the depressed and nondepressed groups but induced elevation of salivary s-IgA only in the depressed group.

Adolescent↗

PubMed2004

Social support and salivary secretory immunoglobulin A response in women to stress of making a public speech.

Acute experimental stressors transiently increase volume of secretory immunoglobulin A (s-IgA) in saliva. The present study examined buffering effects of social support on response of s-IgA to a brief psychological stress (giving a public speech). 24 women were divided at random into three groups, an emotional support group, an informational support group and a no-support group (control). For each group, s-IgA measures were obtained from each person under baseline conditions, during preparation of a speech when social support or no support was given, immediately after the speech and during a 'recovery' period. Level of s-IgA in the control group significantly elevated during preparation for the speech and just after the speech compared to baseline, suggesting that the speech task stimulated secretory immune function. On the other hand, the subjects in the emotional support group showed increased s-IgA during the preparation period but secretion of s-IgA rapidly returned to the baseline after the speech task. Secretion of s-IgA in the informational social support group was unchanged at any measurement point. These results suggest that social support attenuates the affect of a stressor on somatic state.

Adult↗

PubMed2003

The effects of music listening after a stressful task on immune functions, neuroendocrine responses, and emotional states in college students.

The purpose of this study was to examine the effects of listening to high-uplifting or low-uplifting music after a stressful task on (a) immune functions, (b) neuroendocrine responses, and (c) emotional states in college students. Musical selections that were evaluated as high-uplifting or low-uplifting by Japanese college students were used as musical stimuli. Eighteen Japanese subjects performed stressful tasks before they experienced each of these experimental conditions: (a) high-uplifting music, (b) low-uplifting music, and (c) silence. Subjects' emotional states, the Secretory IgA (S-IgA) level, active natural killer (NK) cell level, the numbers of T lymphocyte CD4+, CD8+, CD16+, dopamine, norepinephrine, and epinephrine levels were measured before and after each experimental condition. Results indicated low-uplifting music had a trend of increasing a sense of well-being. High-uplifting music showed trends of increasing the norepinephrine level, liveliness, and decreasing depression. Active NK cells were decreased after 20 min of silence. Results of the study were inconclusive, but high-uplifting and low-uplifting music had different effects on immune, neuroendocrine, and psychological responses. Classification of music is important to research that examines the effects of music on these responses. Recommendations for future research are discussed.

Adult↗

PubMed2003

Interaction of prime and target in the subliminal affective priming effect.

It has been found that an emotional stimulus such as a facial expression presented subliminally can affect subsequent information processing and behavior, usually by shifting evaluation of a subsequent stimulus to a valence congruent with the previous stimulus. This phenomenon is called subliminal affective priming. The present study was conducted to replicate and expand previous findings by investigating interaction of primes and targets in the affective priming effect. Two conditions were used. Prime (subliminal presentation 35 msec.) of an angry face of a woman and a No Prime control condition. Just after presentation of the prime, an ambiguous angry face or an emotionally neutral face was presented above the threshold of awareness (500 msec.). 12 female undergraduate women judged categories of facial expressions (Anger, Neutral, or Happiness) for the target faces. Analysis indicated that the Anger primes significantly facilitated judgment of anger for the ambiguous angry faces; however, the priming effect of the Anger primes was not observed for neutral faces. Consequently, the present finding suggested that a subliminal affective priming effect should be more prominent when affective valence of primes and targets is congruent.

Adult↗

PubMed2003

[Learned helplessness, generalized self-efficacy, and immune function].

Generalized self-efficacy is considered one of important personality traits that determine psychological and physiological stress responses. The present study examined the interaction effects of generalized self-efficacy and controllability of acute stress on salivary secretory immunoglobulin A (s-IgA), task performance, and psychological stress responses in a typical learned helplessness paradigm. Twenty low and 19 high self-efficacy undergraduate women performed two response selection tasks one after another. In the first task, they were exposed to controllable or uncontrollable aversive noise. The second task was identical for all, but perceived controllability was higher for the high self-efficacy group than the low. Performance under uncontrollable condition was lower than controllable condition. The interaction of self-efficacy and controllability was observed only on the s-IgA variable; increase of secretion of s-IgA secretion under stressor uncontrollability was more prominent in the low self-efficacy group than the high. These results suggested that generalized self-efficacy was a moderator of the stressor controllability effect on secretory immunity.

Adult↗