Hideki Ohira

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.

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.

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.

Visual mismatch negativity: new evidence from the equiprobable paradigm.

In visual oddball studies, deviant compared to standard stimuli elicited a posterior negative ERP at around 100-250 ms. To determine the underlying processes of the negativity, we used the equiprobable sequence in which bar stimuli of five types of orientation were presented with equal probabilities (control 20% each) as well as the oddball sequence in which two stimuli with the closest orientation were presented with different probabilities (deviant 20% and standard 80%). Deviant compared to standard stimuli elicited two negativities at around 100-150 ms with no hemispheric dominance and 200-250 ms with right hemispheric dominance, while deviant compared to control stimuli elicited only a negativity at around 200-250 ms with right hemispheric dominance. These results suggest that the early negativity reflects refractory effect, while the late negativity reflects memory-comparison-based change detection effect (visual mismatch negativity).

Effect of negative air ions on computer operation, anxiety and salivary chromogranin A-like immunoreactivity

The effects of negative air ions on computer operation were examined using a biochemical index of the activity of the sympathetic/adrenomedullary system (i.e. salivary chromogranin A-like immunoreactivity (CgA-like IR)) and a self-report questionnaire (State-Trait Anxiety Inventory, Anxiety State--STAI-S). Twelve female students carried out a word processing task for 40 min. The salivary CgA-like IR increased more than three times on the task, but the salivary cortisol did not change. The increase in the CgA-like IR level was attenuated by the exposure to negative air ions during the task. The exposure to the ions during the recovery period following the task was effective for rapidly decreasing the CgA-like IR level that had increased after the task. These effects by negative air ions were also observed using STAI-S. Task performance was slightly but significantly improved by the presence of negative air ions. These results suggest that negative air ions are effective for the reduction of and the prompt recovery from stress caused by computer operation.

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.

Unintentional Temporal Context–Based Prediction of Emotional Faces: An Electrophysiological Study

The ability to extract sequential regularities embedded in the temporal context or temporal structure of sensory events and to predict upcoming events based on the extracted sequential regularities plays a central role in human cognition. In the present study, we demonstrate that, without any intention, upcoming emotional faces can be predicted based on sequential regularities, by showing that prediction error responses as reflected by visual mismatch negativity (MMN), an event-related brain potential (ERP) component, were evoked in response to emotional faces that violated a regular alternation pattern of 2 emotional faces (fearful and happy faces) under a situation where the emotional faces themselves were unrelated to the participants task. Face-inversion and negative-bias effects in the visual MMN further indicated the involvement of holistic face representations. In addition, through successive source analyses of the visual MMN, it was revealed that the prediction error responses were composed of activations mainly in the face-responsible visual extrastriate areas and the prefrontal areas. The present results provide primary evidence for the existence of the unintentional temporal context-based prediction of biologically relevant visual stimuli as well as empirical support for the major engagement of the visual and prefrontal areas in unintentional temporal context-based prediction in vision.

Localizing sensory and cognitive systems for pre-attentive visual deviance detection: an sLORETA analysis of the data of Kimura et al. (2009).

Pre-attentive deviance detection in the visual environment has been known to be reflected by an event-related brain potential (ERP) component, deviant-related negativity. Recently, however, we demonstrated that deviant-related negativity comprises two, temporally and spatially overlapping ERP components, by using an experimental protocol consisting of oddball and equiprobable sequences [M. Kimura, J. Katayama, H. Ohira, E. Schröger, Visual mismatch negativity: new evidence from the equiprobable paradigm, Psychophysiology 46 (2009) 402-409]: (1) visual N1 that reflects a sensory, refractoriness-based deviance detection system and (2) visual mismatch negativity (MMN) that reflects a cognitive, memory-comparison-based deviance detection system. In the present paper, we further elucidated the neural generators of the visual N1 and visual MMN with standardized low-resolution brain electromagnetic tomography (sLORETA). Results showed that the visual N1 was involved in neural activations of the primary and nonprimary visual areas, while the visual MMN was involved in neural activations of the nonprimary visual areas and the prefrontal areas. These results suggest that the sensory and cognitive deviance detection systems subserved by distinct neural structures underlie our efficient pre-attentive visual deviance detection.

Transient responses of inflammatory cytokines in acute stress

It has been demonstrated that concentrations of pro-inflammatory cytokines such as interleukin-1beta (IL-1beta) and interleukin-6 (IL-6) are elevated by acute stress. Although several studies confirmed robust changes in IL-6, how acute stress affects other cytokines was less clear. Therefore, the present study simultaneously examined the effects of acute stress on several pro-inflammatory cytokines. Sixteen male participants were given the Trier Social Stress Test (TSST). Blood samples were collected at baseline, immediately after, and 30, 60, and 90min after the TSST. IL-1beta significantly increased immediately after the TSST and returned to the baseline level after 30min. Additionally, this elevation of IL-1beta was correlated with the perceived intensity of stress. These results showed that the concentration of IL-1beta is rapidly regulated, and that elevation of the IL-1beta level could possibly be attributed to transient mobilization of monocytes caused by sympathetic nervous activation. Moreover, a transient increase of IL-1beta might be conveyed to the brain and play a role in forming negative emotional states.

Effects of Stimulus Valence on Recognition Memory and Endogenous Eyeblinks: Further Evidence for Positive-Negative Asymmetry

Japanese college students viewed a series of positive and negative stimulus words printed in katakana, a Japanese syllabary. Jacobys process-dissociation procedure was used to assess the roles of conscious and unconscious processes in stimulus recognition. There was a stronger conscious recollective component in recognition of negative items and a higher correct rejection rate for negative stimuli, replicating American findings reported by Robinson-Riegler and Winton, and Ortony, Turner, and Antos. In addition, during the encoding phase, negative stimuli were associated with more eyeblinks and longer eyeblink latencies than positive stimuli; this pattern suggests greater cognitive activity in response to negative stimuli, consonant with Taylors mobilization-minimization hypothesis. The eyeblink response, as measured in the present research, represents a new method for assessing the positive-negative asymmetries that are characteristic of the mobilization process.