Takahiro Soshi

Sleep Deprivation Facilitates Extinction of Implicit Fear Generalization and Physiological Response to Fear

BACKGROUND Neuroendocrine hormones, which regulate both homeostasis and stress responses, provide homeostatic recovery and sleep suppression to brains under stress. We examined the effects of total sleep deprivation on subsequent enhancement of aversive event memory, implicit fear recognition, and fear conditioning in healthy humans. METHODS Three different recognitions (explicit event, implicit emotion, and physiological response) were assessed in two groups of 14 healthy young volunteers (sleep control and sleep deprived) with aversive (motor vehicle accident films) and nonaversive episodic memory stimuli. Both groups were tested on Day 1 of the experiment and again on Days 3 and 10; the sleep-deprived group was totally deprived of initial nocturnal sleep after the first trial on Day 1. RESULTS Event recognition performances were similar in both groups throughout the study. Implicit fear recognition remained high for aversive stimuli, with generalization of implicit fear recognition occurring for nonaversive stimuli on Day 3 in the sleep control group. Physiological fear and generalized fear responses were observed for every episode, and delayed enhancement of physiological response was only observed for misidentified aversive episodes in the sleep control group on Day 3. However, in the sleep-deprived group, generalization of implicit fear recognition for nonaversive stimuli on Day 3 and all physiological and generalized fear responses on Days 3 and 10 were comprehensively extinguished. CONCLUSIONS Clinically, trauma-exposed victims often experience acute insomnia, indicating that such insomnia might provide prophylactic benefits in reducing the development of posttraumatic stress disorder via extinction of the fear-magnifying effects of memory.

Schizotypal traits in healthy women predict prefrontal activation patterns during a verbal fluency task: a near-infrared spectroscopy study.

Background/Aims: Previous functional neuroimaging studies have reported that patients with schizophrenia show reduced prefrontal activation during cognitive tasks whereas patients with schizotypal personality disorder (SPD) show preserved or even increased right prefrontal activation, compared to healthy controls; on the other hand, reduced hemispheric laterality is considered to be common to these two disorders. The aim of this study was to examine the possible association between schizotypal traits at a nonclinical level and prefrontal activation patterns during a letter version of the verbal fluency task (VFT). Methods: We examined the relationships of schizotypal traits as measured by the Schizotypal Personality Questionnaire (SPQ) in a nonclinical female population with prefrontal activation patterns during the VFT, using near-infrared spectroscopy. Twenty-seven healthy participants were divided into high (n = 14) and low (n = 13) SPQ groups by the median split of the total SPQ score. Results: Compared to the low SPQ group, the high SPQ group showed significantly larger right prefrontal activation during the performance of the VFT, leading to more bilateral activation. Conclusion: Our results suggest that schizotypal traits at a nonclinical level may be related to relative right prefrontal laterality with overall prefrontal activation being preserved, consistent with previous findings obtained by studies of patients with SPD.

Sleep Deprivation Influences Diurnal Variation of Human Time Perception with Prefrontal Activity Change: A Functional Near-Infrared Spectroscopy Study

Human short-time perception shows diurnal variation. In general, short-time perception fluctuates in parallel with circadian clock parameters, while diurnal variation seems to be modulated by sleep deprivation per se. Functional imaging studies have reported that short-time perception recruits a neural network that includes subcortical structures, as well as cortical areas involving the prefrontal cortex (PFC). It has also been reported that the PFC is vulnerable to sleep deprivation, which has an influence on various cognitive functions. The present study is aimed at elucidating the influence of PFC vulnerability to sleep deprivation on short-time perception, using the optical imaging technique of functional near-infrared spectroscopy. Eighteen participants performed 10-s time production tasks before (at 21:00) and after (at 09:00) experimental nights both in sleep-controlled and sleep-deprived conditions in a 4-day laboratory-based crossover study. Compared to the sleep-controlled condition, one-night sleep deprivation induced a significant reduction in the produced time simultaneous with an increased hemodynamic response in the left PFC at 09:00. These results suggest that activation of the left PFC, which possibly reflects functional compensation under a sleep-deprived condition, is associated with alteration of short-time perception.

Right Prefrontal Activity Reflects the Ability to Overcome Sleepiness during Working Memory Tasks: A Functional Near-Infrared Spectroscopy Study

It has been speculated that humans have an inherent ability to overcome sleepiness that counteracts homeostatic sleep pressure. However, it remains unclear which cortical substrate activities are involved in the ability to overcome sleepiness during the execution of cognitive tasks. Here we sought to confirm that this ability to overcome sleepiness in task execution improves performance on cognitive tasks, showing activation of neural substrates in the frontal cortex, by using a modified n-back (2- and 0-back) working memory task and functional near-infrared spectroscopy. The change in alertness was just correlated with performances on the 2-back task. Activity in the right prefrontal cortex changed depending on alertness changes on the 2- and 0-back tasks independently, which indicates that activity in this region clearly reflects the ability to overcome sleepiness; it may contribute to the function of providing sufficient activity to meet the task load demands. This study reveals characteristics of the ability to overcome sleepiness during the n-back working memory task which goes beyond the attention-control function traditionally proposed.

Emotional Memory Persists Longer than Event Memory.

The interaction between amygdala-driven and hippocampus-driven activities is expected to explain why emotion enhances episodic memory recognition. However, overwhelming behavioral evidence regarding the emotion-induced enhancement of immediate and delayed episodic memory recognition has not been obtained in humans. We found that the recognition performance for event memory differs from that for emotional memory. Although event recognition deteriorated equally for episodes that were or were not emotionally salient, emotional recognition remained high for only stimuli related to emotional episodes. Recognition performance pertaining to delayed emotional memory is an accurate predictor of the context of past episodes.

Post-error action control is neurobehaviorally modulated under conditions of constant speeded response

Post-error slowing (PES) is an error recovery strategy that contributes to action control, and occurs after errors in order to prevent future behavioral flaws. Error recovery often malfunctions in clinical populations, but the relationship between behavioral traits and recovery from error is unclear in healthy populations. The present study investigated the relationship between impulsivity and error recovery by simulating a speeded response situation using a Go/No-go paradigm that forced the participants to constantly make accelerated responses prior to stimuli disappearance (stimulus duration: 250 ms). Neural correlates of post-error processing were examined using event-related potentials (ERPs). Impulsivity traits were measured with self-report questionnaires (BIS-11, BIS/BAS). Behavioral results demonstrated that the commission error for No-go trials was 15%, but PES did not take place immediately. Delayed PES was negatively correlated with error rates and impulsivity traits, showing that response slowing was associated with reduced error rates and changed with impulsivity. Response-locked error ERPs were clearly observed for the error trials. Contrary to previous studies, error ERPs were not significantly related to PES. Stimulus-locked N2 was negatively correlated with PES and positively correlated with impulsivity traits at the second post-error Go trial: larger N2 activity was associated with greater PES and less impulsivity. In summary, under constant speeded conditions, error monitoring was dissociated from post-error action control, and PES did not occur quickly. Furthermore, PES and its neural correlate (N2) were modulated by impulsivity traits. These findings suggest that there may be clinical and practical efficacy of maintaining cognitive control of actions during error recovery under common daily environments that frequently evoke impulsive behaviors.

Neurophysiological modulation of rapid emotional face processing is associated with impulsivity traits

BackgroundSensori-perceptual processing of emotional stimuli under attentive conditions effectively prevents response disinhibition. This is observed saliently in low-impulsive people, because of their high sensitivity to warning signals, such as emotional faces. Results from human neurophysiological studies have been used to develop a dual detector model for early sensori-perceptual processing. A transient detector mechanism is related to automatic neurophysiological arousal in response to warning signals, which is reflected by early frontal event-related potential effects. The memory-based detector mechanism is associated with subsequent mismatch negativity (MMN), which reflects a short-term memory trace of signals. Based on previous findings, we predicted that impulsivity affects functional associations among the dual detector mechanisms, and modulates early frontal and/or MMN activities. In the present study, we recorded electroencephalograms for twenty-one healthy adults using a visual oddball paradigm with neutral faces as frequent stimuli, and angry and happy faces as infrequent stimuli. We measured the impulsivity traits by a self-report scale (the Barratt Impulsiveness Scale, 11th version).ResultsMain findings were that only happy faces increased early frontal negativity and subsequent occipital visual MMN (vMMN) for emotional change, and these neurophysiological effects positively correlated with each other in a temporally causal manner. However, an impulsivity sub-trait positively correlated selectively with vMMN for the happy faces.ConclusionThese findings demonstrate that higher impulsivity is associated with attenuated vMMN for emotional change detection in healthy populations, potentially because of weakened fronto-occipital functional connection that is responsible for the dual detector mechanism.

Increased cerebral blood flow in the right frontal lobe area during sleep precedes self-awakening in humans.

BackgroundSome people can subconsciously wake up naturally (self-awakening) at a desired/planned time without external time stimuli. However, the underlying mechanism regulating this ability remains to be elucidated. This study sought to examine the relationship between hemodynamic changes in oxyhemoglobin (oxy-Hb) level in the prefrontal cortex and sleep structures during sleep in subjects instructed to self-awaken.ResultsFifteen healthy right-handed male volunteers with regular sleep habits participated in a consecutive two-night crossover study. The subjects were instructed to wake up at a specified time (“request” condition) or instructed to sleep until the morning but forced to wake up at 03:00 without prior notice (“surprise” condition). Those who awoke within ± 30 min of the planned waking time were defined as those who succeeded in self-awakening (“success” group). Seven subjects succeeded in self-awakening and eight failed.No significant differences were observed in the amounts of sleep in each stage between conditions or between groups. On the “request” night, an increase in oxy-Hb level in the right prefrontal cortex and a decrease in δ power were observed in the “success” group around 30 min before self-awakening, whereas no such changes were observed in the “failure” group. On the “surprise” night, no significant changes were observed in oxy-Hb level or δ power in either group.ConclusionsThese findings demonstrate a correlation between self-awakening and a pre-awakening increase in hemodynamic activation in the right prefrontal cortex, suggesting the structure’s contribution to time estimation ability.

Diurnal fluctuations in subjective sleep time in humans

Humans have the ability to estimate the passage of time in the absence of external time cues. In this study, we subjected 22 healthy males (aged 21.8±1.9 years) to a 40-min nap trial followed by 80min of wakefulness repeated over 28h, and investigated the relationship between various sleep parameters and the discrepancy (ΔST) of time estimation ability (TEA) during sleep, defined by the difference between actual sleep time (ST) and subjective sleep time (sub-ST) in each nap interval. Both ST and sub-ST were significant diurnal fluctuations with the peak in the early morning (9h after dim-light melatonin onset time, 2h after nadir time of core body temperature rhythm), and subjective sleep duration was estimated to be longer than actual times in all nap intervals (sub-ST>ST). There were significant diurnal fluctuations in discrepancy (sub-ST-ST) of TEA during sleep, and the degree of discrepancy correlated positively with increase in the amount of REM sleep and decrease in the amount of slow-wave sleep. These findings suggest that human TEA operates at a certain level of discrepancy during sleep, and that this discrepancy might be related to the biological clock and its associated sleep architecture.

Risk factors for problematic behaviors among forensic outpatients under the medical treatment and supervision act in Japan

The Medical Treatment and Supervision Act (MTSA) was enacted in 2005 in Japan to promote the reintegration of clinical offenders with mental disorders into society. Under the MTSA, individuals who committed serious crimes in a state of insanity or diminished responsibility are diverted from the criminal justice system to the mental health system. Based on court decisions about MTSA-based treatment, clinical offenders have an obligation to engage in rehabilitation within their local community under the guidance of mental health professionals. However, patients under MTSA-based clinical treatments have faced various problems in the course of treatment, because of psychiatric as well as other static or dynamic factors, and sometimes have committed problematic behaviors, such as violence and medical non-compliance. Hence, this study aimed to clarify factors related to patients’ inclusion in MTSA-based outpatient treatment and additionally, their commitment of problematic behaviors, based on confidential data acquired during a four-year government survey period (National Center of Neurology and Psychiatry) from MTSA enactment (July 15, 2005) to December 31, 2009. In total, we recruited 441 clinical offenders receiving MTSA-based outpatient treatment from 158 nationwide facilities. To evaluate related factors, we collected demographic, psychiatric, forensic, clinical treatment, and social service information. Statistical analyses demonstrated that predominant profiles of patients included male gender, younger age, low school history, psychiatric diagnoses (F1, F2, and F3), and no correctional or outpatient history before MTSA-based treatment. F1 or substance use diagnosis, in particular, was increasingly correlated with other factors, such as male gender, older age, and correctional history before MTSA treatment. Among the 441 patients, 189 (43%) committed problematic behaviors in the course of the MTSA-based outpatient treatment. Risk factors for patients’ commitment of problematic behaviors comprised F1 diagnosis and inpatient history before MTSA-based treatment inclusion. In summary, reduction of overall problematic behaviors under the MTSA outpatient likely makes progress by focal attention to patients with psychiatric disorders caused by substance use and/or a past inpatient history for more severe psychiatric symptoms. This work is of ongoing and future importance in the domain of forensic community treatment, to connect risk-enhancing factors with risk management.