Naoyuki Katagiri

Background: In psychopathology, schizophrenia has been understood as a disorder characterized by disturbances in subjective consciousness. Subjective consciousness and its relationship to interactions between internal representations and external events have been discussed in phenomenology. Recent computational neuroscience conceptualizes the brain as an inferential system that minimizes discrepancies between internal models and latent states inferred from environmental information. From a neurobiological perspective, the frontal–striatal–thalamic circuit may underlie the inferential processing involved in updating internal models based on sensory information derived from the environment. Aim: In this review, we aimed to examine the theoretical point of contact between phenomenology and computational neuroscience from the perspective of inferential processing within the frontal–striatal–thalamic circuit. An imbalance within this circuit may disrupt inferential processes that minimize discrepancies between internal models and latent states. Such maladaptive inferential processes may distort subjective experiences, potentially contributing to the symptoms observed in At-Risk Mental States (ARMS) and Attenuated Psychosis Syndrome (APS), which are considered clinically high-risk states for psychosis. Based on these considerations, we propose a model linking psychopathological phenomena and neurobiological alterations through the dysfunction of the frontal–striatal–thalamic circuit and associated disturbances in inferential processing. We assessed whether this model was theoretically consistent with previous findings and our own longitudinal studies on ARMS/APS. Conclusions: This conceptual model may provide a novel perspective on the information-processing mechanisms, particularly inferential processing, and their alterations across high-risk clinical states for psychosis, including ARMS/APS and broader Clinical High At Risk Mental States (CHARMS) concept.

Background and Objectives: The COVID-19 pandemic globally has negative effects on mental health. Research from Western countries, such as the US, Canada, Australia, and Europe, shows that the COVID-19 pandemic is associated with an increased trend of anorexia nervosa (AN) among children and adolescents. However, the trend after the pandemic in Eastern countries, including Japan, is not well-understood, and it remains unclear whether the pandemic is associated with the trend in these countries. This study aimed to examine the association between the COVID-19 pandemic and the newly diagnosed AN among children and adolescents in Japan. Materials and Methods: Using the nationwide multi-hospital database in Japan, we analyzed the clinical outpatient data in the departments of pediatrics, psychosomatic medicine, and psychiatry. The participants comprised children and adolescents aged 7–19 years newly diagnosed with AN from January 2017 to January 2022. An interrupted time series analysis was used to compare the trends of newly diagnosed AN before and after the COVID-19 pandemic. Estimating the changes in the trends over the pandemic was performed using a Poisson regression model. Results: The total cases of newly diagnosed AN were 41 cases diagnosed in 38 months (1.08 cases per month) before the pandemic and 34 in 23 months (1.48 cases per month) after the pandemic. Notably, in the 7–14 age group, the cases per month increased from 0.74 to 1.13 cases per month over the period. Before the pandemic, a decrease in cases was observed (Incidence Rate Ratio [IRR] = 0.961; 95% CI = 0.932–0.990). Conversely, the after-pandemic period showed a contrasting trend, with increased cases (IRR = 1.096; 95% CI = 1.032–1.176). Furthermore, the number and cases per month in boys increased over the period, from 1 to 5 cases and from 0.03 to 0.22 cases per month, compared to girls from 28 to 26 cases and from 1.05 to 1.26 cases per month. Conclusions: Our findings suggest that sociocultural differences at a national level may not affect the trend of AN after the pandemic. The pandemic and lifestyle changes after the pandemic occurred in both Western and Eastern countries. Considering that, individual, parental, and peer factors related to the pandemic and the consequent lifestyle changes may be more associated with the development of AN. Further research in different countries is needed to elucidate the mechanisms of AN and the long-term impact of the pandemic.

Background: Research from Western countries shows an increased trend of Anorexia Nervosa (AN) among children and adolescents after the COVID-19 pandemic. However, the trend in other countries remains unclear. This study aimed to examine the association of the COVID-19 pan-demic with newly diagnosed AN among children and adolescents in Japan. Methods: Using the nationwide multi-hospital database in Japan, we analyzed the clinical outpatient data in the de-partments of pediatrics, psychosomatic medicine, and psychiatry. The participants comprised children and adolescents aged 7-19 years newly diagnosed with AN from January 2017 to January 2022. An interrupted time series analysis was conducted to compare the trends of newly diag-nosed AN before and after the COVID-19 pandemic. Estimating the changes in the trends over the pandemic was done using a Poisson regression model. Results: The total cases of newly di-agnosed AN was 41 (1.08 cases per month) before the pandemic and 34 (1.48 cases per month) af-ter the pandemic. Notably, in the 7-14 age group, the cases per month increased from 0.74 to 1.13 cases per month over the period. Before the pandemic, a noticeable decrease in cases was ob-served (Incidence Rate Ratio [IRR]= 0.961; 95% CI= 0.932–0.990). Conversely, the after-pandemic period showed a contrasting trend, with an increase in cases (IRR= 1.096; 95% CI= 1.032- 1.176). Conclusions: The COVID-19 pandemic was associated with the increase in newly diagnosed AN among children and adolescents in Japan as well as Western countries. The development of AN after the pandemic might be more affected by individual, parental, and peer factors than soci-ocultural factors.

Frontal-striatal-thalamic circuit impairment is presumed to underlie schizophrenia. Individuals with attenuated psychosis syndrome (APS) show longitudinal volume reduction of the putamen in the striatum, which has a neural connection with the premotor cortex through the frontal-striatal-thalamic subcircuit. However, comprehensive investigations into the biological changes in the frontal-striatal-thalamic subcircuit originating from the premotor cortex in APS are lacking. We investigated differences in fractional anisotropy (FA) values between the striatum and premotor cortex (ST-PREM) and between the thalamus and premotor cortex (T-PREM) in individuals with APS and healthy controls, using a novel method TractSeg. Our study comprised 36 individuals with APS and 38 healthy controls. There was a significant difference between the control and APS groups in the right T-PREM (odds ratio = 1.76, p = 0.02). Other factors, such as age, sex, other values of FA, and antipsychotic medication, were not associated with differences between groups. However, while FA value reduction of ST-PREM and T-PREM in schizophrenia has been previously reported, in the present study on APS, the alteration of the FA value was limited to T-PREM in APS. This finding suggests that ST-PREM impairment is not predominant in APS but emerges in schizophrenia. Impairment of the neural network originating from the premotor cortex can lead to catatonia and aberrant mirror neuron networks that are presumed to provoke various psychotic symptoms of schizophrenia. Our findings highlight the potential role of changes in a segment of the frontal-thalamic pathway derived from the premotor cortex as a biological basis of APS.

Introduction: Aberrant fixation and scan paths in visual searches have been repeatedly reported in schizophrenia. The frontal eye fields (FEF) and thalamus may be responsible for fixation and scan paths. These two regions are connected by superior thalamic radiation (STR) in humans. Studies have reported reduced fixation numbers and shortened scan path lengths in individuals with attenuated psychosis syndrome (APS) and schizophrenia. In this study, we hypothesized that STRs in the white matter fiber bundles of impairments underlie abnormalities in fixation and scan path length in individuals with APS.Methods: Twenty-one individuals with APS and 30 healthy controls participated in this study. All participants underwent diffusion tensor imaging, and fractional anisotropy (FA) values of the left and right STR were analyzed using the novel method TractSeg. The number of eye fixations (NEF), total eye scanning length (TESL), and mean eye scanning length (MESL), derived using the exploratory eye movement (EEM) test, were adopted to evaluate the fixation and scan path length. We compared the FA values of the bilateral STR and EEM parameters between the APS and healthy control groups. We investigated the correlation between bilateral STR and EEM parameters in the APS and healthy control groups.Results: NEF, TESL, MESL, and the FA values of the left STR were significantly reduced in individuals with APS compared to healthy controls. The left STR FA value in the APS group was significantly positively correlated with the MESL (r = 0.567, p = 0.007). In addition, the right STR FA value of the APS group was significantly correlated with the TESL (r = 0.587, p = 0.005) and MESL (r = 0.756, p = 0.7×10^-4).Discussion: These results demonstrate that biological changes in the STR, which connects the thalamus and FEF, underlie abnormalities in fixation and scanning. Recently, aberrations in the thalamus–frontal connection have been shown to underlie the emergence of psychotic symptoms. STR impairment may be a part of the biological basis of APS in individuals with subthreshold psychotic symptoms.

Verbal fluency is one of the most severely impaired components of cognitive function in schizophrenia and is also impaired in at-risk mental states (ARMSs) for psychosis. The aim of this study was to explore the markers of disease progression in subjects with ARMSs by comparing the association between the white matter integrity of the superior longitudinal fasciculus (SLF) and verbal fluency in subjects with ARMSs and healthy control (HC) subjects. The correlations of the fractional anisotropy (FA) values on diffusion tensor imaging (DTI) and the laterality index (LI) values of SLF branches I, II, and III with the verbal fluency performance were analyzed in right-handed subjects with ARMSs (ARMS group; n = 18) and HC subjects (HC group; n = 34) aged 18 to 40 years old. In the HC group compared with the ARMS group, the LI values suggested right lateralization of the SLF II and III. Letter fluency was significantly correlated with the LI of the SLF III in both the ARMS and HC groups. The regression coefficient (β) of this correlation was calculated using the least squares method and yielded a positive number (73.857) in the ARMS group and a negative number (−125.304) in the HC group. The association of the rightward asymmetry of the SLF III with the verbal fluency performance observed in the HC group appeared to be lost in the ARMS group, and this could serve as one of the markers of the pathological progression to psychosis in patients with schizophrenia.

Background The fast-growing migrant population in Japan and globally poses challenges in mental healthcare, yet research addressing migrants’ mental health treatment engagement remains limited. Objective This study examined language proficiency, demographic and clinical characteristics as predictors of early treatment discontinuation among migrants. Methods Electronic health record data from 196 adult migrants, identified from 14 511 patients who received mental health outpatient treatment during 2016 and 2019 at three central hospitals in the Tokyo-Yokohama metropolitan region of Japan, were used. We conducted multivariable regression models to identify predictors of early discontinuation within 3 months. Findings The study cohort (65% women, age range: 18–90 years, from 29 countries or regions) included 23% non-Japanese speakers. Japanese and non-Japanese speakers had similar discontinuation rates (26% vs 22%). Multivariable models revealed younger age (OR=0.97; 95% CI: 0.95, 0.99; p=0.016) and those with a primary diagnosis other than a schizophrenia spectrum disorder (OR=3.99; 95% CI: 1.36, 11.77; p=0.012) or a neurotic, stress-related and somatoform disorder (OR=2.79; 95% CI: 1.14, 6.84; p=0.025) had higher odds of early discontinuation. These effects were more pronounced among the Japanese speakers with significant language-by-age and language-by-diagnoses interactions. Conclusion Younger age and having a primary diagnosis other than a schizophrenia spectrum disorder or a neurotic, stress-related and somatoform disorder increased vulnerability for discontinuing mental health treatment early in Japanese-speaking migrants but not for migrants with limited Japanese proficiency. Clinical implications Understanding language needs within a context of mental health treatment should go beyond assumed or observed fluency. Unmet language needs might increase vulnerability for treatment disengagement among migrants. Targeted clinical efforts are crucial for enhancing early treatment engagement and informing health practices in Japan and countries with growing migrant populations.

Frontal-striatal-thalamic circuit impairment is presumed to underlie schizophrenia. Individuals with attenuated psychosis syndrome (APS) show longitudinal volume reduction of the putamen in the striatum, which has a neural connection with the premotor cortex through frontal-striatal-thalamic subcircuit. However, comprehensive investigations into the biological changes in the frontal-striatal-thalamic subcircuit originating from the premotor cortex are lacking in APS. We investigated differences in fractional anisotropy (FA) values between the striatum and premotor cortex (ST-PREM) and between the thalamus and premotor cortex (T-PREM) in individuals with APS and healthy controls, using a novel method TractSeg. Our study comprised 36 individuals with APS and 38 healthy controls. There was a significant difference between the control and APS groups in the right T-PREM (Odds ratio = 1.76, p = 0.02). Other factors, such as age, sex, other values of FA, and antipsychotic medication, were not associated with differences between groups. However, while FA value reduction of ST-PREM and T-PREM in schizophrenia has been previously reported, in the present study on APS, the alteration of the FA value was limited to T-PREM in APS. This finding suggests that ST-PREM impairment is not predominant in APS but emerges in schizophrenia. Impairment of the neural network originating from the premotor cortex can lead to catatonia and aberrant mirror neuron networks that are presumed to provoke various psychotic symptoms of schizophrenia. Our findings highlight the potential role of changes in a segment of the frontal-thalamic pathway derived from the premotor cortex as a biological basis of APS.

Background: The number of young Japanese Brazilians, who are return migrants with Japanese ancestral roots, is increasing rapidly in Japan. However, the characteristics of their mental health and the relation between mental health and a complex ethnic identity remains unclear. Methods: This cross-sectional study compared 25 Japanese–Brazilian high school students with 62 Japanese high school students living in the same area. Research using self-report questionnaires on mental health, help-seeking behavior tendencies, and ethnic identity was conducted. The Japanese–Brazilian group was also divided into high and low ethnic identity groups, and their mental health conditions were compared. Results: The Japanese–Brazilian group had significantly poorer mental health conditions and lower ethnic identities than the Japanese group and were less likely to seek help from family members and close relatives. Among the Japanese Brazilians, those with low ethnic identity had significantly poorer mental health than those with high ethnic identity. Conclusions: Young Japanese Brazilians may face conflicts of ethnic identity that can disturb their mental health. To build an inclusive society, the establishment of community services to support mental health and to help return migrants develop their ethnic identity is essential.