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Neuroethics is the study of how neuroscience impacts humans and society. About 15 years have passed since neuroethics was introduced to Japan, yet the field of neuroethics still seeks developed methodologies and an established academic identity. In light of progress in neuroscience and neurotechnology, the challenges for Japanese neuroethics in the 2020 s can be categorized into five topics. (1) The need for further research into the importance of informed consent in psychiatric research and the promotion of public-patient engagement. (2) The need for a framework that constructs a global environment for neuroscience research that utilizes reliable samples and data. (3) The need for ethical support within a Japanese context regarding the construction of brain banks and the research surrounding their use. It is also important to reconsider the moral value of the human neural system and make comparisons with non-human primates. (4) An urgent need to study neuromodulation technologies that intervene in emotions. (5) The need to reconsider neuroscience and neurotechnology from social points of view. Rules for neuroenhancements and do-it-yourself neurotechnologies are urgently needed, while from a broader perspective, it is essential to study the points of contact between neuroscience and public health.

The area around the Sea of Okhotsk and the Sea of Japan in the north-western North Pacific provides opportunities for studying the impact of climate oscillations on the evolutionary history of cold-temperate species independent of direct ice sheet development. We conducted a range-wide collection survey of white-spotted charr, Salvelinus leucomaenis, and integrated nuclear DNA and mitochondrial DNA (mtDNA) data to reveal the evolutionary history of this species. Phylogeographic analyses using genome-wide SNP data revealed the presence of five geographically distinct groups with slightly overlapping ranges. Of these, a northern group was widely distributed along the coast of the Sea of Okhotsk, the Sea of Japan and the northern region of Honshu Island, whereas the other four groups were only found on Honshu Island. The population structure of Honshu Island was largely divided into the Sea of Japan and Pacific Ocean groups by the mountain ranges running through the centre of Honshu Island, and was further subdivided by many geological factors, such as river capture and other vicariance processes. There was a discrepancy in the phylogeographic patterns between nuclear DNA and mtDNA, which was likely influenced by a complex population history that involved multiple dispersal and secondary contact events during several glacial-interglacial cycles.

Rainbow trout, Oncorhynchusmykiss, is one of the most widely introduced fish species in the world, and its impacts on native fishes and ecosystems are of considerable concern. One of the rivers inhabited by rainbow trout in the Shiretoko Peninsula is the Chinishibetsu River, and the origin of rainbow trout in this river is thought to be Lake Chinishibetsu in the upper reaches of the system, where the private stocking of rainbow trout was conducted in the 1960s. However, the basic biology of rainbow trout in the Lake Chinishibetsu area is currently unknown. This study addresses this knowledge gap by examining the biology of rainbow trout in the inlet tributaries of Lake Chinishibetsu based on sampling conducted during the rainbow trout spawning season. A total of 104 rainbow trout, ranging in age from 1+ to 8+ years, were collected from the two inlet tributaries of Lake Chinishibetsu. White-spotted charrSalvelinus leucomaenisand Siberian stone loachBarbatula oreas, neither of which is native to the Shiretoko Peninsula, were also collected and had presumably invaded the area at the same time as the rainbow trout. The sampled rainbow trout included immature and mature males and females. The distribution of fork lengths of mature females was bimodal, and the sex ratio of mature rainbow trout was male-biased. Our results indicate that the rainbow trout population in the inlet tributaries of Lake Chinishibetsu is reproducing continuously and exhibits a dimorphic life history with river residents and lake migrants of both sexes. Additionally, rainbow trout continue to be collected downstream of the Chinishibetsu River, which is the primary habitat for this species in the Shiretoko Peninsula. Therefore, unless rainbow trout are eliminated from Lake Chinishibetsu, which serves as a source of non-native species upstream of the Chinishibetsu River, it will be difficult to control rainbow trout distributions and minimize population sizes on the Shiretoko Peninsula.

Subcortical brain structures are the hubs for various psycho-behavioral functions. There is no mega-analysis to simultaneously investigate subcortical volumetric alterations in schizophrenia, bipolar disorder, major depressive disorder, and autism spectrum disorder. Nor are there any neuroimaging data-driven clinical criteria overcoming limitations of the current diagnostic system, which would reflect cognitive/social functioning. We conducted a large-scale multisite study of subcortical volumetric and lateralization alterations in these disorders using T1-weighted images of 5,604 subjects (3,078 controls and 2,526 patients). We found schizophrenia-specific and cross-disorder shared alterations. Moreover, we clustered the 5,604 subjects based on subcortical volumes, and explored whether data-driven clustering results can explain cognitive/social functioning in the subcohorts. We showed a four-biotype classification, namely extremely and moderately smaller limbic regions, larger basal ganglia, and normal volumes, for predicting cognitive/social functioning. Our results will contribute to the future creation of novel biological data-driven psychiatry diagnostic criteria, expected to support appropriate treatment selection.

Freshwater rivers and lakes are particularly vulnerable to anthropogenic disturbance because of their proximity to human occupation. Anthropogenic impacts in fresh water include those caused by dams, water pollution, channelization, and invasive species. One common action to conserve freshwater biodiversity involves supplementing or reintroducing extirpated species, though the benefits of these efforts are controversial. Installation of fishways to dams and removal of invasive alien species has also resulted in recovery of native species. Herein results of long-term monitoring of salmonids in two rivers in Japan are presented. The first case involves a river above a dam where native white-spotted charr Salvelinus leucomaenis and masu salmon Oncorhynchus masou declined rapidly in number following dam construction, where non-native rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta increased in number, and where stocking of native masu salmon was unsuccessful. The second case involves a river formerly dominated by non-native rainbow trout, in which native Dolly Varden charr Salvelinus curilus and masu salmon increased in numbers following removal of non-native species and fishway installation. Results reveal natural recovery of masu salmon in a river within which they were once completely extirpated, without stocking. Because salmonids are migratory fish and return to natal rivers, when locally extinct, human intervention to stock or reintroduce them has often been deemed necessary. However, restoration of wildlife would not require stocking or reintroduction if factors that impede the self-recovery capability of species are removed.

Captive-breeding programs are actively engaged in conservation and resource enhancement for a variety of species around the world, yet captive-bred individuals often experience reduced fitness in the wild due to inbreeding and adaptation to captivity. Increasing wild-type genetic contributions has been proposed as one solution to this problem, but the demographic impacts of these contributions remain unclear. Using data from long-term mass-marking programs conducted by national hatcheries in Japan, we evaluated the effects of wild genes in the parental generation on the survival of captive-bred populations. Our results indicated that increasing the percentage of wild genes improves survival of captive-bred offspring in the wild in two salmonid species. These findings offer insights for future bioresource management efforts that use both wild and captive-bred individuals.

It is known that environmental parameters, such as water depth, size of substrate material, and current velocity, influence the organization of stream fish communities. However, few studies have investigated the effects of these parameters on the sympatric freshwater eels. Here, the habitat use of two anguillid eels, the Indo-Pacific eel (Anguilla marmorata Quoy and Gaimard, 1824) and the Japanese eel (Anguilla japonica Temminck and Schlegel, 1846), coexisting in the same river systems in Japan, was investigated. It was found that the tropical species A. marmorata exclusively used habitats with larger substrate materials, fewer fallen leaves and less leaf detritus, higher current velocity, and lower turbidity than the temperate species A. japonica, and the distributions of the two anguillid eels were clearly segregated. Thus, when both species co-occur in the same river systems, clear flowing mainstems and tributaries are preferred habitats for A. marmorata, whereas stagnant muddy estuaries, backwater areas, irrigation channels, and reservoirs are preferred habitats for A. japonica. These habitat segregations were consistent as body size increased and life-stage developments from elver to yellow eel and did not show ontogenetic shifts. The findings indicated that both species had strong habitat preferences, and these environmental parameters must be considered in the conservation of anguillid eels in sympatric zones.

Birth order is a crucial environmental factor for child development. For example, later-born children are relatively unlikely to feel secure due to sibling competition or diluted parental resources. The positive effect of being earlier-born on cognitive intelligence is well-established. However, whether birth order is linked to social behavior remains controversial, and the neural correlates of birth order effects in adolescence when social cognition develops remain unknown. Here, we explored the birth order effect on prosociality using a large-scale population-based adolescent cohort. Next, since the amygdala is a key region for sociality and environmental stress, we examined amygdala substrates of the association between birth order and prosociality using a subset neuroimaging cohort. We found enhanced prosociality in later-born adolescents (N = 3160), and observed the mediating role of larger amygdala volume (N = 208) and amygdala-prefrontal functional connectivity with sex-selective effects (N = 183). We found that birth order, a non-genetic environmental factor, affects adolescent social development via different neural substrates. Our findings may indicate the later-born people’s adaptive survival strategy in stressful environments.

In mixed fisheries where multiple species are caught, to manage resources sustainably, knowledge about the species-specific vulnerability to fishing is equally or even more important than knowledge of size selectivity of the gear. We compared the vulnerability to bait recreational angling in four salmonid species in natural streams in Japan. The ranking of species-specific angling vulnerability was as follows (from highest to lowest): rainbow trout (Oncorhynchus mykiss), masu salmon (Oncorhynchus masou), white-spotted char (Salvelinus leucomaenis), and southern Asian Dolly Varden (Salvelinus curilus). In all species, larger individuals were more vulnerable to angling, but there were differences in the size dependence between species. In rainbow trout and Dolly Varden (which have a nonanadromous life history in the study area), the probability of being caught monotonically increased with body size, while the vulnerability to angling in masu salmon and white-spotted char (which have an anadromous life history in the study area) showed a domed-shaped pattern. We found that across the species the catch per unit effort showed a hyperstable relationship with population density. Therefore, diminishing local populations are prone to collapse, and this collapse would be hard to foresee based on catch rate data alone.

Background Cognitive impairment is common in people with mental disorders, leading to transdiagnostic classification based on cognitive characteristics. However, few studies have used this approach for intellectual abilities and functional outcomes. Aims The present study aimed to classify people with mental disorders based on intellectual abilities and functional outcomes in a data-driven manner. Method Seven hundred and forty-nine patients diagnosed with schizophrenia, bipolar disorder, major depression disorder or autism spectrum disorder and 1030 healthy control subjects were recruited from facilities in various regions of Japan. Two independent k-means cluster analyses were performed. First, intelligence variables (current estimated IQ, premorbid IQ, and IQ discrepancy) were included. Second, number of work hours per week was included instead of premorbid IQ. Results Four clusters were identified in the two analyses. These clusters were specifically characterised in terms of IQ discrepancy in the first cluster analysis, whereas the work variable was the most salient feature in the second cluster analysis. Distributions of clinical diagnoses in the two cluster analyses showed that all diagnoses were unevenly represented across the clusters. Conclusions Intellectual abilities and work outcomes are effective classifiers in transdiagnostic approaches. The results of our study also suggest the importance of diagnosis-specific strategies to support functional recovery in people with mental disorders.

Subjective quality of life is a clinically relevant outcome that is strongly associated with the severity of clinical symptoms in individuals with ultra-high risk for psychosis and patients with recent-onset psychotic disorder. Our objective was to examine whether longitudinal changes in clinical symptoms are associated with quality of life in ultra-high risk individuals and patients with recent-onset psychotic disorder.Individuals with ultra-high risk and patients with recent-onset psychosis disorder were recruited in the same clinical settings at baseline and were followed up with more than 6 months and less than 5 years later. We assessed five factors of clinical symptoms using the positive and negative syndrome scale, and quality of life using the World Health Organization quality of life questionnaire-short form. We used multiple regression to examine the relationships between clinical symptoms and quality of life while controlling for diagnosis, follow-up period, age, and sex.Data were collected from 22 individuals with ultra-high risk and 27 patients with recent-onset psychosis disorder. The multiple regression analysis results indicated that the more severe anxiety/depression was at baseline, the poorer the quality of life at follow-up. Further, improvement of anxiety/depression and disorganized thoughts were associated with improvement in quality of life. The difference in diagnosis did not affect the association between clinical symptoms and quality of life.These findings suggest that the improvement of anxiety/depression and disorganized thoughts is important in the early stages of psychosis before it becomes severe, affecting the quality of life.

Characterization of brain networks by diffusion MRI (dMRI) has rapidly evolved, and there are ongoing movements toward data sharing and multi-center studies. To extract meaningful information from multi-center data, methods to correct for the bias caused by scanner differences, that is, harmonization, are urgently needed. In this work, we report the cross-scanner differences in structural network analyses using data from nine traveling subjects (four males and five females, 21–49 years-old) who underwent scanning using four 3T scanners (public database available from the Brain/MINDS Beyond Human Brain MRI project (http://mriportal.umin.jp/)). The reliability and reproducibility were compared to those of data from another set of four subjects (all males, 29–42 years-old) who underwent scan-rescan (interval, 105–147 days) with the same scanner as well as scan-rescan data from the Human Connectome Project database. The results demonstrated that the reliability of the edge weights and graph theory metrics was lower for data including different scanners, compared to the scan-rescan with the same scanner. Besides, systematic differences between scanners were observed, indicating the risk of bias in comparing networks obtained from different scanners directly. We further demonstrate that it is feasible to reduce inter-scanner variabilities while preserving the inter-subject differences among healthy individuals by modeling the scanner effects at the level of network matrices, when traveling-subject data are available for calibration between scanners. The present data and results are expected to serve as a basis for developing and evaluating novel harmonization methods.

By nature, humans are “ tojisha (participating subjects/player–witnesses)” who encounter an unpredictable real world. An important characteristic of the relationship between the individual brain and the world is that it creates a loop of interaction and mutual formation. However, cognitive sciences have traditionally been based on a model that treats the world as a given constant. We propose incorporating the interaction loop into this model to create “world-informed neuroscience (WIN)”. Based on co-productive research with people with minority characteristics that do not match the world, we hypothesize that the tojisha and the world interact in a two-dimensional way of rule-based and story-based. By defining the cognitive process of becoming tojisha in this way, it is possible to contribute to the various issues of the real world and diversity and inclusion through the integration of the humanities and sciences. The critical role of the brain dopamine system as a basis for brain–world interaction and the importance of research on urbanicity and adolescent development as examples of the application of WIN were discussed. The promotion of these studies will require bidirectional translation between human population science and animal cognitive neuroscience. We propose that the social model of disability should be incorporated into cognitive sciences, and that disability-informed innovation is needed to identify how social factors are involved in mismatches that are difficult to visualize. To promote WIN to ultimately contribute to a diverse and inclusive society, co-production of research from the initial stage of research design should be a baseline requirement.

Patients with schizophrenia can exhibit intelligence decline, which is an important element of cognitive impairment. Previous magnetic resonance imaging (MRI) studies have demonstrated that patients with schizophrenia have altered gray matter structures and functional connectivity associated with intelligence decline defined by a difference between premorbid and current intelligence quotients (IQs). However, it has remained unclear whether white matter microstructures are related to intelligence decline. In the present study, the indices of diffusion tensor imaging (DTI) obtained from 138 patients with schizophrenia and 554 healthy controls were analyzed. The patients were classified into three subgroups based on intelligence decline: deteriorated (94 patients), preserved (42 patients), and compromised IQ (2 patients) groups. Given that the DTI of each subject was acquired using either one of two different MRI scanners, we analyzed DTI indices separately for each scanner group. In the comparison between the deteriorated IQ group and the healthy controls, differences in some DTI indices were noted in three regions of interest irrespective of the MRI scanners, whereas differences in only one region of interest were noted between the preserved IQ group and the healthy controls. However, the comparisons between the deteriorated and preserved IQ groups did not show any reproducible differences. Together with the previous findings, it is thought that gray matter structures and functional connectivity are more promising as markers of intelligence decline in schizophrenia than white matter microstructures.