Eiji Watanabe

Dimensional theories of emotion propose that affective experiences can be organised along continuous dimensions like Pleasure, Arousal, and Dominance. Recent computational methods for capturing these conceptual structures have relied primarily on word embeddings, requiring substantial technical expertise. This study examined whether prompting GPT4 as a more accessible method, can capture this structure more effectively, by comparing both approaches against human spatial reasoning, with particular focus on analysing extensive emotion vocabularies exceeding constraints of human cognitive capability. Study 1 established validity by testing six basic emotions, prompting showed strong convergence with human judgements, while embeddings produced fundamentally different clustering patterns. Study 2 extended analysis to 99 emotion terms. Both approaches identified two optimal clusters distinguished by both Pleasure and Dominance, though prompting produced clearer cluster separation. Particularly, Arousal emerged only at the larger vocabulary scale as a secondary, component-level dimension rather than a cluster-defining one. Together these results indicated that GPT prompting offers a promising tool for investigating semantic structure of emotion, particularly in terms of uncovering patterns that only become visible when analysing a broader sample of emotion lexicon.

Climbing demands that the performer see, balance, and move as a single act, making it a compelling case for embodied accounts of cognition. Yet climbing research has largely measured body morphology, gaze, or movement in isolation, and gaze has typically been recorded separately from the head that carries the eyes. We recorded gaze and head movement simultaneously, using a head-mounted eye tracker with an integrated inertial sensor, in 22 climbers spanning the full grade range from novice to competition athlete, on a naturalistic bouldering route. Principal component analysis revealed that gaze and head movement did not separate into distinct channels but co-varied as a single dimension reflecting the magnitude of visual-postural exploration; this dimension, together with the temporal organization of head movement, predicted climbing grade (R^2=0.615). The anthropometric measures most emphasized in climbing: arm span, BMI, and ape index, did not predict grade independently of sex, although body morphology helped distinguish climber subgroups. These findings indicate that the eyes and head operate as a single exploration system whose coordination, rather than the body’s structure, marks bouldering expertise, and support an embodied account in which skilled perception and action are inseparable.

Subjective color (SC) refers to chromatic perception induced by achromatic stimuli, as classically demonstrated using Benham's top. Despite nearly two centuries of investigation, the underlying neural mechanisms remain unclear. We developed artificial neural network models trained on natural videos using predictive learning to investigate SC generation. These models successfully reproduced artificial subjective color (ASC) from achromatic testing stimuli that contained no explicit chromatic information. Critically, ASC characteristics were systematically influenced by the colors of moving objects in the training videos. Using progressively simplified stimuli, ranging from natural scenes to 3D computer graphics and 2D animations, we demonstrated that the colors of moving objects primarily determine ASC properties. We propose that predictive learning establishes color associations with motion patterns, causing the arcs on Benham's top to be perceived as moving objects with corresponding colors. These findings suggest that cortical predictive mechanisms may complement retinal processes in generating subjective color phenomena.

Availability of pseudopregnant recipient females is an essential component of embryo transfer in mice. However, conventional methods for sorting females based on estrous signs (proestrus or estrus) require maintaining a large stock of mice, thereby presenting challenges for animal welfare. Furthermore, these large numbers of female mice are often maintained in group housing due to space constraints; and this can induce the Lee-Boot effect, leading to decreased preparation efficiency. Therefore, this study examined a method for preparing pseudopregnant recipient females using mice showing nonestrous signs through a unique approach based on the Whitten effect. Female ICR mice exhibiting metestrus or diestrus characteristics were deliberately sorted and housed with vasectomized males for 3 consecutive days. The Lee-Boot effect was induced through group housing to increase the proportion of females showing nonestrous signs, followed by Whitten effect induction aimed at achieving successful copulation on day 3. Results demonstrated copulation success rates of 74.4% (CLEA Japan, n = 500) and 77.0% (Japan SLC, n = 200) on day 3, significantly higher than random mating controls during the same period (53.5%, Japan SLC, n = 101; December to May). Subsequent embryo transfers achieved high pregnancy rates of 93.1% and 89.6%, respectively. This approach demonstrated the feasibility of using mice showing nonestrous signs, previously overlooked in conventional methods, for preparing pseudopregnant recipient females. When combined with conventional methods, this approach expands the range of mice available for mating and potentially enables more efficient production of pseudopregnant recipient females while minimizing the total number of female mice required. This advancement aligns with the Replacement, Reduction, and Refinement (3Rs) principles of animal experimentation, particularly the reduction principle, and provides a practical strategy for laboratories seeking to perform embryo transfer procedures with smaller mouse numbers.

Biological brain networks flexibly reconfigure functional connectivity between integration and segregation through neuromodulatory systems—noradrenaline (NA) and acetylcholine (ACh)—without altering structural connectivity. Inspired by this mechanism, we propose a modular echo state network (ESN) with context-dependent NA and ACh gain modulation, where NA promotes inter-module integration via response gain and ACh promotes intra-module segregation via multiplicative gain. We evaluate the model on two context-dependent tasks: a segregation/integration task and a context-dependent decision task. Across both tasks, the modulated model consistently outperformed the baseline, with task-appropriate modulation profiles emerging naturally from optimization and functional connectivity analysis confirming context-appropriate dynamic reorganization. These results demonstrate that neuromodulatory gain control enables adaptive, context-sensitive computation in structurally fixed reservoir networks.

Visual illusions are utilized to elucidate mechanism of visual information processing. For example, the Rotating Snakes illusion creates the illusory perception of motion when viewing a static image. This study investigated the difference in perception of illusory rotation between younger and older adults with normal visual acuity. Participants and Methods: The participants included 105 younger adults (mean age: 23.7 years) and 100 older adults (mean age: 74.2 years). Each participant was presented with the Rotating Snakes illusion, then asked to respond whether they perceived the snakes to be "rotating" or "not rotating". The rate of perception of illusory rotation was compared between the two groups. To evaluate the effects of cataracts, a major age-related optical change, comparisons were also made between older participants with bilateral cataracts versus those with bilateral intraocular lens (IOL) implantation. Results: Rotation was perceived by 100% (105/105) of participants in the younger group, but only by 16% (16/100) of participants in the older group, showing a significant difference (p < 0.001). Among the older adults, the IOL and cataract groups had no significant difference in the rate of those who perceived the illusion (6/54 vs 10/45, p = 0.12). Conclusion: Significantly more younger adults perceived illusory motion in the Rotating Snakes illusion versus older adults. Lens opacity due to aging likely does not contribute to this phenomenon.

Subjective color (SC) refers to chromatic perception induced by achromatic stimuli, as classically demonstrated using Benham's top. Despite nearly two centuries of investigation, the underlying neural mechanisms remain unclear. We developed artificial neural network (ANN) models trained on natural videos using predictive learning to investigate SC generation. These models successfully reproduced artificial subjective color (ASC) despite the absence of explicit color information in the training stimuli. Critically, ASC characteristics were systematically influenced by the colors of moving objects in the training videos. Using progressively simplified stimuli, ranging from natural scenes to 3D computer graphics to 2D animations, we demonstrated that the colors of moving objects are the primary determinant of ASC properties. We propose that predictive learning establishes color associations with motion patterns, causing the arcs on Benham's top to be perceived as moving objects with their corresponding colors. These findings suggest that cortical predictive mechanisms may complement retinal processes in generating subjective color phenomena.

Medaka ( Oryzias latipes and O. sakaizumii ) are small freshwater fish native to East Asia, commonly found in shallow waters. However, their presence and behavior in deeper habitats remain poorly understood due to observational challenges. Here, we introduce a novel experimental system—a 9-meter-tall cylindrical tank made from vertically connected transparent PVC pipes—that enables direct observation of medaka diving behavior. Our results demonstrate that medaka voluntarily dive to depths of up to 9 meters and remain at the bottom for extended periods, a behavior contrasting with that of zebrafish ( Danio rerio ), which rarely reached such depths. Moreover, when fish were introduced from the bottom of the tank, zebrafish exhibited repeated vertical movements, ascending and descending but rarely reaching the water surface, whereas medaka consistently remained at the bottom. While primarily descriptive, these findings represent a significant and previously unrecognized aspect of medaka ecology, challenging the traditional view of them as purely surface-dwelling fish. This study provides a unique tool and foundational insight that opens new avenues for ecological and physiological investigations of fish depth preferences.