Biology subjects

Yokoi, I.

Publications and source records attributed to Yokoi, I..

4 recordsLinked to original sources

bioRxiv2026

Tractometry reproducibility and generalizability across scanners, scanner models, and acquisition protocols

Diffusion-weighted magnetic resonance imaging (dMRI)-based tractometry enables the quantification of white matter tissue properties in living humans while preserving anatomical specificity. Although tractometry is highly reproducible when the same scanner and acquisition protocol are used, its generalizability across scanners and protocols remains unclear. To address this gap, we performed a traveling-head experiment involving five subjects to evaluate tractometry across progressively different acquisition conditions, including multiple scanners, different scanner models, and two distinct protocols. Tractometry was performed for 20 major white matter tracts using diffusion tensor imaging metrics, neurite orientation dispersion and density imaging (NODDI) metrics, and a semi-quantitative ratio metric (T1w/b0). Generalizability across dataset pairs was quantified using the intraclass correlation coefficient (ICC). Tractometry showed consistently high ICCs when the scanner and protocol were identical; however, ICCs declined as differences in scanner model and acquisition protocol increased. Fractional anisotropy and orientation dispersion index retained relatively high ICCs across these comparisons, whereas other metrics showed marked declines when scanners or protocols differed. ComBat harmonization partially mitigated these declines, but ICCs did not reach the levels observed for datasets acquired using identical scanners and protocols. Finally, the minimum detectable change (MDC) for tractometry in datasets pooled across scanners and protocols varied by tract; for example, the optic radiation showed a lower MDC than the cingulum hippocampus. These findings highlight both the strengths and limitations of tractometry in multisite studies and highlight the importance of quantifying scanner- and protocol-dependent effects for specific metrics and tracts when interpreting measurements from heterogeneous datasets.

neuroscience↗

bioRxiv2026

Transfer of symbolic numeral adaptation across eyes and hemifields

Visual perception of symbolic numerals is essential for everyday tasks; however, the neural and perceptual mechanisms underlying this ability remain unclear. Partially occluded digital numerals can elicit bistable perception, and adaptation to symbolic numerals alters the perception of these ambiguous stimuli. We aimed to examine how symbolic numeral adaptation is related to hierarchical visual processing by testing its interocular and interhemifield transfer. Experiment 1 tested interocular transfer by presenting the test stimulus to either the same or opposite eye as the adaptation stimulus. Experiment 2 assessed interhemifield transfer by presenting the test stimulus to either the same or opposite hemifield as the adaptation stimulus. Experiment 3 examined the interhemifield transfer of adaptation confined to the upper parts of digital numerals. Our results showed that adaptation to digital numerals induced shifted perceptual interpretations that transferred across eyes. In addition, we found that adaptation to digital numerals induced a relatively small but statistically significant interhemifield transfer. In contrast, adaptation restricted to the upper parts of digital numerals showed no significant interhemifield transfer. These findings suggest that the perceptual interpretation of symbolic numerals involves visual processing stages that integrate information across the eyes and hemifields.

neuroscience↗

bioRxiv2026

The anisotropic sensitivities of perceptual speed between expanding and contracting optic flows

Retinal optic flow provides critical visual cues for locomotion and self-navigation. Forward self-motion, such as walking or driving, typically induces an expanding radial flow pattern on the retina. Despite the predominance of expanding optic flow in everyday self-motion, several studies have reported higher perceptual sensitivity for contracting flow that arises under relatively rare conditions, such as walking backward or falling onto ones back. The underlying basis of this perceptual anisotropy remains elusive. In this study, we compared perceptual sensitivity to speed for expanding versus contracting optic flow, given that speed is a fundamental attribute of motion and that perceptual sensitivity to it provides insight into underlying visual mechanisms. We found that sensitivity in speed discrimination was comparable between expansion and contraction at low and high speeds, but was significantly higher for contraction at an intermediate speed corresponding to ecologically relevant self-motion, such as walking. This anisotropic pattern was observed for both 2D planar (Experiment 1) and simulated 3D (Experiment 2) optic flow stimuli. Together, these findings suggest that anisotropic perceptual sensitivity to expanding and contracting optic flow at ecologically typical egomotion speeds may reflect an adaptive visual mechanism that supports postural stability and balance during relatively rare backward self-motion.

animal behavior and cognition↗

bioRxiv2024

Bistable perception of symbolic numbers

Numerals, i.e., semantic expressions of numbers, enable us to have an exact representation of the amount of things. Visual processing of numerals plays an indispensable role in the recognition and interpretation of numbers. Here, we investigate how visual information from numerals is processed to achieve semantic understanding. We first found that partial occlusion of some digital numerals introduces bistable interpretations. Next, by using the visual adaptation method, we investigated the origin of this bistability in human participants. We showed that adaptation to digital and normal Arabic numerals, as well as homologous shapes, but not Chinese numerals, biases the interpretation of a partially occluded digital numeral. We suggest that this bistable interpretation is driven by intermediate shape processing stages of vision, i.e., by features more complex than local visual orientations but more basic than the abstract concepts of numerals.

neuroscience↗