Haruyuki Kojima

The what and why of perceptual asymmetries in the visual domain.

Perceptual asymmetry is one of the most important characteristics of our visual functioning. We carefully reviewed the scientific literature in order to examine such asymmetries, separating them into two major categories: within-visual field asymmetries and between-visual field asymmetries. We explain these asymmetries in terms of perceptual aspects or tasks, the what of the asymmetries; and in terms of underlying mechanisms, the why of the asymmetries. Tthe within-visual field asymmetries are fundamental to orientation, motion direction, and spatial frequency processing. between-visual field asymmetries have been reported for a wide range of perceptual phenomena. foveal dominance over the periphery, in particular, has been prominent for visual acuity, contrast sensitivity, and colour discrimination. Tthis also holds true for object or face recognition and reading performance. upper-lower visual field asymmetries in favour of the lower have been demonstrated for temporal and contrast sensitivities, visual acuity, spatial resolution, orientation, hue and motion processing. Iin contrast, the upper field advantages have been seen in visual search, apparent size, and object recognition tasks. left-right visual field asymmetries include the left field dominance in spatial (e.g., orientation) processing and the right field dominance in non-spatial (e.g., temporal) processing. left field is also better at low spatial frequency or global and coordinate spatial processing, whereas the right field is better at high spatial frequency or local and categorical spatial processing. All these asymmetries have inborn neural/physiological origins, the primary why, but can be also susceptible to visual experience, the critical why (promotes or blocks the asymmetries by altering neural functions).

Coherence of early motion signals

Oscillation thresholds were evaluated for detecting motion and discriminating relative motion. Three horizontally aligned Gaussian blobs oscillated horizontally, with the center in-phase or out-of-phase with the two flankers. Motion thresholds were well below those for static bisection, and involved small contrast changes (<0.25%). Remarkably, acuity was better for discriminating phase relations than for detecting rigid motion, averaging 8.7 and 11.0 arcsec, respectively, for 100 arcmin between blobs. Phase discrimination acuities were robust over separations of 20-320 arcmin and temporal frequencies of 1.5-6 Hz. Motion phase relations must be coherent among spatially separate retinal signals, carrying information about intrinsic image structure.

Hemodynamic change in occipital lobe during visual search: Visual attention allocation measured with NIRS

We examined the changes in regional cerebral blood volume (rCBV) around visual cortex using Near Infrared Spectroscopy (NIRS) when observers attended to visual scenes. The oxygenated and deoxygenated hemoglobin (Oxy-Hb and Deoxy-Hb) concentration changes at occipital lobe were monitored during a dual task. Observers were asked to name a digit superimposed on a scenery picture, while in parallel, they had to detect an on-and-off flickering object in a Change Blindness paradigm. Results showed the typical activation patterns in and around the visual cortex with increases in Oxy-Hb and decreases in Deoxy-Hb. The Oxy-Hb increase doubled when observers could not find the target, as opposed to trials in which they could. The results strongly suggest that active attention to a visual scene enhances Oxy-Hb change much stronger than passive watching, and that attention and Oxy-Hb increases are possibly correlated.

Hemodynamic responses to visual stimuli in cortex of adults and 3- to 4-year-old children

In this study we used near-infrared spectroscopy (NIRS) to measure relative changes in cortical hemodynamics from 19 adult and 19 preschool children (aged 3-4 years old), while they watched epochs of static and motion pictures extracted from TV programs. The spatio-temporal characteristics of oxygenated and deoxygenated hemoglobin volumes (oxy- and deoxy-Hb) of both subject groups were described and compared where appropriate for five regions of interest (ROIs). These were striate, left and right middle temporal, and left and right temporo-parietal areas. Over these areas, deoxy-Hb volumes did not differ between both groups. Preschool data showed significant increases in oxy-Hb over striate, middle temporal and temporo-parietal areas in response to visual motion stimuli. Static stimuli caused a significant oxy-Hb increase over striate and left middle temporal areas. Surprisingly, changes in adult oxy-Hb were not profound and did not show a significant oxy-Hb increase in striate and middle temporal areas in response to the motion stimuli, warranting further research. In spite of oxy-Hb volume differences, oxy-Hb recovery to baseline followed a similar pattern in both groups in response to both static and motion stimuli. Together, the results suggest that near-infrared spectroscopy is a viable method to investigate cortical development of preschool children by monitoring their hemodynamic response patterns.

Changes in hemoglobin concentration in the lateral occipital regions during shape recognition: a near-infrared spectroscopy study

By using near-infrared spectroscopy (NIRS), we measured the changes in the oxygenated and deoxygenated hemoglobin (oxy-Hb and deoxy-Hb, respectively) concentrations while performing visual tasks. We conducted experiments using two tasks: a shape recognition task and a position recognition task. It was found that the oxy-Hb concentration was substantially higher in the lateral occipital regions during shape recognition than during position recognition. The changes in the oxy-Hb concentration were considered to reflect the activation difference between the two tasks. No difference was observed in the oxy-Hb concentration during the memorization of shape and memorization of position. The deoxy-Hb concentration was different between the two tasks only when different stimuli were used but not when identical stimuli were used. In addition, it was suggested that the deoxy-Hb concentration is more sensitive to activation difference between the hemispheres and the activation at some regions. Measurements of the oxy-Hb and deoxy-Hb concentrations would reflect different aspects of cortical activations. The present results showed that measuring the oxy-Hb and deoxy-Hb concentrations separately can differentiate the activation of the regional cortical functions.

Somatosensory evoked field in response to visuotactile stimulation in 3-to 4-year-old children

A child-customized magnetoencephalography system was used to investigate somatosensory evoked field (SEF) in 3- to 4-year-old children. Three stimulus conditions were used in which the children received tactile-only stimulation to their left index finger or visuotactile stimulation. In the two visuotactile conditions, the children received tactile stimulation to their finger while they watched a video of tactile stimulation applied either to someone else’s finger (the finger-touch condition) or to someone else’s toe (the toe-touch condition). The latencies and source strengths of equivalent current dipoles (ECDs) over contralateral (right) somatosensory cortex were analyzed. In the preschoolers who provided valid ECDs, the stimulus conditions induced an early-latency ECD occurring between 60 and 68 ms mainly with an anterior direction. We further identified a middle-latency ECD between 97 and 104 ms, which predominantly had a posterior direction. Finally, initial evidence was found for a late-latency ECD at about 139–151 ms again more often with an anterior direction. Differences were found in the source strengths of the middle-latency ECDs among the stimulus conditions. For the paired comparisons that could be formed, ECD source strength was more pronounced in the finger-touch condition than in the tactile-only and the toe-touch conditions. Although more research is necessary to expand the data set, this suggests that visual information modulated preschool SEF. The finding that ECD source strength was higher when seen and felt touch occurred to the same body part, as compared to a different body part, might further indicate that connectivity between visual and tactile information is indexed in preschool somatosensory cortical activity, already in a somatotopic way.

The spatial frequencies influence the aesthetic judgment of buildings transculturally

Recent evidence has shown that buildings designed to be high-ranking, according to the Western architectural decorum, have more impact on the minds of their beholders than low-ranking buildings. Here we investigated whether and how the aesthetic judgment for high- and low-ranking buildings was affected by differences in cultural expertise and by power spectrum differences. A group of Italian and Japanese participants performed aesthetic judgment tasks, with line drawings of high- and low-ranking buildings and with their random-phase versions (an image with the exact power spectrum of the original one but non-recognizable anymore). Irrespective of cultural expertise, high-ranking buildings and their relative random-phase versions received higher aesthetic judgments than low-ranking buildings and their random-phase versions. These findings indicate that high- and low-ranking buildings are differentiated for their aesthetic value and they show that low-level visual processes influence the aesthetic judgment based on differences in the stimuli power spectrum, irrespective of the influence of cultural expertise.

Atypical development of the central auditory system in young children with Autism spectrum disorder

The P1m component of the auditory evoked magnetic field is the earliest cortical response associated with language acquisition. However, the growth curve of the P1m component is unknown in both typically developing (TD) and atypically developing children. The aim of this study is to clarify the developmental pattern of this component when evoked by binaural human voice stimulation using child‐customized magnetoencephalography. A total of 35 young TD children (32–121 months of age) and 35 children with autism spectrum disorder (ASD) (38–111 months of age) participated in this study. This is the first report to demonstrate an inverted U‐shaped growth curve for the P1m dipole intensity in the left hemisphere in TD children. In addition, our results revealed a more diversified age‐related distribution of auditory brain responses in 3‐ to 9‐year‐old children with ASD. These results demonstrate the diversified growth curve of the P1m component in ASD during young childhood, which is a crucial period for first language acquisition. Autism Res 2016, 9: 1216–1226.

Configurational asymmetry in vernier offset detection.

Two psychophysical experiments were conducted at the horizontal and vertical orientations respectively, demonstrating substantial main effect of configuration, but no effect of offset direction on vernier acuity. In Experiment 1, a pair of horizontal bars were arranged side by side with a large gap between them. The observers were, on average, significantly better at discriminating a vertical offset if the right-hand bar was below the left-hand bar than vice versa, regardless of which bar they experienced as displaced and which as constant. A similar asymmetry was evident in Experiment 2 where observers judged horizontal offset for a pair of vertically oriented bars, where one was placed above the other. In this case average performance was better if the upper bar was on the right of the lower bar rather than on its left. There were large individual variations in the asymmetrical trend, but the effect could not be explained by subjective response bias. Furthermore, vernier acuity improved significantly and the asymmetry decreased more or less as a function of training. The average asymmetrical trend was consistent across training days and across two orientations, which indicates that the processing of line vernier stimuli is possibly configuration-specific in the cardinal orientation.

The spatiotemporal range of inhibitory interaction in flicker detection

The flicker thresholds of luminous bars were measured as a function of the spatial and/or temporal separation of two flickering stimuli. Each of the bars had an intensity profile of one-half cycle of a sinusoidal wave subtending 2.26 x 0.45 arc deg and each bar was presented twice at two positions with a duration of 10 msec. The spatial separation was defined as the distance between the adjacent flanks of two flickering stimuli, while the temporal separation was determined as the time-lag between the offset of the first flickering stimulus and the onset of the second. We found that the thresholds increased asymptotically with the spatial separation in such a way as to suggest that the spatial extent over which inhibitory interaction could be effective was as large as about 2 arc deg. We also found that the threshold gradually decreased with greater temporal separation; this indicated that the temporal proximity of successive stimuli effects less suppression on the temporal response. These two effects were seemingly additive. These findings suggest that the visual system involves not only local spatial interaction, but also a global mechanism capable of spreading inhibition over several local units after a delay of several msec.