Shin'ichi Fukuzumi

Multiple Equivalent Current Dipole Source Localization of Visual Event-Related Potentials During Oddball Paradigm With Motor Response

Event-related potentials (ERPs) during a visual oddball paradigm with button-pressing responses were recorded in 12 right-handed subjects from 32 scalp electrodes. The single equivalent current dipole (ECD) of the target C1 (weak occipito-parietal negativity from 30-80ms) was consistently located at the primary visual cortex. From the 4-ECD localization of the target P1/N1 (temporally coincident frontal positivity and occipito-temporal negativity), it was suggested that this complex reflected activities from distributed sources along both dorsal occipito-parietal and ventral occipito-temporal areas. The stable multiple ECD solutions for the target P3b were chosen as those including the left primary motor and/or sensorimotor dipole and satisfying goodness-of-fit (GOF) of more than 98% and confidence limit (CL) of less than 1mm. The obtained frontal dipoles were discussed in terms of visual working memory and sustained attention in reference to the previous PET, fMRI and MEG studies. The distributed multiple ECDs may suggest that P3 should be interpreted as being the embodiment of the cortico-limbic-thalamic network which involves Halgren and Marinkovics emotional and behavioral model and Mesulams attentional circuit.

Variation in importance of time-on-task with familiarity with mobile phone models

We studied the extent to which time-on-task is correlated with perception of usability for people who are familiar with a phone model and for those who are not. Our controlled experiment, conducted in Japan, correlated subjective usability assessments with time-on-task for expert and novice users on three different mobile phone models. We found that the correlation between perceived usability and time-on-task is stronger when participants are more familiar with the phone model. While not significant when initially inspecting a new phone model, a negative correlation between time-on-task and perceived usability becomes significant with as little as an hours time doing tasks on the unfamiliar phone. This suggests that designing the UI to make time-on-task as short as possible may not have much effect on the purchase decision, but as experience increases, it may increase the loyalty of existing users.

Luminance and stimulus purify of VDT display color in terms of readability

A study was undertaken to investigate the relations among luminance, stimulus purity, and Visual Display Terminal (VDT) display color readability, and to clarify the relation between readability and color impression. Four levels of stimulus purity for orange, five levels for green, and five for purple blue, and white and black were examined by a paired comparison method and a questionnaire regarding impression observed for the colors under two levels of illuminance and three levels of luminance. Questionnaire replies indicated that each color had an optimal stimulus purity, in terms of readability, which was from 0.2 to 0.5, independently from illuminance and luminance. Mens readability scores for higher stimulus purities than the optimal value, did not notably decrease, while womens scores were severely lower than the optimal value. In case of short dominant wavelength, readability was higher under low luminance than under other luminances. By applying the Semantic Differential method to answers to the...

Study on validity of visual performance and comfort test using Japanese characters

Abstract The validity of applying Japanese characters to a visual performance and comfort test (ISO9241-3 Amendment 1) in conducting an LCD-CRT comparative experiment was studied. The evaluation results from using Japanese characters were similar to those from using alphanumeric characters, while the experiment time was shorter. The test method is thus also valid for Japanese character displays.

Dominant wavelength and stimulus purity for VDT display color in terms of readability

This study was conducted to clarify complex relationships between VDT (Visual Display Terminal) display color subjective readability and dominant wavelength, and between the subjective readability and stimulus purity. In this study, readability was defined to be such that a human could read sentences on a VDT screen. Twelve men and eight women, who were all Japanese and had normal color vision, participated in three experiments. During all the experiments, the vertical illuminances on the screen were 700 Lux and 300 Lux. Contrasts were 3.1:1 and 4.2:1 under 700 Lux and 300 Lux, respectively. In the first experiment, 25 kinds of screen were used, there were 23 different colors and white shown on a black background screen (negative screen), and black shown on a white background screen (positive screen). The colors had six dominant wavelengths, ranging from 460 nm to 606 ran, whose stimulus purities involved three, four, or five levels for each wavelength. In the second experiment, three levels of stimulus p...

Proposal for Indices to Assess Attractiveness on Initial Use of Mobile Phones

It is necessary to determine the attractiveness level of using mobile phone to ensure user satisfaction. This study measured physiological indices of attractiveness during participants’ initial use of a mobile phone. As physiological indices which concern autonomic nervous system activity, nasal skin temperature, pupil diameter, electroencephalography, blinking, and electrocardiography are listed. These indices were selected because preceding studies have suggested “safety and relaxing” and “feelings induced by desire and interest” as factors related to the attractiveness of mobile phones. The results obtained in these experiments that a device’s attractiveness to users can be evaluated using physiological indices. Thus, the present study showed basic perspectives related to attractiveness from the point of physiological response.

14.3: Study on Validity of Visual Performance and Comfort Test (ISO 9241-3 Amendment) for LCD-CRT Comparative Experiment Applied to Japanese Characters

The validity of applying Japanese characters to a visual performance and comfort test (ISO9241-3 Amendment) in conducting an LCD-CRT comparative experiment was studied. The evaluation results from using Japanese characters were similar to those from using alphanumeric characters, while the experiment time was shorter. The test method is thus also valid for Japanese character displays.

Change in Physiological Data for a Filtering Paradigm and a Selective-Set Paradigm

We measured the change of ERP during Filtering Paradigm and Selective-set Paradigm. From experiments using these paradigms, we found P300. For the former stimulus, N1 peak potential in ERP increased and the lead position on the scalp changed by the direction of target stimulus. For the latter stimulus, P1 peak potential in ERP increased by the position of target stimulus. From these results, ERP is useful index to measure the response to human attention positions.