Spatial proximity of signals from different sensory modalities is known to be a crucial factor in facilitating efficient multisensory processing in young adults. However, recent studies have demonstrated that older adults exhibit strong visuotactile interactions even when the visual stimuli were presented in a spatially disparate position from a tactile stimulus. This suggests that visuotactile peripersonal space differs between older and younger adults. In the present study, we investigated to what extent peripersonal space expands in the sagittal direction and whether this expansion was linked to the decline in sensorimotor functions in older adults. Vibrotactile stimuli were delivered either to the left or right index finger, while visual stimuli were presented at a distance of 5 cm (near), 37.5 cm (middle), or 70 cm (far) from each finger. The participants had to respond rapidly to a randomized sequence of unimodal (visual or tactile) and simultaneous visuotactile targets (i.e., a redundant target paradigm). Sensorimotor functions were independently assessed by the Timed Up and Go (TUG) and postural stability tests. Results showed that reaction times to the visuotactile bimodal stimuli were significantly faster than those to the unimodal stimuli, irrespective of age group [younger adults: 22.0 ± 0.6 years, older adults: 75.0 ± 3.3 years (mean ± SD)] and target distance. Of importance, a race model analysis revealed that the co-activation model (i.e., visuotactile multisensory integrative process) is supported in the far condition especially for older adults with relatively poor performance on the TUG or postural stability tests. These results suggest that aging can change visuotactile peripersonal space and that it may be closely linked to declines in sensorimotor functions related to gait and balance in older adults.

Surface treatments for the purpose of contamination elimination and surface passivation were performed to as‐deposited CZTSSe thin films before CdS buffer layer deposition. It was found that HCl etching treatment removes contaminations such as sulfide and oxide on CZTSSe surface and helps enhancement of thiourea treatment carried out after HCl etching. Thiourea treatment drastically improves solar cell characteristics, especially FF and JSC, and it would have the effect of surface passivation, although surface sulfuration does not occur. The improvement of characteristics seems to be due to improvement of the film quality and increase in the width of a depletion layer. As a result, conversion efficiency of CZTSSe solar cells was improved from 6.3% to 10.3% with sequential treatment of HCl etching and thiourea treatment. 10.5% was achieved by air anneal after fabrication with both treatments.