掩蔽刺激对目标识别加工的作用：来自fNIRS的证据
摘要
<p id="C2">When our visual system processes target signals, it usually receives large amounts of irrelevant information from the target, leading to a reduction in the visibility of the target. A wealth of research has shown that visual search for target letters against a masking background is largely determined by the masker type. Informational maskers, such as either randomly positioned and oriented letters or randomly distributed letter fragments, induce stronger masking effects on recognition of target letters than the energetic maskers do, such as the random-phase masker (same spectral amplitude composition as the letter masker but with the phase spectrum randomized) or the random-pixel masker (the locations of the letter maskers’ pixel amplitudes being randomized). However, the mechanisms under informational masking and those under energetic masking are still unknown. The current study examined both cortical activities and behavioral performances in the visual search task, which is determined by whether one of four letters presented at four symmetrically-located positions differs from the others under three masking conditions (random pixels, letter fragments, and random letters). Both the oxygenated hemoglobin concentration (HbO) responses in the primary visual cortex (V1) and secondary visual cortex (V2) with a functional near infrared spectroscopy (fNIRS) were recorded. Twenty (4 males, 16 females) healthy adults (mean age: 22.5 ± 1.67 years) participated in the experiment. Each masking condition contained 5 blocks, and each block contained 8 trails. There was a resting phase of 20 seconds between the two blocks. Spatial registration methods were applied to localize the cortical regions underneath each channel and to define two regions of interest (ROIs), which are the primary visual cortex (V1) and secondary visual cortex (V2). The behavioral results showed that the performance of recognizing target letters improved when the masker type shifted from random l