视觉空间伪忽视与表征伪忽视神经机制的异同

伪忽视是指个体存在的轻微偏左的不对称空间注意，而视觉空间伪忽视和表征伪忽视是其两种主要表现形式。研究初期，研究者认为两种伪忽视基于相同的注意定向左偏机制，但近年来研究发现，它们存在神经机制的差异。本文主要从两种伪忽视神经机制的异同出发，梳理近期研究结果，以期增进对伪忽视的理解。未来研究可以从认知时间进程角度或设计更为完善的研究范式进一步探讨这两种伪忽视神经机制的异同。

Similar and Distinct Neural Mechanisms of Visuospatial Pseudoneglect and Representational Pseudoneglect

Pseudoneglect is “healthy subjects tend to exhibit a subtle bias of visual attention favoring left space”. This tendency to be biased towards the left side of space is not only demonstrated on the tasks of visuospatial attention (called visuospatial pseudoneglect) but also observed in imaginary space attention tasks (called representational pseudoneglect). However, if a common neural mechanism is the source of both visuospatial and representational pseudoneglect is still under debate. Therefore, it is meaningful to untangle the recent results to further study the similarities and differences of neural mechanisms between the visuospatial pseudoneglect and representational pseudoneglect. Attention orienting, maintenance, and allocation functions mainly rely on the parietal cortex. Furthermore, according to the early right hemisphere (RH) dominance theory, lateralization of attention functions is suggested to be the basis of pseudoneglect. Neuroimaging and repetitive transcranial magnetic stimulation(TMS) studies further proved that the right posterior parietal cortex is the common neural basis of both visuospatial pseudoneglect and representational pseudoneglect. Besides, several scholars found that larger superior longitudinal fascicle (SLF) II volumes on the right hemisphere correspond to a greater deviation to the left in the line bisection, which indicates visuospatial pseudoneglect is associated with an unbalanced speed of visuospatial processing between the two hemispheres along the SLF II. Others found that in brain-damaged neglect subjects, only right prefrontal cortex damage is connected to the disappearance of representational pseudoneglect. In other words, damage to the right prefrontal cortex may lead to the impairment of spatial working memory in patients, thus affecting the formation and processing of the left portion of spatial representations. Therefore, the right prefrontal cortex may be a key brain region for representational pseudoneglect.To further prove the mentioned similar and distinct neural mechanisms of two kinds of pseudoneglect, the effects of prism adaptation and stimulus presentation distance on them were discussed. The results revealed that prism adaptation has similar influences on visuospatial pseudoneglect and representational pseudoneglect. Specifically, it adjusts the centerline of the attention allocation in both visual and representational space by affecting the functions of the right posterior parietal cortex. However, stimulus presentation distance modulates the phenomenon of visuospatial pseudoneglect alone, given that left visuospatial bias is attenuated as the stimulus moves from near to far space. This may be related to reduced speed difference of visuospatial information along the SLF II between the two hemispheres in the far distance.Besides, the performance of schizophrenic and developmental dyscalculia patients in visuospatial and representational pseudoneglect tasks also implies distinct mechanisms of them. The damage to the right posterior parietal lobe, which is the common neural basis of two kinds of pseudoneglect, will affect attention function dominance of the right hemisphere, thus leading to the disappearance of visuospatial pseudoneglect. However, in addition to being modulated by attention function, conditions such as learning, experience, and genetics also affect the expression of representational pseudoneglect. When attention functions are impaired, representational attention deficits may be compensated by other strategies to maintain a stable leftward representational spatial bias.In addition, for better understanding the underlying neural mechanisms, future studies can also explore the dissimilarities of time course between visuospatial pseudoneglect and representational pseudoneglect and optimize the paradigm of representational pseudoneglect.