Flevaris Anastasia V, Murray Scott O
Department of Psychology, University of Washington Seattle, WA, USA.
Front Hum Neurosci. 2015 Jan 6;8:1017. doi: 10.3389/fnhum.2014.01017. eCollection 2014.
Individuals with autism spectrum disorder (ASD) exhibit superior performance on tasks that rely on local details in an image, and they exhibit deficits in tasks that require integration of local elements into a unified whole. These perceptual abnormalities have been proposed to underlie many of the characteristic features of ASD, but the underlying neural mechanisms are poorly understood. Here, we investigated the degree to which orientation-specific surround suppression, a well-known form of contextual modulation in visual cortex, is associated with autistic tendency in neurotypical (NT) individuals. Surround suppression refers to the phenomenon that the response to a stimulus in the receptive field of a neuron is suppressed when it is surrounded by stimuli just outside the receptive field. The suppression is greatest when the center and surrounding stimuli share perceptual features such as orientation. Surround suppression underlies a number of fundamental perceptual processes that are known to be atypical in individuals with ASD, including perceptual grouping and perceptual pop-out. However, whether surround suppression in the primary visual cortex (V1) is related to autistic traits has not been directly tested before. We used fMRI to measure the neural response to a center Gabor when it was surrounded by Gabors having the same or orthogonal orientation, and calculated a suppression index (SI) for each participant that denoted the magnitude of suppression in the same vs. orthogonal conditions. SI was positively correlated with degree of autistic tendency in each individual, as measured by the Autism Quotient (AQ) scale, a questionnaire designed to assess autistic traits in the general population. Age also correlated with SI and with autistic tendency in our sample, but did not account for the correlation between SI and autistic tendency. These results suggest a reduction in orientation-specific surround suppression in V1 with increasing autistic tendency.
患有自闭症谱系障碍（ASD）的个体在依赖图像局部细节的任务上表现出色，而在需要将局部元素整合为统一整体的任务上则表现出缺陷。这些感知异常被认为是自闭症许多特征的基础，但其潜在的神经机制却知之甚少。在此，我们研究了特定方向的周围抑制（视觉皮层中一种著名的上下文调制形式）在多大程度上与神经典型（NT）个体的自闭症倾向相关。周围抑制是指当神经元感受野内的一个刺激被感受野外的刺激包围时，该刺激的反应被抑制的现象。当中心刺激和周围刺激具有共同的感知特征（如方向）时，抑制作用最强。周围抑制是许多基本感知过程的基础，已知这些过程在患有自闭症谱系障碍的个体中是不典型的，包括感知分组和感知凸显。然而，初级视觉皮层（V1）中的周围抑制是否与自闭症特征相关，此前尚未得到直接验证。我们使用功能磁共振成像（fMRI）来测量当中心Gabor被具有相同或正交方向的Gabor包围时的神经反应，并为每个参与者计算一个抑制指数（SI），该指数表示相同条件与正交条件下的抑制程度。如通过自闭症商数（AQ）量表所测量的，SI与每个个体的自闭症倾向程度呈正相关，AQ量表是一种旨在评估普通人群自闭症特征的问卷。在我们的样本中，年龄也与SI和自闭症倾向相关，但并不能解释SI与自闭症倾向之间的相关性。这些结果表明，随着自闭症倾向的增加，V1中特定方向的周围抑制作用减弱。
