Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, CA 90024, USA; Desert Pacific Mental Illness Research, Education, and Clinical Center, Greater Los Angeles Veterans Affairs Healthcare System, Los Angeles, CA 90073, USA.
Departments of Neurology, Psychiatry & Biobehavioral Sciences, University of California, Los Angeles, Los Angeles, CA 90024, USA.
Schizophr Res. 2017 Dec;190:102-106. doi: 10.1016/j.schres.2017.03.027. Epub 2017 Mar 17.
People with schizophrenia typically show visual processing deficits on masking tasks and other performance-based measures, while people with bipolar disorder may have related deficits. The etiology of these deficits is not well understood. Most neuroscientific studies of perception in schizophrenia and bipolar disorder have focused on visual processing areas in the cerebral cortex, but perception also depends on earlier components of the visual system that few studies have examined in these disorders. Using diffusion weighted imaging (DWI), we investigated the structure of the primary sensory input pathway to the cortical visual system: the optic radiations. We used probabilistic tractography to identify the optic radiations in 32 patients with schizophrenia, 31 patients with bipolar disorder, and 30 healthy controls. The same participants also performed a visual masking task outside the scanner. We characterized the optic radiations with three structural measures: fractional anisotropy, mean diffusivity, and tract volume. We did not find significant differences in those structural measures across groups. However, we did find a significant correlation between the volume of the optic radiations and visual masking thresholds that was unique to the schizophrenia group and explained variance in masking performance above and beyond that previously accounted for by differences in visual cortex. Thus, individual differences in the volume of the optic radiations explained more variance in visual masking performance in the schizophrenia group than the bipolar or control groups. This suggests that individual differences in the structure of the subcortical visual system have an important influence on visual processing in schizophrenia.
精神分裂症患者在掩蔽任务和其他基于表现的测量中通常表现出视觉处理缺陷，而双相情感障碍患者可能存在相关缺陷。这些缺陷的病因尚不清楚。大多数关于精神分裂症和双相情感障碍的感知的神经科学研究都集中在大脑皮层的视觉处理区域，但感知也依赖于很少有研究在这些疾病中检查过的视觉系统的早期成分。使用扩散加权成像（DWI），我们研究了皮质视觉系统的主要感觉输入途径的结构：视辐射。我们使用概率追踪法在 32 名精神分裂症患者、31 名双相情感障碍患者和 30 名健康对照者中识别视辐射。相同的参与者也在扫描仪外进行了视觉掩蔽任务。我们用三个结构测量来描述视辐射：各向异性分数、平均扩散系数和束流体积。我们没有发现这些结构测量在组间存在显著差异。然而，我们确实发现视辐射体积与视觉掩蔽阈值之间存在显著相关性，这种相关性仅在精神分裂症组中存在，并且可以解释掩蔽表现的方差，超过了先前由视觉皮层差异解释的方差。因此，视辐射体积的个体差异在精神分裂症组中比在双相情感障碍组或对照组中对视觉处理的影响更大。这表明亚皮质视觉系统结构的个体差异对精神分裂症的视觉处理有重要影响。
