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Broader Visual Orientation Tuning in Patients with Schizophrenia

机译:精神分裂症患者的广泛视觉取向调整

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摘要

Reduced gamma-aminobutyric acid (GABA) levels in cerebral cortex are thought to contribute to information processing deficits in patients with schizophrenia (SZ), and we have previously reported lower in vivo GABA levels in the visual cortex of patients with SZ. GABA-mediated inhibition plays a role in sharpening orientation tuning of visual cortical neurons. Therefore, we predicted that tuning for visual stimulus orientation would be wider in SZ. We measured orientation tuning with a psychophysical procedure in which subjects performed a target detection task of a low-contrast oriented grating, following adaptation to a high-contrast grating. Contrast detection thresholds were determined for a range of adapter–target orientation offsets. For both SZ and healthy controls, contrast thresholds decreased as orientation offset increased, suggesting that this tuning curve reflects the selectivity of visual cortical neurons for stimulus orientation. After accounting for generalized deficits in task performance in SZ, there was no difference between patients and controls for detection of target stimuli having either the same orientation as the adapter or orientations far from the adapter. However, patients’ thresholds were significantly higher for intermediate adapter–target offsets. In addition, the mean width parameter of a Gaussian fit to the psychophysical orientation tuning curves was significantly larger for the patient group. We also present preliminary data relating visual cortical GABA levels, as measured with magnetic resonance spectroscopy, and orientation tuning width. These results suggest that our finding of broader orientation tuning in SZ may be due to diminished visual cortical GABA levels.
机译:人们认为,大脑皮层中γ-氨基丁酸(GABA)水平降低会导致精神分裂症(SZ)患者的信息处理缺陷,并且我们先前曾报道过SZ患者视觉皮层中的体内GABA水平较低。 GABA介导的抑制作用在增强视觉皮层神经元的方向调节中起作用。因此,我们预测在SZ中视觉刺激方向的调整会更宽。我们使用心理物理程序测量了定向调整,在该过程中,受试者适应了高对比度光栅后执行了低对比度定向光栅的目标检测任务。确定了一系列适配器-目标方向偏移的对比度检测阈值。对于SZ和健康对照组,对比度阈值随着方向偏移的增加而降低,这表明该调整曲线反映了视觉皮层神经元对刺激方向的选择性。在考虑了SZ中任务执行的普遍缺陷之后,在患者和用于检测目标刺激的对照之间没有差异,目标刺激具有与衔接子相同的方向或远离衔接子的方向。但是,对于中间适配器目标偏移,患者的阈值明显更高。另外,对于患者组,高斯拟合对心理物理取向调整曲线的平均宽度参数明显更大。我们还介绍了与视觉皮层GABA水平相关的初步数据,该水平已通过磁共振波谱和定向调整宽度进行了测量。这些结果表明,我们在SZ中发现更宽的方向调节的发现可能是由于视觉皮层GABA水平降低所致。

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