School of Psychology, The University of Nottingham, University Park, Nottingham, UK.
Eur J Neurosci. 2009 Dec;30(12):2415-26. doi: 10.1111/j.1460-9568.2009.07034.x. Epub 2009 Dec 10.
The ability to detect the motion of objects is critical to survival, and understanding the cortical mechanisms involved in this process remains a key challenge in sensory neuroscience. A relatively new approach to this problem is to temporarily disrupt processing at specific cortical sites and measure the behavioural consequences. Several previous studies have shown that transcranial magnetic stimulation (TMS) of human visual area V5/MT disrupts global motion perception, but reports vary widely in the timescale of this effect. To resolve this issue we employed psychophysical techniques to investigate how discrimination of translational, rotational and radial global motion is affected by TMS. Prior to applying TMS we established baseline coherence thresholds for global motion perception. Adopting each observer's coherence level at threshold we examined how TMS delivered to V5/MT modulated performance. Importantly, we measured the influence of single-pulse TMS over a broad temporal range to reveal the fine temporal structure of the disruption profile for global motion perception. Results show that the disruption profile consisted of two distinct epochs during which global direction judgments were reliably impaired, separated by an interval in which performance was unaffected. The bimodal nature of the distribution profiles is consistent with feedforward and feedback processing between visual areas mediating global motion processing. We present a novel quantitative model that characterizes the contribution of each process to visual motion perception.
检测物体运动的能力对生存至关重要，理解涉及这一过程的皮质机制仍然是感觉神经科学的一个关键挑战。解决这个问题的一个相对较新的方法是暂时中断特定皮质区域的处理，并测量行为后果。几项先前的研究表明，对人类视觉区域 V5/MT 的经颅磁刺激 (TMS) 会破坏整体运动感知，但关于这种效应的时间尺度的报告差异很大。为了解决这个问题，我们采用心理物理学技术来研究 TMS 如何影响平移、旋转和放射状整体运动的辨别。在应用 TMS 之前，我们为整体运动感知建立了基线相干性阈值。采用每个观察者在阈值下的相干性水平，我们研究了 V5/MT 处的 TMS 如何调节性能。重要的是，我们测量了单脉冲 TMS 在广泛的时间范围内的影响，以揭示整体运动感知中断轮廓的精细时间结构。结果表明，中断轮廓由两个不同的时期组成，在此期间，整体方向判断可靠受损，中间有一个不受影响的间隔。分布轮廓的双峰性质与视觉区域之间的前馈和反馈处理一致，这些处理介导整体运动处理。我们提出了一种新的定量模型，该模型描述了每个过程对视觉运动感知的贡献。
