Faculty of Life Sciences, University of Manchester, Manchester M60 1QD, UK.
Exp Brain Res. 2011 Jul;212(2):225-40. doi: 10.1007/s00221-011-2725-9. Epub 2011 May 18.
When humans pursue motion stimuli composed of alternating constant velocity segments of randomised duration (RD), they nevertheless initiate anticipatory eye deceleration before stimulus direction changes at a pre-programmed time based on averaging prior stimulus timing. We investigated, in both the time and frequency domains, how averaging interacts with deceleration cues by comparing responses to stimuli composed of segments that were either constant-velocity ramps or half-cycle sinusoids. RDs were randomized within 6 ranges, each comprising 8 RDs and having differing mean RD. In sine responses, deceleration cues could be used to modulate eye velocity for long-range stimuli (RD = 840-1,200 ms) but in the shortest range (RD = 240-660 ms) cues became ineffective, so that sine responses resembled ramp responses, and anticipatory timing was primarily dependent on averaging. Additionally, inclusion of short duration (240 ms) segments reduced peak eye velocity for all RDs within a range, even when longer RDs in the range (up to 1,080 ms) would normally elicit much higher velocities. These effects could be attributed to antagonistic interactions between visually driven pursuit components and pre-programmed anticipatory deceleration components. In the frequency domain, the changes in peak velocity and anticipatory timing with RD range were translated into non-linear gain and phase characteristics similar to those evoked by sum-of-sines stimuli. Notably, a reduction in pursuit gain occurred when high-frequency components associated with short duration segments were present. Results appear consistent with an adapted pursuit model, in which pre-programmed timing information derived from an internally reconstructed stimulus signal is stored in short-term memory and controls the initiation of predictive responses.
当人类追踪由随机时长的匀速段交替组成的运动刺激时(RD),他们会根据之前的刺激时间平均,在预先编程的时间之前,提前开始对刺激方向变化的预期眼减速。我们通过比较由匀速斜坡或半周期正弦波段组成的刺激的反应,在时频域中研究了平均如何与减速线索相互作用。RD 在 6 个范围内随机分布,每个范围包含 8 个 RD,并且具有不同的平均 RD。在正弦响应中,减速线索可以用于调制长程刺激(RD = 840-1200ms)的眼速度,但在最短范围(RD = 240-660ms)中线索变得无效,因此正弦响应类似于斜坡响应,并且预期时间主要取决于平均。此外,在包含短时长(240ms)的段时,即使在范围内的较长 RD(高达 1080ms)通常会引起更高的速度,也会降低所有 RD 的峰值眼速度。这些效应可以归因于视觉驱动的追踪成分和预编程的预期减速成分之间的拮抗相互作用。在频域中,随着 RD 范围的变化,峰值速度和预期时间的变化被转化为类似于正弦和刺激引起的非线性增益和相位特性。值得注意的是,当存在与短时长段相关的高频成分时,追踪增益会降低。结果与经适应的追踪模型一致,在该模型中,从内部重建的刺激信号中得出的预编程定时信息存储在短期记忆中,并控制预测响应的启动。