運動知覺（ Perceiving movement ）

Chapter 8

• 運動知覺有多重要？– 運動失認症（ motion agnosia ）

• 無法用茶壺倒茶• 無法待在人多的地方• 過馬路有困難

產生運動知覺的四種方式？• 真實運動

– 閾值受周邊因子影響1/6~1/3 VA / second 1/60 VA / second

Fig. 9-1, p. 196

Fig. 9-1a, p. 196

• 似動運動（ apparent motion ）– Exner (1875)– 電影 / 動畫 / 霓虹燈– Wertheimer

• Phi phenomenon• Magni-phi• AM-illusory contour

產生運動知覺的四種方式？

Fig. 9-1b, p. 196

(No motion)

• 與視覺似動運動相近–刺激皮膚產生似動運動時， somatosensory

cortex之神經元也產生反應皮質處理感官訊息時，不論何種感官，均傾向將連續的刺激連結起來

產生運動知覺的四種方式？

– ISI<30ms, 無運動 -- 同時 on/offISI>30ms, 部分運動ISI>60ms, 連續運動ISI>200~300ms, 無運動 -- 先後 on/off（ demo ）

– 距離

觸覺的似動運動

• 誘發運動（ induced movement ）– 周遭的運動引發自身運動的錯覺

• 如，坐在靜止火車中等待會車，相鄰車廂的移動引發自身車廂移動的錯覺， demo– 運動後效（ motion aftereffect ）

• 如瀑布錯覺（ waterfall illusion ）， spiral motion after effect （ demo ）

產生運動知覺的四種方式？

Fig. 9-1c, p. 196

• motion illusion

• Structure from motion– 透過刺激的運動，使原本不清楚的結構（形狀）變得清楚可辨

Figure 9.4 Setup similar to the one used by Wallach and O’Connell (1953) to demonstrate the kinetic depth effect.

Fig. 9-5, p. 199

Fig. 9-3a, p. 198

Fig. 9-3b, p. 198

Fig. 9-3c, p. 198

Figure 8.8 In (a) and (b), Jeremy walks past as Maria observes him. Maria perceives him as moving in (a), when his image moves across her retina, and in (b), when his image stays fixed on her fovea. In (c), when Maria walks through the environment, she perceives the environment as stationary, even though its image is moving across her retina. The text describes how the stimulus information provided by the optic array and global flow helps determine these perceptions.

觀看者運動或不運動的幾種狀況

Motion of a Stimulus Across the Retina

• Aperture problem– Activity of a single

complex cell does not provide accurate information about direction of movement.

Figure 8.12 “Movement of Bar Across an Aperture” demonstration. See text for details.

框架問題（ the aperture problem）

• Solution to aperture problem– Responses of a number

of directionally selective neurons are pooled• This may occur in the

MT cortex (the where/action stream).

– Neurons on the striate cortex respond to movement of ends of objects.

Figure 9.15 (a) Some of the nuclei in the dorsal and ventral streams. The MT cortex, which is a module for movement perception, is in the dorsal stream, and the IT cortex, which is a module for form perception, is in the ventral stream. (b) The location of the MT and IT cortex in the brain.

解決方式—統整不同區域的訊息Module for movement perception

運動知覺的特徵偵測器• V1 複雜細胞之 tuning

curve• 但是神經元是如何偵測運動的？背後的神經迴路是什麼？

• 偵測以後呢？– MT--90% 神經元具有方向選擇性，切除之影響猴子對運動方向的偵測；方位選擇性並具有 columnar structure

also 可由 microstimulation 的方法獲得類似結論– MT 神經元並與 global motion 的偵測有關

• 相關 0.8%-- baseline firing—chance detection相關 12.8%--faster firing—highly accurate detection

Coherence of dot movement↑, Firing of the MT neurons↑ & Judgment of movement accuracy↑

• Lesioning experiment– Normal monkeys can detect motion

with coherence of 1 or 2%.– Monkeys with lesions in MT cortex

cannot detect motion until the coherence is 10 to 20%.

• Activating “preferred downward direction neurons” made monkey change judgment.

• Downward + Rightward

眼球移動的角色Corollary discharge theory

• 運動知覺仰賴三種訊號– 動作訊號（ motor signal, MS ）– 附帶釋放訊號（ corollary discharge signal, CDS ）– 影像移動訊號（ image movement signal, IMS ）

• 當 CDS 或 IMS 到達比較器（ comparator ）時，運動知覺產生；但是當 CDS 與 IMS 同時到達比較器（ comparator ）時，沒有運動知覺

Figure 8.18 According to the corollary discharge model (a) when a motor signal (MS) to move the eyes is sent to the eye muscles, so the eye can follow a moving object, there is a corollary discharge signal (CDS), which splits off from the motor signal. (b) When the CDS reaches the comparator, it sends a signal to the brain that the eye is moving, and motion is perceived.

Figure 9.8 How inputs to the comparator (circle) affect movement perception. When the comparator receives either the corollary discharge signal (CDS) alone, as in (a), or the image movement signal (IMS) alone, as in (b), it sends a movement signal to the cortex, and movement is perceived. When the comparator receives both the CDS and IMS signals, a movement signal is not sent to the cortex, and no movement is perceived.

Figure 9.9 In all four examples shown in the figure, a signal is sent to the eye muscles, and a corollary discharge is generated. However, no image movement signal is generated, so movement is perceived. See text for details.

Fig. 9-10, p. 203

– 沒有 IMS ，但 CDS 引發運動知覺的可能方式 – 這些行為證據支持 corollary discharge theory

Fig. 8.23, p. 191

真實運動神經元

當眼球與刺激都運動時就不活躍

知覺組織與運動知覺• 運動造成知覺組織

– Biological motion• animal• male vs. female• Neurons in monkey’s

superior temporal sulcus respond to man walking forward but less so for other directions of walking

Fig. 9-17, p. 208

生物運動（ biological motion）http://www.biomotionlab.ca/Demos/BMLwalker.html

Figure 9.18 Frames from the stimuli used by Grossman and Blake (2001). (a) Sequence from the point-light walker stimulus. (b) Sequence from the scrambled point-light stimulus.

• Determining whether motion was biological or scrambled– Noise added led to 71%

accuracy.– Transcranial magnetic

stimulation (TMS) applied only to STS caused a decrease in ability to detect biological motion.

Biological motion Scrambled stimulus

Biological motion + noise

Biological motion + noise

Biological motion stimulus

• Other neurons respond to point light walker

• Also, for human, PET activity increases in STS when presented with man walking

• 意義與運動知覺– 意義影響運動知覺 start– 知識影響運動知覺

• 最短路徑規範（ shortest path constraint ）–即使兩個刺激的運動路徑有很多可能性，運動知覺仍會採最短的路徑– 長 SOA(>200 ms ）正常動作 start

短 SOA(<200 ms) 不可能動作 start– PET 研究發現，二者都有頂葉激發，但只有前者有運動皮質的激發

• 顯示–視覺系統需要時間來處理複雜意義的刺激–人體有其特殊性（用其他類型刺激無法得到這個結果）

運動知覺的智慧• Visual heuristics, again

– 由於視覺刺激中的訊息往往不夠明確，所以視覺系統採用一些捷徑來解讀刺激的特性• 「運動朝同一方向進行」經驗法則

–一個物體開始運動後會持續朝同一方向運動（格式塔定律 --good continuation ）

– 「遮蔽」經驗法則• 運動的物體落於同一位置時可能會被遮蔽• Duck demo

• Finger demo

Fig. 9-22a, p. 210

Fig. 9-22b, p. 210

• Implied motion– Representational momentum

Figure 8.28 Stimuli used by Reed and Vinson (1996) to demonstrate the effect of experience on representational momentum. In this example, the test pictures are lower than the memory picture. On other trials the rocket would appear in the same position as or higher than the memory picture.

• back

• back

End

Figure 9.12 Stimuli used to study the neural response to movement: (a) oriented moving bars; (b) fields of moving dots.

Figure 9.13 “Movement of Bar Across an Aperture” demonstration. See text for details.

框架問題（ the aperture problem）

Figure 9.15 (a) Some of the nuclei in the dorsal and ventral streams. The MT cortex, which is a module for movement perception, is in the dorsal stream, and the IT cortex, which is a module for form perception, is in the ventral stream. (b) The location of the MT and IT cortex in the brain.

解決方式—統整不同區域的訊息Module for movement perception

運動知覺的特徵偵測器• V1 複雜細胞之 tuning

curve• 但是神經元是如何偵測運動的？背後的神經迴路是什麼？

• 偵測以後呢？– MT--90% 神經元具有方向選擇性，切除之影響猴子對運動方向的偵測；方位選擇性並具有 columnar structure

also 可由 microstimulation 的方法獲得類似結論– MT 神經元並與 global motion 的偵測有關

• 相關 0.8%-- baseline firing—chance detection相關 12.8%--faster firing—highly accurate detection

知覺組織與運動知覺• 運動造成知覺組織

– Biological motion• animal• male vs. female• Neurons in monkey’s

superior temporal sulcus respond to man walking forward but less so for other directions of walking

Fig. 9-17, p. 208

生物運動（ biological motion）

Figure 9.18 Frames from the stimuli used by Grossman and Blake (2001). (a) Sequence from the point-light walker stimulus. (b) Sequence from the scrambled point-light stimulus.

• Other neurons respond to point light walker

• Also, for human, PET activity increases in STS when presented with man walking

• 意義與運動知覺– 意義影響運動知覺 start– 知識影響運動知覺

• 最短路徑規範（ shortest path constraint ）–即使兩個刺激的運動路徑有很多可能性，運動知覺仍會採最短的路徑– 長 SOA(>200 ms ）正常動作 start

短 SOA(<200 ms) 不可能動作 start– PET 研究發現，二者都有頂葉激發，但只有前者有運動皮質的激發

• 顯示–視覺系統需要時間來處理複雜意義的刺激–人體有其特殊性（用其他類型刺激無法得到這個結果）

運動知覺的智慧• Visual heuristics, again

– 由於視覺刺激中的訊息往往不夠明確，所以視覺系統採用一些捷徑來解讀刺激的特性• 「運動朝同一方向進行」經驗法則

–一個物體開始運動後會持續朝同一方向運動（格式塔定律 --good continuation ）

– 「遮蔽」經驗法則• 運動的物體落於同一位置時可能會被遮蔽• Duck demo

• Finger demo

Fig. 9-22a, p. 210

Fig. 9-22b, p. 210

• Implied motion– Representational momentum

Figure 9.24 Stimuli used by Reed and Vinson (1996) to demonstrate the effect of experience on representational momentum. See text for details.

• back

• back