chapter 4: cortical organization. visual processing streams striate cortex: simple feature detection...
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Chapter 4: Cortical Organization
Chapter 4: Cortical Organization
Visual processing streams
• Striate cortex: simple feature detection
• But how are objects spatially represented in the visual system?– Are signals
representing different objects in a scene go to different places in the brain?
Figure 4-1 p78
Retinotopic map外界物體刺激網膜的空間位置,與物體的大腦皮質表徵,具有空間的對應性Coortical magnification
Figure 4-2 p78
• 皮質放大因子( cortical magnification factor ):中央小窩只占網膜的 0.01% ,但在視皮質卻佔了 8-10% 的區域
Brain Imaging Techniques
• 運用大腦造影技術瞭解皮質放大 • Positron emission tomography (PET)• Functional agnetic resonance imaging (fMRI)
Figure 4-3 p79
物體在手中
物體放在手中操弄
操弄物體
Figure 4-4 p79
• 人類視皮質放大因子• 有個別差異• 所以對於細節的區辨能力除與眼球
特性有關外,也與腦中地圖有關
Figure 4-5 p80
皮質的柱狀( column )結構• Orientation columns• Ocular dominance columns
– 雖然視皮質神經元大多對於左眼與右眼刺激都作反應,但會對其中某一眼刺激的反應較好— ocular dominance
• Location columns– Hypercolumns by Hubel and Wiesel– 對落在某個網膜位置的視覺訊息作完整的分析
Figure 4-7 p81
Figure 4-8 p81
Figure 4-9 p81
Orientation columns
Alsoocular dominance columns
How Do Feature Detectors Respond to a Scene?
• Tiling– location columns working together to cover the
entire visual field– Each location column is focused on a specific area
of the scene
Figure 4-11 p82
Figure 4-10 p82
Figure 4-12 p82
訊息流的路徑—是什麼?在哪裡?如何作?
• Two parallel streams in extrastriate cortex (Ungerleider & Mishkin, 1982)
Figure 4-14 p84
– 物體區辨作業– 地標區辨作業
Figure 4-13 p83
– 運用切除( ablation )法• 測量知覺—切除(破壞,冷凍)腦區域—訓練動
物,再測量知覺• 切除部分頂葉( parietal lobe )與側葉
( temporal lobe )– 結果頂葉切除猴子對於地標區辨產生困難,
側葉切除猴子對於物體區辨產生困難• Where pathway?• What pathway?
背側
腹側
Streams for Information About What and How
• What and how stream (Milner & Goodale, 1995)– the dorsal stream provides information about how to direct
action toward objects (action pathway)– 神經生理證據
• 猴子頂葉有看見物體並試圖觸及物體時才有反應的神經元– 神經心理學( Neuropsychology )證據
• 運用雙重分離( double dissociation )邏輯• (功能)分離( dissociation )
某個功能存在,而另一個功能受損
– 單一分離( single dissociation)某甲產生「功能 X 存在,而功能 Y 受損」,顯示功能 X 與 Y 有不同,但未必彼此完全獨立的機制
– 雙重分離( double dissociation )某甲產生「功能 X 存在,而功能 Y 受損」,某乙產生「功能 Y 存在,而功能 X 受損」,顯示功能 X與 Y 有不同的機制,且彼此也完全獨立
– Patient D.F. (Milner & Goodale, 1995)• 一氧化碳中毒導
致腹側路徑受損• visual form
agnosia• 無法把卡片
match 細縫的方位
• 但可以「寄信」
Figure 4-16 p85
• __分離– 顯示「方位判斷」和「視覺 / 動作協調」為
不同機制• 雙重分離—
– 顯示「方位判斷」和「視覺 / 動作協調」為__機制
單一
有其他有相反狀況的病人
獨立
Behavior of People Without Brain Damage
• Evidence for the separation of perception and action in non-brain-damage subjects.– Ganel et al. (2008)– length estimation task– grasping task
Figure 4-17 p86
視覺處理的模組化( Modularity )• 模組( module )
– 某個腦結構中多數神經元選擇性地處理具有某種特性的訊息,那麼這個腦結構為處理此種特性的一個模組
• Fusiform face area (FFA) – 臉孔辨識的模組
Figure 4-18 p87
Figure 4-19 p87
Figure 4-20 p88
– 臉孔失認症( prosopagnosia )• LH ( Farah, 2000 )• WJ ( McNeil & Warrington, 1993 )
Figure 4-21 p88
Figure 4-22 p89
• The visual system is organized both spatially and functionally
• Spatial– Retinotopic map
• Becomes weaker as moving towards higher cortical regions
• Functional– What/where, how– Modules for specific objects
Where Vision Meets Memory
• MTL structures are extremely important in memory– H.M.– hippocampus
Figure 4-23 p90
Figure 4-24 p90
• 經驗– 神經元按照視覺環境特性發展成為最能適應
環境刺激的模式— experience-dependent plasticity, eg., visual word form area
– eg., selective rearing– eg., expertise related activation in FFA
Figure 4-25 p91