Chap 15 Chemical senses
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日常觀察
為何狗的嗅覺這麼好？ 為何冰的東西比較沒味道？ 吃和聞的味道如何 combine? Flavor = smell + taste
Chemical senses are
守門員- 動用情緒，回憶- 阻止不好的食物進入體內，或者遠離不好的環境
一些問題
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嗅覺（ Olfactory system ）
生存溝通Menstrual synchronyPheromones味道Anosmia
Detection threshold Yes/no procedure
- trials with odors along with “blank” trials
- This can result in bias
Forced-choice - one with odorant and one
without
- Participant indicates which smells strongest
功能 偵測
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嗅覺（ Olfactory system ）
Difference threshold 氣流影響濃度 Ofactometer
Recognition threshold knowing names helps recognition
氣味難以用語言形容
偵測
Neural codes for olfactory quality
Olfactory mucosa is located at the top of the nasal cavity.
- Odorants come in contact with the olfactory receptor neurons (ORN).
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Neural codes for olfactory quality
嗅神經 (olfactory receptor neurons, ORN)- Contains olfactory receptors
- 350 receptors (note: only 4 visual pigments)
- But, only one olfactory receptor for one ORN
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Neural codes for olfactory quality
嗅神經 (olfactory receptor neurons, ORN)- Recognition profile
( 類似三元色論中三種受器的激發組型的解釋）
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Neural codes for olfactory quality
Olfactory bulb
- ORNs of a particular type send their signals to one or two glomeruli
- How do the glomeruli respond to different odorants?
- Optical imaging
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Neural codes for olfactory quality
Olfactory bulb- Uchida 等人 (2000) 老鼠研究發現- 碳鏈結愈長，激發的區域愈偏左
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Neural codes for olfactory quality
Olfactory bulb- 嗅球反應是取決於分子與結構的特性- hardwired response? e.g. cat odor
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Higher Level Olfactory Processing
Signals from the olfactory bulb are sent to - primary olfactory (piriform) cortex in the temporal lobe and amygdala.
- Amygdala plays a role in emotional reactions to odors.
- (then to) secondary olfactory (orbitofrontal) cortex in the frontal lobe.
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Higher order olfactory processing
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Higher order olfactory processing
我們通常都同時聞到並可以分辨兩種以上的氣味
過去經驗影響嗅覺
e.g. 白酒 (Morrot et al., 2001)
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Higher order olfactory processing
de Araujo et al.People were exposed to a mixture of a sweat-like smell and a cheddar cheese flavoring.
On some trials, they saw the label “cheddar cheese,” and on others, the label “body odor.”
Pleasantness ratings were higher for the cheddar cheese trials .
fMRI scans showed activity in the orbitofrontal cortex to be associated with the pleasantness ratings.
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