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9 Cards in this Set
- Front
- Back
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Who studied Parametric adjustment (forward model) and what species? |
Kurtis Bell, 1981 - Electric fish / Sea squirts |
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What do sea squirts show us and how? |
Brains needed for motoricity and perceptual stability 1. At larvae stage, sea squirt is mobile with primitive sensory organs - Statocyst, vestibular, eyes, nervous system 2. Once in adult stage, sea squirt can mate but everything else is lost. Brain is ingested 3. Once brain is ingested, motoricity is also lost as brain is needed to control action and deal with consequences of action |
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What is the model of perceptual stability? |
Effort of will 1. Retina senses environment & signals to the brain (external afference; visual motion signal) 2. Motion is paired with copy of motor commands sent to same areas (efferent copy) 3. In normal situations, the 2 signals null each other out to give sensation of stability (output of summation point is 0 even though retina sees motion) 4. Otherwise, the external signal would be result of the summation point - Anything that is external is informative, while anything internal is taken out of information stream (not informative) - Allows focus on outside world |
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What do sensory consequences of movement depend on? |
Movement & context of the movement |
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What do predictors allow estimation of? |
Consequences. Parameters are continuously updated (like in VOR) |
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What animals were used to study sensory prediction and what is special about them? |
Electric elephant fish 1. Visual senses of these fish replaced by electric field 2. Potential differences large enough to create an eletric field are generated by enlarged neuromuscular junctions 3. This weak electric field is responsible for orientation (find prey / spot predators / interactions) 4. Brain contains enormously enlarged cerebellum-like structure if scaled to human size |
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What did Bell do and find in his study of electric elephant fish? |
Cerebellar-like structure generates & subtracts sensory expectations 1. Bell recorded motor command in neuromuscular junction in electric organ (EOD) from a paralyzed fish that couldn't produce electric fields 2. Sent this motor command back through a delayed electrical stimulation - Command signal was used to generate electric field from an artificial electrode 3. By recording principal cells (similar to human Purkinje cells), in the electrosensory lateral line lobe (ELL), is possible to track the strength of the command sent to the electrical organ. 4. When EOD was deactivated after application of curare (blocks nAchR & leads to silencing of muscles responsible for electric field generation), a homogenous response of the ELL cell to the EOD motor signal was found 5. When electric circuit turned on, activity of the cell in ELL was suppressed just after the command signal 6. After the pairing stimulus is turned off, command signal alone causes immediate burst of activity in ELL cell. Response to the unpaired command signal decreases slowly over time until it becomes homogenous as before pairing |
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What was the interpretation of the electric fish study? |
Forward model: Generates model of consequences, given our actions 1. ELL cell receives feedback from electric organ & updates the prediction of "expected consequences". 2. If expectation is matched by the circuit, sensory info and efferent copy null each other (nothing happens in external world) 3. This mechanism filters out sensory events that are not generated by own activity (e.g. the inhibitory signal on ELL) 4. When there is no consequence to the command signal (system/inhibition is off) anymore, the cell shows strong activation just after the motor command due to mismatch between expectation & sensory inputs 5. This activation decreases over time because of adaptation mechanisms. |
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What is a nicer summary of the electric fish interpretation? --- Previous question was just copied from slides --- |
1. Principal cell (in ELL) gets information that a command has been executed. 2. Also gets sensory inputs from electrical receptors 3. If these 2 signals follow each other rapidly, activity in principal cell cancels out 4. Thus, everything not generated by electric fish itself stands out as it doesn't match expectations 5. Same principle holds for other species' cerebellum - Only alerts them to things that are unexpected |
