THE SENSORIMOTOR INTERFACE 3OCT 9, 2015 – DAY 19

Brain & Language

LING 4110-4890-5110-7960

NSCI 4110-4891-6110

Fall 2015

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Course organization• http://www.tulane.edu/~howard/BrLg/• Fun with https://www.facebook.com/BrLg15/• I am still working on grading.• http://www.tulane.edu/~howard/BrLg/t11-

SensorimotorInterface.html

10/07/15 Brain & Language - Harry Howard - Tulane University

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THE SENSORIMOTOR INTERFACE - REVIEWParietal-temporal Spt

http://www.tulane.edu/~howard/BrLg/t11-SensorimotorInterface.html

10/07/15 Brain & Language - Harry Howard - Tulane University

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The Sylvian parieto-temporal junction

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My first revision

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My second revision

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The car analogy• Imagine driving a car on a racetrack while only looking in the rear-

view mirror. From this perspective, it is possible to determine whether the car is on the track and pointed roughly in the right direction. It is also possible to successfully negotiate the track under one of two conditions: the track is perfectly straight or you drive extremely slowly, inching forward, checking the car's position, making a correction, and inching forward again. It might be possible to learn to negotiate the track more quickly after considerable practice; that is, by learning to predict when to turn on the basis of landmarks that you can see in the mirror. However, you will never win a race against someone who can look out of the front window, and an unexpected event such as an obstacle in the road ahead could prove catastrophic. The reason for these outcomes is obvious: the rear-view mirror can only provide direct information about where you have been, not where you are or what is coming in the future.

10/07/15 Brain & Language - Harry Howard - Tulane University

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The brain's answer• Motor control presents the nervous system with precisely the same problem.

As we reach for a cup, we receive visual and somatosensory feedback. However, as a result of neural transmission and processing delays, which can be significant, by the time the brain can determine the position of the arm based on sensory feedback, it is no longer at that position. This discrepancy between the actual and directly perceived state of the arm is not much of an issue if the movement is highly practiced and is on target. If a correction to a movement is needed, however, the nervous system has a problem because the required correctional forces are dependent on the position of the limb at the time of the arrival of the correction signal — that is, in the future. Sensory feedback alone cannot support such a correction efficiently. As with the car analogy, one way to get around this problem is to execute only very slow, piecemeal movements. The brain, however, clearly does not adopt this strategy. Rather, it favors a solution that involves looking out of the 'front window' or, in motor control terms, comprises generating an internal forward model that can make accurate predictions regarding the current and future states of motor effectors.

10/07/15 Brain & Language - Harry Howard - Tulane University

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State feedback control go to next slide!

10/07/15 Brain & Language - Harry Howard - Tulane University

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State feedback control, my color coding

10/07/15 Brain & Language - Harry Howard - Tulane University

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State feedback control in the dorsal system

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Hierarchical state feedback control

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My second revision, repeated

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Data that has been collected so far

1. Spt becomes active in a. the perception and reproduction by humming of tonal sequences

b. by reading written words

c. listening to words & repeating them sub-vocally

2. the ability to acquire new vocabulary.

3. disruption by lesions: conduction aphasia

4. altered auditory feedback disrupts speech production.

5. articulatory decline in late-onset deafness.

6. the basic neural mechanisms for phonological short-term memory

7. the non-phonological residue of Wernicke's aphasia: deficient self-monitoring

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NEXT TIMEP5

On to the frontal gyrus

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