Transcript Direct visuomotor transformations for reaching (Buneo et al.)

Direct visuomotor transformations
for reaching
(Buneo et al.)
협동과정 뇌과학 김은영
① Retinal reference frame
▽
② The brain computes the
target position with
respect to the hand
▽
③ Determining the muscle
contraction
(Batista, 1999)
Direct transformation :
Subtracting the position of the
hand from the position of the
target directly, using eye
centered coordinate
Indirect transformation :
Transforming target location from
eye- to head- to body-centered
coordinates and then subtracting
the body centered position of the
hand
Eye centered coordinate (area MIP neuron)
The reach plan that generates the largest
response is always the one directly below
the eyes.
(Batista et al., 1999)
Head centered coordinate (area VIP neuron)
Single neuron data for visual receptive filed
mapping in which the RF remains in the
same spatial locationrrirrespective of eye
position.
(Duhamel et al., 1997)
hand centered coordinate (premotor cortex)
When the arm is moved to the left, the
response filed moves along with it.
A, B, C—different eye fixation
ⅠⅡⅢⅣ-stimulus trajectory
(Graziano et al., 1994)
Experiment
Procedure
1) The illumination of both a red and a green
LED.
The red LED – gaze/ the green LED-hand.
2) A green (target) LED at another location
was then briefly illuminated (300 ms
duration).
3) a delay period of 600–1,000 ms
4) The LEDs instructing the initial hand
location and fixation point were turned off.
The animal reached to the remembered
location of the target in complete
darkness while maintaining fixation.
Recording site
AREA5 : a subdivision of the PPC that
projects directly to cortical and subcortical
motor structures
Experiment Ⅰ
Activity similarity:
when target locations were identical in
1) Hand centered coordinate? NO
Between conditions 1 and 2
2) Both hand and body centered coordinate?
NO
Between conditions 3 and 4
3) Both hand and eye coordinates? MAYBE
Between conditions 1 and 4
Between conditions 2 and 3
* area 5 activity was best correlated when target
locations were identical in both eye and hand
coordinates
•
The responses of an idealized neuron coding target location in
- Eye coordinates (panels a, b)
- Hand coordinates (panel d)
- Both eye and hand coordinates (panel c)
 reflecting 'compromise‘ between the eye and hand reference frames
• area 5 (N=89) the distribution of tuning curve shifts : a partial shift
 consistent with a simultaneous coding of target location
in both eye and hand coordinates
Experiment Ⅱ
•
•
Condition :
5(target) X 5(initial hand position)
Area 5
contours (a largely oblique
orientation)
resultants
 a coding of target location and
initial hand location in eye
coordinates
• Condition :
5 (target) X 5 (initial position)
• Comparison area 5 neurons with the
idealized neuron
Area
Comparison
Area 5
PRR
Between eye
coordinate
and hand
coordinate
Eye
coordinate
Contour
• PRR
contour
Resultant
 a coding of target location in eye
coordinates.
• Neurons in the Area 5 :
– employ combined eye centered and hand centered
coordinate frame to represent target location.
– receive visual, proprioceptive and efferent copy signals.
retinal representation
▽
direct transformation
▽
hand centered representation
• Neurons in the PRR :
- ‘gain modulated’ by initial hand location
- transformation may be achieved by vectorially subtracting
hand location from target location, with both locations
represented in eye-centred coordinates.
• Reference
Batista, A., (2002). Inner space: reference frames. Curr Biol
12, R380-3.
Duhamel, J.-R., Bremmer, F., BenHamed, S. and Graf, W.
(1997). Spatial invariance of visual receptive fields in parietal
cortex neurons. Nature 389, 845–848.
Graziano, M.S.A., Yap, G.S. and Gross, C.G. (1994).
Coding of visual space by premotor neurons. Science 266,
1054–1057.