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 coordinateIndirect transformation :Transforming target location from eye- to head- to body-centered coordinates and then subtracting the body centered position of the hand

(Batista et al., 1999)

rr

Eye centered coordinate (area MIP neuron)The reach plan that generates the largest response is always the one directly below the eyes.

(Duhamel et al., 1997)

Head centered coordinate (area VIP neuron)Single neuron data for visual receptive filed mapping in which the RF remains in the same spatial location irrespective of eye position.

(Graziano et al., 1994)

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 fixationⅠⅡⅢⅣ-stimulus trajectory

Experiment Procedure1) The illumination of both a red and a green LE

D. The red LED – gaze/ the green LED-hand.2) A green (target) LED at another location was t

hen briefly illuminated (300 ms duration). 3) a delay period of 600–1,000 ms4) The LEDs instructing the initial hand location a

nd fixation point were turned off. The animal reached to the remembered locati

on 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

Activity similarity:when target locations were identical in1) Hand centered coordinate? NO Between conditions 1 and 22) Both hand and body centered

coordinate? NO Between conditions 3 and 43) Both hand and eye coordinates? MAYBE Between conditions 1 and 4 Between conditions 2 and 3

Experiment Ⅰ

* 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

• PRRcontour

a coding of target location in eye coordinates.

AreaComparison

Area 5 PRR

Contour

Resultant Between eye coordinate and hand coordinate

Eye coordinate

• Condition : 5 (target) X 5 (initial position)

• Comparison area 5 neurons with the idealized neuron

• Neurons in the Area 5 : – employ combined eye centered and hand centered coordinate fra

me 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.