Laterality of fMRI Activation During Grasping and Imagined Grasping of Visual Targets

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Laterality of fMRI Activation During Grasping and
Imagined Grasping of Visual Targets

• J.C. Culham, S. L. Woodward, A. D. Milner,
• J.S. Gati, R.S. Menon and M.A. Goodale

CIHR Group on Action and Perception University
of Western Ontario London, Ontario, Canada
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MONKEY AIPAnterior Intraparietal Area
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HUMAN AIP?
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GRASPING SETUP

• body and head tilted for direct viewing
• grasping below fixation in lower visual field
• arm brace foam packing around head

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THE TASKSCued by Fixation LED color

• Grasping (Green LED)
• precision grip finger thumb
• transport grip components
• requires object processing

• Reaching (Red LED)
• touch object with knuckles
• transport component only
• does not require object processing

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AIP ACTIVATION
Reaching Grasping - ITI
Anatomy
Grasping - Reaching
M1
AIP
L
R
All slides use neurologic convention Left is
Left Right is Right
n 1
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GRASPING - REACHING
1
fMRI Signal ( change)
0
-1
0
4
8
12
Time (s)
Grasp
Reach
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SOMATOMOTOR RESPONSES
S1
M1
AIP
M1
S1
AIP
Subject SW
Grasping (- Reaching)
Finger Movements
Finger Somatostimulation
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VISUAL VS. SOMATOMOTOR RESPONSES
DELAYED MOVEMENTS
Subject JC
10 sec
Grasping (- Reaching)
Visual Stimulus
Hand Movement
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LATERALITY OF AIP

• Monkey AIP
• AIP inactivation preshaping deficits but not
  reaching deficits with contralateral hand
  Gallese et al., 1994

• Human AIP
• AIP lesions in humans lead to grasping deficits
  with the contralateral hand
• Binkofski et al., 1998
• Grasping usually activates AIP contralateral to
  the hand used for grasping
• Faillenot et al., 1997 Rizzolatti et al., 1996
• In addition to contralateral AIP activation with
  grasping, some find weaker activation ipsilateral
  to the hand used for grasping
• Binkofski et al., 1998

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QUESTIONS

• Laterality of Grasping
• Is human AIP activation contralateral to the
  hand used for grasping?
• OR Is AIP lateralized to the left hemisphere
  regardless of the hand employed?
• Laterality of Imagined Grasping
• Is AIP activated by imagined reaching and
  grasping?
• If so, is that activation stronger for grasping
  and stronger for the contralateral hand?

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METHODS

• 7 right-handed subjects
• Single-trial design (one trial every 14 sec)
• - less susceptible to head motion artifacts
• 3 factor design
• reaching vs. grasping
• left vs. right hand
• real movements vs. imagined movements
• - different target object briefly flashed on each
  trial
• - subjects either acted towards the target object
  or mentally imagined doing so

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RESULTS Laterality of Real Hand Actions

• Real Movements (grasping AND reaching)
• M1 was largely activated by contralateral hand
• AIP was more activated by contralateral hand,
  but showed some activity for the ipsilateral hand
  (especially for the left hemisphere/left hand)

p lt 10-6
Talairach Average 7Ss
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RESULTS Laterality of Real Grasping

• Real grasping MINUS reaching
• AIP was bilateral

p lt .001
Talairach Average 7Ss
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RESULTS Laterality of Imagined Hand Actions

• Imagined movements (grasping AND reaching)
• strong activation in frontal cortex
  (FEF/premotor) and SMA
• very weak activation in AIP -- no evidence of
  laterality

p lt .001
Talairach Average 7Ss
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RESULTS Laterality of Imagined Grasping

• Imagined grasping MINUS reaching
• strong activation in frontal cortex
  (FEF/premotor) and SMA
• very weak activation in AIP -- no evidence of
  laterality

p lt .001
Talairach Average 7Ss
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TIME COURSES AIP
CONTRALATERAL
IPSILATERAL
G gt R (p lt .01) G gt 0 (p lt .001) R gt 0 (p lt .01)
G gt R (p lt .01) G gt 0 (p lt .01) R gt 0 (p lt .01)
REAL MOVEMENT
Grasping

Reaching
gt
gt
IMAGINED MOVEMENT
G R (p .4) G gt 0 (p lt .05) R gt 0 (p lt .10)
G R (p .2) G gt 0 (p lt .1) R 0 (p .4)
MR Signal ( change)

Time (2 sec images)
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CONCLUSIONS Real Movements

• Results
• AIP was more activated by grasping than reaching
• AIP activation was bilateral, especially for
  grasping
• Disruption of AIP (inactivation in monkeys,
  lesions in humans) leads to only a contralateral
  deficit in grasping.
• Why does fMRI report bilateral activity?
• Perhaps potential grasps are computed with each
  hand and the hand that affords the best grasp for
  the object is selected
• Perhaps fMRI reflects input to an area
  (Logothetis et al. 2001) and AIP receives
  crosstalk from the opposite hemisphere AIP

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CONCLUSIONS Imagined Movements

• Results
• Imagined movements produced strong activation in
  frontal structures, but weak, largely
  insignificant activity in M1 and AIP
• Why was activation for imagined movements so
  weak?
• Low power with single trial design and high
  variability between subjects
• our AIP may encompass two areas reanalyze
  separately
• Agrees with an earlier study that did not report
  AIP activation for imagined grasping (Grafton et
  al. 1996)

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GENERAL SUMMARY

• AIP is activated by grasping (vs. reaching)
• Activation is bilateral, especially for grasping
• AIP activation for imagined movements is much
  weaker than for actual movements

http//defiant.ssc.uwo.ca/Jody_web
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GRASPING AREA vs. OBJECT AREA
AIP
LOC
Subject JC
Culham et al., Vision Sciences Society 2001
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TIME COURSES M1
CONTRALATERAL
IPSILATERAL
Grasping
REAL MOVEMENT
Reaching
IMAGINED MOVEMENT
MR Signal ( change)
Time (2 sec images)
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PERCEPTUAL GRASPING TASKKourtzi Kanwisher
Subject 1
Grasping Task Can the object be grasped at the
blue points? vs. Object Task Can the object be
split into parts at the blue points?