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Spatial representation and coordinate frames in the brain. Hemispheric Neglect. Unilateral Neglect: failure to attend to (or represent) sensory information in the left (contralesional) side of space , following right brain parietal injury. Neglect as a deficit in representation.
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Hemispheric Neglect Unilateral Neglect: failure to attend to (or represent) sensory information in the left (contralesional) side of space, following right brain parietal injury.
Neglect as a deficit in representation • Bisiach & Luzzati (1978): imagining a familiar scene (e.g., central square of Milan), from opposite view points
Parietal lesions in the right hemisphere are commonly associated with left field neglect Yellow: the lesion typically involves the supramarginal gyrus at the temporoparietal junctionRed: variation in the exact extent of the lesionDriver and Mattinagley, NNS, 1998
Common tests for Visual Neglect • Drawing from memory
Neglect can be in egocentric and/or allocentric reference frames
Scene/view/object centered neglect Hillis & Caramazza 1990
SEF neurons show selectivity for saccade direction Olson 2003
An SEF neuron that shows selectivity on bar-left trials regardless of the saccade’s physical direction
Eye position gain fieldsin parietal cortex Andersen et al., 1985
neurons with head centered RF(in VIP) (Duhamel et al., 1997)
Neuronal activity in area 5dependence on eye & hand position fixed eye position fixed hand position 1 sec Buneo et al., 2002
Target Buttons Initial hand position Initial eye position PRR neuronal activity:Reach Plans in Eye-Centered Coordinates Same eye position Same hand position
Peripersonal space-The immediate space surrounding the body (or a certain body part).Extrapersonal space – unreachable.
Integrated visual-tactile coding of peripersonal space, centered on body parts Tactile RF Visual RF Iriki A. et al., Neuroreport 1996
Response of neuron (spike/sec) Stimulus trajectory Representation of visual information in hand-based coordinates 1 2 3 4 1 2 3 4 Tactile RF Visual stimulus trajectory Graziano MS., PNAS 1999
Neurons with multimodal receptive fields were found in areas: -Ventral premotor -Ventral intraparietal (VIP) -Parietal BA 7b, 5 - Putamen
Postural bimodal neurons in area 5 respond to the seen position of the hand M.S. Grazianoet al., Science (2000)
The effect of the fake arm M.S. Grazianoet al., Science (2000)
The rubber hand illusion It’s mine!
Pointing at my hand? Botvinick and Cohen, 1998, Nature
Brain activity - 2 Linear relationship subjective rating of the illusion vs. level of PM activity R2= 0.3969, P<0.003 R2= 0.3982, P<0.002 * Also found in R. cerebellum.