SLIDE 1
Hemispheric Asymmetries: Early and Mid Level Visual Processing
Lynn C. Robertson
Delis, Robertson, & Efron Neuropsychologia,1986
Hemispheric Asymmetries: Early and Mid Level Visual Processing Lynn - - PowerPoint PPT Presentation
Hemispheric Asymmetries: Early and Mid Level Visual Processing Lynn - - PowerPoint PPT Presentation
Hemispheric Asymmetries: Early and Mid Level Visual Processing Lynn C. Robertson Delis, Robertson, & Efron Neuropsychologia, 1986 S S S S S S S S S S S S S S S S S S S S S S S S Global/Local Standard Left Hand Right
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S
S S S S S S S S S S S S
S S S S S S S S S S S
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Global/Local
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Standard Left Hand Right Hand
YYYYYYYYY Y Y Y Y Y
(From Delis, Kramer & Kiefner 1988)
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Attention Manipulation: 50/50 G/75 L/75
Is there an H or S? Distractors: A E
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Divided Attention
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E E E E E E E E E E E E H H H H H H H H H H H H H
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Local Global Target Reaction Time G/75 L/75 50/50
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Robertson, Lamb & Knight J of Neuroscience, 1988
N = 5 Participants: 11 patients and 9 normal controls N = 6
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Robertson, Lamb & Knight
J of Neurosciences, 1988
G/75 L/75 50/50 Local Global Target Level
LHD
Local Global Target Level
RHD
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Focused Attention
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H H H H H H H H H H H H S S S S S S S S S S S S
Locally Directed: Is the Small Letter and H or S? Presented Centrally and Peripherally
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H H H H H H H H H H H H H H H H H H H H H H H H
Globally Directed: Is the Large Letter and H or S? Presented Centrally and Peripherally
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- 200
- 100
100 200 300 Control Left temporal- parietal Right temporal- parietal Reaction Time (msec) Peripheral Central
Lamb, Robertson & Knight Neuropsychologia, 1989
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Studies showing hemispheric asymmetry for global/local processing:
- Neuropsychological:
– Delis et al., 1986 – Lamb et al., 1989 – Robertson & Delis, 1986 – Robertson & Lamb, 1991 – Robertson et al., 1988 – Robertson, Lamb, M. R., & Zaidel, E., 1993
- Electrophysiological:
– Han & Chen, 1996 – Han et al., 2000 – Heinze et al., 1998
- Functional imaging:
– Fink et al., 1997 – Han et al., 2002 – Martinez et al., 1997 – Weissman & Woldorff, 2005
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HIGH LOW
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High Low
Power Frequency
DFF Theory (Ivry & Robertson, Two Sides of Perception 1998)
Relatively Low Relatively High
Power Frequency Right Hemisphere Frequency Power
Relatively Low Relatively High
Left Hemisphere
RH LH
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Categorical vs. Coordinate (Kosslyn)
Coordinate: Right hemisphere
precise spatial relations
Categorical: Left hemisphere
rough spatial relations Categorical task : Is the dot above or below the line? Coordinate task : Is the dot near or far from the line?
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Left Hemisphere Right Hemisphere Right Eye Left Eye
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- Categorical Task: Faster for LH
- Coordinate Task: Faster for RH
RH LH
Categorical Coordinate
RT
* *
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DFF account
- LSFs facilitate
coordinate (near/far) task -- RH
- HSFs facilitate
categorical (up/down) task -- LH
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CB(HSF) BB Removing LSFs should harm RH: Coordinate
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Okubo & Michimata, 2002
- Eliminating LSF affects in coordinate task
RH LH
Categorical Coordinate
RT BB
Categorical Coordinate
CB
* * *
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LSF BB
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Okubo & Michimata, 2004
- Eliminating HSFs affects categorical task
RH LH
Categorical Coordinate
RT
BB
Categorical Coordinate
LSF
* * *
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DFF theory has done pretty well Can it be applied to more complex stimuli? e.g. Faces
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N170
5
- 5
µV Bentin, et al., 1996
Left Right
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Face Detection: N170
- N170: well-investigated index of
relatively early processing of faces
Itier, R.J. & Taylor, M.J. (2004)
µV
P8
ms
100 200 300 400
- 6
- 2
2 6
N170 faces mushrooms traffic signs tools lions houses flowers textures
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Anastasia Flevaris Shlomo Bentin
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Low spatial frequency (LSF) 0.9 cycles/degree 4 cyncles/face Hi spatial frequency (HSF) 5 cycles/degree 22 cycles/face
Task: Respond to flowers
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LSF cutoff 0.9 c/deg ) HSF cutoff 5 c/deg )