Increasing Hemispheric Independence: Bilateral Presentation in Lexical Decision

1
Increasing Hemispheric Independence Bilateral
Presentation in Lexical Decision
Leonardo Fernandino¹, Marco Iacoboni , Eran
Zaidel1 Department of Psychology, University of
California, Los Angeles2 Brain Mapping Center,
University of California, Los Angeles 3 Brain
Research Institute, UCLA
1, 3
2, 3

• Introduction
• In the normal brain, the two cerebral
• hemispheres work in close cooperation. In
• order to study the properties of each
• hemisphere alone, it is desirable to create
• conditions that reduce this cooperation to a
• minimum by maximizing hemispheric
• independence.
• We investigated the effects of bilateral
• presentations in lateralized lexical decision
  to
• test the hypothesis that a distractor
  presented
• to the visual hemifield contralateral to the
• target would increase hemispheric
• independence. The condition of maximal
• independence allows for a better measure of
• left hemisphere specialization for word
• recognition.
• A previous experiment with mixed unilateral
• and bilateral stimuli found an increase in

• Results
• The presence of a distractor
• contralateral to the target affects the
• processing of words and nonwords in
• different ways, increasing the right visual
• field advantage for words, but not for
• nonwords. This accentuates the
• dissociation between the two visual fields
• observed in unilateral presentations.
• With bilateral presentations, the right visual
  
• field advantage (RVFA) for words
• increases, but the RVFA for nonwords is
• reversed. The overall RVFA remains the
• same as in unilateral presentations.
• Conclusions
• These results indicate that bilateral
• presentations make processing within each
• hemisphere more independent from the
• other, providing more adequate conditions

Example
hand life
horse
Unilateral Bilateral
Contact fagundes_at_ucla.edu