Visuospatial Processing and
the Right Hemisphere
Interpreter
P.M. Corballis
Presented by:
Cristina, Holly, and Sophie
Bit of History
• Broca’s Area
– Language Production
• Wernicke’s Ares
– Language
Comprehension
John Hughlings Jackson
 Challenged the notion of left hemisphere
dominance instead both hemispheres
process specialized abilities.
 “Imperception” or visual neglect associated
with damage to right hemisphere.
 Asymmetrical Lobe Development
Callosotomy Surgery
• The surgical sectioning of
he corpus callosum and
in some cases other
forebrain commissures
• Experiments from splitbrain patients from the
1960’s supported the
notion of left-hemisphere
dominance, however,
non-verbal test showed
right hemisphere activity
Classic Split Brain Research
Left Hemisphere Interpreter
• Confabulation
– when a split-brain patient makes
perceptual interpitations
• The interpreter
• Ganzzaniga explains Confabulation as
evidence for an interpreter that elaborates
perceptual information to create a (cohesive)
“story” or schema to make sense of the world
Left Hemisphere Domination
• Language
• Better fine motor control
• Superior cognitive abilities?
Vision in the Right
Hemisphere
•
•
•
•
Line Drawing
Block Design
Visual-Spatial
Tasks
Studies
• Mirror Image
• Left vs Right
Hemisphere
Visual System
• Early Information
• Redundant
processing
• Asymmetries
Visual Perception as an
Intelligent Process
• Visual system allows us to navigate and
interact with the world
• Problem: 3-D world, 2-D retinal image
• von Helmholtz: visual perception is topdown as well as bottom up
– Retinal image
– Experience and goals
• Hoffman: visual “problem solving”
Visual Perception as an
Intelligent Process
• Low-level: data-driven
– No conscious awareness of stimulus
• High-level: abstract/experience-driven
– Phenomenon of visual perception
Is there a Right
Hemisphere Interpreter?
• So far, data indicates that:
– “Intelligent” aspects of visual processing
are high-level processes
– High-level processes are more likely
lateralized than low-level processes
Hemispheric asymmetry can be viewed as
an asymmetry in visual intelligence
Is there a Right
Hemisphere Interpreter?
2 experiments showing asymmetry in
visual processing
– Kanizsa Square
– Illusory Line Motion
Kanizsa Square
• “Modal
Completion”
• Both
hemispheres
are capable of
completing
the illusion
Kanizsa Square
• “Amodal
Completion”
• Contour must
be inferred
• Right
hemisphere is
better at this
illusion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
Illusory Line Motion
• Both hemispheres influenced by
flashing dot
• Right hemisphere more likely to be
influenced by a match in width or color
• Equivalent to cognitive errors of left
hemisphere?
Questions and Further
Research
• They attribute certain aspects of the illusions
to a “higher-level” processing
– fMRI in normal or split brain subjects
– Should see lateralized activity in the parietal and
temporal lobe
• Does the idea of a right-hemisphere
interpreter provide an evolutionary
advantage?