Visual Awareness

Psy315 - Class 17

(This page last updated 5 March, 2009.)

Patient DF

• Damage to ventral (WHAT) pathway producing visual agnosia
• Unable to report orientation of slot
• Can adjust orientation of card to fit in slot
• Can adjust finger position to grip object, but unable to report shape of object
• Intact WHERE pathway is guiding motion, but outside of awareness
• WHAT pathway apparently key to visual awareness

Blindsight

• Damage to part of V1 produces scotoma
  • Patient reports being blind in that area
• When asked to guess, patient can report properties of objects in scotoma with some accuracy
• They have access to visual information that they can use in making discriminations, even though they are not aware of it.

Blindsight Without Brain Damage

• Left eye: array of left-oriented shapes with small target region containing right-oriented shapes
• Right eye: array of right-oriented shapes with small target region containing left-oriented shapes
• When both eyes open, the patterns from each eye are combined. The target region is indistinguishable from the rest of display.
• Accuracy of "guesses" about target location are better than chance.

Conclusions

• Activity in WHAT pathway linked to visual awareness.
• Other visual information can be used in motor control and in some discriminations, but is outside awareness.

next class: The Modal Model of Memory

Psych 315: Cognitive Psychology Kyle Cave Psychology Dept. U. Mass.