THE ROUGH GUIDE TO PSYCHOLOGYstraight ahead, with the result that anything then presented to the right
of this point will be processed by their left hemisphere, and anything
presented to the left will be processed by the right hemisphere.
Gazzaniga’s team found that if they presented one of these epilepsy
patients with a picture of an apple to their right hemisphere, the patient
couldn’t say what it was because in most people the right hemisphere
doesn’t have the capacity to produce speech. Meanwhile, the left hemi-
sphere, which can produce speech, couldn’t see the apple. But if the
patient were next presented with a bag of objects including an apple,
they’d reach with their left hand (controlled by the right hemisphere) and
pick out the apple, thus indicating that they had seen the earlier picture.
It gets odder. So long as the researchers made sure the held apple was out
of view of the left hemisphere, the participant when asked wouldn’t be
able to say what he was holding, because that information was confined
to the right hemisphere. Most of us have a sense of wholeness and unity,
a feeling that we’re one person with one stream of consciousness. The
split-brain studies suggest our unified selves can be divided in two by the
slice of a surgeon’s scalpel.
WATCHING THE BRAIN IN ACTION
While studies of brain damaged patients continue to be fruitful, research
into brain function has been revolutionized over the last few decades
by technological advances in imaging. Using techniques like functional
Broca’s areaWernicke’s areaThese two key language areas of the brain are joined by a bundle of nerve
fibres called the arcuate fasciculus. A parallel, more circuitous, connection was
discovered in 2004 and named Geshwind’s territory.