Split-Brain Flashcards
What are split brain cases?
The neurosurgical separation of the hemispheres by the severing of the corpus callosum (myelinated axons)
How do patients appear after surgery?
Appear normal under most circumstances but experiments that isolated information from reaching one hemisphere reveal disunities in their behaviour and experience
How do the hemispheres respond to the same stimulus?
Left responds to function and right responds to physical characteristics
How is fundamental sensory information represented bilaterally?
Both hemispheres receive ascending projections from a common brainstem. Enables duplicate representations of much basic sensory information. Support similar arousal levels within each hemisphere
How is interhemispheric communication limited in split brain patients?
CC carries majority of information, especially higher-order. Without it, only simple information can cross
What is subtle cross-cueing behaviour?
Moving head, talking aloud, making symbolic hand movements. These can be eliminated under experimental conditions
What is cross cueing?
The attempt by one hemisphere to inform the other about current experiences
What did Holtzman and Gazzaniga 1985 find?
Split brain patients more readily identified whether a stimulus had been presented than normal controls in tasks with simultaneous and bilateral presentation of streams of stimuli
How do split brain patients respond to searching a visual array that spans both visual fields?
Show reduced response delay as the array increases in size, relative to controls. Luck et al 1989
Do hemispheres operate independently with integration?
Most representations, without CC, are computed intra-hemispherically. The two hemispheres may develop separate stores of knowledge, reflecting individualised learning and experiences. Can allocate attention independently, but the two hemispheres share a limited pool of central attentional resources
What happens when split brain patients are presented with a difficult task in one hemisphere?
When one hemisphere performed a difficult task, the other hemisphere performed worse on a simultaneous task. Holtzman and Gazzaniga 1982
What is agenesis of the corpus callosum?
A failure to develop the corpus callosum. Can result from disruption in any one of the multiple steps of callosal development
What did Sperry 1966 believe about consciousness and split brain?
Indication that people are left with two separate minds, and two separate spheres of consciousness, which has been demonstrated in regard to perception, cognition, volition, learning and memory
What did Eccles 1965 believe about consciousness and split brain?
Consciousness is not split, and there are not two separate minds. Right hemisphere cannot truly think or have knowledge even if it is capable of ‘mere consciousness’. Language and human thought are provenance of left hemisphere
What is believed about the left hemisphere?
Hemispheres are co-conscious but only the left conscious awareness can be directly assessed by verbal query. Gazzaniga et al called the left hemisphere the ‘interpreter’
