Sperry

• Distinct areas of right and left hemisphere dealing with speech production + comprehension showing function localisation- Broca and Wernikes areas are only found in left hemisphere
• Primary motor cortex situated in the frontal lobe + areas in the right hemisphere receive information from and concerned with activities from left side of the body and vice versa
• Sperry- studies involving split-brain patients show more as commissurotomy disconnects the two hemispheres so they work independently
• Myers + Sperry- split brain animals showed behavioural effects
• Sperry- humans + monkeys who had undergone surgical severing of the corpus callosum suggested behavioural effects may be less severe that other cerebral surgery
• Sperry- appropriate tests showed large number of behavioural effects that correlate directly with loss of neocortical commissures
• each hemisphere must posses independent stream of conscious awareness- separate chain of memories inaccessible to the other
• Quasi/ natural experiment

  IV- having a split brain or not- cant be manipulated- ppts already had surgery to reduce severe epilepsy- no control group needed as functions and abilities of visual fields already know

  DV- ppts ability to perform a variety of visual + tactile tasks
• Extensive tests on a small sample- could be considered a collection of case studies
• 11 patients who had 'an extensive midline section of the cerebral commissures in effort to control severe epileptic convulsions not controllable by medication'
• First patient- surgery 5.5 years before

  second patient 4 years before

  Others had surgery not long before
• Presentation of visual info- ppt had one eye covered, gaze centred on a fixed point in the centre of an upright translucent screen
• visual stimuli- presented on 33mm transparencies projected at a 10th of a second or less- too fast for eye movements to get information to wrong visual field- everything projected to the left of the central meridian of the screen passed via LVF and vice versa
• Tactile information- below screen was a gap so ppts could reach objects but not see hands, objects placed in left/right hand or both

  -objects placed in left hand processes by right hemisphere and vice versa
• participants did both tests
• apparatus called a tachistoscope
• Visual tests- information shown and responded to by one visual field can only be recognised again if shown to same field
• Info presented to RVF could be described to speech and writing (with right hand) if same info presented to LVF ppt insisted they did not see anything or there was only a flash of light- info could not be described in speech or writing however ppt could point with left hand to matching picture/object presented among line up
• If different info presented to different visual fields ppt could draw the LVF with left hand but would say they saw RVF
• Tactile tests- objects in right hand could be described in speech or writing- objects with left hand only wild guesses were made with some unaware they were holding anything- objects only recognised if felt by same hand twice
• if two objects presented simultaneously to both hands then hidden in a pile each hand selected their own object
• Concluded- people with split brains have two separate visual inner worlds
• Concluded- split brain patients have two independent streams of consciousness each with own memories, perceptions and impulses