bio - sperry

• Roles of right hemisphere?


  Drawing

  spatial awareness

  arts

  creativity
• Roles of left hemisphere?

  Language

  Words

  Understanding

  Reasoning
• What is the corpus callosum?

  A bundle of nerves that connect the two brain hemispheres
• What is epilepsy characterised by?

  - epileptic seizures:can range from a brief loss of consciousness , to going into a trance-like state, or severely thrashing arms and legs uncontrollably
• What is hemisphere deconnection

  -A solution to help stop epileptic seizures

  -surgeons cut the corpus callosum connecting the 2 hemispheres and separate them

  =stops electrical storms from spreading throughout the entire brain
• Aim of study?


  to study the functions of separated and independent hemispheres
• Left hemisphere controls which hand?

  Right
• Right hemisphere controls which hand?

  Left
• Left hemisphere controls which visual field?

  Right
• Right hemisphere controls which visual field?

  Left
• What is a visual field?

  Not right and left eyes but your peripheral vision
• Can both eyes see both visual fields?

  Yes
• What was controlled/kept standardised?

  -same images and words shown to ensure all images and words were of the same level of difficulty to identify

  -shown for the same length of time, 1/10th of a second so all had same time to process the image

  -same experimenter used to prevent researcher bias

  -same objects placed in hands to ensure all objects of same difficulty
• What does lateralisation of function mean


  The role of each hemisphere
• Type of research method?


  Quasi experiment: split brain (IV) is naturally occurring
• What was the IV

  Split brain patients or having a normal brain
• What was the DV

  Performance on various tactile (touch )and visual tasks that used 1 hemisphere
• Describe the tactile tasks

  1.patiens sat at desk with hands shielded from view

  2.objects e.g key placed on desk=sheilded from patients view

  3.patients asked to pick up objects without looking using right hand and left hand

  4.had to say out loud what they was holding
• describe visual tasks


  -patients sat infront of a piece of apparatus called a tachistoscope (screen that can have images and symbols projected onto it) with one eye covered

  -asked to stare at a fixation point in centre of screen

  -a stimulus was projected ($or ?)for one tenth of a second either to the right of dot/left/to both

  Then asked to either:

  -say the stimuli

  -draw the stimuli with either hand

  -pick up what they had just seen from a group of objects placed infront of them
• Why was stimuli only flashed for one tenth of a second?

  -If it was shown any longer both visual fields would be able to see the information at the same time

  -this means info would be passed onto left and right hemispheres

  -so no difficulties in identifying objects to the left visual field would be apparent
• Results in tactile task?(right hand)

  -when objects picked up by right hand left hemisphere was being used

  -left hem controls language

  -therefore participants could name objects out loud
• Results in tactile task?(left hand)


  -objects by left hand=right hem

  -right hem isn't in control of language

  -therefore when p's asked to identify what they were holding outlaid they couldn't, they would say 'my hand is numb'

  -however when asked to choose an object they could point to the object they were just holding
• Results in visual task?( right visual field)

  -right visual field is controlled by left hem=language

  -as of this, p's could name the stimuli flashed on screen
• results in visual task? (left visual field)

  -left visual field is controlled by right hem (not in control of language)

  -when asked to name stimuli that was flashed up p's would say they didn't see anything

  -their left hand would point towards object they had just said they didnt see

  -e.g when word key flashed to right hem left hand would point to key on table
• Sample?


  11 split brain patient. First patient (male) had the surgery over 5 years ago. Second patient (female) had surgery more than 4 years ago. Other 9 had surgery not long before study was conducted
• Experimental design?


  Independent measures
• What did sperry conclude?

  -left hem controls language and right side of body

  -both hems have own functions (lateralisation)

  -right hem controls spatial awareness and left side of body

  -due to split brain neither hem can access info from the other

  -sperry: 2 hemispheres are almost like 2 separate minds e.g left hem would claim it didn't see anything to left visual field
• -Split brain didnt affect ____ or ____

  -P's experienced short term ____, limited ____ and ____ problems

  -Split brain p's can ____ in ____ as both ____ have access to ____ what the p ___


  -split brain p's didn't affect p's intelligence/personality

  -they experienced short term memory problems,limited concentration spans and orientation problems

  -split brain p's can function normally in everyday life as both visual fields have access to all of the info of what the p sees
• Strength of method?


  Quasi experiment so IV is natural so results on hemisphere deconnection are more ecologically valid
• Weakness of method


  No manipulation of IV by researcher so hard to establish cause and effect on the results of split brain patients
• Sample weakness


  Only 11 ps so not representative
• Sample strength


  diff patients had surgery at diff times and representative of diff ages
• Strength of data


  Qualitative= insight into details on split brain patients= valid results
• Weakness of data


  Qualitative= hard to compare and analyse results on hemisphere deconnection with normal people
• Ethical strengths?


  -study used quasi method so no manipulation of IV so more ethical

  -got informed consent, and were debriefed about the end being told about lateralisation of function, no harm to P as they already had the surgery
• Ethical weakness?


  -harm to p's as of label of normal group = treated as someone different
• Reliability strength


  standardised procedure same images and words shown for 1/10th of a sec so results on hemisphere deconnection reliable
• Validity strength


  -High in internal validity as p's had an image flashed to left or right visual field for 1/10th of a second so they were all tested in the same standardised way increasing internal validity.

  -High in face validity as it measured what it claimed to measure.perry was clearly measuring the effects of hemisphere de-connetion.
• Validity weakness


  Low ecological validity as stimuli was delivered to one hemisphere this doesnt happen in real life so not representative of everyday experience of split brain patient
• Application strength


  -useful for split brain patients and doctors to understand their condition