Biological Psychology – Mod. 3 & 4 The Split-Brain Phenomenon Left-handedness Synaptic Plasticity Biomedical Therapies General Psychology 1 February 15, 2005 Class #7 The Split-Brain Phenomenon Corpus Callosum The two sides of our brains serve different functions (lateralized or specialization of tasks): Large band of neural fibers that connects the two brain hemispheres Left hemisphere: Language, math, logic Right hemisphere: spatial abilities, face recognition, visual imagery, musical and artistic abilities, emotional tasks. This is the case for almost all righthanders (about 95%) and about half of lefthanders Important aspects of this divided brain phenomenon Information from left half of field of vision is received only by your right hemisphere, and information from the right half of your field of vision is received only by your left hemisphere Don’t get confused here as each eye receives sensory information from both right and left visual fields. But this information is only transmitted from a particular visual field to a particular brain hemisphere Important aspects of this divided brain phenomenon The left hemisphere receives information from and controls movements of the right side of the body, whereas the right hemisphere receives input from and controls movements of the left side of the body Tests show that almost all right-handers (over 95%) process speech in the left hemisphere Important aspects of this divided brain phenomenon Left-handers are more diverse: 60% process speech in the left hemisphere 5% process speech in the right hemisphere 35% use both hemispheres about equally (half of the time) Split-Brain Experiments Vogel and Bogen (1961) Sperry and Gazzaniga Conducted many experiments from 1960’s through the 1980’s The Split-Brain Phenomenon LEFT FIELD OF VISION RIGHT When the patient is asked “What do you see?” They answer… LEFT HEMISPHERE RIGHT The Split-Brain Phenomenon LEFT FIELD OF VISION RIGHT When the patient is asked “What do you see?” They answer… LEFT HEMISPHERE RIGHT The Split-Brain Phenomenon RIGHT LEF T FIELD OF VISION The same patient who has just said they could not see the picture is now asked to take their left hand and touch the ‘happy face” picture… What happens now??? LEF T HEMISPHERE RIGHT The Split-Brain Phenomenon RIGHT LEF T FIELD OF VISION Now, with the object in the patient’s hand, he/she is asked “what is in your hand”…what is their answer this time??? LEF T HEMISPHERE RIGHT Severed Corpus Collusom: Video 1st scene: “Joe” is flashed words in his right field of vision (“storm” and “piano”) and has no trouble saying them He is then flashed the word “phone” in the left field of vision…and he can’t say it “didn’t see that” But when asked to draw a picture of what he saw with his left hand…he draws a telephone but since its still in his left field of vision he still can’t verbalize what he just drew Severed Corpus Callosum: Video But then when asked to draw it with his left hand but in his right field of vision…he is able to say what he drew (“oh, phone”) Very interesting… Severed Corpus Collusom: Video 2nd scene: Joe is flashed words simultaneously in both fields of vision – “toad” in left field and “stool” in right field… He can’t say “toad” but can draw it with left hand He can say ‘stool” and by speaking it, he is able to let the right hemisphere in on the “secret” Severed Corpus Collusom: Video 3rd scene: Again, two words simultaneously…”bell” appears in his left field of vision and “music” in his right field of vision When asked to point with his left hand to what he saw, Joe points to a picture of a bell but is not really sure why so he makes up a story that seems to be plausible…he’s basically trying to figure out what's going on Severed Corpus Callosum : Video Joe’s left hemisphere is trying to interpret what is going on – trying to find a cause and effect Left hemisphere is responsible for making sense out of the mystery According to Gazzaniga: “the left hemisphere is where the action is”… Severed Corpus Callosum : Video Final scene: Pictures are shown of faces made out of fruit, meat, etc. Right hemisphere specializes in locating faces and left is better at finding elements involved… So what happens? Right hemisphere sees it as a face and left hemisphere sees it as a fruit Still being performed but now very rare Cutting apart the two hemispheres of the human brain is a drastic step, and it is one of the most controversial operations ever performed Yet it can succeed, when all else fails, in relieving violent, drug-resistant epileptic seizures This surgery is becoming more and more rare – Instead, neurosurgeons are using a variety of neuroscience techniques to reduce the amount of tissue removed in brain surgery Hardly ever performed now because also because of new and effective medications that help prevent seizures Left Handedness: Curse or Blessing Around ten percent of Americans are left-handed, and of those, there are twice as many lefty males as females A curse??? Possible disadvantages Medical literature reports that lefties are more accident prone…Lefties are six times likelier to die in an accident, and four times likelier to die while driving For example: they are more likely to have their fingers amputated by power-tools, suffer more wrist fractures (Corliss, 1984) Lefties are more susceptible to allergies, reading disabilities, and migraine headaches (Geschwind and Behan, 1984) Or a blessing??? Possible advantages Lefties are more common among professional baseball and cricket players, architects and artists Corpus callosum is about 11% greater in lefthanders… Leading to greater integration of both brain hemispheres in processing information The Effects of the Brain on Handedness: Some Theories Damage to the brain, an insufficient supply of oxygen to the brain, and a difficult birth are thought to cause lefthandedness… This theory has been accepted by many, as the number of lefties who fall under these categories is surprisingly high An unusually high percentage of mentally retarded children are left-handed The Effects of the Brain on Handedness: Some Theories Twins are notorious for having difficult births, and have a high rate of lefthandedness too...about 20%, which is twice the normal rate It is also thought that the tendency to have difficult births is genetic, which would back up the statistics for lefthandedness to run in the family Brain Reorganization: Synaptic Plasticity Synaptic Plasticity Often when one area of the brain is damaged, other areas may in time reorganize and take over its function Example: Professor at Iona College – a stroke victim It is not uncommon for stroke patients who have lost the ability to speak or to move a limb to regain function after several weeks of convalescence How does the brain recover? Essentially what is occurring is a “remodeling” of the cerebral cortex after an injury in which sometimes a large part of it simply dies Of course, this is the exception and not the rule Not all stroke victims recover Even better chances: Plasticity in children Before the functions of young children’s cortical regions become fixed, their brains are especially plastic…if the speech areas of an infant’s left hemisphere are damaged, the right hemisphere will usually take over with no noticeable impairment of language… Left hemisphere damage does not permanently disrupt language until age 8 Case study: see hand-out Illustrates that the brain has extraordinary powers of reorganization, especially when damaged before it is fully developed Plasticity vs. split-brain So, if you have a split-brain operation there is no sharing of information Yet, if you remove one side of the brain at an early age you will see synaptic plasticity take place and he/she will likely live a normal life Biomedical Therapies Psychosurgery Lobotomies Electroconvulsive Therapy (ECT) Drug Therapies Psychosurgery This is one type of treatment used for some of the most devastating psychological disorders (like schizophrenia) in which surgery is performed that removes or destroys brain tissue in an effort to change behavior This is a drastic biomedical intervention A last resort operation Lobotomies Egas Moniz (1935) Developed the best known psychosurgical operation – the lobotomy Moniz found that when he surgically cut the nerves that connect the frontal lobes with the emotion-controlling centers of the inner brain, uncontrollably emotional and violent patients were calmed His hope was to disconnect emotion from thought Lobotomies During the 1940’s and 1950’s around 50,000 or more severely disturbed individuals were “lobotomized” and Moniz was honored with a Nobel Prize Some of his patients are still alive today Lobotomies At first, his procedure was welcomed by the medical community… Immediate relief from emotional anguish Unfortunately, the side effects were drastic… Although, intellect appeared virtually unaffected – these patients showed serious changes in their personality Becoming irresponsible and childish Lobotomies They lost the ability to carry out plans and most became unemployed The lobotomy had produced a permanently lethargic and immature personality So, although the pathological emotional problems had been eliminated – so too had the normal aspects of that person’s personality No longer performed… Lobotomies are no longer performed for obvious reasons… Electroconvulsive Therapy (ECT) This is the controversial practice of “shock” treatment A less-drastic manipulation of the brain than psychosurgery First introduced in 1938 Early treatments… A wide-awake person was strapped to a table and jolted with about 100 volts of electricity to the brain Produced violent convulsions and momentary unconsciousness Convulsions sometimes caused injury Separated shoulders, etc. Today… Its done differently as the patient is given a general anesthetic and muscle relaxant See video clip Used primarily to treat severely depressed individuals, schizophrenics, OCD sufferers, etc. Only used after drug treatments have been unsuccessful Drug Therapies By far the most widely used biomedical treatment… They were introduced in 1950’s and have greatly reduced the need for hospitalization Antipsychotic, antianxiety, and antidepressant drugs have been used effectively to help calm individuals, reduce emotional stress in people and lift the spirits of the clinically depressed Effectiveness??? Drugs such as antianxiety drugs and antidepresants are not a cure…but they do reduce the symptoms and help a person function… See video clip