Biological Psychology – Mod. 3 & 4 The Split-Brain Phenomenon Left-handedness Synaptic Plasticity Biomedical Therapi

Biological Psychology – Mod. 3 & 4The Split-Brain PhenomenonLeft-handednessSynaptic PlasticityBiomedical Therapies General Psychology 1 February 15, 2005 Class #7

The Split-Brain Phenomenon • Corpus Callosum • Large band of neural fibers that connects the two brain hemispheres • The two sides of our brains serve different functions (lateralized or specialization of tasks): • 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 FIELD OF VISION RIGHT LEFT When the patient is asked “What do you see?” They answer… LEFT RIGHT HEMISPHERE

The Split-Brain Phenomenon RIGHT LEFT 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??? LEFT HEMISPHERE RIGHT

The Split-Brain Phenomenon RIGHT LEFT 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??? HEMISPHERE LEFT 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 left-handers… • 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 left-handedness… • 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 left-handedness 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 left-handedness 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

Biological Psychology – Mod. 3 & 4 The Split-Brain Phenomenon Left-handedness Synaptic Plasticity Biomedical Therapi