Brain Plasticity & Our Divided Brain

To what extent can a damaged brain reorganize itself? Brain plasticity: brain’s ability to change, esp. during childhood, by reorganizing after damage or by building new pathways based on experience. *i.e.: constraint induced therapy: aims to rewire brains by restraining a fully functioning limb & forcing use of the “bad hand”…gradually reprograms the brain, improving the use of a brain-damaged child or adult stroke victim. {The damaged brain functions migrate to other brain regions.} –stroke victim cleaning tables w/ good arm & hand restrained…bad arm recovers its normal skills.

Other examples of plasticity: *Blind person uses one finger to read Braille, brain area dedicated to that finger expands as the sense of touch invades the visual cortex * Deaf person who use sign language, the temporal lobe area dedicated to hearing waits eagerly for stimulation…it then looks for other signals to process, such as those from the visual Sx…enhanced peripheral vision. *Lose a finger & the sensory cortex that received its input will begin to receive input from adjacent fingers, which then become more sensitive *Phantom Limb Phenomenon: hand amputated, but stroking the arm of the person, they report feeling sensations not only on arm but also on the “phantom limb” b/c sensory fibers that terminate on adjacent areas had invaded the brain area vacated by the hand.

Rosenzweig Rat Study

Neurogenesis Humans are able to generate new brain cells. “baby” neurons originate deep in the brain & may then migrate & form connections with neighboring neurons. Implications for stem cells & stem cell research Natural promoters of neurogenesis: exercise, sleep & nonstressful but stimulating environments.

Hemispherectomy An entire hemisphere is removed (seizures) but the remaining hemisphere can take over the functions of the one removed. The younger the patient, the better the recovery in terms of plasticity & neurogenesis. Able to retain memory, personality, intelligence & humor.

What do split brains reveal about the functions of our two hemispheres? Split Brain: Condition resulting from surgery that isolates the brain’s 2 hemispheres by cutting the fibers of the corpus callosum (eliminate seizures)

Hemispherectomy: How Much Brain Do We Really Need? http://www.youtube.com/watch?v=Z_EG2mSv8f8 http://www.youtube.com/watch?v=qt85tT0vkpU

Visual information directed to each side of the brain comes from visual fields, not from each eye. The left eye doesn’t send info to the right hemisphere & vice versa – the right halves of each eye send information to the right hemisphere & vice versa…

So then…what happens with a split brain patient? Severed Corpus Callosum – Alan Alda Another Split Brain Demo

* The “Two-Brain” Myth There is no activity to which only 1 hemisphere makes a contribution! { i.e.: when you read a story, the R hem. may play special role in decoding visual info, while the L hem. plays role in understanding syntax.} Logic is not confined to the L hem.! {In fact, patients w/ R hem. damage show more major problems in this area than do patients w/ L hem. damage.

There is no evidence that either creativity or intuition is an exclusive property of the R hem.! {Researchers have found that both hem. are equally skilled in discriminating musical chords} It is impossible to educate 1 hem @ a time! {The R hem. is educated as fully as the L in a literature class; the L hem. is educated as much as the R in art class. There is no evidence that people are purely “left-brained” or “right-brained.”