Chapter_2.docx

Chapter 2: Neurolinguistics 2/6/12 10:06 AM Monday: February 6, 2012 Neuro-Anatomy Crash Course Neuron [Like a computer circuit] Nucleus Cell Body Axon Synapse Basic Function of a Neuron A stimulus in the environment activates a neuron The neuron fires and an electrical charge is carried along the axon to the synaptic cleft. neurotransmitters are released (serotonin, dopamine etc.) the signal is picked up by the dendrites of the connecting neuron and carried to the neuron?s nucleus and if the nucleus is so programmed, the process continues along the determined route ~ All the thoughts we have boil down to connections between neurons~ Learning Eric Kandel Aplysia ? sea slug Studied the brains of sea slugs, they have very few neurons so it is possible to count them and record them. He attached a sensor to their gills {siphon, gills, and feet}. When they are scared they have a gill reflex and they tighten up their gills. The sensor allowed him to measure how strong the reflex is and when it happens. Then he put and electrode on the foot and trained it to anticipate an electric shock. Tickle to the siphon, shock to the foot, and it would tighten its gills. It learned when it?s siphon was tickled it was about to be shocked. He found more neuronal connections and more neurotransmitters being released from the sea slugs being shocked. ~Your brain physically changes its structure during learning. William Greenough Experience affects neural development He took triplet rats and raised them in the same environment and one is raised in a box. group 2 was raised with other rats. group 3 was raised in a box with other rats with toys. Then he kills the rats and examines the brain and count neurons. He found that group 1 had the least amount of neurons, group 2 had more and group 3 had the most neurons and neuronal connections. ~experience is important to development. the more experience a child has, then the more their language develops~ Pruning synaptic growth in the first 2 years is massive A 1 year old would have more neurons than I do. There is a huge over-production of synapses Early plasticity of the brain makes it highly malleable in response to the environment Neurons begin to be pruned back at about 8 months What gets pruned is determined by the child?s experiences. EX: Mice are born with barrel cells and whiskers. When you remove the whiskers, the barrel cells are pruned out. Things are pruned according to your experiences Development and Genetics Epigenisis ~Gene Expression~ Early experiences control which genes are switched on (expressed). Child is set on a trajectory by biological endowment, but the environment can knock the child off a beneficial trajectory or nudge them toward it. Perhaps even children with biological impairments can move towards a healthy development if provided with the right environment. Input Where is Language (?) in the brain? Brain Lesions Paul Broca Broca?s Area - near the temple Broca?s Aphasia ?non-fluent aphasia?. Speech is telegraphic, halting, speech is labored and slow. Syntax and morphology are minimally produced. Word finding difficulties. Comprehension generally OK. Karl Wernike Wernike?s Area- behind the ear Wernike?s aphasia ?Fluent aphasia?. Articulation unaffected. Melodic contour unaffected. speech is semantically meaningless. Syntax and morphology occur, but are again meaningless. Comprehension usually impaired to some extent. Caused by: Blount trauma, tumor, epilepsy, and a Stroke- bleeding in the brain which causes pressure in an area of the blood. Other stroke where there is blockage in the brain and that area usually dies. Friday: February 10, 2012 Left Brain/Right Brain? Disrupting Language Wada Test A way to put one side of the brain to sleep by injecting sodium amobarbitol into the carotid artery. This is temporary. Used to find out which hemisphere of the brain control language. The nervous system has contra lateral. The right side of the body is controlled by the left side and vice versa. One of the big findings of this test is that the left hemisphere sub serves language for most people. 95% of right handed males have language in the left temporal lobe. about 75% of left handed males have language in the left temporal lobe. This is slightly fewer in females. Evidence of this is the Wada test, strokes, and epilepsy. ?Split-Brain? patients Corpus Callosotomy Gazzaniga ? studied many split brain patients. When brain matter is pulled away you will find the corpus callosum. If you cut the corpus callosum, you cut of connections between the left and right hemispheres. Electro-Stimulation of the surface of the brain The brain has no feeling. Done to patients before surgery to see where they can cut and where they cant cut. Dichotic Listening People can process things in the right ear better than the left because the right side communicates with the left hemisphere. What about Development? What things would we expect to find in children if UG (universal grammar) or and LAD is there at birth? If there was damage to the left temporal lobe then you would expect language problems. What if the left hemisphere is specialized at birth (or one of the specific language areas)? What would we expect to find? When might it mean if a person stops speaking / understanding /using syntax (etc.) When area X is knocked out? X could be a connector of language X could be one of many areas that control language X could be in control of motor abilities. you still have language you just cant talk. All experiments are corrilational not cause and effect. No one has found the LAD or UG in the brain Evidence Suggests that language is processed by the left hemisphere while non-speech sounds are processed in the right hemisphere (Molfese and colleagues + many replications). Children use both hemispheres to process language more than adults do. Mills and colleagues (1995) show greater degrees of lateralization for adults than children. Recovery from aphasia is more complete in children and faster; they generally catch up if injury occurs before language acquisition begins (through some slight delays often remain) Early right hemisphere damage impairs language acquisition. Test Questions Why is language in adults primarily found in the left hemisphere and in children it is in both the right and left hemisphere? Why is the left hemisphere where language is? The left hemisphere is better at processing language. Three Hypotheses The left hemisphere isn?t ready to process language at the beginning. It takes a while to mature. The right hemisphere processes language until the child learns grammar (or maybe the patterns in the input??). Then the left takes over. Children process the incoming signal with the right hemisphere, but that the left is better at the processing and continues to get better so that the right eventually stops processing it altogether The brain has to learn where to send the signal and eventually learns that the left hemisphere is better so it sends the signal there.