Language Disorders

Studies by Ojemann et al.

• Stimulation of the brain of an English-Spanish bilingual shows different areas for each language
• Stim of inferior premotor frontal cortex:
• Arrests speech, impairs all facial movements
• Stim of areas in inferior, frontal, temporal, parietal cortex:
• Impairs sequential facial movements, phoneme identification
• Stim of other areas:
• lead to memory errors and reading errors
• Stim of thalamus during verbal input:
• increased accuracy of subsequent recall

Williams Syndrome

• Caused by the deletion of a dozen genes from one of the two chromosomes numbered 7
• Shows dissociation between language and intelligence, patients are:
• Fluent in language
• But cannot tie their shoe laces, draw images, etc.
• Developmental process is altered:
• Number skills good at infancy, poor at adulthood
• Language skills poor at infancy, greatly improved in adulthood

Lateralization of the Brain

• Human body is asymmetrical: heart, liver, use of limbs, etc.
• Functions of the brain become lateralized
• Each hemisphere specialized for particular ways of working
• Split-brain patients are good examples of lateralization of language functions

Lateralization of functions (approximate)

• Left-hemisphere:
• Sequential analysis
• Analytical
• Problem solving
• Language

• Right-hemisphere:
• Simultaneous analysis
• Synthetic
• Visual-Spatial skills
• Cognitive maps
• Personal space
• Facial recognition
• Drawing
• Emotional functions
• Recognizing emotions
• Expressing emotions
• Music

Split-brain

• Epileptic activity spread from one hemisphere to the other thru corpus callosum
• Since 1930, such epileptic treated by severing the interhemispheric pathways
• At first no detectible changes (e.g. IQ)
• Animal research revealed deficits:
• Cat with both corpus callosum and optic chiasm severed
• Left-hemisphere could be trained for symbol:reward
• Right-hemisphere could be trained for inverted symbol:reward

Left vs. Right Brain

• Pre and post operation studies showed that:
• Selective stimulation of the right and left hemisphere was possible by stimulating different parts of the body (e.g. right/left hand):
• Thus can test the capabilities of each hemisphere
• Left hemisphere could read and verbally communicate
• Right hemisphere had small linguistic capacity: recognize single words
• Vocabulary and grammar capabilities of right is far less than left
• Only the processes taking place in the left hemisphere could be described verbally