Brain and Language

Separating the two hemispheres Commisurotomy: sever the corpus callosum Left visual field disconnected from language center ● CLAP ● LAUGH (left half of their world has been disconnected from their language center)

RH and Syntax Gazzaniga & Hillyard (1971) –Participants saw picture –Presented 2 sentences (in left ear) –Which sentence accurately describes picture? The girl is drinking/The girl will drink The boy kisses the girl/The girl kisses the boy The dog jumps over the fence/The dogs jump over the fence The girl is sitting/The girl is not sitting Only distinction they could make!

Right hemisphere and language Compensates for left hemisphere damage (esp. with children) Word semantics (Beeman 1998) –Processing relatedness of words –Activates less-likely meanings of words Understanding discourse, speaker’s intention –Interpreting narrative script, jokes Metaphor (Brownell 1988) –More blood flow to the RH when asked to judge metaphor plausibility “The inventors were squirrels collecting nuts”

Handedness and lateralization Most of us are strongly left- lateralized for language 9% of population is left- handed –only 1/5 of left-handed persons have language primarily in the RH (The corpus callosum for left- handers and ambidextrous people is 11% larger) Left Hemisphere

Are we lateralized at birth? Sucking tasks – infants respond to linguistic stimuli better with Right Ear, and to musical stimuli with Left Ear (Bertoncini, Morais, Bijeljac-Babic, McAdams, Peretz, & Mehler, 1989) ERPs – more brain activation in LH with linguistic stimuli, in RH with music & noise, infants between 1 week – 1 month (Molfese & Betz, 1988) Animals lateralized too?

The anatomy of the brain 4 lobes: Frontal Parietal Occipital Temporal Sylvian Fissure: S eparates the Frontal and Parietal lobes from the Temporal lobe

Major Language Areas:

Frontal Lobe Broca’s area – responsible for grammar, language production Motor area – on perimeter of the parietal lobe, specific regions dedicated to the motor abilities of specific body parts Other areas: –Supplementary motor area – programs motor sequences –Prefrontal area – highest level of brain function, intellect, will, emotions – thought during speech –Anterior Cingulate Gyrus – concentration (in the limbic system)

Motor Area

Temporal Lobe Primary Auditory Area –Contralateral, in the Sylvian fissure –Receives auditory information first Auditory Association Area –site of high-level functions that process information such as language and music Wernicke’s Area –Speech comprehension, semantic retrieval (except for axial commands – see p. 367) Auditory Visual Association Area –Involved in visual language processing and lip reading

Parietal and Occipital Lobes Parietal Lobe: Parietal Association Area –communication fibers from all lobes densely connected –general somaesthetic sensing (feeling in arms, face, legs…) –visual and auditory senses also associated Occipital Lobe: Primary Visual Area –very rear part of the brain Visual Association Area –around primary visual area, recognizes shape, color, movements

REVIEW

Is language due to brain size? No! The average human adult brain weighs about 3 lbs, which is nothing compared to an elephant’s brain Not due to high “brain mass: body mass” ratio –The brain mass : body mass ratio is the same for a 13-year-old boy a 3-year-old chimpanzee

Is language in one area? No…in fact, pinning down the area of the brain that’s specialized for language is very difficult! Researchers thought they’d found the language center: –planum temporale (the horizontal part of the Sylvian Fissure) –Differences in the lengths of this region correspond to the development of the different hemispheres –Deacon (1968) examined 100 human brains and found that 68 had enlarged planum temporale on the left side, so determined that he’d found the “control center” for language also seems to be an area largely responsible for language processing and production, since this is where the auditory association cortex receives signals from the ear, which are processed and sent to other parts of the brain –But Gannon and colleagues (1998) were examining chimp brains looking for asymmetries, and they found that 17 out of 18 chimp brains had enlarged plana temporale on left side! So chimps are more specialized for language than humans?