Language and the brain

The human language organ is the brain

In most adults:  the perisylvian area of the left hemispheric cortex.

Brain structure:

cerebrum -divided into right and left hemispheres

                  - hemispheres connected by the corpus callosum

                  - cerebrum contains a subcortex and a cortex

Contralateral neural control - right hemisphere controls left side of body

                                                      - left hemisphere controls right side of body

Asymmetrical specialization (lateralization of skills)

- right hemispheric cortex controls spatial acuity, music, art, 3D movement

- left hemispheric cortex controls logic, math skills, language, right handedness

            monolineal progression:  step-by-step buildup of detail

How do we know the left hemispheric cortex controls language?

1. PET scans show more neural activity in the left during word problems.

2. if corpus callosum is severed, stimuli coming from the left ear or eye        cannot reach the language center and cannot be verbalized about.

3. Aphasia (language loss due to brain damage) most often results when the            left hemisphere is damaged.

4. Sodium amytol into left carotid artery disrupts language

5. Electric shock to left hemisphere produces involuntary vocalization

6. Music best perceived through left ear; language tones through right.

7. Harder to solve word problems when tapping fingers of the right hand.

8. Perisylvian area of the left hemispheric cortex actually bulges outward,

      denting the bones of the skull.

Animal communication center in the subcortex rather than the cortex.

In humans, the subcortex controls built-in emotional responses such as

   the urge to laugh, sneeze, cry, etc.

What can language disorders tell us about brain function?

Tourette's syndrome - involuntary discharging of the emotional response      centers of the subcortex.

Williams syndrome - flair for language, but cognitive development retarded

SLI (Specific Language Impairment) - genetic defect, whereby children are             born without the ability to absorb syntactic patterns.

SUMMARY:  FOUR facts

1. Children are normally born with a language learning instinct

2. This instinct diminishes with the onset of puberty, when language is         lateralized to a small portion of the left hemisphere.

3. The seat of language in most adults is

      the perisylvian area of the left hemispheric cortex.

4. Of all species, only humans use this area of the brain for communication.

      Communication systems of other species is analogous to

      set emotional responses in humans rather than to creative language

What happens when the perisylvian area of the left hemispheric cortex is damaged? 

        The individual experiences aphasia, or language loss.

Studying aphasia reveals a great deal about how language is stored in the brain.