Brain and Behavior - University of Texas at Arlington - Chapter Thirteen

Lateralization

The right hemisphere has different cognitive functions from the left hemisphere. One set of axons connects the two halves at the level of cortex. These axons are called the corpus collosum. Two smaller sized cross connections, the anterior commisure and hippocampal commisure, also help. There are also lsight anatomical differences. The planum temporale is slightly bigger in the left hemisphere for 65% of people (responsible for auditory processing, speech recognition, and receptive language).

Split-Brain People

People with cut corpus collousm, usually as a treatment for epilepsy to prevent seizures from forming by crossing between the two hemispheres. They maintain normal intellect, motivation, and body activity. Have cognitive difficulty with coordination of both sides of body with one task for complex or novel tasks. use hands independently in a way other cant and respond to stimulus on only one side of body differently.

Emotion and Language

Left is better at language processing in regards to complex grammar while right is better at body gestures and vocal tone to recognize emotion. People with right hemisphere damage fail to read tone of voice and tend to speak with a flat effect. Right is also better at spatial awareness. Usually left focuses on details while right focuses on overall patterns, though this only becomes obvious after damage has been dealt to the left hemisphere, thus limiting interference from it.

Language By-Product View

Proposes that language formed as an accidental by-product of human’s intelligence. Faces several problems:

• People with full size brain and normal overall intelligence can show language deficits

  • 16 of 30 in a big family can have severe grammar deficits because of a particular gene

  • genetic conditions can impact language but leave other aspects of intelligence intact

  • Genetic mutation gene FOXP2 impacts the development of the jaw and throat (phonatic organs), impairing language development

• Williams Syndrome is a rare disorder in which people with impaired mental intelligence develop surprisingly better language but have limited abilities in other regards

  • Poor at math, visuospatial skills, and spatial perception

  • Show normal or close to normal language performance and in some cases show very good language skill (such as poetic description).

Suggests language is more than a by-product of intelligence

Language Specialization View

Proposes language evolved as a specialized, built-in brain mechanism as the intelligence is developed by interacting with one’s environment.

• Supported by children learning language with amazing ease and learning language is related to a period of dependency in childhood during which social interactions are evident among people

• Evidence for biologically preparing for language development: FOXP2 gene and greater control between motor cortex that control the vocal cords and the rest of the cortices enables more complex and detailed control of sound protection

Studies proved that language has a critical learning period and language evolves as a specialization as language develops.

Age and Language

Adults are better are better at memorizing vocabulary of a second language, children have a greater advantage on learning pronunciation with less accent and grammar. Bilinguals show substantial bilateral brain activity during speech for both languages and show thicker than average temporal and frontal cortices.

Brocca’s Area

Part of the frontal lobe of the left cortex near the motor cortex. Damage to this area results in impaired language production. Helps organize and execute speech.

Wernicke’s Area

an area of the temporal lobe of the left cortex located near the primary auditory cortex. Damage results in impaired language comprehension.

Broca’s Aphasia

Speak meaningfully by only using nouns and verbs. For English speakers, they omit pronouns, prepositions, conjunctions, auxiliary verbs, qualifiers, and tense and number endings. Cognitive deficit in producing language, not pronouncing words. Can still recognize basic grammar mistakes.

Wernicke’s Aphasia

Patients can speak smoothly but speech is nonsensical and have anomia which makes it difficult to recall names of people or things. They also struggle to understand others written or spoken language.

Dyslexia

Learning disability in conversion between symbols and sounds. when one hears or sees a letter or number, they cant speak or write down the spelling. The planum temporale is the same size in both hemispheres in people with dyslexia, when its usually bigger in the left hemisphere in other people. The visual word-forming area in the left temporal lobe, adjacent to the facial recognition area, becomes highly responsive when people learn to read and write. Damage to this area or less response to words impairs reading which leads to dyslexia.

• Dysphonetic Dyslexia: because of auditory-processing difficulty, have trouble connecting sounds to symbols. Have a hard time sounding out words and when they’re unsure about pronunciation they guess. Have complex auditory disorders usually which impair ability to detect temporal order of sounds. Show less than normal response to speech sounds in brain and show lack of focus/attention to speech sounds.

• Dyseidetic Dylsexia: Have trouble recognizing the spelling of a word while seeing it. Inability to visualize gestalt of word and have difficulty reading and spelling. Have more difficulty with long words. Only weak activation of the areas connecting visual stimulus and words.

• Both show difficulty with shifting attention to either written or spoken language.