Language and Lateralization

Language

Communication is essential for survival, generation and understanding of written, spoken, and gestural communication is language

Phonemes

Basic speech sounds

Semantics

Meanings of words or sentences

Syntax

Grammatical rules for constructing phrases and sentences

Mirror Neurons

Critical to develop language, active during imitation of others’ actions and overlap Broca and Wernicke areas

Early Plasticity for language

Hemispherectomy for epilepsy

Bilingualism

If learned before age 11, same brain regions used for both languages and if after, different regions are used. Language acquisition is more difficult in adulthood, diminished plasticity

Asymmetry of Planum Temporale

Larger on left - reflects innate verbal specialization of left hemis, present by week 30 gestation and within Wernicke’s area

Music

Activates right hemis more than the left since right plays major role in perception

Corpus Callosotomy

Last-ditch effort to control epilepsy and results in brain split

Present Picture to left visual field (right brain)

Subject will report they dont know what it was, left hand can show you what it was but right hand cant

Present Picture to right visual field (left brain)

Left hemis can tell you what it was and right hand can show you, left hand cant

Dichotic Listening

Presents different sounds to each ear at different or the same time. Thus, LEFT hemis is dominant for language and right handers identify verbal stimuli delivered to right ear more easily - “advantage”

WADA Test

Injection of amobarbital into carotid artery briefly sedates that hemis. Right handers: language restricted to left 95%. Left handers: only 70% have left lateralization, 15% right, and 15% both

Aphasia

Impaired language ability,

Dysphasia

Any language disorder

Dysarthria

Impaired anility to speak clearly

Dyspraxia

Impaired ability to sequence a complex motor act

Dysgraphia

Impaired ability to write

Dyslexia

Impaired ability to read, disorder of both visual and auditory processing and brain uses more of the right hemis to read but improves with training

Aphasia Wernicke-Geschwind Model - Disconnection Theory

Language impairment from loss of connections among brain regions

Nonfluent (or Broca’s) Aphasia

Brain lesion producing aphasia, difficulty producing speech but comprehension is good. May occur with anomia (inability to name people or objects)

Fluent (Wernicke’s) Aphasia

Complex verbal output with many paraphasia’s (word salad), patients cannot understand what they read or hear

Global Aphasia

Broca’s + Wernicke’s, total inability to understand or produce language. Large left-hemis lesions, affecting all speech zones and prognosis is poor

ASL

Uses same brain mechanisms as spoken language, lesions typical of aphasia in normal speakers impair ASL use in deaf. fMRI studies: signers and normal speakers have similar activation in language tasks but signers additionally activate right hemis

Recovery from Aphasia

Right hemis can take over language following left hemis damage, if injury occurs early in life and damage occurs later, lang control is mire likely to shift into bordering areas in left hemis

Melodic Intonation Therapy

Aphasia uses the fact that singing often is intact after a left hemis stroke

Surface Dyslexia

Errors in reading restricted to details and sounds of letters, error early in auditory processing

Deep Dyslexia

Errors in reading one word as another, related in meaning country - nation, error in later in auditory processing

Micropolygyria

Excessive cortical folding

Ectopias

Clusters of extra cells