Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
1. Major neural substrates of expressive and receptive language processes - language is localized to the left hemisphere in 95% or right-handed people and in most lefthanders - about 15% of left-handed people are right hemisphere dominant for language and 15% have bilateral representation for language - Broca’s area: opercular/triangular parts of inferior frontal gyrus; planum temporale superior surface of temporal lobe behind auditory cortex - Wernicke’s area: posterior superior temporal gyrus; angular/supramarginal gyri - Broca’s area, Wernicke’s area, and their connection the arcuate fasciculus perisylvian (located around left sylvian fissure, the lateral sulcus) - arcuate fasciculus necessary to repeat something heard - some aspects of language rely on extrasylvian regions of left hemisphere (and right hemisphere) Compare/contrast areas involved in processing of sound and production of speech Comprehension of Language - auditory pathway involves cochlea, CN VIII, brainstem, bilaterally after cochlear nuclei lateral lemniscus inferior colliculus inferior brachium thalamus, MGN internal capsule primary auditory cortex; auditory info from primary auditory areas projects to Wernicke’s area - visual pathway for written language involves the retina optic nerve optic tract LGN of thalamus internal capsule primary visual cortex in occipital lobe; higher level processing of written info relies on adjacent areas in the temporo-parietal association areas Production of Language Speech - speech production involves moving muscles, bones, and cartilage involved in articulation, in lower airway, larynx, pharynx, and mouth; speech is the motor act that carries the linguistic message - dysarthria refers to imprecise articulation due to muscle weakness or incoordination resulting from damage to motor areas (motor cortex, basal ganglia, cerebellum, UMN, LMN, NMJ, or muscle) - Apraxia of speech motor speech disorder reflecting impaired motor programming for speech that results in difficulty planning and sequencing sound Language - representation of conceptual knowledge in left inferior temporal lobe and left inferior frontal lobe - ability to retrieve words or name things can be disrupted by damage to perisylvian or extrasylvian regions of the left hemisphere - Expressive language formulation involves Broca’s area; Broca’s area critical for motor planning for speech production (verbal output) as well as syntactic (word ordering) aspects of language - written language network including posterior temporal lobe (spelling) and fronto-parietal regions involved in motor planning and control of the hand 2. Aphasia - acquired language deficit characterized by impaired word selection, language production, and language comprehension - paraphasia incorrect word choice and sound substitution - alexia reading impairment - agraphia writing impairment - common causes include ischemic stroke of left middle cerebral artery blood to perisylvian cortical language areas - extrasylvian aphasias are called transcortical aphasias; lesions here are isolated from regions involved in semantic processing and production of volitional speech - slow onset from brain tumors or focal cortical atrophy - transient ischemic attacks (TIA), migraine, seizures transient aphasia 3. Aphasia classification - based on fluency, auditory comprehension, repetition, and naming Fluency - fluent aphasias good verbal output consisting of well-articulated utterances of normal length and prosody (variations of pitch, loudness, rhythm) - fluent aphasias associated with posterior lesions (Wernicke’s) that spare anterior cortical regions for motor control of speech (Broca’s) - nonfluent aphasias sparse, effortful utterances of short phrase length and disrupted prosody; struggle with articulation; few nouns, ever fewer verbs; associated with anterior lesions comprising motor and premotor cortical regions involved in speech production (Broca’s) Auditory comprehension - usually defective in most aphasias to some degree; anterior lesions result in minor impairments; posterior lesions result in significant impairment of auditory processing Repetition - repetition of spoken words requires an intact perisylvian region (Wernicke’s, Broca’s, and arcuate fasciculus); lesions anywhere in perisylvian region disrupt repetition - extrasylvian region lesions have preserved repetition, but reduction of spontaneous speech, comprehensions disturbance, or both Naming - anomia is word finding difficulties; can occur in isolation in anomic aphasia - perseveration is repetition of word - neologism is making up a word (and perhaps repeating it) Classic Aphasia Syndromes - look at table on next page