CSD 2230

Nervous System

Aphasia

  1. Cerebral Cortex - Structures that make up the 2 hemispheres of the brain are referred to the Cerebral Cortex.
    1. Physical Differences between the 2 hemispheres:
      1. Left is somewhat larger than right side in most adults.
      2. Different blood supply.
    2. Functional Differences: In most adults, the left controls language behavior. About 90% of the population is left brain dominant. Remaining 10% are right brain dominant or mixed brain dominant (different hemispheres serve predominantly for different activities).
      1. Dominant Hemisphere (Usually left) Functions
        1. Processing and storage of individual sounds of language is a function of the dominant hemisphere.
        2. Formulation and production of speech sounds is controlled by the dominant hemisphere.
      2. Nondominant Hemisphere Functions
        1. Processing of speech melody patterns (intonation) appears to be a function of the nondominant hemisphere.
        2. Production of nonspeech sounds is controlled by this hemisphere.
  2. Lobes
    1. Anterior - Anterior portion of this hemisphere is responsible for the planning and execution of overt acts such as those result in speaking, writing, gesturing.
    2. Frontal - Important landmark of the frontal lobe includes Broca's area, which programs the oral and phonatory mechanisms for the movements of speech. Broca's area responsible for the expression of language and motor programming for articulation.
      1. A lesion in Broca's area produces apraxia of speech and this area is prominent in the site of damage resulting in Broca's aphasia.
        1. Spontaneous speech is nonfluent and agrammatical. It may sound slow, labored, and telegraphic, with function words like articles, conjunctions, and prepositions missing. Speech becomes slow and labored.
        2. Sentences are grammatically incomplete, giving speech a telegraphic quality, but responses generally makes sense.
        3. Speech articulation is slurred.
        4. Comprehension is not seriously affected.
        5. If writing is involved, spontaneous writing is usually poor, but reading comprehension is better.
    3. Posterior - Posterior portion of this hemisphere is devoted to tasks having to do mainly with the reception of sensory stimuli through the auditory, visual, and somatosensory (body sensations) systems.
    4. Temporal - Important landmark in this area is Wernicke's area. The interpretation of auditory language input is the left hemisphere is handles here. It is essential to comprehension and formulation of both spoken and written language.
      1. A lesion in this Wernicke's area for left hemisphere produces Wernicke's aphasia.
        1. Sentences are spoken fluently and with normal inflections. But lacking in meaning.
        2. Words are often inappropriate, if not sheer nonsense.
        3. Speech is uttered fluently but is virtually incomprehensible to the listener.
        4. Auditory comprehension is impaired.
        5. Repetition is impaired.
        6. Spontaneous writing shows well formed letters, but reading comprehension is poor.
      2. Arcuate Fasciculus: The large pathway that interconnects Broca's area with Wernicke's area.
        1. Transmits linguistic information to anterior areas from posterior area.
        2. If this area is injured:
          1. Impairs ability to repeat words accurately
          2. Wrong sounds are combined in wrong sequences.
            1. Stop may come out pots, tops, post.
          3. Hearing word repeated correctly does not improve performance.
          4. Neither the ability to comprehend speech nor the ability to generate spontaneous statements fluently is impaired.
    5. Parietal - This region responsible for tactile recognition and visuospatial orientation. Damage to this areas may result in astereognosis or construction apraxia, causing difficulties in copying geometric forms and drawing from memory.
      1. Angular Gyrus
        1. Integrates visual, auditory, and tactile information. Symbolic integration for reading
        2. If this area is injured:
          1. The visual cortex is disconnected from Wernicke's area, which interferes with reading and writing.
        3. Patient sees the word but cannot read them, they are meaningless lines. Equivalent to a Westerner looking at Chinese writing.
      2. Supramarginal Gyrus
        1. Symbolic integration for writing.
        2. If this area is injured: Writing disorders or agraphia.
    6. Occipital - This region responsible for the reception of visual input.
      1. Damage to this area for either hemisphere results in hemianopsia (half field visual deficit).

 

 

 

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