Aphasia Overview

• Aphasia: Loss or impairment of language comprehension or expression.
• Usually caused by damage to specific areas of the brain involved in language.

Key Brain Areas

• Wernicke’s area: Located in the left temporal lobe (for most people).
  • Responsible for language comprehension.
• Broca’s area: Located in the left frontal lobe.
  • Responsible for speech production and articulation.

Types of Aphasia:

1.  Receptive Aphasia (Wernicke’s Aphasia)

• Damage to Wernicke’s area in temporal lobe (usually on left side).
• Person cannot understand written or spoken language.
• Speech is fluent but meaningless (word salad).
• Can’t interpret language correctly.

2.  Expressive Aphasia (Broca’s Aphasia)

• Damage to Broca’s area in temporal lobe (usually on left side).
• Person can understand language but cannot speak or write properly.
• Speech is garbled or slow.
• Little or no articulation.

3.  Global Aphasia

• Damage to both Wernicke’s and Broca’s areas, or their connecting pathways.
• Severe:
  • Cannot understand or produce language.
  • Results from large strokes affecting both regions.

4.  Dysphasia (Aphasias of partial loss)

• Mild or partial impairments.
• Prefixes:
  • a-: without or absent (e.g., aphasia).
  • dys-: bad or difficult.

Other Language-Related Disorders

1.  Dysarthria

• Impaired articulation due to damage to cranial nerves controlling speech muscles.
• Words tend to be slurred or poorly articulated.
• Not a language problem per se but muscle control problem.

2.  Agraphia

• Inability to write.
• Results from damage to language or motor pathways involved in writing.

3.  Alexia

• Impaired reading ability (dyslexia is a related developmental disorder).
• Damage to visual or reading centers.

4.  Agnosia

• Inability to recognize objects or people.
• Results from damage to specialized recognition areas in the brain.
  • Object agnosia: unable to recognize objects.
  • Facial (prosopagnosia): unable to recognize faces.
• Example from Oliver Sacks’ cases: patients unable to recognize people or objects due to focal brain damage as depicted in his book “The Man Who Mistook His Wife for a Hat”.

Summary

• Aphasia affects language comprehension and output based on lesion location.
• Recognition deficits (agnosia) involve perception of objects or faces.
• These conditions highlight the specialized functions of different brain regions.