Lateralization of Brain Functions

Lateralization of Function

• Corpus Callosum: A bundle of nerve fibers connecting the left and right brain hemispheres.
• Lateralization: Localization of a function in one brain hemisphere.
• Left Hemisphere (Right Hand Dominance):
  • Primarily responsible for language and speech, writing (right-handed individuals), mathematical abilities, and logical processing. Processes information from the right visual field and controls the right side of the body.
• Right Hemisphere (Left Hand Dominance):
  • Concerned with spatial relations, processing information from the left visual field, controlling the left side of the body, and artistic/intuitive functions. Also involved in music, art, and understanding prosody (acoustic qualities). Can process numbers and short words.
• Split Brain Operation: Severing the corpus callosum to treat severe epilepsy. Has shown that the hemispheres can function independently, leading to some interesting observed oddities.
• Commissures: Connections between the brain's hemispheres (e.g., anterior and hippocampal commissures).
• Handedness and Language Lateralization: Approximately 96% of right-handers and 70% of left-handers have language localized to the left hemisphere.
• Savant Behaviors: Exceptional skills in specific areas despite other disabilities, typically linked to right-hemisphere function (e.g., art, music, spatial skills).
• Sex Differences in Lateralization: Androgens are hypothesized to contribute to differences in cognitive tasks between males and females; females show more functional symmetry in the brain, whilst males show more right hemisphere dominance in visuospatial and mathematical tasks.
• Anatomical Anomalies (e.g., missing cerebellum): Associated with motor control issues like dizziness, nausea, and balance problems, sometimes slowing speech development.

Language Disorders

• Language: Communication of thoughts and feelings through arbitrary signals (e.g., voice sounds, gestures, written symbols). Includes semantics (meaning) and syntax (grammar).
• Case Study: "Tan": A patient with speech deficits that primarily communicated using isolated syllables ('tan') but retained intellect and other abilities. This was a case of significant damage to the left inferior frontal region (Broca's area).
• Aphasia: Partial or complete language impairment.
  • Broca's Aphasia (Production Aphasia): Difficulty producing speech, characterized by slow, labored speech, grammatical mistakes, and trouble with word endings. Comprehension is still relatively intact.
  • Anomia (BA): Difficulty retrieving words.
  • Wernicke's Aphasia: Fluent but meaningless speech. The speaker is often unaware of their non-sensical communication.
  • Conduction Aphasia: Fluent speech and good comprehension but impaired repetition and naming. Damage to the arcuate fasciculus, connecting Broca's and Wernicke's areas.
  • Global Aphasia: Loss of all language functions (speaking, comprehending, reading, writing).
  • Transcortical Aphasia: Fluent speech but with repetition, impaired comprehension, and other symptoms. Associated isolation of language areas.
• Disorders of Reading and Writing:
  • Alexia: Reading disturbance/word blindness.
  • Agraphia: Writing deficit. Types include phonological and orthographic agraphia.
  • Dyslexia: Difficulty with reading, potentially linked to minor differences between the planum temporale areas of the brain.

Intelligence

• Intelligence: The ability to learn and solve problems, influenced by genetics and the environment. Social factors (family/peer groups) also play a part.

Explore the fascinating concept of brain lateralization, which refers to the specialization of the left and right hemispheres in performing different functions. Learn about the corpus callosum, the roles of each hemisphere, and the implications of split brain surgery. This quiz delves into how lateralization affects language, spatial awareness, and more.