140. Association Cortex, Cerebral Asymmetry, Lobes of the Brain, and Cortical Plasticity – Quiz

📌 Professor’s Notes: Quick Revision

High-yield revision notes for rapid review before university examinations.

• The association cortex (neocortex) is the largest and most recently evolved part of the cerebral cortex. It integrates sensory, motor, and limbic information to perform higher cognitive functions such as language, reasoning, memory, judgment, planning, attention, learning, decision-making, creativity, and personality. It does not directly produce movement or primary sensation.
• The association cortex is divided into four functional regions:
  • Prefrontal association cortex: Executive functions, planning, judgment, attention, working memory, personality, and decision-making.
  • Parietal-temporal-occipital association cortex: Integrates sensory information for perception, language, and spatial orientation.
  • Temporal association cortex: Object recognition, auditory processing, memory, and emotional integration.
  • Limbic association cortex: Emotion, motivation, learning, memory, and behavior.
• The neocortex consists of six layers with extensive feedback circuits, mainly through pyramidal neurons. Layer IV receives most thalamocortical inputs. These circuits refine information processing and form the basis of cortical plasticity.
• Cerebral asymmetry (cerebral dominance) refers to specialization of the two cerebral hemispheres.
  • The dominant (categorical) hemisphere—usually the left hemisphere—controls language, speech, reading, writing, logical reasoning, and sequential processing.
  • The nondominant (representational) hemisphere specializes in visuospatial perception, facial recognition, music, artistic ability, and emotional interpretation.
  • The corpus callosum connects both hemispheres and allows integration of their functions. Around 96% of right-handed people have left hemispheric language dominance.
• Functions of the cerebral lobes:
  • Frontal lobe: Voluntary movement, motor planning, speech production (Broca area), executive functions, personality, attention, and working memory.
  • Parietal lobe: Somatic sensation, stereognosis, two-point discrimination, proprioception, spatial orientation, attention, and sensorimotor integration.
  • Temporal lobe: Hearing, language comprehension (Wernicke area), object recognition, memory, emotion, and olfaction.
  • Occipital lobe: Primary center for vision and visual interpretation.
• Effects of cortical lesions:
  • Frontal lobe: Impaired planning, judgment, working memory, personality changes, perseveration, poor concentration, and frontal lobe syndrome.
  • Parietal lobe: Hemineglect, astereognosis, impaired spatial perception, constructional apraxia, attentional deficits, and loss of cortical sensory functions.
  • Temporal lobe: Prosopagnosia, auditory discrimination defects, memory impairment, and Klüver–Bucy syndrome after bilateral amygdalar lesions.
  • Lesions of the dominant hemisphere commonly produce language disorders, whereas nondominant hemisphere lesions mainly affect visuospatial functions.
• Cortical plasticity is the ability of the brain to modify its structure and function in response to development, experience, learning, or injury.
  • It is greatest during early postnatal life but persists throughout adulthood.
  • Recovery after injury occurs mainly by axonal sprouting, strengthening of existing synapses, and formation of new neuronal connections.