Lecture Notes: The Parietal Lobe

Introduction

• The brain is divided into main lobes:
  • Frontal Lobe: Motor cortex (action area)
  • Parietal Lobe: Sensory cortex
  • Occipital Lobe
  • Temporal Lobe
• Insula: Located beneath the temporal lobe, considered the "ground floor" of the cerebral cortex.

Parietal Lobe Overview

• Functions primarily as the sensory cortex.
• Processes sensory information from the body and environment.
  • Key sensory inputs: touch, proprioception, temperature, and pain.

Anatomical Margins

• Central Sulcus:
  • "Central" because of its mid-brain location; "Sulcus" because it is a dip.
  • Adjacent to it are gyri: bumps in the brain.
  • Pre-central Gyrus: Part of the frontal lobe, primary motor cortex.
  • Post-central Gyrus: Part of the parietal lobe, primary somatosensory cortex.

Sensory Homunculus

• Map of the body on the post-central gyrus.
  • Sensitive areas (e.g., hands, lips) are larger on the map due to more sensory neurons.
• Two-point discrimination:
  • Ability to distinguish two points as separate.
  • Finer in hands (millimeters) vs. broader in the back (centimeters).

Proprioception

• Definition: Awareness of body position and movement.
• Relies on receptors in joints and muscles.

Neuroplasticity

• Neuroplasticity: Brain's ability to reorganize by forming new connections.
  • Example: In individuals who lose a limb, nearby neurons (e.g., face) may stimulate neural pathways originally associated with the lost limb.

Association Cortex

• Location: Surrounds the somatosensory cortex.
• Function: Integrates sensory information with past experiences to identify objects.
  • Example: Recognizing a coin by touch involves multiple sensory inputs.

Supramarginal and Angular Gyri

• Supramarginal Gyrus:
  • Role: Posture and position (proprioception) of self and others.
  • Connected to the mirror neuron system, aiding in empathy.
• Angular Gyrus:
  • Function: Important for word choice and language processing.
  • Works with Wernicke's area in speech and text comprehension.

Wernicke's Area

• Location: Spans parts of both the parietal and temporal lobes.
• Function: Recognition and interpretation of spoken and written language.
  • Damage can lead to difficulties in language comprehension.

Conclusion

• The parietal lobe plays a crucial role in sensory processing and interpretation.
  • Primary somatosensory cortex: Immediate sensory input.
  • Association cortex: Deeper interpretation and object identification.
  • Gyri like the supramarginal and angular gyrus contribute to empathy and language processing.