Regulation and Integration of the Body

Functional Areas of the Cerebral Cortex

• Types of Functional Areas:

  • Motor areas
  • Sensory areas
  • Association areas

• Key Characteristics:

  • Each hemisphere controls opposite side of the body (contralateral).
  • Hemispheres are structurally symmetrical but have functional lateralization.
  • Functional areas interact extensively with one another.

Motor Areas

• Primary Motor Cortex:

  • Located in the precentral gyrus (frontal lobe).
  • Controls voluntary movements via large pyramidal cells.
  • Forms pyramidal tracts (e.g., corticospinal tracts) projecting to the spinal cord.
  • Somatotopy: body is spatially mapped according to motor control.
  • Larger areas correspond to regions requiring more precise control (e.g., face, hands).

• Premotor Cortex:

  • Anterior to primary motor cortex.
  • Involved in planning and sequencing movements.
  • Coordinates complex tasks that depend on sensory feedback (e.g., typing).

• Broca's Area:

  • Located anterior to inferior region of the premotor area (usually in the left hemisphere).
  • Directs muscle movements required for speech.
  • Active during speech preparation and planning other voluntary movements.

• Frontal Eye Field:

  • Controls voluntary eye movements.

Sensory Areas

• Primary Somatosensory Cortex:

  • Located in the postcentral gyrus (parietal lobe).
  • Receives sensory input from skin and proprioceptors, enabling spatial discrimination.
  • Body representation is spatially mapped.

• Somatosensory Association Cortex:

  • Just posterior to the primary somatosensory cortex.
  • Integrates sensory inputs to understand object properties (e.g., size, texture).

• Visual Areas:

  • Primary Visual Cortex: Located at the posterior tip of the occipital lobe, processes visual information from the retina.
  • Visual Association Area: Surrounds primary visual cortex; interprets visual stimuli using past experiences.

• Auditory Areas:

  • Located in the temporal lobe, processes sound pitch, loudness, and location.
  • Auditory association area interprets sounds (e.g., speech, music).

• Olfactory and Gustatory Cortex:

  • Olfactory Cortex: Located in the temporal lobe, processes smell.
  • Gustatory Cortex: In the insula, involved in taste perception.
  • Both relate to the limbic system affecting emotions and memories.

Multimodal Association Areas

• Function: Integrate information from multiple senses and relate it to memory and emotions.
• Anterior Association Area (Prefrontal Cortex):
  • Involved in intellect, cognition, recall, and personality.
  • Handles complex tasks like planning and abstract reasoning.
• Posterior Association Area:
  • Integrates sensory information, recognizes patterns, and localizes spatial awareness.
• Limbic Association Area:
  • Emotional context of experiences, involved in memory formation.

Lateralization of Cortical Function

• Cerebral Dominance:
  • Generally, the left hemisphere dominates language and logic; right hemisphere handles spatial and creative activities.
• Lesions and Functions:
  • Damage to the left hemisphere may impair language skills, while right hemisphere damage can affect spatial awareness.

Cerebral White Matter

• Types of Fibers:
  • Association Fibers: Connect parts within the same hemisphere.
  • Commissural Fibers: Connect corresponding areas between hemispheres (e.g., corpus callosum).
  • Projection Fibers: Connect the cortex to lower brain and spinal cord.
  • Internal Capsule: Contains projection fibers that serve as a pathway between the thalamus and cortex.
  • Corona Radiata: Contains radiating fibers above the internal capsule.

Basal Nuclei

• Function: Involved in movement regulation, encompassing subcortical nuclei.
• Commonly referenced in clinical practice for movement disorders.

Clinical Notes

• Damage to specific areas can lead to loss of voluntary control or impairment in performing learned skills without affecting muscle strength.
• Examples include loss of speech, inability to recognize objects, or functional blindness, depending on the areas affected.