Limbic System

Sections

USMLE HIGHLIGHTS

Limbic System Anatomy

key structures

Limbic gyrus

• Cingulate gyrus
• Parahippocampal gyrus

Intralimbic gyrus

• Hippocampus
• Amygdala

Important anatomic landmarks: the corpus callosum, basal frontal lobe, thalamus, and the septum pellucidum.

Select Papez Circuit Components

• Anterior nuclei of the thalamus
• Mammillary body of the hypothalamus

Limbic gyrus (which forms the outer limbic ring)

• Cingulate gyrus (lies above the corpus callosum)
  • The anterior cingulate gyrus is part of the anterior network of motivation, attention, and behavior and is associated with the amygdala.
  • The posterior cingulate gyrus is part of the posterior network of learning and memory and is associated with the hippocampus.

• Parahippocampal gyrus
  -Channels information to and from the hippocampus to help in memory consolidation; an efficient parahippocampal gyrus is necessary for effective memory processing.

• Uncus (the gyral fold at the anterior tip of the parahippocampal gyrus).

Intralimbic gyrus (which forms the intralimbic ring).

• Hippocampus
  • The memory processing center.

• Amygdala (aka amygdaloid body, almond-shaped)

The simplest way to understand the amygdala is to divide it into a corticomedial group and a basolateral group. Both groups connect to a wide variety of brain regions:

• The corticomedial group connects, most notably, to the olfactory system and hypothalamus for autonomic function.

• The basolateral group connects, most notably, to the thalamus and prefrontal cortex for more conscious-related processes such as sensory processing of visual, auditory, and somatosensory stimuli.

Clinical Correlation: Klüver Bucy syndrome

USMLE HIGHLIGHTS

Limbic gyrus (which forms the outer limbic ring)

• Cingulate gyrus (lies above the corpus callosum)
  • The anterior cingulate gyrus is part of the anterior network of motivation, attention, and behavior and is associated with the amygdala.
  • The posterior cingulate gyrus is part of the posterior network of learning and memory and is associated with the hippocampus.
• Parahippocampal gyrus
  • Channels information to and from the hippocampus to help in memory consolidation; an efficient parahippocampal gyrus is necessary for effective memory processing.
• Uncus (the gyral fold at the anterior tip of the parahippocampal gyrus).

Intralimbic gyrus (which forms the intralimbic ring).

• Hippocampus
  • The memory processing center.
• Amygdala (aka amygdaloid body, almond-shaped)

The simplest way to understand the amygdala is to divide it into a corticomedial group and a basolateral group. Both groups connect to a wide variety of brain regions:

• The corticomedial group connects, most notably, to the olfactory system and hypothalamus for autonomic function.
• The basolateral group connects, most notably, to the thalamus and prefrontal cortex for more conscious-related processes such as sensory processing of visual, auditory, and somatosensory stimuli.