Crossing between two like regions of the nervous system constitutes a commissure.

• Crossing between two like regions of the nervous system constitutes a commissure.

• The objective is to relate functions of the bilaterally symmetrical nervous system.

• The corpus callosum is the largest commissure connection pyramidal cells by their axons to the same circuitry of the opposite side. The hippocampal and olfactory (anterior) commissures is an extension the corpus callosum but for the older parts of the cerrebral cortex.

• Others are:

• Superior and inferior collicular commissures
• Posterior commissure
• Ventral white commissure is not a commissure but a descussation.