LAYERS OF THE CEREBRAL CORTEX

Question 1

•Closet to the skull
• Prevalent Cell Types: Horizontal Cells of Cajal: cells lining on its side
• Running across, tangentially
• Fiber Formation: Tangential Layer (Plexus of Retzius)
• Fiber Type: Projection fibers from Thalamus, Marrinotti Fibers from deep layers, Projection fibers from deeper pyramidal,
stellate, and fusiform cells
• Receives a tremendous amount of information

Answer 1

I - Molecular Layer (Plexiform)

Question 2

• Prevalent Cell Types: Small Granular, Pyramidal, & Stellate
• Fiber Formation: Dysfibrous Layer
• Hardly any fibers afferent going up as one layer
• Fiber Type: Mostly efferent cells to the Deeper Cortical Regions

Answer 2

II - External Granular Layer

Question 3

• Prevalent Cell Types: Small/medium Pyramidal Cells
• Fiber Formation: Suprastriate Layer
• Vertical (inside out and outside in)
• Fiber Type: Many afferent and efferent cells Deeper Cortical Regions

Answer 3

III - External Pyramidal Layer

Question 4

• Prevalent Cell Types: Closely Packed Stellate cells
• Fiber Formation: External Band of Ballinger
• Fiber Type: Dense horizontally oriented fibers

Answer 4

IV – Internal Granular Layer

Question 5

• Most important in relation to humans
• Prevalent Cell Types: Medium to Large Pyramidal Cells, and Martinotti cells
• Fiber Formation: Interstriate Layer (Internal Band of Ballinger)
• Deep striated layer
• Very densely stained
• Fiber Type: Primary Cortical Output Layer, many axons and dendrites

Answer 5

V – Internal Pyramidal Layer

Question 6

• Prevalent Cell Types: Fusiform and Martinotti cells
• Fiber Formation: Infrastriate Layer: 6A: interstraite 6B: Myelinated fibers
• Fiber Type: Projection fibers to deeper cortical white matter, marrinotti cells project to more superficial layers (Layer I)

Answer 6

VI – Multiform Layer