1. 1° Visual Cortex
• Cell-stained section (Nissl)
• most 6 cell layers

2. •neuron density varies
Layer 1
Layers 2 & 3
Layer 4
Layer 5
Layer 6
•neuron density varies

3. Brodmann’s cytoarchitectonic areas
Over 50 areas
Defined on basis of histology
Somatic sensory areas:
1° somatic sen. cx = 1, 2, 3a, 3b

4. Somatic Sensory Cortical Areas for Mechanosensations
sensory cortex
Area 5 (3° SScx)
Skin receptors
Central sulcus
Postcentral gyrus
Postcentral sulcus
Area 7 (Posterior
Parietal cortex)
2° somatic
sensory cortex
Deep receptors

5. from to Other cortical back to Thalamus areas Thalamus
Pyramidal neuron:
projection neuron
Layer 1
back to
Thalamus
to Other cortical
areas
Layers 2 & 3
Layer 4
Stellate
Neuron:
interneuron
from
Thalamus
to Subcortical areas
Layer 5
Layer 6

6. 1° Somatic Sensory Cortex Output Systems
VP lateral
VP medial
Mechanosensation

7. Cortical Pain Representations
Thalamus
Cortex
Behavior
Emotional/salience/ valence
Behavioral
Autonomic
??Localization/ Discrimination
Ventral med. Post.
(VM po)
Ventral posterior
(VPL/VPM)
Medial dorsal
Mid-insular
cortex
1° SS
Cortex
Anterior cingulate
Amygdala
Limbic cortex

8. Cingulate gyrus:
emotional/valence
Postcentral gyrus:
localization
Insular pain representation:
behavioral (autonomic; react)

9. Summary
Early morphological specialization of DRG neurons sets stage for separate mechanosensory and pain/temp/itch systems
Different ascending pathways to distinct subcortical and cortical sites
Single thalamic mechanosensory nucleus and 1° ctx
Multiple thalamic pain nuclei and cortical areas
Parietal lobe projections may play role in stimulus localization, esp. for touch
Cortical pain representations closely tied to emotions