Anatomical Substrates of Somatic Sensation

1
Cell-stained section (Nissl)
1 Visual Cortex
most 6 cell layers
2
Layer 1
Layers 2 3
Layer 4
Layer 5
Layer 6
neuron density varies
3
Brodmannscytoarchitectonicareas
4
Somatic Sensory Cortical Areasfor
Mechanosensations
1 somatic sensory cortex
Area 5 (3 SScx)
Postcentralgyrus
Centralsulcus
Postcentralsulcus
Area 7 (Posterior Parietalcortex)
2 somatic sensory cortex
5
Pyramidal neuron projection neuron
Layer 1
Layers 2 3
Layer 4
Stellate Neuron interneuron
Layer 5
Layer 6
6
1 Somatic Sensory Cortex Output Systems
VP lateral VP medial
Mechanosensation
7
Cortical Pain Representations
Thalamus
Behavior
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