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• Cell-stained section (Nissl). 1° Visual Cortex. • most 6 cell layers. Layer 1. Layers 2 & 3. Layer 4. Layer 5. Layer 6. •neuron density varies. Over 50 areas Defined on basis of histology. Somatic sensory areas: 1° somatic sen. cx = 1, 2, 3a, 3b.
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• Cell-stained section (Nissl) 1° Visual Cortex • most 6 cell layers
Layer 1 Layers 2 & 3 Layer 4 Layer 5 Layer 6 •neuron density varies
Over 50 areas Defined on basis of histology Somatic sensory areas: 1° somatic sen. cx = 1, 2, 3a, 3b Brodmann’scytoarchitectonicareas
Skinreceptors Deepreceptors Somatic Sensory Cortical Areasfor Mechanosensations 1° somatic sensory cortex Area 5 (3° SScx) Postcentralgyrus Centralsulcus Postcentralsulcus Area 7 (Posterior Parietalcortex) 2° somatic sensory cortex
from Thalamus to Other cortical areas back to Thalamus to Subcortical areas Pyramidal neuron: projection neuron Layer 1 Layers 2 & 3 Layer 4 Stellate Neuron: interneuron Layer 5 Layer 6
1° Somatic Sensory Cortex Output Systems VP lateral VP medial Mechanosensation
Emotional/salience/valence Medial dorsal Anterior cingulate Ventral med. Post. (VM po) Mid-insular cortex Limbic cortex Behavioral Autonomic Amygdala Ventral posterior (VPL/VPM) 1° SS Cortex ??Localization/Discrimination Cortical Pain Representations Thalamus Cortex Behavior
Cingulate gyrus: emotional/valence Postcentral gyrus: localization Insular pain representation: behavioral (autonomic; react)
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