Somatosensory Pathways

• 2 Pathways—Dorsal & Spinothalamic

  • The dorsal columns carry information related to fine touch & kinesthesia (very localized)
    • Info crosses after medulla
  • The spinothalamic tract carries pain and temperature signals (poorly localized)
    • Info crosses at the spinal cord

• Somatosensory cortex is organized into columns like in vision

• Damage ? Tactile Agnosia

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Somatosensation info comes from the PNS via the trigeminal nerve (a cranial nerve) ? CNS; both the dorsal and spinothalamic pathways carry different information and both cross (contralateral connection to the primary somatosensory cortex in parietal lobe) but decussate (or cross) at different regions of the brain.

Recall that in vision, the striate (primary visual cortex) had columns that are sensitive to orientation & spatial frequency; similar here in the skin.

Somatosensory cortex is organized into columns to give particular stimulus response or feeling at a particular body location.

Damage to the somatosensory system (parietal lobe) leads to tactile agnosia where the person cannot recognize objects by touch BUT still is sensitive to touch and sensory skin stimulation & may be able to discriminate objects (how rough, etc).