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Touch and pain Chapter 8 (cont.). Somatosensation includes a variety of submodalities. Fine touch pain temperature kinesthesis joint position muscle stretch interoception. Somatosensation involves a variety of receptors. Transduction usually involves stretch.
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Somatosensation includes a variety of submodalities • Fine touch • pain • temperature • kinesthesis • joint position • muscle stretch • interoception
Somatosensory input ascends to cortex Ventral posterolateral nucleus of the thalamus
Somatosensory agnosias • Astereognosia – can’t recognize objects with hands • Anosognosia – deny neurological symptoms • Asomatognosia- deny ownership of body parts • Neglect – neglect of left half of body and external world in grooming, drawing, etc.
More complicated pain phenomena • Phantom limb pain • Suggests that one can experience pain without a transduction event • Chronic pain syndromes • Sometimes pain persists in the absence of any evidence of trauma
Phantom limb pain • Feelings of pain, pressure, burning in missing limb • Walls’ theory does not account for facts very well • Melzack hypothesizes that there is a complex ‘neurosignature’ that composes the perception of self
Merzenich and neural plasticity • Following amputation, considerable re-arrangement of neocortex takes place
Vilayanur Ramachandran • rearrangement of sensory cortex is responsible for phantom limb pain
Functional imaging of somatosensory cortex in a right limb amputee (From Ramachandran, 2000)
Possible treatment for phantom limb pain? • Mirror imaging of limbs