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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
Input from different receptors is carried by different fibres
Input from different parts of the body is segregated into dermatomes
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