11/16/2023 0 Comments Cortical fragment definitionThis understanding of the general organization of the somatosensory pathways will be used in the clinical assessments of somatosensory function.ĥ.1 Sensory Pathways Decussate before Reaching the Thalamus The first part of this chapter will present additional details about the general organization of the somatosensory system and how somatosensory information is represented and processed in the parietal cortex. So how does one have a sense of "oneness" of the body and how does one identify an object by handling it? One can do so because somatosensory information converges in the parietal lobe of the cerebral cortex to provide a cohesive perception of the body and of somatosensory stimuli. The resulting spatial maps provide the anatomical basis for our ability to localize somatosensory stimuli and for our sense of a 'body image".Īs described above, the nervous system reduces somatosensory experience into parallel streams of neural activity - a decomposition of the experience into stimulus fragments spread over body pieces. In addition to this parsing of stimulus information, the somatosensory system is also organized to provide a somatotopic representation of the body surface and parts. Recall that the receptor's extraction of somatosensory information is very specific (e.g., during limb movement, muscle spindles respond to muscle stretch, whereas Golgi tendon organs respond to muscle contraction) and the processing of this extracted information is kept separate along most of the ascending pathway. For example, sharp-pricking pain is mediated in the neospinothalamic (information channel) pathway, whereas proprioception is mediated in the medial lemniscus pathway. The specificity of the receptors forms the basis for a parsing (i.e., a sorting) of somatosensory experience into separate “information channels” or pathways. Previous chapters described the ways in which the different somatosensory receptors respond to specific types of somatosensory stimuli and that the receptors, by virtue of their selective sensitivities, extract specific information about the somatosensory stimulus.
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