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Homologues

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Transcript of "Homologues"

  1. 1. Homotopic Callosal Connections
  2. 2. Equipotentiality vs homotopic principle
  3. 3. EEG site pairings
  4. 4. Callosal Connections
  5. 5. Principle of Callosal Homotopy • The general principle of callosal homotopymthat the corpus callosum unites "corresponding and identical regions" (Meynert, 1872, p. 405), was initially proposed by Arnold (1838-1840) in his anatomy tables and later popularized by Meynert (1872). • Bruce (1889-1890) criticized Meynert's endorsement, calling it speculation and opinion, ungrounded in physiological fact. • Bremer (1958), however, continued to advance this principle, based on the anatomical and electro- physiological research of his day (Curtis, 1940a,b).
  6. 6. Principle of Callosal Homotopy • CITATIONS • Arnold, F (1838-1840). Tabulae anatomicae. London: Black & Armstrong. • Bremer, F. (1958). Physiology of the corpus callosum. Research Publications for the Assessment of the Nervous and Mental Disability, 36, 424-428. • Bruce, A. (1889-1890). On the absence of the corpus callosum in the human brain, with description of a new case. Brain, 12, 171-190. • Curtis H.J. (1940a). Intercortical connections of > corpus callosum as indicated by evoked potentials. Journal of Neurophysiology, 3, 407-413 • Curtis H.J. (1940b). An analysis of cortical potentials mediated by the corpus callosum. Journal of Neurophysiology, 3, 414-422. • Meynert T (1872). The brain of mammals. In S. Stricker (Ed.) Manual of human and comparative histology, Vol II, (pp 367-537). London: The New Syndenham Society.
  7. 7. Principle of Homotopy Four types of cortico-cortical projections: 1) homotopic, 2) homoareal, 3) heterotopic, and 4) ipsilateral less than 1% of all connections are heterotopic Arnold (1838-1840) – Anatomical tables – first mention of callosal homotopic connectivity Myers (1850s) – popularized homotopic principle Bremer (1956) – “general principle of homotopy” based on Curtis (1940;1944) electrophysiological studies
  8. 8. Reciprocity in Callosal Connections • Representation of the reciprocity of callosal connections: strong homotopic connectivity, and wherever there is heterotopic connections, there is normally ipsilateral connections to the same areas.
  9. 9. Callosal Function Models • 1. Transfer of information • 2. Inhibition of opposite side processing • 3. Homotopic inhibition, generating complementary percepts
  10. 10. Conduction Time
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