1. CEREBRAL TRACTS

2. Categories of Tracts • Association: Confined to a given hemisphere. Connect regions of the same hemisphere. • Commissural: Interconnect the two hemispheres.

3. Categories of Tracts • Projection Tracts: Form internal capsule. Make up ascending and descending tracts. Connect hemispheres to other parts of brain and spinal cord.

4. Association Tracts: Examples • Arcuate • Cingulum • Superior longitudinal fasciculus • Superior occipitofrontal fasciculus • Inferior occipitofrontal fasciculus • Uncinate fasciculus

5. Arcuate Tracts • Interconnect adjacent gyri.

6. Cingulum • Connects frontal, parietal and temporal cortical areas on the medial side of each hemisphere.

7. Superior Longitudinal Fasciculus • Interconnects areas within the frontal, parietal, occipital, and temporal lobes.

8. Superior Occipitofrontal Fasciculus • Located in medial part of hemisphere underneath lateral extension of corpus callosum. • Interconnects the frontal lobe with more posterior parts of hemisphere.

9. Inferior Occipitofrontal Fasciculus • Runs between the occipital and frontal lobes in the lateral part of each hemisphere under the insula.

10. Uncinate Fasciculus • Makes a sharp bend around the lateral fissure. • Interconnects the orbital surface of the frontal lobe with the rostral part of the temporal lobe.

11. Commissural Tracts: Examples • Corpus callosum • Anterior commissure • Posterior commissure • Hippocampal commissure

12. Corpus Callosum • Contains about 300 million fibers. • Interconnects neocortical areas in all lobes. • Unifies awareness and attention between the two lobes. • Permits a sharing of learning and memory.

13. Corpus Callosum: Subdivisions • Splenium = Wide caudal part. • Body = Large midportion. • Genu = Anterior part. • Rostrum is continuous with lamina terminalis.

14. Anterior Commissure • Interconnects areas within the two temporal lobes.

15. Posterior Commissure • Connects cerebral hemispheres with superior colliculi.

16. Hippocampal Commissure • Interconnects two hippocampal formations.

17. Projection Tracts: Types • Corticopetal: To cerebral cortex. • Corticofugal: From cerebral cortex.

18. Corticopetal Projection Fibers • Mostly from thalamus. • Form part of internal capsule. • Diverge toward cerebral cortex. • Form part of corona radiata.

19. Corticofugal Projection Fibers • Originate in different parts of cerebral cortex. • Converge toward: Basal nuclei. Thalamus. • Form part of corona radiata. • Form part of internal capsule.

20. Projection Tract Examples • Thalamic radiation • Corticopontine • Corticobulbar • Corticospinal • Corticoreticular • Optic radiation • Fornix

21. Thalamic Radiation • Corticothalamic fibers project within internal capsule from cerebral cortex to thalamus. • Thalamocortical fibers project within internal capsule from thalamus to cerebral cortex.

22. Corticopontine Projections • Corticopontine fibers projects to pontine nuclei in the pons. • Pontine nuclei project to cerebrellum.

23. Corticobulbar Projections • Part of pyramidal tracts. • Originate mostly in motor cortex. • Project to cranial nerve nuclei in brainstem.

24. Corticospinal Projections • Part of pyramidal tracts. • Originate mostly in motor cortex. • Project to cell groups throughout all parts of spinal cord.

25. Corticoreticular Projections • Originate in motor and somatosensory cortex. • Project to brainstem reticular formations.

26. Optic Radiation • = Geniculocalcarine tract. • Originates in lateral geniculate body. • Runs in lateral direction in the internal capsule. • Makes a sharp bend (= Meyer’s loop). • Runs in caudal direction toward calcarine fissure in occipital lobe.

27. Fornix • Major projection system between the hippocampus in temporal lobe and the diencephalon.