Lateralization of Cortical Function: Division of labor between hemispheres

1. 12 The Central Nervous System: Part B

2. Lateralization of Cortical Function • Lateralization • Division of labor between hemispheres • Cerebral dominance • Designates the hemisphere dominant for language (left hemisphere in 90% of people)

3. Lateralization of Cortical Function • Left hemisphere • Controls language, math, and logic • Right hemisphere • Insight, visual-spatial skills, intuition, and artistic skills • Left and right hemispheres communicate via fiber tracts in the cerebral white matter

4. Cerebral White Matter • Myelinated fibers and their tracts • Responsible for communication • Commissures (in corpus callosum)—connect gray matter of the two hemispheres • Association fibers—connect different parts of the same hemisphere • Projection fibers—(corona radiata) connect the hemispheres with lower brain or spinal cord

5. Commissural fibers (corpus callosum) Longitudinal fissure Superior Lateral ventricle Association fibers Basal nuclei • Caudate Corona radiata • Putamen • Globuspallidus Fornix Internal capsule Thalamus Gray matter Third ventricle White matter Projection fibers Pons Decussation of pyramids Medulla oblongata (a) Figure 12.10a

6. Basal Nuclei (Ganglia) • Subcortical nuclei • Consists of the corpus striatum • Caudate nucleus • Lentiform nucleus (putamen + globus pallidus)

7. Fibers of corona radiata Caudate nucleus Thalamus Lentiform nucleus • Putamen • Globus pallidus (deep to putamen) Tail of caudate nucleus Corpus striatum Projection fibers run deep to lentiform nucleus (a) Figure 12.11a

8. Anterior Cerebral cortex Cerebral white matter Corpus callosum Anterior horn of lateral ventricle Caudate nucleus Putamen Lentiform nucleus Globus pallidus Thalamus Tail of caudate nucleus Third ventricle Inferior horn of lateral ventricle (b) Posterior Figure 12.11b (1 of 2)

9. Functions of Basal Nuclei • Though somewhat elusive, the following are thought to be functions of basal nuclei • Influence muscular control • Help regulate attention and cognition • Regulate intensity of slow or stereotyped movements • Inhibit antagonistic and unnecessary movements

10. Diencephalon • Three paired structures • Thalamus • Hypothalamus • Epithalamus PLAY Animation: Rotating brain (sectioned)

11. Thalamic Function • Gateway to the cerebral cortex • Sorts, edits, and relays information

12. Hypothalamus • Forms the inferolateral walls of the third ventricle • Contains many nuclei • Example: mammillary bodies • Paired anterior nuclei • Olfactory relay stations • Infundibulum—stalk that connects to the pituitary gland

13. Paraventricular nucleus Dorsomedial nucleus Anterior commissure Fornix Preoptic nucleus Posterior hypothalamic nucleus Anterior hypothalamic nucleus Lateral hypothalamic area Supraoptic nucleus Ventromedial nucleus Supra- chiasmatic nucleus Mammillary body Arcuate nucleus Optic chiasma Pituitary gland Infundibulum (stalk of the pituitary gland) (b) The main hypothalamic nuclei. Figure 12.13b

14. Hypothalamic Function • Autonomic control center for many visceral functions (e.g., blood pressure, rate and force of heartbeat, digestive tract motility) • Center for emotional response: Involved in perception of pleasure, fear, and rage and in biological rhythms and drives

15. Hypothalamic Function • Regulates body temperature, food intake, water balance, and thirst • Regulates sleep and the sleep cycle • Controls release of hormones by the anterior pituitary • Produces posterior pituitary hormones

16. Epithalamus • Pineal gland—extends from the posterior border and secretes melatonin • Melatonin—helps regulate sleep-wake cycles

17. Cerebral hemisphere Septum pellucidum Corpus callosum Interthalamic adhesion (intermediate mass of thalamus) Fornix Choroid plexus Thalamus (encloses third ventricle) Interven- tricular foramen Posterior commissure Pineal gland (part of epithalamus) Anterior commissure Corpora quadrigemina Mid- brain Cerebral aqueduct Hypothalamus Optic chiasma Arbor vitae (of cerebellum) Pituitary gland Fourth ventricle Mammillary body Choroid plexus Pons Cerebellum Medulla oblongata Spinal cord Figure 12.12

18. Brain Stem • Three regions • Midbrain • Pons • Medulla oblongata

19. Brain Stem • Controls automatic behaviors necessary for survival • Associated with 10 of the 12 pairs of cranial nerves

20. View (a) Optic chiasma Optic nerve (II) Diencephalon Crus cerebri of cerebral peduncles (midbrain) • Thalamus • Hypothalamus Thalamus Diencephalon Mammillary body Hypothalamus Midbrain Oculomotor nerve (III) Pons Brainstem Trochlear nerve (IV) Medulla oblongata Trigeminal nerve (V) Pons Middle cerebellar peduncle Facial nerve (VII) Abducens nerve (VI) Vestibulocochlear nerve (VIII) Glossopharyngeal nerve (IX) Hypoglossal nerve (XII) Pyramid Vagus nerve (X) Ventral root of first cervical nerve Accessory nerve (XI) Decussation of pyramids Spinal cord (a) Ventral view Figure 12.15a

21. Midbrain Nuclei • Nuclei that control cranial nerves III (oculomotor) and IV (trochlear) • Corpora quadrigemina—domelike dorsal protrusions • Superior colliculi—visual reflex centers • Inferior colliculi—auditory relay centers

22. Pons • Forms part of the anterior wall of the fourth ventricle • Fibers of the pons • Connect higher brain centers and the spinal cord • Relay impulses between the motor cortex and the cerebellum • Origin of cranial nerves V (trigeminal), VI (abducens), and VII (facial) • Some nuclei of the reticular formation • Nuclei that help maintain normal rhythm of breathing

23. Medulla Oblongata • Joins spinal cord at foramen magnum • Forms part of the ventral wall of the fourth ventricle • Contains a choroid plexus of the fourth ventricle • Pyramids—two ventral longitudinal ridges formed by pyramidal tracts • Decussation of the pyramids—crossover of the corticospinal tracts

24. Medulla Oblongata • Cranial nerves VIII, X, and XII are associated with the medulla • Vestibular nuclear complex—mediates responses that maintain equilibrium • Several nuclei (e.g., nucleus cuneatus and nucleus gracilis) relay sensory information

25. Medulla Oblongata • Autonomic reflex centers • Cardiovascular center • Cardiac center adjusts force and rate of heart contraction • Vasomotor center adjusts blood vessel diameter for blood pressure regulation

26. Medulla Oblongata • Respiratory centers • Generate respiratory rhythm • Control rate and depth of breathing, with pontine centers

27. Cognitive Function of the Cerebellum • Recognizes and predicts sequences of events during complex movements • Plays a role in nonmotor functions such as word association and puzzle solving

28. Medulla Oblongata • Additional centers regulate • Vomiting • Hiccuping • Swallowing • Coughing • Sneezing

29. The Cerebellum • 11% of brain mass • Dorsal to the pons and medulla • Subconsciously provides precise timing and appropriate patterns of skeletal muscle contraction

30. Anatomy of the Cerebellum • Two hemispheres connected by vermis • Each hemisphere has three lobes • Anterior, posterior, and flocculonodular • Arbor vitae—distinctive treelike pattern of the cerebellar white matter

31. Anterior lobe Cerebellar cortex Arbor vitae Cerebellar peduncles Posterior lobe • Superior • Middle Choroid plexus of fourth ventricle • Inferior Medulla oblongata Flocculonodular lobe (b) Figure 12.17b

32. Cerebellar Processing for Motor Activity • Cerebellum receives impulses from the cerebral cortex of the intent to initiate voluntary muscle contraction • A “blueprint” of coordinated movement is sent to the cerebral motor cortex and to brain stem nuclei