2. General Organization of the Brain

· neuropil: dendritic trees where most synapses occur

· left hemisphere: intellectual, rational, verbal, analytical thinking

- dominant for language (except: prosody, inflection: right)

· right hemisphere: emotional, non-verbal, intuitive thinking

· axon collaterals

· axons of the corticospinal tract decussate in medulla

Divisions of brain

1. Telencephalon = cerebrum

neocortex: 6 layers

paleocortex, archicortex: 3 layers

basal ganglia, amygdale, claustrum, nucleus basalis of Meynert

White matter

a. Projection fibers (ascending/descending)

b. Commisural fibers

c. Association fibers

2. Diencephalon

lateral to third ventricle

a. thalamus

with few exceptions, all pathways destined for the cortex must synapse here

b. hypothalamus

3. Mesencephalon = midbrain

parasympathetic divisision of III exits here

fits through tentorial notch

divided by aqueduct of Sylvius into tectum and tegmentum

SC (visual), IC (auditory)

contains nuclei: substantia nigra

4. Metencephalon

a. pons

connects cerebellum to brainstem

b. cerebellum

integrates sensory information à coordinated motor response (timing, coordination, skilled movement, cognitive learning)

5. Myelencephalon = hindbrain

a. medulla oblongata = bulb

contains: long pathways, reticular formation (consciousness, heart rate/rhythm, breathing, etc.)

continuous with spinal cord at foramen magnum

corticobulbar pathway: cortexàcranial nerve motor nuclei in medulla

Landmarks

· Longitudinal cerebral = sagittal fissure

· Lateral = Sylvian fissure

· Central sulcus = sulcus of Rolando

· Parieto-occipital sulcus

Lobes

· frontal lobe (Sylvian fissure à central sulcus of Rolando)

o precentral sulcus

o precentral gyrus = Area 4: primary motor cortex

o Broca’s area: 44, 45 (pars triangularis, pars opercularis)

o Motor planning

§ Area 6: premotor cortex

§ Area 8: frontal eye fields (conjugate eye movements to contralateral side)

o Prefrontal cortex (mores, complex intellectual functions, imagination; re-organizes in adolescents)

§ prefrontal association area

§ limbic association cortex

o depression: associated with left frontal lobe lesions

o mania: associated with right frontal lobe lesions

· parietal lobe (central sulcus of Rolando à Sylvian fissure à parieto-occipital sulcus)

o postcentral sulcus

o postcentral gyrus = Area 3,1,2: primary somatosensory cortex (pain, temperature, touch, pressure, proprioception)

§ 4 separate body representations (different submodalities kept separate)

§ pain does not require cortex (thalamus)

o intraparietal sulcus: divides:

§ superior parietal lobule

· Area 2,5: somatosensory agnosia

· Area 5,7: coordinates visual and somatosensory information

§ inferior parietal lobule (agraphia, alexia)

· Area 40 = supramarginal gyrus

· Area 39 = angular gyrus

· occipital lobe

o calcarine cortex = Area 17

§ cuneus gyrus (above calcarine fissure)

§ lingual gyrus (below calcarine fissure)

o Area 18,19: visual association areas, visual agnosias

· temporal lobe (Sylvian fissure à parieto-occipital sulcus)

o superior/inferior temporal sulci

o Area 41 (transverse temporal gyri of Heschl): primary auditory cortex

o Area 22 (Wernicke’s Area): auditory association area