51. Cerebral Cortex, Localization of Function

Question 1

What are the three evolutionary types of gray matter?

Answer 1

1. Neocortex: everything else
   Allocortex:
2. Archicortex: hippocampus
3. Paleocortex: olfactory cortex, limbic system

Question 2

What are the 6 layers of neocortex and their functions? In what order are they developed?

Answer 2

Inside out: layer I - youngest
I: molecular layer - interconnecting axons for local communication
II: External Granular Layer
III: External Pyramidal Layer
(II/III): short/long cortico-cortical axons, including callosal axons for local communication and comm via C.C. to corresponding cortex on other hemisphere
IV: Internal Granular Layer: receives all input from thalamus (sensory)
V: Internal Pyramidal Layer: long subcortical projection axons (motor output)
VI: Multiform Layer: output back to thalamus, corticothalamic reciprocal axons

Motor cortex: Large V, small IV
Sensory cortex: Large IV, small V

Question 3

What are the 5 long cortical assoc. fibers?

Answer 3

1. Superior Longitudinal Fasciculus
2. Inferior Longitudinal Fasciculus
3. Arcuate Fasciculus
4. Uncinate Fasciculus - from frontal to temporal pole
5. Cingulate Fasciculus - medial parts of cortex

Question 4

What thalamic nuclei do the STT and DC-ML somatosensory pathways synapse through? What thalamic nuclei does the visual system use? What is the path of the auditory relay?

Answer 4

STT/DC-ML: VPL (ventral posteriolateral)
Vision: LGN

Auditory

1o: cochlear nerve to cochlear nucleus
2o: to superior olivary nucleus
3o: to inf col via lateral lemniscus
4o: to MGN
5o: to auditory cortex
6o: to Heschl’s gyrus

Question 5

What are the functions of the frontal lobe (include specific location if possible)? Parietal lobe? Temporal lobe? Occipital lobe?

Answer 5

F: Movement (Pre-central Gyrus), Planning, Affect, Personality, Speech (Broca’s area on left)
P: somatic sence (Post-central gyrus), Space, Attention, Multimodal Sensation (Auditory, Visual, Somatosensory)
T: hearing, sensory memory, language (Wernicke’s Area on Left), Visual Processing
O: Vision

Question 6

What is aphasia? What are the types of aphasia?

Answer 6

Aphasia: loss of ability to produce/comprehend language
Broca’s aphasia: non-fluent aphasia, unable to produce language (damage to pars triangularis and opercularis of inf frontal gyrus), but can understand language
Wernicke’s aphasia: fluent aphasia, unable to understand language (damage to temporal plane of temp lobe), but can produce language

Question 7

What occurs with damage to the frontal lobe? Parietal Lobe? Corpus Callosum?

Answer 7

Frontal lobe lesions: imitation and utilization
Damage R Parietal Lobe: spatial neglect - can’t process left spatial field
Damage L Parietal Lobe: apraxia - inability to plan/execute movements
Sever Corpus Callosum: visual fields cannot communicate. only Right visual field objects can be described and picked up by right hand

Question 8

What are the functions/projections of medial descending system (beyond CS tract)

Answer 8

Tectospinal tract: to neck muscles - for attention/orientation
Reticulospinal tract: to neck/back/leg - muscle tone, pain control, neuromodulation
Vestibulospinal tract: to neck/back/leg - balance reflexes with muscle tone
Rubrospinal: fine hand movements