HMB200H1S L19; March. 20, 2012
Cortex: From Limbic to Association
Cortex go from 3 layers to 6 layers, very difficult to DEFINE.
How it evolved from limbic cortex to association cortex!
Evolution of Cerebral Cortex how layers have evolved
Subcortex: e.g. basal ganglia, extended amygdala.
Paleocortex: e.g. basal forebrain, olfactory.
Archicortex & transitional: e.g. medial prefrontal, insular,
Limbic cortex: orbitofrontal, cingulate, parahippocampal.
Primary neocortex: Motor, somatosensory, visual, auditory.
Association neocortex: Frontal, Parietal, Temporal.
Distribution of functional zones in relation to Brodmanns map of
Start w motor cortex to frontal pole. then started in center again &
went to posterior area
Mammalian brain has large Neocortex recently discovered
o Sometimes called Isocortex only found in mammals, not birds
o 2mm thick
Blue = Primary Cortical Areas
Layers of neocortex
Paleocortex: 0.5mm thick, 3 layers o After primary is higher order assn cortex = combo of senses
Association: gets a lot of cortical input, outer layers = thicker, primary working together
o A1 has connection w speech
cortices inner layers = thinner? Green = Limbic
Transitional: includes hippocampus (evolved from paleocortex, o Old, thin
slightly thicker), orbitofrontal cortex which evolves to primary cortex o Cingulate gyrus, parahippocampal gyrus, temporal pole, into
Primary: difficult for anatomists to find these layers
o Can see layers III & IV dominant here since receiving direct frontal cortex
thalamic visual & auditory input o Pyriform cortex = Olfactory cortex
Other sensory cortex like visual & somatosensory
o 2mm thick? Evolution: Green Blue Yellow Pink
Cerebellar cortex: 3 layers o Limbic Primary Unimodal assn Higher assn
Oldest dortex = Basal Forebrain Colonoergic 0.5mm, thinnest cortex HMB200H1S L20; March. 21, 2012
Speech and Language
Paleocortex: 3 layers
o Gradual transition to 6 layers as layers added on over long time Bird Song and Left Hemisphere
Transitional cortex: 36 layers.
o Hippocampus = highly developed, has 3 or 4 layers
Limbic: Visceral inputs (taste, olfaction, hypothalamus, dopamine).
Primary neocortex: Somatic inputs from thalamus.
o Layers 4 & 5 dominate.
o Evolved from hippocampal to 6 layers
Association neocortex: Corticaland non-primary thalamus inputs
(mediodorsal n, pulvinar)
Brodmanns Areas (1-42)
Go thru neurogenesis in spring, degredation in winter
Testosterone helps regeneration in left hemisphere sing differently
each summer for male courtship calls
Growth only on left side of brain lateral fn
o idea that speech is lateralized in left hemisphere
97% have left hemisphere injury.
o Injury to Brocas Area = Brocas Aphasia
o 3% right hemisphere injury Brocas Tan. No ifs, ands, or buts
Wernickes Aphasia. Lots of meaningless words.
o Poor understanding, and recovery.
o Fluent speech but poor comprehension
Wernickes Theory of Speech and Reading.
o Sound reaches ear auditory system processes the sounds
neaural signals reach auditory cortes
o Sounds dont become words unless identified by Werknickes
o To repeat the words: Word-based signals sent from Wernickes
to Brocas via Arcuate Fasciculus muscular movement for
speech (go to motor cortex)
o Visual info can reach Brocas w/o going thru angular gyrus
o Can produce words w HIGH MEANING & poor grammar
o Speaking very gradually
o Writing is NOT consistent
o Lack Flow within sentences
o Can't say many words Damage to Arcuate fasciculus Conduction aphasia
o = PRODUCTION APHASIA inability to produce words. o Hard to repeat speech
Temporal Lobe damage includes Wernicke`s Area
o Speech problems
o Don't understand speech well Output from Arcuate fasciculus, arching around Sylvian fissure
Brocas speech info processed
o Damage to auditory association cortex in temporal lobe, includes Brocas organizes speech patterns
ventral parietal lobe. Both B & W lesioned many losses within brain
o MEANINGLESS SPEECH o Global Aphasia
o Able to speak perfectly Learn language from mothers, presented in auditory mode
o Can easily say "No, ifs, ands and buts!"