BRAIN ORGANIZATION Flashcards
Anterior or Rostral
Front
Posterior or Caudal
Back
Dorsal
Top
Ventral
Bottom
Lateral
Side
Medial
Middle
Frontal lobe
Decision-making, planning, motor control
Parietal lobe
Touch, spatial transformations
Occipital lobe
Vision
Temporal lobe
Hearing, higher-level vision
FIrst-order thalamic areas
Thalamic areas that recieve major input directly from the sensory periphery (eye, ear, skin)
Prefrontal association area
Personality
Limbic association area
Emotional behavior
Wernicke’s area
Language comprehension
Cerebral cortex can be thought of as being hierarchically organized
– Cerebral cortex contains primary sensory areas, secondary sensory areas, higher-order areas
– Low-level (i.e., simple) sensory information represented in primary sensory areas
e.g., line orientation in primary visual cortex
– Higher-level (i.e., more complex/abstract) information represented in higher-order areas
e.g., objects in inferior temporal cortex; or goals in prefrontal cortex
Feedforward pathways are directed from posterior to anterior cortical areas
– Feedforward pathways generally carry information about the sensory environment
– Higher-level information is processed more anteriorly along the pathway
Feedback pathways are directed from anterior to posterior cortical areas
– Feedback pathways carry information about, e.g., goals, attention priorities, or predictions
– Feedback tends to modulate (increase or decrease) neural activity in more posterior areas
e.g., to amplify or filter out information based on behavioral context
What is the role of the indirect pathways between the cortical areas via the higher-order thalamus?
Hypothesis: Indirect pathways facilitate processing of only the behaviorally relevant info in the cortex
Direct pathways between cortical areas carry detailed info about sensory stimuli
Neocortex has 6 layers
But different brain areas show different layering
Cytoarchitectonics
Arrangement of neurons in the brain
Cytoarchitectonic maps:
– For example, Brodmann (1909)
Vertical (radial) organization of neurons in the cortex:
– If you move an electrode into the brain, perpendicular to the
cortical surface, cells tend to share similar response properties
– E.g., cells may signal the same location and/or stimulus feature
– These cells are interconnected and/or share extrinsic connections
Scale of vertical organization
Cortical column
macrocolumn
– Extends down through cortical layers
– About 0.4-0.5 mm in diameter
Columns and minicolumns repeat across the cortex
Scale of vertical organization
Cortical minicolumn
microcolumn
– Column comprised of minicolumns
– Minicolumn about 30-50 microns in diameter
Columns and minicolumns repeat across the cortex
Cell types in the cerebral cortex
Inhibitory cells hyperpolarize post-synaptic cells
Excitatory cells depolarize post-synaptic cells
Prefrontal cortex predominantly granular frontal cortex
Rodents do not have a granular (sizeable - layer 4 present) frontal cortex
Cell level
Think about whether cell is excitatory or inhibitory and about size and orientation of the dendritic field
Large dendritic field integrates input from more cells over larger area
Circuit level
Think about lamination pattern (layering) or other arrangement of cells, whether connections are feedforward or feedback, and circuit connections and which are absent
Systems level
Think about which brain areas are connected and which are not. Are there reciprocal connections? Unidirectional?
Unidirectional connection imposes constraints on processing
Canonical microcircuit of the cerebral cortex
– Layer 4 receives feedforward input from thalamus or another cortical area
– Layer 2/3 sends feedforward output to another cortical area
– Layer 5 sends feedforward output to subcortical areas
– Layer 6 sends feedback output to the thalamus or another cortical area
– Layer 1 receives feedback input from another cortical area (and thalamus)
