lecture 3 - neuroanatomy Flashcards
brain components from small to large
- neurons
- glia cells
- vasculature
ligand-gated ion channels
- glutamate & GABA
- ionotropic
- direct electric effect
neurotransmitter binds -> channel opens -> ions flow across membrane
G-protein-coupled receptors
- DA, NA, SE, etc.
- metabotropic
- modulatory effect
neurotransmitter binds -> g-proteins are activated -> g-protein subunits or intracellular messengers modulate ion channels -> ion channe opens -> ions flow across membrane
arterial-venous segmentation
(supply - removal)
artery -> arterioles -> cappilaries -> venules -> veins
The artery brings oxygenated blood and nutrients to the tissue (supply), and the vein carries deoxygenated blood and waste materials away from the tissue (removal).
what we see in BOLD signals
-
veins:
anything that we record is biased towards larger draining veins - downstream effect:
the big veins show up better on BOLD signals, so you’re measuring the downstream (after) effect of a neuron, not the direct activation
-> (measuring the consequence)
Brodmann areas
areas have distinct histological features
Knowing which Brodmann area is active during a task helps in understanding the brain’s division of labor and how complex processes are handled.
Cyto-architecture - areas have distinct histological features
subcortex
- basal ganglia: action, inhibition, reward
-> caudate, stratium, GP, putamen, nucleus accumbens - midbrain: emotion, regulation, reward
-> subthalamic nucleus, substantia nigra - archicortex: memory, emotion, navigation
-> amygdaloid body, hippocampus - thalamus: relay station
-> thalamus, pulvinar, geniculate nucleus
frontal lobe
- primary motor cortex
- premotor cortex
- dlPFC
- lateral frontopolar cortex
progressively more abstract, higher order control (caudal to rostral/posteror to anterior)
motor and sensory map
motor
- precentral gyrus (towards frontal lobe)
- primary motor cortex
- selection and execution
sensory
- postcentral gyrus (towards visual cortex)
- primary sensory cortex
- sensory processing
the homunculus model
- somatosensory and motor representations in the brain
- proportional to the amount of cortex dedicated to processing functions for that part
-> homunculus is not “linear”—it does not proportionally represent the human body but reflects the density of nerve endings and the precision of motor control.
integrate-isolate model
more complex representation of the motor and sensory areas, suggesting that certain actions are represented in both integrated and isolated ways in the motor cortex
representation can vary from person to person
the somatotopic maps of somatosensory and motor cortex are grossly, but not perfectly, aligned on opposite banks of the central sulcus.
default mode network
- set of areas in the parietal, temporal, and frontal cortex
- strongly connected to the hippocampus
- considered to be on one side of a gradient between sensory processing and memory-related processing
- ifg, mfg, sfg (frontal gyrus)
- angular gyrus
- cingulate cortex
- vmpfc
- premotor cortex
- medial temporal cortex
DMN - semantic, memory-based representations
on one hand integration of sensory experiences with memory
on the other hand gradient towards more semantic, memory-based representations
gradient maps show
1) visual representation of place concept
2) language representation of place concept
3) both
4) neither
Interactions between Frontal lobe and Basal Ganglia
should i stay or should i go
- planning of action and inaction
- many disorders (addiction, depression, parkinson’s etc) involve dysfunction of these systems
- neuromodulation by dopamine and noradrenaline plays an important role in these systems
major dopaminergic pathways
- mesocortical pathway
- mesolimbic pathway
- nigrostriatal pathway
- tuberoinfundibular pathway
Different neuromodulators are distributed differently
major noradrenaline pathways
- The prefrontal cortex
- The hypothalamus
- The basal forebrain
- The thalamus
- The amygdala and hippocampus
- midbrain
- Additional projections to the sensory cortices, cerebellum, and spinal cord
Different neuromodulators are distributed differently
majority of brain cells
glial cells
the reason that white matter is called white matter, and also why it shows up as white in a T1-weighted scan
white matter contains all the axon bundles, and these contain a major portion of the fat in the brain
-> e.g., myelin
temporal lobe
language, learning, memory
parietal lobe
language, spatial reasoning, touch
cerebellum
balance, coordination of movement
frontal lobe
reasoning, planning, movement
occipital lobe
vision
