ISR 201R

invertebrates nervous systems

simple nervous systems, 100+ neurons, interprets sensory stimuli and executes motor responses in a reactive matter

brain and body size

human cerebral cortex larger than expected

brains take up 2% of body mass but uses ~20% of energy at rest; human brain PREDICTS rather than just reacts

growth of brain

~2 million years ago some change triggered an almost exponential growth of human brain size

significant growth of association cortex/networks (disproportionately expanded) with smaller sensory and motor areas dispersed; may account for language, mental exploration (memory, envisioning future, other perspectives, mentally navigating physical world), and cognitive control

maps of myelination patterns

from fetal to early childhood development, starts in the middle (near central sulcus) then spreads outward, with frontal and lower/lateral temporal lobe last

first myelinated areas are the same areas where we have the most similar quantities of cortex as cousins; expansion areas developed later

first order networks

myelinated first, least expanded; sensory and motor networks; organized in a local and hierarchical manner; mental exploration, language

effectors, inter-effectors, primary auditory cortex, primary visual cortex, primary somatosensory and motor cortex

effectors

motor regions that follow somatotopic organization in concentric circles, required for fine motor skills

inter-effectors

(somato-cognitive action network) regions between effectors, disrupt somatotopy, whole body movements, connected to cingulo-opercular network

not present at birth, appear during first year of life and are present in adult non-human primates

primary auditory cortex

heschl’s gyrus of temporal lobe, organized tonotopically

primary visual cortex

calcarine sulcus (and beyond) in occipital lobe, organized retinotopically

primary somatosensory and primary motor cortex

straddle central sulcus, extend into post and precentral gyri, organized somatotopically (somatotopy of primary motor cortex likely overly simplified)

second order

anchored to sensory and motor networks but are distributed like third order; goal directed behavior

dorsal attention, premotor, salience, cingulo-opercular

dorsal attention

top-down attention; mental map of necessary steps, directing attention to focus on information that is most important

premotor

motor planning

salience

perceives internal and external stimuli and responds to homeostatic demands (hunger, thirst, temperature, etc.)

cingulo-opercular

bottom-up attention; unexpected or surprising but relevant information from environment, allows for adjustments in planning

third order

made of association networks, furthest from first-order networks; distributed, parallel (mirrored in all lobes), neotenous (develops later, plastic/maleable the longest), functionally flexible and specialized, competitive, constructive

supra-areal association megaclusters, default networks, frontal parietal control network, language

supra-areal association megaclusters

make up association cortex and include third-order networks

default networks

internal mentation - thinking make up of internally-generated representations not surrounding environment, focused internally, mind wandering, conversations with self, etc.

default network A

remembering past, imagining the future, forming cognitive map

default network B

theory of mind (putting in shoes of someone else)

frontal parietal control network

at least two networks, support cognitive control - coordination of cognitive processes to achieve a goal

• self monitoring, cognitive planning, inhibitory control, cognitive flexibility

subcortical representations

networks highlighted in cerebral cortex also represented in subcortical structures

tonotopy

primary auditory cortex is organized tonotopically (where sounds are processed varies on frequency)

inner loops of organ of corti have lowest frequencies, outer highest frequencies; towards front of brain senses lowest frequencies and towards back of brain senses highest frequencies; upper area of temporal lobe near parietal lobe

retinotopy

primary visual cortex is organized retinotopically; location in brain where light is processed is where light calls on the retina

somatotopy

Primary somatosensory and primary motor cortex are organized somatotopically; point-for-point correspondence between the body and brain

postcentral gyrus: somatosensory cortex

precentral gyrus: motor cortex

lips, tongue, hands have high concentrations of sensation

task-based fMRI

patients perform tasks such as lying still vs tapping fingers and compare activation of brain areas

functional connectivity MRI

relationship between fluctuations of ___ activity (indirect measure of brain activity)

primary motor cortex organization

task activation vs resting state functional connectivity MRI; additional homologous regions