"CH 2 Integration" (Cortex, Neuron types)

Nissl Stain

a type of stain used to highlight the cell bodies in a tissue
lets us count the # of cells and their size in a region
important since it helps us to see which areas have more neurons

Golgi stain

highlight the dendrites, axons of few neurons.
cons it doesn’t stain many cells, but gives very detailed samples
helps us see how close together neurons are without touching

Weiger stain

stains myelin, so it stain areas with white matter (axons)
lets us see white matter tracts

6 layers of the cortex

Layer 1: Molecular layer

Layer 2: External Granular
Layer 3: External Pyramidal
Layer 4: Interal Granular
Layer 5: Internal Pyramidal
Layer 6: Multiform

layers 1-3 is involved with connections to different areas of the cortex

layer 4 shows connections to and from the thalamus

layer 5: related to motor control

aniography

when cerebral blood vessels are filled with a radiopaque dye to increase the contrast of brain x-ray (technique of the past)

Layer 1: Molecular layer

outer has fewer neuron bodies, more dendrites and axons, and in involved with connections. weiger stain most visible

Layer 2: External Granular

contains small neurons best seen with nissl stian.

very little white matter, few dendrite/axon stained with golgi stain

Layer 3: External Pyramidal

medium sized pyramidal cells. triangle shaped neurons. shown across all stains best seen with nissl stian.

Layer 4: Internal Granular

stellate and small pyramidal cells

Layer 5: Internal Pyramidal

large pyramidal cells called Betz cells

Layer 6: Multiform

has white matter (connected), and a mix of neurons

Pyramidal cells

the boldest neuron in the cortex, has a triangle shaped cell body. visible in layers 3 and 4.

it has a apical dendrite that extends to the outermost cortex

its basal dendrites spread deom its sides (horozontial)

its largest ver: Betz cells

Stellate Cells

its dendrites from the cell body like a star, processes incoming sensory information. connects to other neurons to paas on sensory info

Layer Thickness across cells

thickness between cortex layers are different depending on their function:
Layer 6 has stellate cells which pass sensory info and are thicker in the sensory cortex

Layer 5 has large pyramidal cells/ it is thicker in the motor cortex. it passes signals from the brainstem to the cortex

cortical columns

neurons in the cortex are arranged in columns that are perpendicular from the cortex

synapse interconnections are mostly lay vertical

neurons work in parallels so neurons in the same column are going to be processing the same sort of information

Connections between cortical regions

the cortical regions pass information through axons with varying lengths

short axons are used to nearby regions, long axons are used for further regions

corpus callosum (bundle of white matter) connects both hemispheres

long multisynaptic chains thorugh subcortical regions

Tract tracers

substances that are absorbed by neurons, highlighting their pathways by moving through their axons

ex. brainbow: florescent proteins on neurons, making rainbow (map)

connectome

a map of all neural connections in the nervous system
shows how brain structures are related to their functions

may allow for us to simulate the mind

(needs to be done by AI due to too many neurons, and activity for us)

studying the connectome would help us figure out how environment and genes relate

neocortex

a crumpled sheet of brain (thought to contain the secret to intelligence)

functional connectivity

information exchange, and coordination between separate brain regions which help higher order functioning

different brain areas can work in parallel doesnt equal direct physical connection

neuroplasticity

when our neural development is affected by environment. can happen in childhood and adulthood
(influences number, size of neurons, and the strength of their connections)

CAT / CT Scan

Computerized Axial Tomography. (non-invasive, takes in x-ray radiation from many angles around the brain, and generates them into a med resolution image)

X-ray scans in an arc around the brain. on opposite sides of the brain a detector measures the amount of radiation that has been absorbed (in proportion to the tissue density it has passed through).

This process is repeated from many angles and mathematically combined into a generated image of the brain reflecting tissue density.

the photos are med resolution, useful for finding tumors, strokes.

MRI

Magnetic Resonance Imaging (expensive, detailed. high resolution, using magnetic fields, and radio waves. non-invasive, no risk of radiation)

The persons head is put inside a very strong circular magnet which causes the protons in the brain to sit in parallel (normally random)

strong radio waves are then used then knock down the protons. when the frequency is turned off, the protons return to normal position but echo/release those the radio waves. 

these waves are different for various areas or tissues, and those differences are recorded by the computer. the density based info then creates a highly detailed cross sectional image of the brain

(shows size and shape of certain areas and amount of myelin)

DTI

Diffuser Tensor Imaging: MRI which measures white matter (collections of axons) using the diffusion of water molecules in the axons.

fractional antitropy: protons of water inside the axons diffuse after radio waves are off, showing the axonal connections between different areas of the brain

using math images of the axon pathways can be generated (mapping the brain) - DTI tractography

isotropy

when the (protons of) water molecules in the brain relax/diffuse (can be in any direction) after being magnetized and knocked over by radio waves

Fractional ansiotrophy (fiber tracking)

protons of water inside the axons diffuse after radio waves are off, showing the axonal connections between different areas of the brain

DTI tractography

calculating the waves from fractional antitropy to create visuals of white matter tracts (by DTI)

PET

Positron Emission Tomography is used to see brain activity. radioactive chemicals are sent to the brain via bloodstream, and radiation detectors outside the head track where the chemicals are going. usually this is done while the client performs a task to see the brain region that is active

color coded image can be generated to see activity (helps track since most the chemicals are headed to most vital regions)

calculate metabolic maps to see specific functions for brain regions

how do we isolate a specific brain activity from PET?

a math technique where you subtract the brain activity during one behavioural condition form the brain activity during a different (control) behavioural conditon.

the isolated brain activities from different b=people can be layered to see an overall average effect

fMRI

Functional Magnetic Resonance Imaging: does MRI scan at a fast speed (temporal resolution) at good quality (spatial resolution)
does so by detecting changes in oxygen blood flow and finds active regions.

better than PET scans

measures BOLD (blood oxygen level dependent)

fMRI cons or clarification

because this technique detects the local blood flow (oxygen), it detects synaptic inputs rather than neuronal outputs
the regulation of blood flow also is detecting the local processing, and local glial cell

needs to be updated in system due to aging, and dieases

fNIRS

functional near infrared Spectroscopy uses infared light to measure patterns in brain activity.

the infared wavelengths pass through the skin, and skull and dectors around the head pick up the reflections of the light.

some responses reflect bloodflow while other reflect neural signals
its fast, cheap, non-invasive

TMS

Transcranial Magnetic Stimulation uses magnetic field to directly alert/activate neurons of the cortex, then it is tracked using brain imaging techniques

rTMS

repetitive transcranial magnetic stimulation: it repeats the process of activation several times per sec

SQUIDs

detects the magnetic fields from neurons (used in MEGs)

MEGs

Magnetic Electrophalenceogrophy uses a bunch of SQUIDs to map the cortical activity (during cog processing/task) in real time.

It is used with MRI to study rapid changes in brain activity

brain leisons

regions of damage in the brain

Why are imaging techniques good?

they give us insight into brain structure, brain actitivties without having to perform leisons. and they have lead to discovereies *ex. vegetative coma patients still have brain activity

What is the speed-accuracy trade off

it is when there is high spatial resolution (detailed tracking) it often takes so long to develop it doesnt track rapid brain activity well - fMRI

when there is high temporal resolution (tracks fast)  the images developed are lower resolution and harder to interpet -EEG, MEG

Social neuroscience

the study of how our brains work while interacting with others/socializing

hyperscanning

a technique used to detect brain activity of two or more induvial as they socialize.

participants are able to act naturally using an EEG but they don’t have good spatial resolution like fMRI. but employing fMRI would make socializing unnatural

dfMRI

dyadic functioning Magnetic Resonance Imaging lets people get scanned side by side in the machine, and they communicate through a small window, helps add validity to findings, allows for some touch, observation of small movements