- the Neuron Doctrine - fundamental structural and functional unit is the neuron - neurons are discrete cells - neurons have axon, dendrites and somas - father of modern Neuroscience

- Neurologist Broca's Patient: produced only "tan" - comprehension good - post-mortem exam revealed lesion in inferior frontal cortex - area associated with language production NOT COMPREHENSION

Phineas Gage - damage to what area? - what changed?

- railroad worker - damage to the prefrontal cortex - changes in mood and personality - he kinda became a dick

- had intractable epilepsy - medial temporal lobe removed - damage to hippocampus - unable to create new memories - feedforward network: loops of neurons that get into feedback circles: in the hippocampus with memories

- Primary motor cortex and motor homunculus - stimulated parts of the brain in order to see what if affect in the body

- multielectrode array - record extracellularly from many neurons at once - when an area of cells lights up and is active - allows us more insight into brian regions

- distinguish epileptic seizures from other things, like non-epileptic seizures and migraines - characterize seizures for treatment - way to test if someone is "brain dead" - make decisions about someone if they are in a coma - monitor effects of anesthesia - biofeedback and Brain-Computer Interfaces - deafness in infants

Technologies for Studying the Brain Flashcards by andrea shelton

Golgi Stain

used by…?

what does it stain?

used by Roman y Cajal
stains the soma, dendrites, dendritic spines, and axon in brown/black
randomly stains a portion of cells in their entirety
outlines the cells
cellular level
no one knows exactly the chemistry
alternate bathing tissue in potassium dichromate and silver nitrate, repeat for days, weeks, months, years…

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Staining

subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

subject state: post-mortem, brain tissue slices
tech: inject stains in live system. Process brain tissue
costs: sacrifice subjects
Temp Res: none
spatial resolution: good, per stain type
functional: NO
EX: Golgi, Nissl, Weigert

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Ramon y Cajal

the Neuron Doctrine
- fundamental structural and functional unit is the neuron
- neurons are discrete cells
- neurons have axon, dendrites and somas
father of modern Neuroscience

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Nissl Stain

get a sense of….?

gets you more cell bodies and see more density
good at staining the nucleus! counting cell bodies !
get a sense for how many cell bodies are in a slice of tissue
stains various parts of the cell body blue by attaching a chemical dye to the RNA/DNA molecules
input and output layers are really dense
you can see that different regions of brain have different architectures
Brodmann’s areas correlation to the different architectures

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All enzymes are…

proteins

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Lesions

subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

subject state: alive or post-mortem. Brain damaged, naturally or experimentally

tech: ablation surgery, process brain tissue
costs: can include damaging subjects

temporal resolution: none

spatial res: GOOD, per damaged area

functional: YES, per deficits

Ex: phineas gage, H.M.

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TAN case study

Neurologist Broca’s Patient: produced only “tan”
comprehension good
post-mortem exam revealed lesion in inferior frontal cortex
area associated with language production NOT COMPREHENSION

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Phineas Gage

damage to what area?
what changed?

railroad worker
damage to the prefrontal cortex
changes in mood and personality
he kinda became a dick

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Patient HM

had intractable epilepsy
medial temporal lobe removed
damage to hippocampus - unable to create new memories
feedforward network: loops of neurons that get into feedback circles: in the hippocampus with memories

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limitations to lesions

patients are extremely rare
human brain damage is organic - the spatial and temporal extent is not under experimental control
solution: use animal brains
prior to modern imaging, localizing the lesions had to wait until after death

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Penfield Map

Primary motor cortex and motor homunculus

- stimulated parts of the brain in order to see what if affect in the body

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EEG

subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

electro-encephalogram
you can record resting states of brain: aroused, relaxed, sleepy, asleep, deep sleep
electric field created by neurons is detected on the gyri of the cortex
subject state: alive. record from external array of sensors, worn on scalp
tech: cap of electrodes, record electric dipoles, perpendicular to brain surface, generated by changes of potential in thousands of cells. Oscilloscope output over time.
costs: relatively inexpensive tech

temp res: GOOD, per realtime (ongoing) brain activity

spatial res: POOR, dipole an overall effect of activity in many cells

functional: weak, per associated activity

EX: stages of sleep

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multi-cell recording

multielectrode array
record extracellularly from many neurons at once
when an area of cells lights up and is active
allows us more insight into brian regions

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ERP

subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

Event Related Potential
subject state: alive. record from external array of sensors, worn on scalp. engaged in task
tech: same as EEG. examine average of the EEG responses that are TIME LOCKED TO STIMULUS/TASK exposure, over repeated trials
costs: relatively inexpensive tech
temp res: GOOD, for particular moment re-onset of task
spatial resolution: POOR from mean differences across areas
functional: YES, per associated activity
EX: N400 in language processing, p200 in visual attention

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EEG uses

distinguish epileptic seizures from other things, like non-epileptic seizures and migraines
characterize seizures for treatment
way to test if someone is “brain dead”
make decisions about someone if they are in a coma
monitor effects of anesthesia
biofeedback and Brain-Computer Interfaces
deafness in infants

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ERP uses

get rid of extraneous noise
way to analyze EEG signals
MAIN problem: brain has ongoing activity
tells you how fast you can gage things
N400 ERP component: linguistic processing: voltage is more negative when stimulus meaning is more unpredictable

MEG uses

electric field created by neurons is detected in the sulci
much better spatial accuracy than EEG
magnetic fields are not conducted or scattered by tissue
precise localization possible with help from MRI

MEG

subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

magneto-encephalogram
subject state: alive. Head fixed in large apparatus
tech: apparatus records MAGNETIC FIELDS, parallel to brain surface, generated by changes of potential in thousands of cells. Requires super-conducting materials to detect subtle fields
costs: more expensive magnetic detectors (SQUIDS)
temp res: GOOD, per realtime (ongoing) brain activity
spatial res: POOR, field an overall effect of activity in many cells
functional: weak, per associated activity
EX: cortical activity

applications of MRI: Diffusion Tensor Imaging (DTI)

manipulate the MRI signal to measure white matter tract cohesiveness

more mature white matter is more cohesive and constrict the random motion of water more

CAT

older tech
really good for detecting abnormalities in the structure (lesions)

uses x-rays to give rough image of brain

used to detect major abnormalities, like tumors or areas affected by stroke

fMRI

indirect measure of brain activity = BOLD signal
BOLD = Blood Oxygen Level Dependent signal
figure out discrete things

PET

uses radioactive tracers attached to a biologically active molecule
after a waiting period, the tracers release gamma rays, which are detected and analyzed by the matching
a number of different tracers can be used to map different systems: glucose, neurotransmitters, amyloid plaques
TRACERS ARE CHALLENGING AND EXPENSIVE

Anatomical Exams

typically invasive

staining

lesions

electrical stimulation

Recordings of Endogenous EM Radiation

measuring electrical current

direct measure of brain activity

single cell recording

EEG

ERP

MEG

Images produced by perturbation of system

measuring of tissue properties bad temporal resolution MRI fMRI PET CAT

MRI subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

magnetic resonance imaging Subject State: alive. lying in a large, loud drum Tech:Magnetically align proton spin in hydrogen atoms (in water) using magnet and radio waves, then release. Use energy released by return to natural alignment to expose image. Differentiate structures, tumors, myelin, lesions, etc. Costs: Expensive, loud Temporal Resolution: NONE Spatial Resolution: BEST, high resolution functional: NO Ex: detailed brain images, cortical and sub-cortical; Detection of disease: Multiple Sclerosis (MS)

fMRI subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

- functional MRI - Subject State: Alive. Lying in large, loud drum. Engage in sensory or cognitive task - Tech: like MRI, but record how DEOXYGENATED HEMOGLOBIN in blood, at ACTIVE SITES, responds. Images color-coded per differences during task relative to baseline - Costs: Expensive, loud. - Temporal Resolution: POOR, few seconds - Spatial Resolution: VERY GOOD, high resolution - Functional: Yes, per associated activity - Ex: listen to music, examine faces, imagine objects, etc.

PET subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

- Positron Emission Tomography - Subject State: Alive. Head fixed in apparatus. Engage in sensory or cognitive task - Tech: Gamma Rays from decay of injected RADIOACTIVE FLUID absorbed with GLUCOSE (at ACTIVE SITES). Images color coded per differences during task relative to baseline. - Costs: Radioactive materials, expensive - Temporal Resolution: POOR ~30 sec - Spatial Res: GOOD - Example: Listen to music, examine faces, imagine objects

CAT subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

- Computed Axial Tomography - Subject State: Alive or post-mortum. Head in apparatus. - Tech: X-Rays: Tissues vary in penetration/shade of image. Build up 3D from 2D images - Costs: X-Ray exposure, less expensive - Temp Res: NONE - Spatial Res: OK, less resolution - functional: No - Ex: Anatomy of brain and other structures

Electrical Stimulation subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

Subject State: alive. electrical probe on surface or inserted in brain. Local (scalp) anesthetic Technology: micro-electrode probe (stimulation) & map of (e.g. Brodmann) brain areas costs: invasive temporal res: none spatial res: GOOD, per stimulation site functional: YES, per awake subject reactions, descriptions EX: Penfield Map

Single Cell Recording subject state? technology? costs? temporal resolution? spatial resolution? functional? example?

measures the difference in voltage between inside and outside of a neuron (cell): how we know how action potentials work types of data: look at the firing rate Subject state: alive. recording probe inserted in brain. local (scalp) anesthetic. engaged in task tech: micro-electrode probe (stimulation) & map of (e.g. Brodmann) brain areas costs: invasive temp res: GOOD, for target cell, but highly localized costs: invasive temporal resolution: GOOD, per recording site functional: YES, per associated activity, subject report EX: face cells, mirror neurons

MEG

recording magnetic fields produced by electrical currents occurring naturally in the brain, using very sensitive magnetometers.