Technologies for Studying the Brain

Question 0

Golgi Stain

used by…?

what does it stain?

Answer 0

• 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…

Question 1

Staining

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

Answer 1

• 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

Question 2

Ramon y Cajal

Answer 2

• 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

Question 3

Nissl Stain

get a sense of….?

Answer 3

• 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

Question 4

All enzymes are…

Answer 4

proteins

Question 5

Lesions

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

Answer 5

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.

Question 6

TAN case study

Answer 6

• 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

Question 7

Phineas Gage

• damage to what area?
• what changed?

Answer 7

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

Question 8

Patient HM

Answer 8

• 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

Question 9

limitations to lesions

Answer 9

• 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

Question 11

Penfield Map

Answer 11

• Primary motor cortex and motor homunculus

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

Question 13

EEG

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

Answer 13

• 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

Question 14

multi-cell recording

Answer 14

• 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

Question 15

ERP

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

Answer 15

• 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

Question 16

EEG uses

Answer 16

• 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

Question 17

ERP uses

Answer 17

• 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

Question 18

MEG uses

Answer 18

• 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

Question 19

MEG

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

Answer 19

• 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

Question 20

applications of MRI: Diffusion Tensor Imaging (DTI)

Answer 20

• 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

Question 21

CAT

Answer 21

• 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

Question 22

fMRI

Answer 22

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

Question 23

PET

Answer 23

• 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

Question 24

Anatomical Exams

Answer 24

typically invasive

staining

lesions

electrical stimulation

Question 25

Recordings of Endogenous EM Radiation

Answer 25

measuring electrical current

direct measure of brain activity

single cell recording

EEG

ERP

MEG

Question 26

Images produced by perturbation of system

Answer 26

measuring of tissue properties bad temporal resolution MRI fMRI PET CAT

Question 27

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

Answer 27

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)

Question 28

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

Answer 28

- 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.

Question 29

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

Answer 29

- 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

Question 30

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

Answer 30

- 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

Question 31

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

Answer 31

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

Question 33

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

Answer 33

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

Question 34

MEG

Answer 34

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