Biopsychology Exam 2

research method framework for all studies

biopsych seeks to understand these relationships

ways to relate brain to behavior

correlation and causation

correlation

- Brain changes co-occur with behavioral changes

- 3rd variable problem – correlation does NOT equal causation

causation tests for...

necessity and sufficiency

4 research techniques

1. Anatomical techniques
2. Functional removal of structure
3. Functional activation of structure
4. Recording of activity of structure (correlational)

anatomical techniques (1)

non-invasive: CT & MRI scans

invasive: histological processing

CT & MRI scans

provides precise images of brain STRUCTURE (no info on activity)
- can differentiate between white and gray matter

histological processing

brain 'staining'
- includes Nissl, Myelin, Golgi

Nissl stain

stains DNA and RNA

- cell nucleus (cell body) and endoplasmic reticulum

- can see that cortex has a lower density of cells than the cerebellum

Myelin stain

all axons are stained, no contrast
- so, cannot make out neuron structure

Golgi stain

shows dendritic branches and actual neuronic structure
- only certain neurons stain (we are unsure why, low % of them stain)

Immunocytochemistry

technique for detection and visualization of proteins or antigens in cells using antibodies specifically recognizing the target of interest

- using immune response to manufacture antibodies

- Dopamine in green, GABA in red

gene insertion and expression

uses fluorescent imaging
- brainbow, clarity

fluorescent imaging

shining one wavelength of light on a fluorescent substance causes it to emit light of a different wavelength
- via filters, you can see just the emitted light

brainbow

random expression in each neuron of several fluorescent proteins results in variety of colors

clarity

hydrogel mesh holds brain intact and opaque fats are removed
- producing transparent brains that can then be fluorescently tagged

what does CRISPR-Cas9 stand for?

clustered, regularly interspaced short palindromic repeats

CRISPR-Cas9

in bacteria, serves as primitive immune system
- Bacteria incorporate foreign viral DNA within these palindromic repeats

role of Cas9 protein

recognizes this DNA sequence between the repeats, and then cuts this pattern in the host DNA

example of CRISPR-Cas9

This Cas9 enzyme is bound to a guide RNA, which is complementary to a desired sequence in the DNA. The Cas9 protein can then cleave out the matching DNA, leading it to repair itself or insert a gene.

tract tracing

staining method that can be used to determine projections of neurons - not just where they are located, but WHO they are talking to

2 types of tract tracing

anterograde and retrograde

anterograde tracing

inject into cell body, moves down axon towards axon terminal, stains the terminal at the target site

retrograde tracing

inject into target site, taken up by axon terminal, and moves backwards into the cell body

removal of structure / functional group (2): necessity or sufficiency?

necessity

experimental lesions

neurotoxins

non-experimental lesions

case studies

drug administration

systemic or microinjections

microinjections

antagonists or channel blockers

transcranial magnetic stimulation (TMS)

non-invasive, handheld probe that induces magnetic field that briefly shuts down neuron activity

2 types of genetic knockout animals

conventional and conditional / inducible

conventional knockout

point mutation of amino acid sequence, changing protein function; removing gene early in development (substantial effect)

conditional / inducible knockout

gene is present / active until drug disrupts
*gene in red mouse (offspring) turns into loxP

optogenetics

a treatment that uses a combination of light stimulation and genetics to manipulate the activity of individual neurons

step 1/5 of optogenetics

Piece together genetic construct (promoter (to drive expression) + gene encoding ospin (light-sensitive ion channel)

step 2/5 of optogenetics

Insert construct into virus

step 3/5 of optogenetics

Inject virus into animal brain; opsin is expressed in targeted neurons

step 4/5 of optogenetics

Insert 'optrode' (fiber-optic cable plus electrode)

step 5/5 of optogenetics

Laser light of specific wavelength opens ion channel in neurons

insertion of halorhodopsin gene

reversibly shuts down cell activity (sleep)

insertion of channelrhodopsin gene

turns on cell activity (wake); opposite of halorhodopsin

optogenetic activation and inactivation of Locus Coeruleus neurons

- blue light = activation
- yellow light = inactivation
- also using fluorescent tracer and immunocytochemistry

activation of structure / functional group (3)

- Electrical stimulation
- Drug administration
- TMS
- Transgenic mice (conventional & inducible)
- Optogenetics
- Chemogenetics - DREADDs

does drug administration for activation use antagonists or agonists?

agonists; whereas removal of structure uses antagonists

recording activity (4)

- Intracellular and extracellular recording (single or multisite)
- Local field potential
- Calcium imaging
- EEGs and ERP
- MEG (magnetoencephalography)
- Microdialysis (voltammetry)
- fMRI, PET, rCBF
- autoradiography (2-DG)

single extracellular recording

recording from single neuron with extracellular electrodes
- voltage potential from extracellular recording in striatum over time
- indicate time at which 'spike' (action potential) occurred

spike sorting

detecting and separating spikes corresponding to different neurons

peri-event raster

response to a light onset

peri-event histogram

culmination of many peri-event raster events

extracellular recording with peri-events

- red line = onset of a light

- each row of the peri-event raster = a different trial

- each tic = an action potential

- high rate of spike after light went on, low rate of spike before light came on

- performed many times to prove that light is inducing activity in neuron

neuropixels probe 1.0

simultaneously records AP (action potential) and LFP (local field potential)
- signals from 960 selectable, low-impedance TiN electrodes densely tiled along a 10-mm long, 70 x 24 µm cross-section straight shank

local field potential

primarily reflects inhibitory neuron activity in human / monkey cortex

- low frequency waves, slow fluctuation

- aggregate activity of spatially restricted (??) dendritic potentials

calcium imaging

genetically encoded calcium indicator

2-photon microscopy in calcium imaging

stimulate micrometer sized area with two different long wavelength light using laser and scan across area
- can image deeper than the surface

steps of calcium imaging

1. GECI expression
2. Cranial window & 2P calcium imaging
3. Signal analysis

EEGs

surface electrodes

what do EEGs induce?

induce EPSPs and IPSPs in target neurons

- leads to voltage fluctuations that are picked up on the scalp

fluctuation of EEGs at different states

- Deep sleep = delta waves
- Asleep = theta waves
- Relaxed = alpha waves
- Aroused = beta and gamma waves

event-related potential (ERP) technique

EEG and ERP have high temporal resolution (i.e., millisecond precision) but bad spatial resolution due to electrodes on outside of skull and the “inverse” problem

- LFP is similar but is in vivo

Microdialysis

a technique for assessing the chemical composition of a very small area of the brain

more on microdialysis

- Resolution in the several seconds to minutes range

- Perfusion with artificial CSF + dialysate sample with serotonin (5-HT)

- Probed into mouse brain (concentric microdialysis)

- At the tip of the probe: 1 mm long membrane

- In vivo voltammetry (newer) provides similar information (neurochemical amount at site)

functional MRI (fMRI)

non-invasive dynamic measure that investigates human neural activity
- identifying specific areas of brain that are active

how is an fMRI different from MRI?

fMRI can track blood flow

what is an fMRI a result of?

difference between oxygenated and deoxygenated hemoglobin's magnetism

contrast of fMRI

BOLD
- blood-oxygen level dependent

fMRI image

fMRI results to the left reflect the difference between experimental (auditory stimulation) and control conditions

fMRI issues

1. oxygenated vs un-oxygenated hemoglobin differentially alters the magnetic field, leading to difference in rate of decay

2. change in BOLD activity of 1-4%: so, signal strength / noise is a prevalent issue

3. 100,000 + voxels in brain: needs statistical correction (many fluctuations due to chance)

4. Type 2 errors occur using fMRI (ex: failure to detect signal)

PET and fMRI subtraction method

Stimulation activity - control activity = difference activity

what does 'difference activity' signify?

brain activity due to the experimental manipulation
- brain is not 'dead' in scanner, it's highly active

issue of the PET and fMRI subtraction method

losing individual differences

Canonical Hemodynamic Response

fMRI has poor temporal resolution but “good” spatial resolution

- peak = increased oxygenated blood 6-7 seconds after stimulus is presented

voxel

a cubic millimeter
(but this corresponds to a million neurons)

does an fMRI pick up individual neuron firing?

no, just mass blood flow

animal tasks

- Pavlonian and operant conditioning
- Radial arm maze
- Open field and conditioned place preference
- Forced swim test

operant conditioning

rewards and punishments to modify behavior

pavlonian conditioning

ring bell = give dog food (dog salivates) -> ring bell = dog salivation

radial arm maze

spatial reference memory and working memory

- animal learns where in maze food is, so will visit those ‘arms’ of the maze, even if food is not there now

open-field system

testing anxious behavior through reinforcement potential of novel drugs

- put animal in open space (which they dislike)

- see if drug (increasing dopamine) will cause animal to venture more in open space

conditioned place preference

reinforcement potential of novel drug
- one light one dark space (preference = dark)
- give drug that increases dopamine and force rat in light space
- then rat prefers the light space

forced swim test

testing anti-depressant activity; measures behavior change with novel drug

- put mouse in beaker of water, mouse will struggle to swim and then give up

- if you give mouse anti-depressant, they will struggle longer / not give up as easily

- Fluoxetine = SSRI

Desipramine = tricyclic anti-depressant

(mixed NE & 5-HT reuptake inhibitor)

neuropsychology techniques

Wisconsin Card Sort Test and Iowa Gambling Taslk

Wisconsin Card Sort Test

Testing efficacy of frontal lobe
- presented 4 cards, put new card in 'appropriate' deck (could be based on number, color, or shape) & experimenter picks rule

what happens to frontal lobe lesion patients in the Wisconsin Card Sort Test?

they will perseverate in their strategy

- ex will continue to use ‘shape’ rule even if it becomes incorrect after that round

Iowa Gambling Task

- Flip over card (large win/loss or small win/loss) (ex: decks A and B have high winning at first, but average loss over time (opposite with C and D))

- autonomic galvanic skin response: average person sweats more picking A/B and less in C/D (suggesting A and B are risky), then eventually consciously realize

what happens to frontal orbital patients in the Iowa Gambling task?

- will state that decks A & B are "bad" but continue to choose losing decks (have knowledge but do not match their behavior)

- don't show galvanic skin response to bad choices

- patients are more likely to participate in risky behavior in life generally

spikes =

action potentials

listening to the nervous system

- Picking up spikes (aps), and fluctuating baseline

- Use ‘filtering’ (high pass and low pass) to differentiate frequencies from slower fluctuations

- Relate spike rates to an outside event (stim)

neuron recording movies

allow you to hear pop-like sound every time there is a spike - we can listen for the frequency of popping (aka how much cell is firing action potential)

for what/why do action potentials fire?

only fire for a particular stimulus in a particular place

perievent histogram

- there is a baseline firing rate

- when stimulus is presented, fires at a greater (or less) rate, then drops down to baseline rate again

- looking for how stimulus changed neural activity

sensory receptor

converts one type of energy (ex: mechanical - pressure on skin) to a change in membrane potential

sensory transduction

when the membrane is stretched, there is an excited section and the pores stretch open (easier for ions to flow through)
- ex: when we put pressure on skin

Sensory receptors elicit ___ potentials that are proportional in amplitude to sensory event (i.e., like EPSPs)

graded

graded membrane potential producing an AP

- ap produced at some threshold voltage

- The graded potential produces NT release in proportion to strength

- weak stim = cannot reach threshold

- moderate stim = just under threshold

- strong stim = spike potential

are there action potentials in visual and auditory systems?

no

a sensory event is transformed into a representation by...

spikes

how is information coded?

1. rate coding (firing rate)
2. temporal coding (spike timing)

rate coding (firing rate)

frequency = # of spikes/time
- Labeled lines

what do labeled lines represent in rate coding?

visual information is carried by neurons that project to visual cortex, auditory info projects to auditory cortex

what is the labeled lines coding scheme also for?

different qualities/positions within a modality (i.e., temperature vs. pressure for somatosensory system)