Chap 16 - Kinds of Research

anatomy

study of structure

how did scientists first observe neurons

histological techniques

histology

thin slice of brain tissue; add color to contrast or bring out specific structures; view w/ light miscroscope

how light microscope works & magnification

passes visible light through the thin slice and lenses - 1,000 times larger

Histology

study of how cells form tissues

what Histological techniques can reveal

changes in the density of cell types or the presence of molecules that can suggest a particular disease

what has histology help reveal

brain changes underlying some neurodegenerative disorders.; eg)

what did electron microscopy help answer

Are neurons individual cells or a mesh of physically interconnected cell bodies?

Electron microscopes

produce useful detailed images of cellular structures magnified many 100,000s of times by directing a beam of electrons through very thin slices of tissue, then enlarging and focusing the image with electromagnetic lenses

method for mapping the signaling pathways within neuronal networks

injecting radioactive molecules or “tracers” into the cell body of a neuron

how do tracers work

researchers monitor the movement of radioactivity down the neuron’s axon, showing where that neuronal path leads; even across synapses

MRI (stands for)

Magnetic Resonance Imaging

MRI is used for ______

to view a detailed image of brain structure

how do MRIs work

uses radio waves and strong magnets to create images of the brain based on the distribution of water within its tissues

does MRI hurt patients

harmless and painless to the person being scanned, although it does require sitting or lying in a narrow tube, and the procedure can be quite noisy

what can MRI help differentiate in the brain

tell the difference between the brain’s gray matter and white matter & cerebrospinal fluid

Gray matter

the cell bodies of neurons, as well as their dendrites and synapses

White matter

axons wrapped in the fatty myelin coating

how does MRI differentiate different aspects of the brain

by distribution of water in the tissues,

what does electrophysiology study

activity of neuronal pathways

how does electrophysiology study neuronal pathways

changes in the electrical charge of individual neurons

how does electrophysiology work

glass electrode is placed inside a neuron to measure the voltage across its cell membrane, which changes when the neuron is activated

what is electrophysiology tested on

brains of living lab animals such as rats or mice,

advantage of electrophysiology on live animals

enables scientists to study how neurons transmit electrical information in their normal physical context

how is electrophysiology studied on inanimate objects

slice of brain can be kept “alive” for a short time in a Petri dish, in the right environment

advantage of electrophysiology in petri dishes

researchers can better identify the exact cell they are recording from and can infuse drugs to determine their effects on the brain

which methods help scientists make critical discoveries about synaptic plasticity

electrophysiology

synaptic plasticity

the capacity of a synapse to become stronger or weaker in response to sensory inputs or other activity

disadvantage of electrophysiology

techniques are highly invasive.

what records human brain activity without invasive or harmful procedures

EEG

what does EEG stand for

electroencephalography

how does EEG work

20 thin metal discs are placed on the scalp. Each disk is connected by thin wires to a machine that records the activity of neurons near the brain surface

what does/doesn’t EEG help us understand

useful for understanding epilepsy and the stages of sleep. However, it does not provide information at the level of individual neurons

what does two-photon microscopy help look at

individual neurons in a living brain

what are subjects of two-photon microscopy

A lab animal that is genetically modified so that some of its neurons produce a protein that glows when a laser beam shines on them

how many pairs of DNA bases are there

3 billion

what are 2 methods scientists study genetics

following diseases or other traits through family pedigrees & identifying the the DNA “sequence” that codes for a given trait

what do genetic linkage studies show

specific gene locations

how do genetic linkage studies work

It attempts to locate a disease-causing gene by identifying genetic markers of known chromosomal location that are co-inherited with the trait of interest.

Huntington’s disease cause

overabundance of copies or repeats of a stretch of DNA

How researchers identify variations in gene copy number

DNA chips or microarray

how microarrays work

thousands of spots arrayed in rows and columns on the surface of the chip; each spot contains a known DNA sequence or gene, which can grab onto corresponding bits of the genome being analyzed

CRISPR meaning

Clustered Regularly Interspaced Short Palindromic Repeats

what can CRISPR do

edit the genome precisely and efficiently

Optogenetics

allows researchers to control brain activity with flashes of light

how does optogenetics work

Scientists genetically modify a lab animal so that its neurons produce a light-responsive protein. Then, optical fibers are inserted into the brain to allow light to shine on those neurons — either activating or silencing them

what do Optogenetics help scientists better understand

how neurons work together in circuits

when do epigenetic changes happen

in cells when chemical tags are placed on the regulatory regions of certain genes; the tags influence whether those genes will be turned on or off

epigenetics

the study of how your behaviors and environment can cause changes that affect the way your genes work

Lissencephaly

the surface of the brain is smooth, unlike normal brains whose surfaces have ridges and grooves; associated with LS1 gene

what happens to babies with lissencephaly

start having spasms in the first months of life and develop drug-resistant epilepsy and severe intellectual and motor disabilities

Kabuki syndrome

intellectual disabilities, a distinctive facial appearance, slow growth in infancy, and other physical problems; most patients have KMT2D mutated gene

is It possible for a person to carry a mutation but exhibit no outward signs & eg)

yes; Fragile X syndrome - some people may not be affected, they are carriers with a risk of passing it on to their children

Fragile X syndrome

most common form of congenital intellectual disability in males, is caused by an excessive number of DNA sequence (CGG) repeats within the FMR1 gene.

what happens when CGG repeats during Fragile X syndrome

The protein product of the FMR1 gene, which is important for synapse function, is disrupted

how do researchers understand how brain function drives behaviors in humans

often turn to animal models.

what makes Aplysia good for studying behavior

a has relatively few neurons, some are large enough to be seen with the naked eye ///also exhibits simple behaviors that can be modified with training

what is Drosophila used to study

how genes control behavior

what discoveries have scientists made in regards to animals & addiction

changes in the brains of animals exhibiting such addiction-like behaviors similar to humans/// identified genes that were differentially turned on or off in breeds that had different susceptibility to addiction

how was mapping of human behaviors to specific brain regions done

by observing personality changes in people who had lost small regions of their brain due to injuries or surgeries

how do people who have lost their frontal lobe act

inconsiderate and impulsive

what is microdialysis used for

to monitor neurotransmitters in action//deliver compounds to the brain

how does microdialysis work

thin tubes are inserted into the brain to collect tiny volumes of liquid from just outside neurons and then analyze the compounds in that liquid

Pharmacology

study of the effects of drugs//identifying new drugs to treat conditions//understanding addiction and other negative consequences of drug use

what does mass spectrometry study

study the molecules and chemicals at work in the brain

how does mass spectrometry work

sample is collected — the compounds it contains are ionized (given an electric charge) and then sent through an electric or magnetic field. The behavior of each molecule in that field indicates its mass

what does Functional MRI study

follow changes in the brain activity of a person lying inside an MRI scanner

how does fMRI work

detects blood flow/differences in oxygen-rich and oxygen-poor blood ---an indirect indication of neuron activity, it can pinpoint brain activity to fairly small regions.

what concept is fMRI based on

that more active regions of the brain need more oxygen and nutrients, which are supplied by fresh oxygenated blood

fMRI vs MEG

indirect view of neuron activity, //actual electrical currents coursing through groups of neurons.

what does MEG stand for

magnetoencephalography

how can MEG view neuron activity

When neuron activities are synchronized, their combined electrical currents produce weak magnetic fields that its equipment can detect

(NIRS) stands for

Near-infrared spectroscopy

NIRS vs fMRI

both monitors the flow of oxygenated blood as a way to estimate neuron activity --- the first is only useful for measuring activity near the surface of the brain and does not provide as much detail; however, it is far less expensive, comfortable and cumbersome than the 2nd

what is NRIS good for

useful for studying brain activity during tasks

(PET) stands for

Positron emission tomography

what does PET do

detects short-lived radioactive compounds that have been injected into the bloodstream; can also detect the amyloid plaques that are a hallmark of Alzheimer’s disease; lacks detail resolution like MRI

how does PET work

traces where radioactive compounds go in the body.

(TMS) stands for

transcranial magnetic stimulation

how does TMS work & what is it used for

magnetic field can penetrate the skull, temporarily activating or silencing a region of the cortex. TMS is used to treat psychiatric disorders

what is a phenomena showed by EEG

shows that several different brain regions have characteristic rhythms or oscillations that are not understood

computational neuroscience

develop theories or models about how the brain processes information, then test these models against real-world data