chapter 4 (yes, we skipped- we will be back!) methods in neuroscience
TRANSCRIPT
CHAPTER 4 (YES, WE SKIPPED- WE WILL BE BACK!)
Methods in Neuroscience
Research, Theory and Science
Relies on EMPIRICAL DATA as its means of acquiring knowledge
Relies on SCIENTIFIC METHOD hypothesis testing and theories operational definitions systematic observations
Common sense and folklore may or may not be “true”
Science differs from folklore and tradition because it uses empirical method
Science (and thus neuroscience) is Tentative
Conclusions based on current information New information always being acquired This creates a problem: what was true yesterday is probably not
true today, and what is true today is probably not true tomorrow!
Science is evolving, rapidly changing, and ambiguous
Relies on theories: Integrative interpretation of diverse observations Attempt to explain some phenomenon Based on evidence Conclusions pulled together logically Explains current facts Suggests new hypotheses and experiments to constantly test
and refine the theory
Methods of Research
Rules for conducting research Scientific Ethical Many techniques
Two main methods: correlational experimental method sub-areas of these, as well
Correlational method
NON experimental
looking at relation between two variables effect of X on Y
Correlation DOES NOT IMPLY CAUSATION
values of -1.0 to 0 to +1.0 closer to 1.0 is stronger relationship if value is close to 0, little relationship
Two types of correlations
Positive correlation: 0 to 1.0 as X goes up so does Y rate of waterskiing and outside temperature
Negative correlation: 0 to -1.0 as X goes up, Y goes down rate of hot chocolate intake and outside temperature
Examples of correlations
Experimental Method
Allows us to conclude causation
Uses general experimental method hypothesis to test uses INDEPENDENT and DEPENDENT variables
Conducting an Experiment
Need independent and dependent variables Variable = any characteristic or condition which is
subject to change Independent variable: what the experimenter
manipulates or changes Dependent variable: what the experimenter measures,
what was changed by the I.V. Experimenter manipulates IV, measures DV
WAY that the IV is manipulated is important: assumes using a random sample control for extraneous (extra or outside) variables use systematic observations
Types of Groups of IV
Experimental group: gets the treatmentControl group:
does not get the “treatment”, but otherwise equal to the experimental group
Placebo Group: a control group “thinks” they got the treatment
Many Research Techniques in Neuroscience
Which are correlational? No random assignment to groups Linking or relating A to B
Which are causal? Random assignment Researcher manipulates independent variable
Does it make a difference?
Techniques include
Cell work: study brain cells or slices
Measuring brain activity in live organisms: Scans of functioning brains Implanting measurement tools and measuring
Animal models
Post-mortem examination
Research techniques in neuroscience:Staining and imaging neurons
Golgi stain method: randomly stains about 5%
of neurons in slice Places them in relief
against background Can see patterns
Myelin stains: Stain taken up by fatty
myelin that insulates axon Stain helps identify neural
pathways
Nissl stains: Stain taken up by
neurons Identify cell bodies of
neurons
Research techniques in neuroscience:Staining and imaging neurons
Autoradiography Use fluorescent dye:
flurogold Make neurons stand out Importantly: tells which
neurons are active Can correlate with
behavior
Also use radioactive tracers: 2-DG (2-deoxyglucose) Make this sugar
radioactive Is taken up by neuron Can trace where it went
Can also stain for neurotransmitters or other brain chemicals
Light and Electron Microscopy
Electron microscope: Passes beam of electrons through
thin slice of brain tissue onto photo plate
Different parts of tissue block or pass electrons at different degrees
Electrons produce image based on this variance
Scanning electron microscope: Beam of electrons causes specimen
to emit electrons itself These are captured by photo plate Not as great of magnification, but
image is 3-D
Measuring Brain Activity
Electroencephalography or EEG Hans Berger, 1929 Recorded from two electrodes on
scalp over area of interest Electronic amplifier detects
combined electrical activity of all neurons between these two neurons
Can graph activity Terrific temporal resolution: 1
millisecond recording Spatial resolution is poor
Why use? Detecting changes in brain patterns
or arousal Can average several readings to
obtain evoked potential Signal – background noise Gives better estimation of patterns
Often used for detecting epilepsy and other brain disorders, sleep disorders
Stereotaxic techniques:
Stereotaxic device: Allows precise
positioning in brain of electrode or other device
Holds head in position 3-D: height x depth x
width Use stereotaxic atlas to
find locations Brain atlas!
Several kinds of things might be put into brain Cannula Electrode
Stereotaxic techniques:
Allows one to ablate or lesion precise areas of brain Alter specific area to
determine function Examine pathways
Several kinds of measures Electrophysiology Electrodialysis Fast scan cyclic
voltammetry
All allow measurement of brain electrical and chemical changes
Brain Imaging
CT or CAT scan: Computed tomography X ray scanning Produces series of x
rays taken from different angles
Combined using computer to create series of 2-d horizontal cross sessions or slices
Presented as series to make 3-D
Brain Scanning: MRI
Magnetic Resonance Imaging or MRI Measures radio-
frequency waves emitted by hydrogen atoms when they are subjected to strong magnetic field
Extremely fast Can scan very small
areas clearly
Brain Scanning: PET
PET: positron emission tomography Involves injecting radioactive
substance into bloodstream Is taken up by parts of brain
according to how active each area is
Often radioactive 2-DG Use other radioactive tracers
to mark bloodflow, oxygen uptake
Requires lots of training and access to cyclotron Cyclotron supplies radioactive
substances
Provides estimates of brain activity and changes in brain activity
Brain Scanning: fMRI
fMRI: functional magnetic resonance imaging
Measures brain activation by detecting increase in oxygen levels in active neural structures
Can be used as individual is engaging in a behavior or cognitive task
Can see changes as behavior changes Important: don’t have to
ablate or lesion to determine function
Allows use of human subjects
Studying heritability and genetics
Family studies: Determine how strongly a
characteristic is shared across family members
Quantify Correlate degree of heritability
Adoption studies Compare adopted and biological
children Compare behavior in adoptive vs
biological family
Twin studies Identical vs. fraternal twins
Concordance rate: frequency with which relatives are alike in characteristics
Genetic Engineering
Genetic engineering: Manipulation of organism’s
genes or their functioning
Knockout technique: Nonfunctioning mutation is
introduced into isolated gene
Altered gene is transferred into embryo
Antisense RNA procedure: Blocks participation of
messenger RNA in protein construction
Genetic Engineering
Gene Transfer: Gene is inserted into an
animal’s cells
Transgenic animal: Gene is inserted into
animal embryo Embryo now has that
trait
Genetic Engineering Manipulate genes to turn
on/off different traits Goal is to be of
therapeutic use
Research Ethics
Regulatory Animal research:
IACUC: Institutional animal care and use committee 5 federal agencies have federal guidelines
NIH human subjects use
Problems: Plagiarism Fabrication of data
Ethical dilemmas Gene therapy Stem cell therapy