Psych 275 Midterm 2

Theory

integrates and interprets diverse observations in an attempt to explain a phenomenon

• use tentative language so it can be disproven

Reasons for tentative language in theories

• studies may be flawed

• New data may change interpretation of old studies

• Laws of probability suggest results could be random

types of studies that use observations

• naturalistic observations

• Case studies

• Surveys

• Experiments

• Correlational studies

Experimental study

researcher manipulates independent variable to produce change in the dependent variable

• attempts to eliminate extraneous variables

• sacrifice realism for control

Correlational study

researcher observes whether two variables are related

• Cannot determine cause and effect.

• Chance of confounding variables

• Results are valuable, but require careful interpretation

Golgi stain

Randomly stains about 5% of neurons on a slide

Myelin stain

Taken up by the fatty myelin surrounding axons

Nissl stain

Identified cell bodies of neurons

Retrograde stains

Taken up by neuron terminals and transported up the axons to cell bodies

Autoradiography

Stains and reveals which neurons are active

Immunocytochemistry

Use antibodies attached to a dye to identify cell components (protein)

In situ hybridization

Construction of DNA strands which complement an mRNA strand

• Same thing as immunocytochemistry but targets mRNA strand that creates the protein instead of the protein

Messenger ribonucleic acid (mRNA)

Copy of one DNA strand carried from cell to nucleus into cytoplasm

• directs construction of proteins

Light microscopy

Can only magnify 1500X

Electron microscopy

Magnify up to 250 000X

Transmission electron microscopy

Passes beam of electrons through thin slice of tissue

• magnified image up to 50 million times

Scanning electron microscope

beam of electrons induces specimen to emit electrons

• Enhancement of transmission electron technique

• Magnifies images up to 2–3 million times

• Produces 3-D image

• Confocal laser scanning microscope and two-photon microscope

Electroencephalogram (EEG)

electronic amplifier detects electrical activity of all neurons between two electrodes

• temporal resolution: events close as 1 Ms apart

• Spatial resolution: imprecise unless electrodes are applied directly to brain surface (10-15 mm)

• Event related potential

Event-related potential

averaging many recorded responses to stimulus

• Cancels out background noise

• Reveals brain’s unique response to stimulus

• Uses EEG

Stereotaxic instrument

device allowing precise positioning of a probe in the brain

• Probes typically fine-wire electrodes

• Microelectrodes can monitor and stimulate a single neuron

Optogenetic techniques

light-sensitive channels can be inserted in specific types of neurons

• More precise than electrical stimulation

different types of staining for neurons

• golgi stain

• Myelin stain

• Nissl stain

• Retrograde stain

• Autoradiography

• immunocytochemistry

• In situ hybridization

Microdialysis

More complex variation of of cannulation

Cannulation

a common, minimally invasive medical procedure involving the insertion of a plastic tube (cannula) into a vein, most often in the hand or arm, to provide direct access for administering fluids, medication, or blood products

Natural experiments

historically, brain damaged patients were a rich source of brain research

• Damage may overlap different functional areas

• Damage may fail to affect the entirety of a functional area

Ablation

Surgical removal of brain tissue

• used for large areas - imprecise

• Often done by aspiration

Lesioning

Surgical damaging of neural tissue

• precise and sometimes reversible

Transcranial magnetic stimulation

noninvasive technique using a magnet coil to induce a voltage

• Device held over scalp and pulsed at varying rates

• Valuable in both research and therapeutically

Computed tomography

produces series of X-rays, then composites them into a 3-D image

• “False colors” added for contrast

• image shows differing densities of blood vessels in the brain

• Time: less than 1 s

• Spatial mm: 0.2-0.5

Magnetic resonance imaging

measures radio-frequency waves emitted by hydrogen atoms exposed to magnetic field

• Most hydrogen atoms within water molecules

• Non-hydrogen elements can now be measured

• Time: 3-5 s

• Spatial mm: 1-1.5

Diffusion tensor imaging

MRI variant measuring the movement of water molecules

Positron emission tomography

observation of brain regions through a radioactive substance injected into bloodstream

• Scanner picks up emitted positrons to form a color-coded image

• indicates relative activity of brain regions

• Difference scans

• Cannot detect changes less than 30 s in duration

• Results do not image the brain

• Time: 30 s

• Spatial mm: 2-3

Functional magnetic resonance imaging (fMRI)

detects increases in blood flow and oxygen usage during neural activity

• tracks changing activity

• Suitable for repeated measurements

• Good spatial resolution

• Alternative to PET scans

• Costly due to expense of equipment

• Time: 1 s

• Spatial mm: 1-2

• Low sensitivity

Brain imaging

• main experimental technique in neuroscience

• Test-retest reliability is low

• Types

  • CT (structural)

  • MRI (structural)

  • PET (functional)

  • FMRI (functional)

  • EEG (functional)

Temporal resolution

How well it detects real time changes

Spatial resolution

the minimum size of objects or the level of detail that an imaging system, such as a sensor, camera, or satellite, can distinguish and record

Family study

Determines how characteristic is shared among relatives

• heredity effects typically confounded by environment

• Require correlation coefficient

Correlaton

degree of relationship between two variables

• Expressed with correlation coefficient

Correlation coefficient

Number between 0.0 and ± 1.0

Positive correlations: both variables are high

 Negative correlations: when one variable is high, the other is low