Chapter 5 – Research Methods of Biopsychology
5.1 Methods of Visualizing & Stimulating the Living Human Brain
Contrast X-Rays: Involve injecting into one compartment of the body a
substance that absorbs X-rays either less than or more than the surrounding
tissue – heightens contrast between the compartment & surrounding tissue.
o Cerebral Angiography- uses the infusion of a radio-opaque dye into a
cerebral artery to visualize the cerebral circulatory system.
X-Ray Computed Tomography: CT is a computer-assisted x-ray procedure
that can be used to visualize the brain and other internal structures of the
Magnetic Resonance Imaging: MRI is a procedure in which high-resolution
images are constructed from the measurement of waves that hydrogen atoms
emit when they are activated by radio-frequency waves in magnetic field.
o Spatial Resolution- the ability to detect and represent differences in
spatial location (MRI has high spatial resolution)
Positron Emission Tomography: PET was the first brain imaging technique to
provide images of brain activity rather than images of brain structure
o I.e., radioactive deoxyglucose is injected into patients carotid artery
Functional MRI: fMRI produces images representing the increase in oxygen
flow in the blood to active areas of the brain. Signal recorded is the BOLD
(blood oxygen level dependent).
Magnetoencephalography: MEG measures changes in magnetic fields on the
surface of the scalp that are produced by changes in underlying patterns of
neural activity – temporal resolution: can record fast changes in activity.
Transcranial Magnetic Stimulation: TMS is a technique for affecting the
activity in an area of the cortex by creating a magnetic field under a coil
positioned next to the skull.
5.2 Recording Human Psychological Activity
Scalp Electroencephalography: EEG is a measure of the gross electrical
activity of the brain; it is recorded through large electrodes by a EEG
machine. In humans it records from disk-shaped electrodes.
o EEG waves accompany events and are called event-related
potentials – sensory evoked potential; change in cortical EEG signal
that is elicited by the momentary presentation of a sensory stimulus.
o Signal Averaging: a method used to reduce the noise in the back.
o Far-Field Potentials: small waves that originate far away from brain.
Muscle Tension: Electromyography is the usual procedure for measuring
muscle tension; the record is an EMG – usually recorded with 2 electrodes
taped to the surface of the skin. Muscles are composed of millions of fibers.
Eye Movement: Electrooculography is used to measure eye movement and
records an EOG, based on the fact that there is a steady potential difference
between the front (positive) and the back (negative) of the eyeball.
Skin Conductance: Skin Conductance Level (SCL): is a measure of the
background level of skin conductance that is associated with a particular
situation. Skin Conductance Response (SCR): is a measure of the transient
changes in the skin conductance that is associated with discrete experiences. Chapter 5 – Research Methods of Biopsychology
Cardiovascular Activity: 2 parts – the blood vessels and the heart, system for
distributing oxygen and nutrients to the tissues of the body, removing
metabolic wastes, and transmitting chemical activity.
Heart Rate: Electrical signal that is associated with each heartbeat can be
recorded through electrodes placed on the chest. ECG or EKG
Blood Pressure: Measuring blood pressure with the measurement of the peak
pressure during the periods of heart contraction – systoles, and a
measurement of the minimum pressure during the relaxation – diastoles
o Hypertension: chronic blood pressure of more than 140/90 mmHg
Blood Volume: Changes in the volume of blood in particular parts of the body
are associated with psychological events. Plethysmography: refers to the
various techniques for measuring changes in the volume of blood in body.
5.3 Invasive Physiological Research Methods
Stereotaxic Surgery: The first step in many experiments – the means by
which experimental devices are precisely positioned in the depths of the
brain. Stereotaxic Atlas is used to locate brain structures in much the same
way that a geographic atlas is used to locate geographic landmarks.
Stereotaxic Instrument has a head and a holder, which firmly hold each
subjects brain in the prescribed position and orientation.
Lesion Methods: * very hard to interpret *
o Aspiration: When a lesion is to be made in an area of cortical tissue
that is accessible to the eyes and instruments of the surgeon.
o Radio-Frequency Lesions: passing radio freq. commonly makes
small subcortical lesions current through the target tissue from the tip
of a stereo taxically positioned electrode.
o Knife Cuts: Sectioning is used to eliminate conduction in a
o Cryogenic Blockade: When coolant is pumped through the implanted
cryoprobe, neurons near the tip are cooled until they stop firing.
o Bilateral & Unilateral: Uni = restricted to half of the brain, Bi = both
sides of the brain.
Electrical Stimulation: Usually delivered across the two tips of a bipolar
electrode: two insulated wires wound tightly together and cut at the end.
Invasive Electrophysiological Recording Methods:
o Intracellular Unit Recording: Provides a moment-by-moment
record of the graded fluctuations in one neuron’s membrane potential.
o Extracellular Unit Recording: Provides a record of the firing of a
neuron but no info about the neuron’s membrane potential.
o Multiple-Unit Recording: The electrode tip is much larger than that
of a microelectrode; picks up signals from many neurons.
o Invasive EEG Recording: Recorded through the large implanted
electrodes rather than scalp electrodes. Chapter 5 – Research Methods of Biopsychology
5.4 Pharmacological Research Methods
Routes of Drug Administration: 1) Fed to the subject, 2) Injected through a
tube into the stomach, 3) Injected hypodermically into the peritoneal cavity
of the abdomen, large muscle, fatty tissue beneath the sk