Module 1.3

contrast x-ray techniques

involve injecting into one compartment of the body a substance that absorbs x-rays
either less than or more than the surrounding tissue. The injected
substance then heightens the contrast between the compartment and the
surrounding tissue during x-ray photography

cerebral angiography

• One contrast x-ray technique — uses the infusion of a radio-opaque dye into a cerebral artery to visualize the cerebral circulatory system during x-ray photography.

• — are most useful for localizing vascular damage, but the displacement of blood vessels from their normal position also can indicate the location of a tumor.

computed tomography

is a computer- assisted x-ray procedure that can be used to visualize the brain and other internal structures of the living body. During cerebral — , the
neurological patient lies with his or her head positioned in the center of a large
cylinder.

positron emission tomography

was the first brain imaging technique to provide images of brain activity (functional brain images) rather than images of brain structure (structural brain images)

fluorodeoxyglucose (FDG)

in one common version of PET, radioactive— is injected into the patient’s carotid artery (an artery of the neck that feeds the ipsilateral cerebral hemisphere). Because of its similarity to glucose, the primary metabolic fuel of the brain, — is rapidly taken up by active (energy-consuming) cells

magnetic resonance imaging

is a structural brain-imaging procedure in which high-resolution images are constructed from the measurement of radio-frequency waves that hydrogen atoms emit as they align with a powerful magnetic field.

diffusion tensor MRI

• one of the most innovative of these new MRI techniques has been —

• is a method of identifying those pathways along which water molecules rapidly diffuse

• Because tracts (bundles of axons) are the major routes of rapid water diffusion in the brain, —provides an image of major tracts.

functional MRI

• produces images representing the increase in oxygenated blood flow to active areas of the brain.

• — is possible because of two attributes of oxygenated blood. First, active
  areas of the brain take up more oxygenated blood than they need for their energy requirements, and thus oxygenated blood accumulates in active areas of the brain

• Second, oxygenated blood has different magnetic properties than does deoxygenated blood, and this difference influences the radio-
  frequency waves emitted by hydrogen atoms in an MRI.

BOLD signal (the blood-oxygen-leveldependent signal)

• The signal recorded by fMRI is called the —.

• The —indicates the parts of the brain that are active or inactive during a cognitive or behavioral test, and thus it suggests the types of analyses the brain is performing.

• Because the — is the result of blood flow through the brain, it is important to remember that it is not directly measuring the electrical activity of the brain

Functional ultrasound imaging

is a new imaging technique that uses ultrasound (sound waves of a higher
frequency than we can hear) to measure changes in blood volume in particular brain regions. When a brain region becomes active, blood levels increase there, and alter the passage of ultrasound through that brain region

Transcranial magnetic stimulation (TMS)

• — is a technique that can be used to turn off an area of human cortex by creating a magnetic field under a coil positioned next to the skull

• is often employed to circumvent the difficulty that brain-imaging studies have in determining causation.

• Using different stimulation parameters, — can also be used to “turn on” an area of cortex

transcranial electrical stimulation

is a technique that can be used to stimulate (“turn on”) an area of the cortex by applying an electrical current through two electrodes placed directly on the scalp. The — temporarily increases activity in part of the brain while the effects of the stimulation on cognition and behavior are assessed

transcranial ultrasound stimulation

is a technique that, like tES and TMS, can be used to activate particular brain structures. However, unlike tES and TMS, which can only be used to stimulate cortical structures, — can also be used to activate subcortical structures

electroencephalogram

• is a measure of the gross electrical activity of the brain.

• The scalp — signal reflects the sum of electrical events throughout the head. These events include action potentials and postsynaptic potentials as well as electrical signals from the skin, muscles, blood, and eyes

magnetoencephalography

— measures changes in magnetic fields on the surface of the scalp that are produced by changes in underlying patterns of neural activity. Because the magnetic signals induced by neural activity are so small, only those induced near the surface of the brain can be recorded from the scalp

electromyography

is the usual procedure for measuring muscle tension

electromyogram

the resulting record of electromyography is called an — . — activity is usually recorded between two electrodes taped to the surface of the skin over the muscle of interest

electrooculography

• The electrophysiological technique for recording eye movements

• is based on the fact that a steady potential difference exists between the front (positive) and back (negative) of the eyeball. Because of this steady potential, when the eye moves, a change in the electrical potential between electrodes placed around the eye can be recorded

electrooculogram

the resulting record of the electrooculography is called an —

skin conductance level and skin conductance response

two most commonly employed indexes of electrodermal activity are the —

skin conductance level

is a measure of the background level of skin conductance that is associated with a particular situation

skin conductance response

is a measure of the transient changes in skin conductance that are associated with discrete experiences

electrocardiogram

The electrical signal associated with each heartbeat can be recorded through electrodes placed on the chest. The recording is called an —

70 beats per minute

the average resting heart rate of a healthy adult is about

systoles and diastoles

Measuring arterial blood pressure involves two independent measurements

systoles

measurement of the peak pressure during the periods of heart contraction

diastoles

measurement of the minimum pressure during the periods of relaxation

blood pressure

is usually expressed as a ratio of systolic over diastolic blood pressure in millimeters of mercury (mmHg)

130/70 mmHg

The normal resting blood pressure for an adult is about

hypertension

A chronic blood pressure of more than 140/90 mmHg is viewed as a serious health hazard and is called

sphygmomanometer

You have likely had your blood pressure measured with a — it is a crude device composed of a hollow cuff, a rubber bulb for inflating it, and a pressure gauge for measuring the pressure in the cuff

plethysmography

refers to the various techniques for measuring changes in the volume of blood in a
particular part of the body

stereotaxic surgery

is 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. Accordingly, the brain is represented in a — by a series of individual maps, one per page, each representing the structure of a single, two- dimensional frontal brain slice.

bregma

the point on the top of the skull where two of the major sutures (seams in the skull) intersect

1. stereotaxic atlas

2. stereotaxic instrument

Two things are required in stereotaxic surgery

1. head holder

2. electrode holder

stereotaxic instrument has 2 parts

head holder (stereotaxic instrument)

which firmly holds each subject’s brain in the prescribed position and orientation

electrode holder (stereotaxic instrument)

which holds the device to be inserted

anterior-posterior, dorsal-ventral, and lateral-medial

a system of precision gears allows the electrode holder to be moved in 3 dimensions

aspiration lesions

• When a lesion is to be made in an area of cortical tissue that is accessible to the eyes and instruments of the surgeon, — is frequently the method of choice. The cortical tissue is drawn off by suction through a fine-tipped handheld glass pipette.

• Because the underlying white matter is slightly more resistant to suction than the cortical tissue itself, a skilled surgeon can delicately peel off the layers of cortical tissue from the surface of the brain, leaving the underlying white matter and major blood vessels undamaged.

radio-frequency lesions

• Small subcortical lesions are commonly made by passing radio-frequency current (high frequency current) through the target tissue from the tip of a stereotaxically positioned electrode. The heat from the current destroys the tissue.

• The size and shape of the lesion are determined by the duration and intensity of the current and the configuration of the electrode tip

sectioning (cutting)

is used to eliminate conduction in a nerve or tract. A tiny, well-placed cut can unambiguously accomplish this task without producing extensive damage to surrounding tissue

reversible lesions

• are useful alternatives to destructive lesions.

• are methods for temporarily eliminating the activity in a particular area of the brain while tests are being conducted.

• advantage of— is that the same subjects can be repeatedly tested in both the lesion and control conditions.

electrical brain stimulations

is usually delivered across the two tips of a bipolar electrode—two insulated wires wound tightly together and cut at the end. Weak pulses of current produce an immediate increase in the firing of neurons near the tip of the electrode

Halstead-Reitan Neuropsychological Test Battery

• The most widely used standardized test battery has been the —

• is a set of tests that tend to be performed poorly by brain-damaged patients in relation to other patients or healthy controls; the scores on each test are added together to form a single aggregate score. An aggregate score below the designated cutoff leads to a diagnosis of brain damage

Wechsler Adult Intelligence Scale

test of general intelligence

digit span subtest

the most widely used test of short term memory

sodium amytal test and dichotic listening test

two widely used tests of language lateralizations

sodium amytal test

involves injecting the anesthetic sodium amytal into either the left or right
carotid artery in the neck. This temporarily anesthetizes the ipsilateral (same-side) hemisphere while leaving the contralateral (opposite-side) hemisphere largely unaffected

dichotic listening test

sequences of spoken digits are presented to volunteers through stereo headphones. Three digits are presented to one ear at the same time that three different digits are presented to the other ear. Then, they are asked to report as many of the six digits as
they can

repetition priming tests

have proven instrumental in the assessment and study of this pattern.
Patients are first shown a list of words and asked to study them; they are not
asked to remember them. Then, at a later time, they are asked to complete a
list of word fragments, many of which are fragments of words from the initial
list.