PSYC 2410 Lecture Notes - Lecture 6: Goose Bumps, Microdialysis, Semipermeable Membrane
27 Jun 2018
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Methods of studying the nervous system:
Methods of visualizing the living human brain
oContrast X-rays: beams of x-rays are passed through an object and parts of the object
that absorb x-rays differentially will be distinguishable on the photographic plate placed
below the object. With contrast x-rays a radio-opaque material is injected so that it can go
to the structure of interest creating a denser area that will absorb the x-rays to a higher
degree than surrounding structure - this creates the contrast on the photographic plate
oComputerized Tomography (CT): rotation of the x-ray gun and x-ray detector in
apposition around the brain at one level and taking a series of measurements creates an
image of one section. CT scan image is not high resolution
oMagnetic Resonance Imaging (MRI): the radio-frequency waves in a magnetic field
stimulate hydrogen atoms to emit waves that can be measured and used to construct a high
resolution image of brain structures - images are clearer than those created by CT scans.
This method also provides a higher spatial resolution which allows 3D images to be created
oPositron Emission Tomography (PET): this method is different from the previous
methods because it provides a functional image of the brain (areas of brain activity rather
than brain structure). A radioactive glucose is injected and then the glucose is taken up by
active cells in the brain. The level of radioactivity is measured and colour coded maps are
created. Only an estimate can be made about a specific brain structure related to the
activity
oFunctional MRI (fMRI): when areas of the brain are active they take up more oxygenated
blood than is necessary for energy requirements. The magnetic property of oxygenated
blood produces the bold signal that provides a measure of brain activity in different areas of
the brain. Advantages of fMRI over PET are: no injection of radioactive material, provides
both structural and functional information, spatial resolution is better, and can produce 3D
activity images over entire brain
oMagnetoencephalography (MEG): this method records changes in neural activity by
measuring changes in magnetic fields on the surface of the scalp
oBrain Image Archives: an archive of raw data (images) that can be shared among
researcher
oTranscranial Magnetic Stimulation (TMS): by using a magnetic field generated in a coil
near the skull researchers can temporarily disrupt cognitive function in specific areas of the
brain to evaluate the importance of this area for cognitive activity
Recording human psychophysical activity - provides information on the methods used to record
physiological activity from the body surface
oScalp Electroencephalography (EEG): gross measure of the electrical activity of the brain
that is recorded through an array of electrodes placed on the scalp. EEG waves reflect the
sum total of all electrical events in the head - specific EEG waves are associate with specific
states of consciousness. The temporal resolution of brain activity is very good with EEG's
and it is a valuable diagnostic tool for pathologies such as epilepsy, but spatial resolution is
poor
oMeasures of somatic nervous system activity
Muscle Tension; Electromyography (EMG): two large electrodes are placed on
the skin above a large muscle and electrical current is applied. The changing difference
in charge between the two electrodes indicates the level of tension in the muscle.
High resting levels of tension in the muscle is an indicator of anxiety
Eye Movement; Electrooculography ((EOG): changes in the steady potential
difference between the front and back and the left and right sides of the eye can be
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measured and direction of movement can be inferred - these changes are recorded by
four electrodes placed around the eye
oMeasures of autonomic nervous system activity:
Skin Conductance: this method measures the level of electrical charge on the
skin that may be due to the functioning of sweat glands. It is generally considered to
be an assessment of emotional thoughts and experiences - one application of this
method is the lie detector test
Cardiovascular Activity: these are measures of the two parts of the
cardiovascular system: the heart and blood vessels. Heart rate reflects changes in
emotion and is measured by an electrocardiogram. Blood pressure is a measure of
arterial blood pressure that involves a measure of peak pressure (systole) and
minimum pressure (diastole). Chronic high blood pressure is called hypertension and
is a serious health hazard. Blood volume changes are associated with psychological
events. Plethysmography is the technique for measuring blood volume and is done
either with a strain gauge or measuring the amount of light absorbed by the area of
interest
Invasive physiological research methods - research evaluating direct manipulations or measures
of the brain is usually conducted using laboratory animals
oStereotaxic Surgery: the type of surgery allows accurate placement of lesions, probes,
electrodes and other devices into the brain. The head of the animal is placed in a stereotaxic
frame that eliminates movement of the head during surgery and holds probes or electrodes
for placement in specific structures of the brain - most common reference point is bregma,
the point where the two main plates of the skull naturally fuse together
oLesion Methods: these methods destroy a specific area of the brain to evaluate the
importance of the structure for behavioural functioning - lesions invariably damage
surrounding structures and rarely remove the targeted structure entirely. Histological
evaluation of lesions is conducted after the study to determine accuracy of the lesion
Aspiration: removal of cortical tissue
Radio-frequency: current passed into structure; heat destroys tissue
Knife cuts: severe tracts
Cryogenic blockade: tissue is temporarily cooled to eliminate function;
reversible lesion
oElectrical Stimulation: a current is passed across the tips of a bipolar electrode that is
placed in a structure of interest, immediately increasing the firing of neurons near the tip of
the electrode. The effect of electrical stimulation is often opposite to those of a lesion, it
initiates behaviours. The type of behavior is dependent upon the location of the electrode
Intracellular unit recording: method that records changes in membrane
potential of one neuron
Extracellular unit recording: method that records the firing of a neuron without
providing any information about the membrane potential
Multiple-unit recording: method that uses a larger electrode tip allowing
recording of signals from many neurons
Invasive EEG recording: method that uses electrodes implanted just below the
skull and above the cortex (similar to EEG scalp electrodes in humans)
Pharmacological research methods - methods for administering drugs that either increase or
decrease the effects of neurotransmitters and monitor behavioural consequences of these
manipulations
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Document Summary
Methods of visualizing the living human brain o. Contrast x-rays: beams of x-rays are passed through an object and parts of the object that absorb x-rays differentially will be distinguishable on the photographic plate placed below the object. Computerized tomography (ct): rotation of the x-ray gun and x-ray detector in apposition around the brain at one level and taking a series of measurements creates an image of one section. This method also provides a higher spatial resolution which allows 3d images to be created o. Positron emission tomography (pet): this method is different from the previous methods because it provides a functional image of the brain (areas of brain activity rather than brain structure). A radioactive glucose is injected and then the glucose is taken up by active cells in the brain. The level of radioactivity is measured and colour coded maps are created. Only an estimate can be made about a specific brain structure related to the activity o.
