Task 4 Flashcards
Contrast X-ray techniques are useful for
visualizing the brain
contrast X-ray techniques work:
injecting a substance that absorbs the X-rays less or more than the surrounding tissue.
A contrast X-ray technique
cerebral angiography: which uses the infusion of a radio-opaque dye into a cerebral artery to visualize the cerebral circulatory system during X-ray photography.
- Useful for localizing vascular damage (and tumors)
X-ray computed tomography (CT)
a computerassisted X-ray procedure that can be used to visualize the brain and other internal structures.
how does CT work
The X-ray makes photographs and the computer combines these horizontal brain section pictures into one 3D image of the brain
Magnetic resonance imaging(MRI)
a procedure which high-resolution images are constructed from the measurement of waves that hydrogen atoms emit when they are activated by radio-frequency waves in a magnetic field.
Pro of MRI
- MRI provides clearer images than CT.
- It provides high spatial resolution
- It produces images in 3 and 2 dimensions
spatial resolution
the ability to detect and represent differences in spatial location
Positron emission tomography (PET)
First brain imaging technique that provides images of brain activity rather than brain structures
How does PET work
In one version, radioactive 2-DG is injected into the persons carotid artery. Because of 2-DG’s similarity with glucose, the primary metabolic fuel of the brain, it is rapidly taken up by active cells. However 2-DG is cannot be metabolized. It therefor accumulates in active neurons or in associated astrocytes. Eventually it is broken down. Each PETscan is a an image of the levels of radioactivity
Functional magnetic resonance imaging (fMRI)
produces images representing the increase in oxygen flow in the blood to activate areas of the brain.
fMRI is possible because of two attributes of oxygenated blood
- active areas in the brain take up mor oxygenated blood than they need for their energy requirements–> and thus oxygenated blood accumulates in active areas of the brain
- oxygenated blood has magnetic properties, the oxygen influences the effect of magnetic fields on iron in the blood
the signal recorded by fMRI
BOLD signal (blood-oxygen-level-dependent signal)
4 advantages of fMRI (over PET)
- Nothing has to be injected into te subject
- it provides both structural and functional information in the same image
- its spatial resolution is better
- it can be used to produce 3D images of activity over the entire brain
downside of fMRI
fMRI technologie is often too slow to capture many neural responses.
magnetoencephalography (MEG)
A technique used to monitor the brain activity. It measures changes in magnetic fields on the surface of the scalp that are produced by changes in underlying patterns of neural activity.
Advantage of MEG (over fMRI)
MEG can record fast changes in neural activity
transcranial magnetic stimulation (TMS)
is a technique for affecting the activity of an area of the cortex by creating a magnetic field under a coil positioned next to the skull. The effect is that it temporarily turns of the brain while the effets of the disruption on cognition and behaviour are assessed.
psychophysiological recording methods
methods of recording physiological activity from the surface of the human body.
5 psychophysiological recording methods
- scalp EEG : measures brain activity
- muscle tension ; measures of somatic nervous system activity
- eye movement ; ‘ ‘
- skin conductance: measures of autonomic nervous system activity
- cardiovascular activity: ‘ ‘’
scalp electroencephalogram (EEG)
- measure of the gross electrical activity in the brain. It is recorded through large electrodes by a device called: electroencephalography.
- scores high on temporal resolution, but low on spatial resolution
What does the scalp EEG signal reflect
the sum of electrical events throughout the head. Which reflects that some wave fors are aasociated with particular states of consciousness or particular types of cerebral pathology
eventrelated potentials (ERPs)
EEG waves that accompany certain physiological events
one type of ERP is
sensory evoked potential : the change in the cortical EEG signal that is elicited by the momentary presentation of a sensory stimulus
sensory evoked potential has two components
- the response to the stimulus (signal)
2. ongoing background EEG activity (noise)
problem with EEG
the noise (part of a recording that is NOT of interest) is often so great that the sensory evoked potential is masked
method used to reduce noise
signal averaging
Muscle tension
indicator of physical arousal
procedure for muscle tension
electromyography, the resulting record is called an electromyogram (EMG)
EMG activity is recorded between
two electrodes taped on the surface of the skin over the muscles of interest. An increase in the amplitude of the raw EMG signal reflects the number of muscle fiers contracting at any on time.
electrooculography
the electrophysiological technique for recording eye movement, the recorded record is called electrooculogram (EOG)
How does EOG work?
There is a steady potential difference between the front (+) and back (-) of the eyeball. Because of this steady potential, when the eye moves, a change in electrical potential can be recorded (with electrodes). “ electrodes on each side of the eye measure horizontal movements, 2 electrodes above and below the eye measure vertical movements
2 employed indexes of electrodermal activity
- skin conductance level (SCL)
- skin conductance response (SCR)
emotional thoughts and experiences are associated with increases in the ability of the
skin to conduct electricity
SCL measures
the background level of skin conductance that is associated with a particular situation
SCR measures
the transient changes in skin conductance that are associated with discrete experiences
cardiovascular system has two parts
- heart
2. blood vessels
Three different measures of cardiovascular activity that are employed in psychophysiological research
- heart rate
- arterial blood pressure
- local blood volume
Electrocardiogram (ECG)
records an electrical signal that is associated with each heartbeat, through electrodes that are being placed on the chest
measuring blood pressure involves two different measures:
1 a measurement of the peak pressure during the periods of the heart contraction (systoles)
- a measurement of the minimum pressure during periods of relaxation (diastoles)
hypertension
140/90mmHg –> high blood pressure
blood pressure is measured with
a sphygmomanometer
various techniques that measure changes in blood volume in certain parts of the body is called
Plethysmography
Changes in de blood volume in particular parts of the body are associated with
psychological events
stereotaxic surgery
the means by which experimental devices are precisely positioned in the depths of the brain
two things required in stereotaxic surgery
- stereotaxic atlas: used to locate brain structure. All distances are given in mms from a designated reference point.
- An instrument to get to the location targeted in the brain.
designated reference point in the stereotaxic atlas
bregma: the point on the top of the skull where two of the major sutures intersext
Instrument for stereotaxic surgery has two parts
stereotaxic instruments:
- a head holder , which firmly holds each subject’s brain in the prescribed location
- electrode holder, which holds the device to be inserted
What are lesion methods
A part of the brain is removed, damaged or destroyed. After the behaviour of the subject is assessed in order to determine the functions of the lesioned structure
4 types of lesions
- aspiration lesions
- radio-frequency lesions
- knife cuts
- cryogenic blockade
aspiration lesions (when and how)
- Lesion is to be made in an area of cortical tissue
- the cortical tissue is drawn off by suction. Because the underlying white matter is slightly more resistent to suction than the cortical tissue itself, the layers of the cortical tissue can be peeled of without damaging underlying white matter and blood vessels
radio-frequency lesions (when and how)
- small subcortical lesions
- done by passing radio-frequency current through target tissue, the heat destroys the tissue.
knife cuts (another word and when)
- sectioning (cutting)
- used to eliminate conduction in a nerve or tract
cryogenic blockade
- reversible lesions
- a coolant is pumped through an impanted cryoprobe, neurons near the tip are cooled until they stop firing
- there is no structural damaged after warming it up again, the neurons start firing again
- this technique also eliminated the contribution of a particular area of the brain
unilateral lesions
lesions restricted to on ehalf of the brain
bilateral lesions
lesions involving both sides of the brain. Most experimental studies use this form because the behavioural effects are easier to detect.
how does electrical stimulation work
electrical brain stimulation is derived across two tips of a bipolar electrode. Weak pulses of current produce an immediate increase in the firing of neurons near the tip of the electrode
4 types of invasive electrophysiological recording methods
- intracellular unit recording
- extracellular unit recording
- multiple unit recording
- invasive EEG recording
What does intracellular unit recording provide?
a moment-by-moment record of the graded fluctuations in one neuron’s membrane portential
what do you record with extracellular unit recording and how does it work
- you record the action potentials of a neuron through a microelectrode whose tip is positioned in the extracellular fluid next to it.
- each team a neuron fires there is an electrical
disturbance and a blip is recorded at the electrode tip
multiple-unit recording (is different from extra and intracellular recording because?)
Is a recording which makes a graph of the total number of recorded action potentials per unit of time.
- electrode tip is larger than that of a microelectrode
- picks up signals from many neurons
- slight shifts in its position due to movement of the subject have little effect on the overal signal
Invasive EEG recording
EEG signals are recorded through large implanted electrodes rather than through scalp electrodes ( which is the case with normal EEG)
in psychopharmacological experiments drugs can be administered in 3 ways:
- fed to the subject
- injected through a tube into the stomach = intragastrically
- injected hypodermically into the peritoneal cavity of the abdomen , muscle, fatty tissue, surface vein.
How do you overcome the blood-brain barrier
By administering drugs in small amount through a fine, hollow tube, called Cannula, that has ben implanted in the brain
neurotoxins pro
easier to interpret the effects because they don’t effect all the neurons in the target area. It is possible to make some selective lesions by injecting the neurotoxin that have an affinity for certain components of the nervous system
2 techniques for measuring chemical brain activity
- 2-DG technique
- Cerebral Dialysis: method of measuring extracellular concentration of specific neurochemicals in behaving animals.
- Involves implantation in the brain of a tube with a short semipermeable section from which the extracellular chemicals will diffuse into the tube.
special about Cerebral dialysis
Animal doesn’t have to be killed
