Psyc20006 Biological Psychology (Melbourne Uni) Lecture 9-10

Front 1

EEG is a...

Back 1

method for detecting neural activate by placing electrodes on the scalps (these electrodes pick up the electrical signals of the underlying neurones in in the brain allowing infernos about neural activity to be made)

Front 2

Why choose EEG?

Back 2

EEG allows for mind reading, it's non-invassive, ethical, fairly-inexpesive, well studied. -huge historical significance.

Front 3

EEG history (Hens Berger)

Back 3

1st EEG sigal w/ electrodes attached to scalp of human. Hans Berger in 1924. Electrical signal varied w/ characteristic fq of 8-13 Hz (alpha rhythm). USED 2 ELECTRODES - 1 attached to the front of head 1 to the rear. Recorded the potential (voltage) difference btwn them. Fluctuation caused by neural activity.

Front 4

EEG history (Richard Carson)

Back 4

placed electrodes directly on the brain of dogs and apes. detected small electrical impulses (results reported in 1875- largely ignored)

Front 5

EEG vs fMRI

Back 5

CHEAPER AND HIGHER RESOLUTION faster

Front 6

EEG and consciousness

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- arousal (aspect of consciousness). - EEG fq increases w/ arousal of object. Used to monitor the state of consciousness /arousal of a patient under anesthetic

Front 7

Origins of EEG signal

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- electrical signal generated by neurone, elec final recorded n EEG exp. EEG reflects the summation of electrical potential generated by millions of neurones. - a angle neurone does NOT generate a large enough electrical potential to be detectable by an electrode placed on the scalp.

Front 8

EEG signals originate primarily from the ........... .............

Back 8

cerebral cortex (sheet of neural matter on the outside of the brain)

Front 9

Artifact removal

Back 9

most common is eye movement.

Front 10

Names of frequency ranges: D........... T.......... A............. B........... G...............

Back 10

Delta is the frequency range up to 4 Hz. It tends to be the highest in amplitude and the slowest waves. It is seen normally in adults in slow wave sleep. It is also seen normally in babies. It may occur focally with subcortical lesions and in general distribution with diffuse lesions, metabolic encephalopathy hydrocephalus or deep midline lesions. It is usually most prominent frontally in adults (e.g. FIRDA - Frontal Intermittent Rhythmic Delta) and posteriorly in children (e.g. OIRDA - Occipital Intermittent Rhythmic Delta).


theta waves.
Theta is the frequency range from 4 Hz to 7 Hz. Theta is seen normally in young children. It may be seen in drowsiness or arousal in older children and adults; it can also be seen in meditation.[39] Excess theta for age represents abnormal activity. It can be seen as a focal disturbance in focal subcortical lesions; it can be seen in generalized distribution in diffuse disorder or metabolic encephalopathy or deep midline disorders or some instances of hydrocephalus. On the contrary this range has been associated with reports of relaxed, meditative, and creative states.


alpha waves.
Alpha is the frequency range from 8 Hz to 12 Hz. Hans Berger named the first rhythmic EEG activity he saw as the "alpha wave". This was the "posterior basic rhythm" (also called the "posterior dominant rhythm" or the "posterior alpha rhythm"), seen in the posterior regions of the head on both sides, higher in amplitude on the dominant side. It emerges with closing of the eyes and with relaxation, and attenuates with eye opening or mental exertion. The posterior basic rhythm is actually slower than 8 Hz in young children (therefore technically in the theta range).


sensorimotor rhythm aka mu rhythm.
In addition to the posterior basic rhythm, there are other normal alpha rhythms such as the mu rhythm (alpha activity in the contralateral sensory and motor cortical areas that emerges when the hands and arms are idle; and the "third rhythm" (alpha activity in the temporal or frontal lobes).[40][41] Alpha can be abnormal; for example, an EEG that has diffuse alpha occurring in coma and is not responsive to external stimuli is referred to as "alpha coma".


beta waves.
Beta is the frequency range from 12 Hz to about 30 Hz. It is seen usually on both sides in symmetrical distribution and is most evident frontally. Beta activity is closely linked to motor behavior and is generally attenuated during active movements.[42] Low amplitude beta with multiple and varying frequencies is often associated with active, busy or anxious thinking and active concentration. Rhythmic beta with a dominant set of frequencies is associated with various pathologies and drug effects, especially benzodiazepines. It may be absent or reduced in areas of cortical damage. It is the dominant rhythm in patients who are alert or anxious or who have their eyes open.


gamma waves.
Gamma is the frequency range approximately 30–100 Hz. Gamma rhythms are thought to represent binding of different populations of neurons together into a network for the purpose of carrying out a certain cognitive or motor function.[2]
Mu ranges 8–13 Hz., and partly overlaps with other frequencies. It reflects the synchronous firing of motor neurons in rest state. Mu suppression is thought to reflect motor mirror neuron systems, because when an action is observed, the pattern extinguishes, possibly because of the normal neuronal system and the mirror neuron system "go out of sync", and interfere with each other.[38]

Front 11

iEEG

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intracranial electroencephalography. recorded from grids of electrodes implanted in the cortex of patients typically used to (precisely) locate the focus of epileptic seizures. MORE precise than EEG as it avoids the blurring effect

Front 12

Clinical uses of EEG

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A routine clinical EEG recording typically lasts 20–30 minutes (plus preparation time) and usually involves recording from scalp electrodes. Routine EEG is typically used in the following clinical circumstances:
to distinguish epileptic seizures from other types of spells, such as psychogenic non-epileptic seizures, syncope (fainting), sub-cortical movement disorders and migraine variants.
to differentiate "organic" encephalopathy or delirium from primary psychiatric syndromes such as catatonia
to serve as an adjunct test of brain death
to prognosticate, in certain instances, in patients with coma
to determine whether to wean anti-epileptic medications