EEG is a non-invasive method to measure electrical activity in the brain. It can help in psychiatry by ruling out physical causes for psychiatric symptoms, aiding in differential diagnosis and treatment selection, and predicting prognosis. EEG findings can provide clues to underlying conditions in disorders like schizophrenia, mood disorders, OCD, panic attacks, dementia, delirium, and substance abuse. However, EEG findings in psychiatry are often nonspecific and EEG has limitations due to only recording cortical activity from the scalp. It currently has no definitive role in diagnosing Axis I or II psychiatric disorders.

1. EEG IN PSYCHIATRY
- DR. DEEPIKA SINGH,
2ND YR RESIDENT,
DEPT. OF PSYCHIATRY,
GSMC & KEM HOSPITAL

2. WHAT IS EEG
Electroencephalography is non-invasive method for
investigation of electrical activity of brain.
Used to measure cortical neuronal activity through
detection of potential differences across scalp

3. HOW IT CAN
PSYCHIATRY:
HELP
IN
To rule out physical or
neurological causes before
making psychiatric diagnosis
May help in
diagnosis
and
selection
May help
prognosis
in
differential
treatment
predicting

4. OVERVIEW
How EEG is recorded
Normal EEG findings
Factors affecting EEG
Application of EEG
EEG in psychiatric disorders

5. How to record EEG
Electrode Placement
•10-20 percent system is used
•This system measures the distance
between readily identifiable
landmarks on the head and then puts
electrodes at 10 percent or 20 percent
of that distance in an anteriorposterior or transverse direction
•Even number for right hemisphere
and odd number for left hemisphere.

6. How to record EEG
Sensitivity:
Frequency
filter
setting
The amplification used in EEG recording
can be adjusted to visualize low-voltage
signals. Accepted standards across
laboratories for most recordings are
7microvolts for each millimeter of pen
deflection.
For clinical purpose frequency falls within
the range of 0.5 to 40.0 or 50.0 Hz. Setting
frequency filter appropriately helps to rule
out frequencies generated by non brain
sources.

7. SPECIAL ACTIVATIONS:
HYPERVENTILATION: Done with eyes closed and over breathing
through mouth. It is especially effective in eliciting Petit Mal
Seizure pattern.
PHOTIC STIMULATION: Done by placing an intense strobe light 12
inches in front of subject’s closed eyes and flashing at frequency
ranging from 1 to 50 Hz. More useful in detecting psychiatric
disorders
SLEEP: More useful in eliciting paroxysmal discharges
SLEEP DEPRIVATION: can be useful in eliciting paroxysmal
discharges

8. BRAIN WAVE
It is the difference in electric potential measured
between any two EEG electrodes which fluctuates
rapidly, many times a second leading to a “squiggly
line”.

9. NORMAL EEG TRACING

10. NORMAL EEG TRACING
ALPHA RHYTHM
•Highly rhythmic with a frequency range from 8 to 13 Hz
•Constitute the dominant brain wave frequency of the normal eyes-closed
wake EEG.
•Alpha activity is also most prominent over the posterior cortex, particularly
the parietal, posterior temporal, and occipital cortex
•Occipital region being best suited to show this activity..
•Alpha activity is abolished by eye opening, and alpha activity also
disappears with drowsiness and sleep.
•Alpha activity can be highly responsive to cognitive activity, such as focused
attention or concentration. Example ,alpha can be blocked or attenuated by
engaging in visual imagery, numeric calculation etc.

11. NORMAL EEG TRACING
BETA RHYTHM
•Frequencies that are faster than the upper 13 Hz limit
•They are common in normal adult waking EEGs
•Particularly seen over frontal-central regions.
•The voltage of beta activity is also almost always lower
than that of activity in the other frequency bands
described previous

12. NORMAL EEG TRACING
THETA RHYTHM
•Waves with a frequency of 4.0 to 7.5 Hz
•It is a prominent feature of the drowsy and sleep tracing
•Although theta activity is limited in the waking EEG,
•A small amount of sporadic, arrhythmic, and isolated
theta activity can be seen in many normal waking EEGs,
particularly in frontal-temporal regions
•Excessive theta in wake, generalized or focal in nature,
suggests a focal pathological process

13. NORMAL EEG TRACING
NORMALRHYTHM
DELTA EEG TRACING
•Delta activity (equal to or less than 3.5 Hz) is not present in the
normal waking EEG
•Is a prominent feature of deeper stages of sleep.
•The presence of significant generalized or focal delta in the wake
EEG is strongly indicative of a Pathophysiological process
GAMMA RHYTHM
Evidence has been provided that high frequency oscillations
within the gamma band (>30Hz) reflect mechanisms of
cortical integration

14. FACTORS AFFECTING EEG
Changes with Age
•Preponderance of irregular medium- to highvoltage delta activity in the tracing of the infant
•EEG activity gradually increases in frequency and
becomes more rhythmic with increasing age
•Rhythmic activity in the upper theta–lower alpha
range (7~to 8 Hz) can be seen in posterior areas by
early childhood
•By mid-adolescence EEG has the appearance of
an adult tracing.

15. FACTORS AFFECTING EEG
Changes with sleep
•The rhythmic posterior alpha activity of the
waking state subsides during drowsiness and is
replaced by irregular low-voltage theta activity.
•As drowsiness deepens, slower frequencies
emerge, and sporadic vertex sharp waves may
appear at central electrode sites
•The progression into sleep is marked by the
appearance of 14-hz sleep spindles (also called
sigma waves)
•Which, in turn get replaced by high-voltage
delta waves as deep sleep stages are reached.

17. FACTORS AFFECTING EEG
Artifacts
•Artifacts are electric potentials of
nonbrain origin that are in the frequency
and voltage range of EEG signals and that
are detected by scalp electrodes.
•Common artifacts include eye blinks,
vertical or lateral eye movements, muscle
potentials from jaw clenching, perspiration
artifacts (galvanic skin response), and head
movement.
•Automatic artifact rejection programs
exist for some computerized research
applications, but they have not strongly
entered the clinical arena.

18. FACTORS AFFECTING EEG
Changes with Medications
•Benzodiazepines always generate significant
amount of diffuse beta activity.
•The highest proportion of abnormal EEGs occurred
with Clozapine followed by lithium
•Lithium is capable of causing abnormal generalized
slowing, paroxysmal activity, or both, including a 10
percent incidence of toxic delirium
•The highest incidence of EEG abnormalities was
associated with clozapine >olanzapine > risperidone,
fluphenazine >haloperidol. There was no EEG
abnormalities seen with quetiapine.

19. EEG IN PSYCHIATRIC DISORDERS
Currently there is no accepted indication of EEG in diagnosing either axisI or II disorders

20. :
EEG IN
SCHIZOPHRENIA
•EEG abnormalities have overall frequency of 20-60%.
•May predict conversion of subjects at risk into
psychosis
•Their presence indicate worse outcome.
•It helps to identify those with comorbid epileptic
condition.
•Epileptiform variants are found in affective disorder
with psychotic feature and schizoaffective disorder but
not in schizophrenia.
EEG in Catatonia
EEG abnormalities in schizophrenia :
•Dysrhythmia
•Spike and spike –and- wave
•Generalized slowing
EEG can help to find out specific
etiology of catatonia as catatonia
may be caused by several organic
disorders

21. EEG IN MOOD DISORDERS:
•Abnormal EEG found in 20-40% of patients
•In bipolar patients increase in beta activity and
decrease in alpha activity noted
•Acute mania has increased posterior slow rhythms
•An asymmetric alpha activity in left frontal region
has been reported in depression
•Unipolar and bipolar depression have sleeping EEG
recording abnormality i.e., short REM latency,
increased REM density and reduction in stage 3 and
4 of sleep.
•Frequent increase sharp spikes,6/sec spike in
patients with suicidal ideation

22. EEG in OCD:
EEG in OCD
EEG abnormalities present in varying frequency]
Widespread increase in slow waves reported
EEG in Panic
disorders
•25-30% of panic attack patients have
EEG abnormalities
•Helps in differentiating panic attack from
epilepsy
•focal paroxysms of sharp wave activity
coinciding with spontaneous onset of
panic attack is noted

23. EEG in
DEMENTIA
•Increased slow activity and
decreased mean frequency are
correlated
with
cognitive
impairment and measures clinical
severity of Alzheimer's dementia
•The amount of theta activity shows
the best correlation with cognitive
deterioration
•Increased delta appears to be
correlate of severe advanced
dementia, occurring subsequent to
increased theta

24. EEG in
DELIRIUM
•Hallmark of delirium usually is the slowing of
the background EEG rhythm
•This is positively correlated with the degree
of severity of the condition
•Exception is in delirium tremens (DT), which
usually shows a normal EEG record with fast
rhythms.
•Delirium accompanying the neuroleptic
malignant syndrome shows only a mild diffuse
slow wave.
•Delirium can be differentiated from
dementia, and the significant factors are an
increased theta activity

25. EEG in Alcohol and
Substance Abuse
• Acute Alcoholic intoxication shows slowing in the EEG, seen
as decreased alpha frequency and abundance & increased
amount of theta, and even some generalized delta rhythm
• These slow waves have a relationship with the degree of
intoxication. The extent of the disturbance of consciousness
is related to the amount of slow activity
• Reports have appeared of an increased beta (relative
power) in alcohol dependence
• Increased alpha power, especially in anterior regions, has
been reported in withdrawal, as well as after acute exposure
to cannabis

26. PROBLEMS WITH EEG IN
PSYCHIATRY
•Nonspecificity of findings
•Problem with placing electrodes in
psychiatric patients
•Limitations of scalp EEG i.e.,Only onethird of brain can be covered,EEG
activity of sub-cortical area can’t be
recorded
•Currently there is no accepted
indication of EEG in diagnosing either
axis-I or II disorders