1. EEG Definitions EEG1: electroencephalogram—i.e., the “data”
EEG2: electroencephalographic—i.e.,
the “equipment”
EEG3: electroencephalography—i.e.,
the “technique”

2. states of consciousness

3. EEG Strengths Non-invasive Assesses “system-level” states
Millisecond time-scale resolution
Signals add linearly (i.e., the whole = the sum of its parts)
Low cost (relative to MEG, PET, fMRI)
Simple to use

4. EEG Weaknesses An Analogy...
Electrode more sensitive to proximal neurons
The CSF distorts/smears the electric fields/potentials
The skin, skull, and meninges distorts the E-fields
You’re blind to certain activity if it isn’t persistent/correlated in time/space

5. EEG Weaknesses—The Analogy
Stairwell  EEG
People  Neurons
Singing  Neural Activity
Reverberant Quality  CSF (distortion of scalp potentials)
Door  Skin, Skull, Meninges (distortion of scalp potentials)
Microphone  Electrode (proximity effects)
The EEG is a highly distorted and incomplete representation of true neural activity

6. EEG: The Technique

7. EEG: Continuous (Raw) Data

8. 10-20 system - electrodes positioning (monopolar montage)
…the reason why a cap is useful…

9. Origin of the signal - noninvasive measurement - direct measurement.
skull
CSF
tissue
MEG
EEG B
orientation
of magnetic
field
recording
surface
scalp
current
flow
- noninvasive measurement
- direct measurement.

10. requires sensitive detectors (low noise-high gain amplification)
How small is the signal?
Earth field
Intensity of magnetic signal(T)
EYE (retina)
Steady activity
Evoked activity
LUNGS
Magnetic contaminants
LIVER
Iron stores
FETUS
Cardiogram
LIMBS
Steady ionic current
BRAIN (neurons)
Spontaneous activity
Evoked by sensory stimulation
SPINAL COLUMN (neurons)
HEART
Cardiogram (muscle)
Timing signals (His Purkinje system)
GI TRACK
Stimulus response
Magnetic contaminations
MUSCLE
Under tension
Urban noise
Contamination at lung
Heart QRS
Biomagnetism
Fetal heart
Muscle
Spontaneous signal
(a-wave)
requires sensitive detectors (low noise-high gain amplification)
Signal from retina
Evoked signal
Intrinsic noise of SQUID

12. origin of EEG signals (1)
afferent inputs
excitatory
pyramidal cortical
neurons +
current source -
current sink + -
dipole
amplifier
macroscopic
depolarization
~V
ref

13. origin of EEG signals (2)
resistance
low conductor

14. from neurophysiology to electrophysiology (1)
What is recorded with EEG?
synchronized neural populations - transmembrane currents of pyramidal neurons apical dendrites
Why not action potentials?
spike vs. dendritic currents - synchronization
dendritic electrical dipoles vs. AP propagation - cancellation
spike rate vs. dendritic time constant - duration

15. what is being recorded and what is not
Closed-fields
cancellation
Open fields

16. EEG: Continuous (Raw) Data

17. Epoching

18. Signal Averaging

19. Emergence of the ERP

20. The ERP: Amplitude and Latency

21. The Broadband Response

22. Filtering: Filter Types

23. induced vs.phase-locked responses BOTH are stimulus-driven
induced rhythm vs. locked response

24. Characteristic Auditory Evoked Related Potentials

25. Hillyard

26. Updating, transient memory
spectral EEG
Characteristic Bands
Frequency
Range
Correlates (?)
Delta 
2 – 4 Hz
sleep
Theta 
4 – 7 Hz
memory
Alpha 1
8 – 10 Hz
sensory, attention
(more A) 2
10 – 12 Hz
(more V)
Beta 1
12 – 18 Hz ? 2
18 – 25 Hz
Mu/motor
Gamma
Phase-locked 
25 – 35 Hz
Updating, transient memory
Induced 
35 – 80 Hz
Cognitive binding

27. •power spectrum •bandpass filtering

28. The 40-Hz “Driven” Response (BPF)

29. Driven Responses

30. The Evoked Gamma Band Response

31. Evoked GBR Properties Total Duration: ~100 ms Cycle Duration: ~ 25 ms
Spectral Energy Range: ~25-75 Hz
Latency: ~ 50 ms
Amplitude: < 1 uV
Generator Source: Cortex (MEG Studies)
Generated by stimulus onset