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EEG Lab

+EEG

n In 1929, Hans Berger attached electrodes to the scalp of human subjects and recorded systematic fluctuations in voltage over time

n These fluctuations are called the electroencephalogram (EEG)

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+EEG

n Result of postsynaptic potentials from many thousands of neurons

n These potentials spread as they travel from the brain to the scalp

n The maximum voltage on the scalp may be very far from the site of the neural activity

+EEG

n  Synchronized oscillations n  Synchronized activity over a

network of neurons

Epilepsy

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+EEG Waves n  Beta

n  Asynchronous waves n  18-30 Hz, lower

amplitude n  Awake and directed

attention

n  Alpha: 10-12 Hz n  Awake but at rest n  Stage 1 NREM

n  Theta n  4-7 Hz; Large amplitude n  Stage 2 and 3 NREM

n  Delta n  Slow waves, < 4 Hz

frequency n  Stage 3 and 4 NREM

+How do we quantify our data?

n  Integration: RMS (Root Mean Squared) n  Square:

n  Square Samples 1-30

n  Mean:

n  Average all of those points

n  Gives you one number for that whole window

n  Smoothing

n  Root:

n  Take the square root of that number (to scale it back down)

n  Repeat for the next 30 samples

n  Gives you a running window – absolute value average