Princípios EEG

Question 1

Frequências

Answer 1

• 8-13 Hz = alfa (vigília, mais proeminentes com o fechamento ocular)
• > 13 Hz = beta (pode ser aumentada po BZD, barbitúricos, sonolência e sono leve)
• 4-7 Hz = teta (aumentam com concentração, durante tarefas mentais, hiperventilação e sono)
• < 4 Hz = delta (sono, bebês e idosos)

Question 2

Conceitos Básicos

Answer 2

• sensitivity = gain - microvolts per millimeter
• epoch = time
• Posterior dominant rhythm (PDR) - relaxed and with eyes closed
  Variations: temporal alpha (older patients), frontal alpha (drugs, anesthesia or following arousal from sleep) - if invariant and unreactive to any stimuli = pathological; alpha coma pattern
• 10-20 electrode site placement strategy -> between nation and inion // and between auricular positions

Question 3

Achados Normais

Answer 3

• eye closure: eye is a dipole; with Bell phenomenon, cornea approaches frontal region -> positive potential (negative wave) followed by negative
• Mu rhythm -> alpha-range-frequency over central head regions, can be uni ou bilateral, prominent during drowsiness, reactive to movement (attenuate with thumb wiggle)
  Can be seen in 20-40% normal adults
• Lambda waves -> elicited by pattern viewing; positive wave occipitally predominant
• hyperventilation -> minimal change in adults
  In children, adolescents and young adults -> normal finding = prominent high-amplitude ou hyper-synchronous background-slowing = “build-up”
• photic stimulation -> no change or symmetrical “photic driving response”= entrainment of background alpha rhythm to the same harmonic frequency variant of administered flashing lights (posteriorly predominant)
  Can be similar to ERG artifact -> retinal depolarization - more anterior and can be blocked by covering one eye

Question 4

Sono

Answer 4

• N1: V-waves, slow eye movement
• N2: K (knock) complexes = suppression of environmental sounds; sleep spindles (consolidation of memory - thalamus-cortical connections)
• SWS = repair: delta > 20%; slow frequency waves
• REM: desynchronized, REMs, sawtooth waves - making connections and replaying scenarios related to episodic memory