Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
1
XLIII. Electroencephalography
XLIV. Evoked potentials
XXXIII. Estimation of visual acuity
Physiology I – practice
Autumn, week 10-12
© Kateřina Fialová

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
2
Electroencephalography (EEG)
̶Method used for the registration of electrical potentials of the brain
̶Hans Berger (1929)
̶
̶Scalp EEG
̶Electrocorticogram (ECoG)
̶Stereoelectroencephalogram (SEEG)
̶
̶Macro EEG
̶Micro EEG
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Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
3
Electroencephalography
̶Placement of electrodes: system 10-20
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Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
4
Electroencephalography
̶Attachment of electrodes during scalp EEG
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www.dreamstime.com

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
5
Electroencephalography
̶Alpha rhythm
̶Frequency 8-13 Hz, noticeable with eyes closed, in the awake, healthy and mature brain, especially
in parietooccipital lobes
̶Beta rhythm
̶Frequency 14-30 Hz, noticeable with open eyes, sometimes constantly over the frontal area. The
phenomenon of suppression of the alpha rhythm by opening eyes – alpha attenuation reaction (AAR).
̶Theta rhythm
̶Frequency 4-7 Hz, noticeable in children, in healthy adults only during shallow sleep stages
̶Delta rhythm
̶Frequency 1-3 Hz, in neonates and infants,  in healthy adults only during deep non-REM sleep

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
6
EEG waves

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
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EEG record - example

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
8
Evoked potentials (EP)
̶Electrical manifestation of brain activity triggered by external sensory stimulus
̶Evaluation of the functional state of the nerve pathway
̶Types of EP:
̶VEP (visual)
̶AEP (auditory)
̶SEP (somatosensoric)
̶MEP (motoric)
̶SSEP (stable)
̶ERP (cognitive)
̶

Adobe Systems
Department of Physiology, Faculty of Medicine, Masaryk University
9
Evoked potentials
̶Wave p300 (mean latency 300 ms)
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Adobe Systems
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Visual acuity examination – optotypes
Snellen
Landolt
Pflüger

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Visual acuity examination – optotypes
̶Physiological background:
̶the eye can distinguish 2 points as 2 points when the light rays from these two points fall on the
retina at an angle of 1 arc minute
̶
̶Examination:
̶Each row of optotypes has a number on the side that expresses the distance from which the rays
from 2 points (for their differentiation and correct reading of the sign) fall on the retina at an
angle of 1 arc minute
̶The most frequently used distance is 5 m
̶The result of the examination:
̶Visus – we write it as a fraction: the numerator is the distance from which we are examining, the
denominator is the number of the line read without error
for the right eye ….VOD = 5/5 …….. healthy eye, good visual acuity
for the left eye…… VOS = 5/10 …. an eye with impaired visual acuity
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