Biomedical Engineering Reference
In-Depth Information
6.1 AWARENESS AND ALERTNESS
Awareness can be defined as a state of mind in which we are conscious
of the here and now situation. Alertness is the conscious focus on a
specific task or stimulus. Alertness always involves selection within
sensory perception; some stimuli get full attention, others are ignored.
The brain consists of about 10 billion cells that have the special ability
of communicating with each other. This communication is done batch
wise; all the brain cells in an area send their signals at the same time. The
amount of batches per second is an indicator of the speed of the commu-
nication. Awareness is strongly related to this speed, which on average is
12 Hertz
1
but can vary from 0.5 to 80 Hertz. Although there is a ten-
dency for the speed of areas in the brain to more or less follow each
other, it often happens that that some parts are more active than others,
depending on which areas need to be very active. The brain uses differ-
ences in frequency to distinguish brain functions in the same way that we
tune in on a certain radio frequency. Once we have tuned in on one fre-
quency, we can focus on the messages of that particular sender.
Every activity has is own optimum speed level. In the following
schedule, you can find the brain frequencies during different activities.
Brain Frequency
in Hertz
Main activity
Level of awareness
0.5 to 4
Deep sleep
Absent
Rapid eye movements
4 to 8
Normal sleep
Almost absent, only conditioned for
specific noises, e.g., a crying child
8 to 13
Relaxed mode, comfort zone
During breaks and meditation
Normal
Good for absorbing information and
learning (toolbox meeting)
13 to 30
Normal working mode
High
High-risk detection (LMRA)
30
Working under high stress
Normal to low, tunnel vision
1
Incidentally also at moments of
brilliant ideas
1
The brain speed is measured by an EEG, electroencephalography, an external monitoring of
brain activity by the use of multiple electrodes placed on the scalp. The EEG mostly measures the
activity of the neocortex, the modern brain, because this cortex lies closest to the surface of the
brain. The EEG cannot measure any deeper activity from the emotional and basic brain.
