The principal difficulty with sleep
recordings, is that unlike during wakefulness, the neurons' activities
are not sustained, but there are many "pauses". These pauses are
called "down states" and they occur during the slow waves produced by
the brain during sleep. An example of this activity is depicted in
the following raster:
||Figure 1: Raster of excitatory neurons during slow-wave sleep.
One can see very well vertical bands, which shows that there are many
silences in the activity. The neurons were mapped on the C-major diatonic
To listen to that example, click on
"Sleeping Bells". One can hear very well the intermittent
character of the neuronal spikes (compare with the similar sound during
Even if this intermittency may seem
problematic at first sight, it can be exploited to obtain nice musical
effects. For instance, one can play the excitatory cells above to a
slow sound. To listen to that example, click on "Sleeping Waves".
This gives a clear impression of slow "waves", and indeed they are entirely
generated by the neuronal activity of a sleeping subject!
We can also use sounds intermediate
between fast and slow, which allow us to better hear the melody played by
neurons. To listen to that example, click on "Sleeping Mid-Waves". These are all generated from the
same set of excitatory neurons.
Activity of inhibitory
neurons during slow-wave sleep
The intermittent character of neuronal
discharges during sleep also applies to inhibitory cells. For example,
pooling together 4 inhibitory cells (chosen for their rhythmicity), gives the
||Figure 2: Raster of 4 inhibitory neurons pooled together during
To listen to these cells, played on
a bass, click on
"Sleeping Bass", or played on a drum kick:
In this example, one can clearly hear
that the intermittent character is also present in inhibitory cells, but it
does not alter their rhythmic capabilities.
As above for excitatory cells, one can
also use inhibitory neurons to drive slow sounds. For example, one can take
a subset of 5 inhibitory neurons, corresponding to the raster:
3: Raster of 5 inhibitory neurons in a sleeping human subject, mapped
on the C-major diatonic scale.
To play those cells on the same
slow "Woo-Woo" sound considered in Wake Beats, click on
The same can also be done for a
different subset of inhibitory neurons, corresponding to the raster:
4: Raster of 11 inhibitory neurons in a sleeping human subject
(C-major diatonic scale).
In the latter case, however, the
neurons were mapped to a minor scale. To play those cells on the
"Woo-Woo" sound, click on
"Sleeping Minor-Woo". Here again, one can hear very well
the intermittent character of the neuronal discharges during sleep.
Assembling it all
Let us now listen to the full song,
where the first 2 minutes were made from the sounds described above:
By listening to this song, one can
clearly hear that the intermittent character of neuronal discharges is well
coordinated between cells. This coordination makes the music coherent because
all sounds are modulated by the same envelope, this envelope corresponds to
the "slow waves" of sleep, which we hear musically.
Similar to the Wake Beats song, the activity of the
different neurons is strictly respected, as well as the respective
timing of the spikes of the different cells, but here for the whole
duration of the song. In the last part of the song (after the
second minute), different slow sounds were used to further augment
the impression of "slow waves". Here again, all the music comes
from neuronal activity.
Alain Destexhe and Luc Foubert,
UNIC, CNRS, Gif sur Yvette, July 2016.
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