text one, chapter four: part one

       the cheeping of a chick:
             an example of information and action
              emerging out of the nervous system

I first encounter the concept of non-linear oscillation
in the 1960s during research into the neural organization
of an expressive behaviour -
to wit, the cherpings of the chick.
        
for my sins I tortured baby chicks
to see what makes them tick
to see how they make their noises
I jolted their brains with electricity
and took them apart.
Physically, for the chick,
three things are involved in making a sound.

1 ~ it has to blow (expire forcefully) air
over a membrane which then vibrates.
this membrane is called the syrinx;

2 ~ it has to maintain air-pressure
in the thoracic air-sac in which the syrinx sits.
It does this by opening and closing a valve; and
3 ~ it modulates the tension of the syrinx and hence
the pitch/tone of the called note
by the contraction on a pair of muscles
(the extrinsic syringeal muscles).

The chick has the following repertoire of calls:

If you startle it it trills

if you grab it, it trills (because it's startled)
and then it "shrieks"and then it peeps.

If it is (happily) interested in something
it does calls an excited ascending tweet-tweet

and if it is just tootleing along
it does another sort of twittering

if it is distressed it peeps

In its twittering
      
we see that it is calling portions of its trill,
and we see that when it is happily interested
it calls the ascending portions of the trill,

but when it is distressed it calls the descending portion.
To do this the oscillating motor out put to
the syringeal muscles and to the air-sac valve
must be more or less matched for frequency
but must vary/shift in phase.
There are occasions on which we can see
these two forms/signals manifest in the calls
           
It appears as if the air-valve.signal on occasion can
spill over into the syringeal muscle signal.
this spill over is quite regularly seen
in the excited tweet-tweet

So a continuum from approach/interest/(pleasure?)
through to avoidance/distress
is manifest in the chicks calls
as a shift in relative phase
between the two cycles,
one driving the syringeal muscles
and another driving the air-valve.
 
    
We see a second continuum in the chick vocal repertoire.
When we evoke calls by electrically stimulating
a particular area of the brain
(the Call Motor Area of the Optic Tectum overlaps,
but is not confined to, the Lateral Mesencephalic Nucleus)
we get a series of calls that segregates into bouts
   
                              (this is in the anaesthetised animal)
and we see the peep emerge
the same peep we see in the unhappy chick

            
so here we see breath and we see "quenching"
(as breath grows large the trill modulation is blown out)

the repertoire maps out in two dimensions
(plus a single step seen in the startle:trill)
y) force of expiration / exertion
x) approach / avoid,  pleasure / distress,  nice / nasty
z) rate of arousal (the single step seen in the startle:trill)

Judgement: does approach / avoid,  pleasure / distress
imply, represent, reflect
a judgement?
Is judgement (here in our baby chick) manifest in a phase shift?
(Is judgement a  quality solely of mind?
don't machines make judgements and decisions?)

I'm also reminded of Madame Blavatsky.
In my doctoral thesis I ventured (in a footnote)
that the chick's repertoire smacked of Madame B.
and her good and bad vibrations

see: Norman Allan's doctoral dissertation
"The Central Control of Vocalization
in the chick of the Domestic Fowl."
Sussex University: 1971

Chapter 4: neural nets

       email:normanallandr@yahoo.ca