CASSIDY-FELTGEN at worldnet.att.net:
>Can anyone tell me what mechanism causes the rapid, brief headache pain
>when a cold substance is ingested quickly? Related to this is my
>question regarding the brain not sensing pain during brain surgery, but
>a person's perception of headaches as localized pain within the brain?
>Is this a paradox or are headaches not actually occuring within the
I'll take a swing at this.
Intracranial pain is a regular part of life. The pain signals
originate in the meninges, which are several protective layers
sandwiched between the brain and the cranium. In brain surgery, local
anasthetic is injected into the meninges before an incision is made,
or perhaps general ansthetic is used at first and local anasthetic is
injected after the incisions are made, but before the patient returns
to consciousness (I am Not A Doctor).
My guess about brain freezes (ice cream scream) is that the meninges
above and behind the mouth, on the other side of the cranial
"bulkhead," are being cooled to a temperature that alarms them, and
that they are set up to fire off pain signals at these temperatures,
as a warning that continuing whatever you're doing will lower a
portion of the brain to a temperature it is uncomfortable with.
To my knowledge, there are no sensors inside the brain itself that
upon activation cause sensation of pain (though of course there are
non-sensory structures that upon appropriate (inappropriate?)
activation cause an arbitrarily grave sensation of pain). There are,
however, non-pain sensors in the brain itself, for blood chemistry and
temperature, and for light (very very ancestral cells in the pineal
gland). These sensors can not be directly included in the conscious
experience, but dysfunction in certain of them is a life-threating