And so long as we're at it, here's one more weird eye-movement thing associated with brains, or lack thereof. Cold calorics testing-- used to do this all the time with potential organ donors. Also had the interesting experience of feeling what this is like when my doc irrigated my ear with alcohol....cooooolllldddd.... and I felt my eyes jerrk uncontrollably. Weird.
From the Wikipedia:
It is commonly used by physicians, audiologists and other trained professionals to validate a diagnosis of asymmetric function in the peripheral vestibular system. Calorics are usually a subtest of the electronystagmography
(ENG) battery of tests. It is one of several tests which can be used to test for brain stem death.
One novel use of this test has been to provide temporary pain relief from phantom limb pains
in amputees 
It can also induce a temporary remission of anosognosia
, the visual and personal aspects of hemispatial neglect
, and other consequences of right hemispheric damage.
 Technique and results
Cold or warm water
or air is irrigated into the external auditory canal
, usually using a syringe. The temperature difference between the body and the injected water creates a convective current in the endolymph
of the nearby horizontal semicircular canal
. Hot and cold water produce currents in opposite directions and therefore a horizontal nystagmus in opposite directions.
In patients with an intact brainstem:
- If the water is warm (44°C or above) endolymph in the ipsilateral horizontal canal rises, causing an increased rate of firing in the vestibular afferent nerve. This situation mimics a head turn to the ipsilateral side. Both eyes will turn toward the contralateral ear, with horizontal nystagmus to the ipsilateral ear.
- If the water is cold, relative to body temperature (30°C or below), the endolymph falls within the semicircular canal, decreasing the rate of vestibular afferent firing. The eyes then turn toward the ipsilateral ear, with horizontal nystagmus (quick horizontal eye movements) to the contralateral ear.
- Absent reactive eye movement suggests vestibular weakness of the horizontal semicircular canal of the side being stimulated.
In comatose patients with cerebral damage, the fast phase of nystagmus will be absent as this is controlled by the cerebrum. As a result, using cold water irrigation will result in deviation of the eyes toward the ear being irrigated. If both phases are absent, this suggests the patient's brainstem reflexes are also damaged and carries a very poor prognosis.
Mnemonic One mnemonic used to remember the FAST direction of nystagmus is COWS
old water = FAST phase of nystagmus
to the side O
pposite from the cold water filled ear
arm water = FAST phase of nystagmus to the S
ame side as the warm water filled ear
In other words: Contralateral
is applied and ipsilateral