2. Prepare a soft silastic cannula about 10 cm long (a convenient source is a butterfly scalp vein needle set; cut off the butterfly and needle).

3. Obtain appropriate informed consent. This is a painful procedure. We find that female subjects are often better able to tolerate the discomfort. Vertigo and nausea are common outcomes (although I do not think that it helps to emphasise this in advance). I have learnt the acupressure points for nausea and the application of pressure to these points has helped many subjects after the stimulation procedure.

4. Have the subject recline on a couch or an easy chair so that the coronal plane of the head is inclined about 30 deg from horizontal (Crown up...chin down) while the midsagittal plane is vertical. Have the subject look at the ceiling and avoid extreme deviations of gaze.

5. Attach the cannula to a 50 ml syringe full of ice water. (I usually leave the syringe and cannula immersed in ice water until stimulation starts).

6. Place a towel and a small receptacle (e.g. kidney tray or specimen jar) under the chosen ear to catch the run off.

6. Gently feed the cannula into the chosen canal until it reaches the tympanum. Warn the subject what you are about to do and have them signal you when they feel the cannula hit the drum (there is a loud sudden feeling). The subject will usually show some sign of this (flinching, a vocalisation).

7. Gently expel the ice water, watching the eyes for nystagmus (there is a set of Frenz goggles with inbuilt magnifiers and lights that are specifically designed for theis purpose. The goggles also have the beneficial effect that they blur the subjectís visual world and thereby prevent the vertigo...at least until the goggles are taken off).

8. When nystagmus appears, fast phase to the opposite side syringed, keep syringing for a minute or two.

9. Wait until the nystagmus has stopped before allowing the subject to get up and move to the experimental situation.

(Note that this procedure is routinely used in many clinics and medical schools around the world. Close enquiry reveals that clinics using cold water tend to avoid stimulating the left ear. While this is a very common observation, it is rare in my experience for there to be any conscious recognition of the reasons for the entrenched practice.

In my own study of university students I found that word quickly circulated about the negative mood effects of Left ear cold water stimulation, with the result that many students would refuse stimulation of this side. When a German hospital group suggested that I may have been exaggerating the mood consequences of left ear stimulation, I discoverd that while this hopital always stimulated the left ear, there was a crucial difference in their procedure that  brought them into line with my interpretation...........they used warm water for irrigation....which stimulates the ipsilateral hemisphere! In other words, there seems to be a universal experience that Right hemisphere stimulation has negative mood effects compared with Left hemisphere mood effects.

Warm water stimulation is more pleasant for the subject (setting aside the mood effects of hemispheric activation). But warm water stimulation is also less conveniently carried out than ice water stimulation. If warm caloric stimulation is used, one has to bear in mind that polarity is reversed....right ear warm caloric stimulation will activate the Right hemisphere with the subject in the posture I described above).
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