THE EFFECT OF ANXIETY INDUCTION ON THE REGIONAL UPTAKE OF TC-99M-EXAMETAZIME IN SIMPLE PHOBIA AS SHOWN BY SINGLE-PHOTON EMISSION TOMOGRAPHY(SPET)

Ten patients suffering from DSM-III-R simple phobia were studied under two conditions: (a) while listening to a 4 min relaxation tape, and ( b) while listening to a 4 min audio tape describing exposure to the ph obic stimulus. During each condition, subjects were injected with Tc-9 9m-Exametazime, a marker of regional cerebral blood flow. Subjective a nd psychophysiological measures indicated a marked effect of the anxie ty induction procedure. Ratio analysis of the SPET data revealed reduc tions in tracer uptake largely confined to posterior cerebral regions bilaterally. Analysis of brain regions of interest normalised to the w hole brain slice showed reductions confined to right temporal/occipita l regions. In general there was no clear association between subjectiv e and physiological variables and changes in regional uptake of tracer as a consequence of the anxiety induction procedure. The changes in t racer uptake were dissimilar to those previously reported for other co gnitive activation paradigms, providing some reassurance that those fu nctional brain changes were not artefacts of non-specific changes in s tate anxiety. These posterior brain changes may reflect alterations in activation of the GABA/benzodiazepine complex.