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The method of comparing premorbid versus current intellectual ability has become established clinical practice in the differential diagnosis of dementia versus depression. Recently, Schlosser & Ivison (1989) suggested that the comparison of premorbid ability versus current memory function may offer a more sensitive method of assessing early dementia. In the present study, a variety of within-subject discrepancy analyses comparing premorbid estimates with current measures of memory and intellectual functioning were compared across three groups: patients with dementia of the Alzheimer type, patients with major depression and healthy controls. The results revealed that, while mean group differences were easily demonstrated, the overlap between Alzheimer and depressed patients was large. It is concluded that none of the simple neuropsychological discrepancy analyses examined in the present study can be recommended for use in clinical practice for the differential diagnosis of dementia from major depression.

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Day-time plasma beta-endorphin/beta-lipotrophic hormone (beta-ENDO/beta-LPH), ACTH and cortisol have been determined in 26 patients with major depression and 25 controls. beta-ENDO/beta-LPH and cortisol were significantly elevated in patients, while ACTH was not. Cortisol levels were significantly negatively correlated with age in controls as were beta-ENDO/beta-LPH and ACTH. In patients, by contrast, cortisol levels were positively, albeit not significantly, related to age. Peptide levels were not related to age in the patient group. Instead, beta-ENDO/beta-LPH was negatively correlated with clinical ratings of symptom severity in patients and positively associated with an acute psychosocial precipitant. The findings cast further light on beta-ENDO/beta-LPH as a measure of hypothalamic-pituitary over activity in depressive illness. A negative association with symptom severity suggests that beta-ENDO/beta-LPH responses are, like those of ACTH, down-regulated in the course of depressive illness.

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The uptake, at rest, of 99mTc-exametazime into different brain regions was compared using SPECT for 20 elderly subjects with major depressive disorder, 20 with Alzheimer-type dementia, and 30 age-matched normal volunteers. Uptake was referred to calcarine-occipital cortex as a reference sensory area. Cross-sectional differences between the three groups were highly statistically significant, but reflected primarily the reductions in cortical uptake in the Alzheimer group. A detailed comparison of depressed patients and controls identified decrements in anterior cingulate, temporal and frontal cortex and in caudate and thalamus in men only. These decrements were correlated with impairment of performance on a trail-making task, but were also associated with continuing treatment with antidepressants or benzodiazepines. However, most depressed patients had quantitatively normal scans for posterior parietal association cortex, and this suggests that SPECT may find a limited role in the differential diagnosis of depression and dementia. The reduced brain function in some depressed patients may parallel the findings from studies of brain structure in elderly depressives; there was between good outcome at 6-18 months and increased tracer uptake in subcortical areas.

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Ten patients with Alzheimer-type dementia and nine age-matched normal controls were examined with SPECT, using split-dose 99mTc-labelled exametazime. The baseline condition involved repetition of the word 'yes' or 'no'. The activation condition involved recognition (indicated by a 'yes' or 'no') of words from a previously learned list presented along with distractor words. Patients who performed this task successfully were selected, and efforts were made to match the patients with controls according to their performance on the task, although this was not fully achieved. Uptake of 99mTc-exametazime was estimated at baseline and during the word-recognition task for predetermined regions of interest drawn from a standard neuroanatomical atlas. The baseline task appeared to normalise tracer uptake for frontal, temporal and parietal cortex in the patient group. However, during the recognition task, controls but not patients showed activation effects. These were most prominent in dorsolateral frontal cortex and adjacent anterior cingulate cortex. Among patients, successful performance was correlated with activation of dorsolateral frontal and parietal cortex on the left side. The results confirm the central role of frontal mechanisms in a recognition memory task. The study highlights some of the difficulties of using cognitive challenge tests in clinical groups.

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The effects of a single oral dose of the acetylcholinesterase inhibitor velnacrine maleate on word and object recognition memory and regional uptake of 99mTc-exametazime were examined in patients with Alzheimer's disease. Word recognition memory was marginally improved 2 h after 75 mg velnacrine. With the same dose of velnacrine a relative increase in superior frontal uptake of 99mTc-exametazime was shown with single photon emission computed tomography (SPECT). This suggests increased regional perfusion and metabolism as a consequence of cholinergic stimulation. The effect did not co-vary with the degree of memory improvement, but, instead, more cognitively impaired patients showed a greater increase in tracer uptake after velnacrine, suggesting cholinergic hypersensitivity in the brains of Alzheimer patients.

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