RESUMO
Here, ERPs were employed to characterise the residual face processing of FE, a patient with extensive damage to the ventral temporal-occipital cortex and a dense prosopagnosia. Alarge N170 was present in FE and he performed well in tests of face structural processing. Covert recognition of the faces of personal acquaintances was demonstrated with P300 oddball experiments. The onset latency of the P300 effect was normal, indicating fast availability of covert memory. The scalp topography of this component in FE was different from that of the P3b, presenting a centro-frontal maximum. FE also presented larger skin conductance responses to familiar than to unfamiliar faces. The amplitudes of both the single-trial P300s and the SCRs triggered by familiar faces were positively correlated with the degree of person-familiarity that FE had for the poser. He performed at chance when asked to select between the face of a familiar person and that of an unfamiliar person on the basis of explicit recognition, whereas he selected more the previously known face if the forced choice was based on trustworthiness or a vague sense of familiarity. The results suggest that in FE, early face processing was relatively intact and covert recognition was fast. Neural structures involved in the processing of emotional or social cues possibly mediate the covert recognition present in FE.
RESUMO
INTRODUCTION: There is interference between emotional factors and intellectual output in the elderly, in whom there is a high prevalence of depression. Low output in conventional psychological tests may lead to false positive diagnoses of dementia. PATIENTS AND METHODS: We evaluated 48 patients aged between 50 and 84 years with regard to their emotional and intellectual state by means of the SCAN system. We also used a test designed by ourselves to implicitly examine memory. This consisted of a task involving naming objects. Six stimuli were repeated three times, seeking an effect of perceptual representation of 'priming' which facilitated later recall. RESULTS: The results showed that patients with dementia recalled 0 to 2 of the repeated stimuli, as a result of weakened priming. Meanwhile the non-demented persons, in spite of having other neurological disorders answered between 4 and 6 times. Multivariate analysis of the variance showed that measurement of memory, both implicit and explicit, allowed discrimination between patients with and without dementia. However, the explicit results were not independent of the effects of depression. CONCLUSIONS: Implicit measurements of memory were superior to direct or explicit measurements in the diagnosis of dementia. Patients with other degenerative conditions, such as Parkinsonism and multisystemic atrophy, had above average results. This corroborates the view that the neurological basis of this type of memory is not at subcortical level.