This approach, describing the 14 years preceding dementia, provides a clear illustration of the particularly long and progressive prodromal phase of AD, and shows the successive emergence of cognitive deficits, depressive symptoms, and functional impairment during this phase.

Despite the numerous studies focused on priming performances in Alzheimer's disease (AD), the question of whether word-stem completion priming persists in AD is still prone to controversy. Methodological variations, such as encoding instructions, have been proposed to explain the discrepancy of word-stem completion priming results in AD. We conducted a meta-analysis on 678 AD patients and 640 controls to assess whether word-stem completion priming in AD differs according to instructions provided at encoding. When the data across the different encoding instructions were combined, the results showed that AD patients manifest significant completion priming, even though the magnitude of priming is reduced. Taking into account the different encoding conditions, the results suggested that whereas completion priming is impaired in AD when encoding conditions consist in reading or rating words, priming is equivalent to that of controls when encoding conditions require semantic judgments or generating words. In this latter condition in particular, self-generating a word at encoding may provide an aid to partially overcome conceptual deficits of the patients and increase the degree of adequacy between cognitive operations employed at encoding phase and those triggering implicit retrieval.

No abstract

Gender differences in visuospatial cognition favoring men are larger in tasks requiring active information manipulation than in tasks requiring passive storage. This study was designed to determine whether male advantage in active manipulation of visuospatial information can still be evidenced in Alzheimer's disease (AD). Twenty male and 20 female AD patients with equivalent age, education, dementia severity (Mini-Mental State Examination and Mattis Dementia Rating Scale), and visual discrimination abilities were recruited. We administered the forward span of Corsi block-tapping task and Vecchi's matrix memory task involving passive temporary retention of stimuli location. Active manipulation of visuospatial information was assessed with the backward span of Corsi block-tapping task and Vecchi's pathway task in which patients were required to mentally generate a pathway within a matrix. The results showed that scores on the tasks involving passive storage of visuospatial information were equivalent between the two groups of patients, whereas men performed significantly better than women in tasks requiring active manipulation of visuospatial information. This result was limited to visuospatial processing since no difference between male and female patients was evidenced in the verbal short-term memory tasks, neither when the task involved passive storage nor when the task required active processing. Therefore, this study suggests that, besides other variables such as education or lifestyle factors, gender might also modulate the cognitive manifestation of AD.

No abstract

Studies investigating implicit memory in Alzheimer's disease suggest that priming abilities disappear over time. This study investigates long-term priming in Alzheimer's disease. A total of 20 patients with Alzheimer's disease and 20 controls underwent the Free and Cued Selective Reminding test. After a 30-minute delay, participants were submitted to a word identification task comprising the studied words and new words. The patients exhibited a long-term priming effect similar to that presented by the comparison group. Therefore, whereas explicit retrieval is definitely impaired in Alzheimer's disease, implicit processes allowing the retrieval of that same information operate relatively normally, including after a long delay.

The relative abundances of species at 18 sampling sites were used to perfom some comparisons. The sampling sites similarity indexes and the species distances were calculated and hierarchicaly clustered for each of the sampling seasons. A multivariate analysis was also carried out including al1 the information avalaible.The cluster analysis for the sampling sites yield the expected spring versus mouth organization, except for some neighbourg permutations. T h e unique and clear alteration in the sites succesive ordination was the station 2 in winter due to a pollution effect observed a t this station in that period. Anyway, the general grouping in al1 the seasons can be summarised as follows: An upper group of sampling stations with low similarities, a medium group with the highest similarities (dueto the presenceof a reduced number of abundant species), and finally, the sites in the lower reaches. At the upper reaches the benthic fauna is diverse and composed by riverine species, in the central reaches the uniformization in macroinvertebrate fauna is produced by a moderate pollution and the scarcity of the fauna in lower sites is a result of the very high pollution.Based on field observations and on the sorting experience, six groups of species were stablished in a cluster analysis. The results of species clustering yield some of the groups constant for the three different seasons. These correspond to the spring species, the central reaches species (inhabiting the central uniform zone) and the pollution resistent species (inhabiting the lower part of the river). Other groups are composed either by non significant species (mainly present in the tributaries) or species present in the upper reaches where the community s t m m r e is much more complex.In the ~r i n c i p a l component analysis (PCA) the three first factors (accounting for 15'5%, 10'5% and 8% of the were analized. The first factor is loaded by the abundant species in central reaches and the third one is 10aded bv the indicator species on any group.A~cording with this results we believe that neither a continous model can be stated in the community structure along the river channel nor a discrete one. Although some continous structure is notice in the upper reaches, in the central and lower part and also in spring zone defined communities can be distinguised. But these defined groups of species are produced either by disturbance introduced by man as pollution (in central and lower reaches) or by a great constancy in some abiotic factors (as temperature in the spring zone).