No abstract

Unexpected cognitive lucidity and communication in patients with severe dementias, especially around the time of death, have been observed and reported anecdotally. Here, we review what is known about this phenomenon, related phenomena that provide insight into potential mechanisms, ethical implications, and methodologic considerations for systematic investigation. We conclude that paradoxical lucidity, if systematically confirmed, challenges current assumptions and highlights the possibility of network‐level return of cognitive function in cases of severe dementias, which can provide insight into both underlying neurobiology and future therapeutic possibilities.

Whilst forest policy promotes cultivation and regeneration of beech dominated forest ecosystems, beech itself is a highly drought sensitive tree species likely to suffer from the climatic conditions prognosticated for the current century. Taking advantage of model ecosystems with cool-moist and warm-dry local climate, the latter assumed to be representative for future climatic conditions, the effects of climate and silvicultural treatment (different thinning regimes) on water status, nitrogen balance and growth parameters of adult beech trees and beech regeneration in the understorey were assessed. In addition, validation experiments with beech seedlings were carried out under controlled conditions, mainly in order to assess the effect of drought on the competitive abilities of beech. As measures of water availability xylem flow, shoot water potential, stomatal conductance as well as d 13 C and d 18 O in different tissues (leaves, phloem, wood) were analysed. For the assessment of nitrogen balance we determined the uptake of inorganic nitrogen by the roots as well as total N content and soluble N compounds in different tissues of adult and young trees. Retrospective and current analysis of d 13 C, growth and meteorological parameters revealed that beech growing under warm-dry climatic conditions were impaired in growth and water balance during periods with low rain-fall. Thinning affected water, N balance and growth mostly of young beech, but in a different way under different local climatic conditions. Under cool, moist conditions, representative for the current climatic and edaphic conditions in beech forests of Central Europe, thinning improves nutrient and water status consistent to published literature and long-term experience of forest practitioners. However, beech regeneration was impaired as a result of thinning at higher temperatures and under reduced water availability, as expected in future climate.

Pedospheric nitrate uptake is a strongly regulated process adapted to the N demand of the whole plant. Pre-requisites for an integrating regulatory system are signal substances communicating the N demand of the shoot to the roots. In the current study it was shown that an additional atmospheric N source results in activation of cytokinins in the shoot as indicated by an increase in the trans -hydroxylation ratio, and in increased shoot-to-root transport of cytokinins in the phloem. Phloem mobility and basipetal transport of cytokinins were also demonstrated by feeding zeatin riboside into the phloem. The resulting enrichment of cytokinins in the roots caused an increased expression of a highaffinity nitrate transporter, the enrichment of amino compounds (Glu, Val, Phe, Lys) in the fine roots and a significant decrease in nitrate net uptake. Significant enrichment in amino acids -accompanied by decreased nitrate net uptake but not by increased expression of the highaffinity nitrate transporter -was also observed when Gln the major long-distance transport form of nitrogen in beech was fed into the phloem. These results provide experimental evidence that, in addition to amino compounds, cytokinins that are known to cycle within the plant are also communicating changes in N metabolism from the shoot to the roots. Apparently increased cytokinin contents in the root can transiently increase nitrate uptake, but this upregulation may be overridden by transcriptional and posttranscriptional down-regulation mediated by amino compounds.

In this article, we present the results of a literature survey on case reports of the unexpected return of mental clarity and memory shortly before death, which we have called "terminal lucidity." We focus specifically on terminal lucidity in mental disorders, of which we have found 81 case references. Of these, we were able to retrieve 49 case reports, most of which had been recorded before 1849. Thereafter, comparatively few reports of terminal lucidity have been published. Some more recent publications referred to terminal lucidity in patients suffering from schizophrenia and dementia. We draw parallels and distinctions between terminal lucidity and remissions attributable to febrile illness in neurosyphilis. We recommend in-depth studies on the psychopathology and neuropathology involved in terminal lucidity, since they might enable the development of both improved therapies and a better understanding of unresolved aspects of cognition and memory processing.