Preservation of long-term memory and synaptic plasticity despite short-term impairments in the Tc1 mouse model of Down syndrome

Down syndrome (DS) is a genetic disorder arising from the presence of a third copy of the human chromosome 21 (Hsa21). Recently, O’Doherty and colleagues in an earlier study generated a new genetic mouse model of DS (Tc1) that carries an almost complete Hsa21. Since DS is the most common genetic cause of mental retardation, we have undertaken a detailed analysis of cognitive function and synaptic plasticity in Tc1 mice. Here we show that Tc1 mice have impaired spatial working memory (WM) but spared long-term spatial reference memory (RM) in the Morris watermaze. Similarly, Tc1 mice are selectively impaired in short-term memory (STM) but have intact long-term memory (LTM) in the novel object recognition task. The pattern of impaired STM and normal LTM is paralleled by a corresponding phenotype in long-term potentiation (LTP). Freely-moving Tc1 mice exhibit reduced LTP 1 h after induction but normal maintenance over days in the dentate gyrus of the hippocampal formation. Biochemical analysis revealed a reduction in membrane surface expression of the AMPAR (α-amino-3-hydroxy-5-methyl-4-propionic acid receptor) subunit GluR1 in the hippocampus of Tc1 mice, suggesting a potential mechanism for the impairment in early LTP. Our observations also provide further evidence that STM and LTM for hippocampus-dependent tasks are subserved by parallel processing streams.     

Stripes within words affect reading

In a series of eight studies it is shown that the first peak in the horizontal autocorrelation of the image of a word (which captures the similarity in shape between the neighbouring strokes of letters) determines (i) the appearance of the words as striped; (ii) the speed with which the words are read, both aloud and silently; and (iii) the speed with which a paragraph of text can be searched. By subtly distorting the horizontal dimension of text, and thereby reducing the first peak in the horizontal autocorrelation, it is shown that the speed of word recognition can be increased. The increase in speed is greater in poor readers.     

The Neuropsychology of HIV/AIDS in Older Adults

Highly active antiretroviral therapy is allowing increasing numbers of adults to age with HIV. The neuropsychological effects of aging with HIV are reviewed through three types of studies. First, the separate effects of HIV and aging on cognition are examined in studies that compare younger adults with HIV with neurologically normal older adults. Second, studies examine the impact of aging within samples of adults with HIV only. Third, providing the most critical evidence, are studies that assess cognition in younger and older adults with HIV relative to younger and older adults without HIV. In general research findings are inconclusive. Large individual differences among older adults with HIV as well as co-factors (APOE4 and detectable viral load) may account for inconsistent findings in the literature. A subgroup of older adults with HIV may be at greater risk for cognitive impairment, especially in attention functioning.     

Clarifying the paradigm for the ethics of donation and transplantation: Was 'dead' really so clear before organ donation?

Recent commentaries by Verheijde et al, Evans and Potts suggesting that donation after cardiac death practices routinely violate the dead donor rule are based on flawed presumptions. Cell biology, cardiopulmonary resuscitation, critical care life support technologies, donation and transplantation continue to inform concepts of life and death. The impact of oxygen deprivation to cells, organs and the brain is discussed in relation to death as a biological transition. In the face of advancing organ support and replacement technologies, the reversibility of cardiac arrest is now purely related to the context in which it occurs, in association to the availability and application of support systems to maintain oxygenated circulation. The 'complete and irreversible' lexicon commonly used in death discussions and legal statutes are ambiguous, indefinable and should be replaced by accurate terms. Criticism of controlled DCD on the basis of violating the dead donor rule, where autoresuscitation has not been described beyond 2 minutes, in which life support is withdrawn and CPR is not provided, is not valid. However, any post mortem intervention that re-establishes brain blood flow should be prohibited. In comparison to traditional practice, organ donation has forced the clarification of the diagnostic criteria for death and improved the rigour of the determinations.     

Revisiting the Stanford prison experiment: could participant self-selection have led to the cruelty?

The authors investigated whether students who selectively volunteer for a study of prison life possess dispositions associated with behaving abusively. Students were recruited for a psychological study of prison life using a virtually identical newspaper ad as used in the Stanford Prison Experiment (SPE; Haney, Banks & Zimbardo, 1973) or for a psychological study, an identical ad minus the words of prison life. Volunteers for the prison study scored significantly higher on measures of the abuse-related dispositions of aggressiveness, authoritarianism, Machiavellianism, narcissism, and social dominance and lower on empathy and altruism, two qualities inversely related to aggressive abuse. Although implications for the SPE remain a matter of conjecture, an interpretation in terms of person-situation interactionism rather than a strict situationist account is indicated by these findings. Implications for interpreting the abusiveness of American military guards at Abu Ghraib Prison also are discussed.     

Tolerant (In)civility? A Longitudinal Analysis of White Conservative Protestants’ Willingness to Grant Civil Liberties

Past research has found conservative Protestants to be less willing than most Americans to grant civil liberties to unpopular groups. In light of evidence of high and growing civility by Smith (2000) and Hunter (1984), there is good reason to believe that conservative Protestants are becoming less distinctive with regard to granting civil freedoms. We update and expand previous research on conservative Protestants and civil liberties by examining the civil liberties measures in the General Social Survey over a 26-year period, with special attention to explaining conservative Protestantism's rejection of civil liberties. In comparison to mainline Protestants and Catholics, we find that conservative Protestants are still less willing to grant civil liberties to unpopular groups, though important qualifications apply. Various explanations are examined.     

The Hard Road to Presentism

It is a common criticism of presentism – the view according to which only the present exists – that it errs against truthmaker theory. Recent attempts to resolve the truthmaker objection against presentism proceed by restricting truthmaker maximalism (the view that all truths have truthmakers), maintaining that propositions concerning the past are not made true by anything, but are true nonetheless. Support for this view is typically garnered from the case for negative existential propositions, which some philosophers contend are exceptions to truthmaker maximalism. In this article, we argue that a ‘no truthmakers’ approach to the truthmaker objection is critically flawed.