Post-training reversible inactivation of the hippocampus enhances novel object recognition memory

Research on the role of the hippocampus in object recognition memory has produced conflicting results. Previous studies have used permanent hippocampal lesions to assess the requirement for the hippocampus in the object recognition task. However, permanent hippocampal lesions may impact performance through effects on processes besides memory consolidation including acquisition, retrieval, and performance. To overcome this limitation, we used an intrahippocampal injection of the GABA agonist muscimol to reversibly inactivate the hippocampus immediately after training mice in two versions of an object recognition task. We found that the inactivation of the dorsal hippocampus after training impairs object-place recognition memory but enhances novel object recognition (NOR) memory. However, inactivation of the dorsal hippocampus after repeated exposure to the training context did not affect object recognition memory. Our findings suggest that object recognition memory formation does not require the hippocampus and, moreover, that activity in the hippocampus can interfere with the consolidation of object recognition memory when object information encoding occurs in an unfamiliar environment.The medial temporal lobe plays an important role in recognition memory formation, as damage to this brain structure in humans, monkeys, and rodents impairs performance in recognition memory tasks (for review, see Squire et al. 2007). Within the medial temporal lobe, studies have consistently demonstrated that the perirhinal cortex is involved in this form of memory (Brown and Aggleton 2001; Winters and Bussey 2005; Winters et al. 2007, 2008; Balderas et al. 2008). In contrast, the role of the hippocampus in object recognition memory remains a source of debate. Some studies have reported novel object recognition (NOR) impairments in animals with hippocampal lesions (Clark et al. 2000; Broadbent et al. 2004, 2010), yet others have reported no impairments (Winters et al. 2004; Good et al. 2007). Differences in hippocampal lesion size and behavioral procedures among the different studies have been implicated as the source of discrepancy in these findings (Ainge et al. 2006), but previous studies have not examined the consequences of environment familiarity on the hippocampus dependence of object recognition memory.Previous studies addressing the role of the hippocampus in recognition memory relied on permanent, pre-training lesions (Clark et al. 2000; Broadbent et al. 2004; Winters et al. 2004; Good et al. 2007). Permanent lesions inactivate the hippocampus not only during the consolidation phase, but also during habituation, acquisition, and memory retrieval, potentially confounding interpretation of the results. Furthermore, permanent lesion studies require long surgery recovery times during which extrahippocampal changes may emerge to mask or compensate for the loss of hippocampal function. To overcome these problems, we reversibly inactivated the dorsal hippocampus after training mice in two versions of the object recognition task. We infused muscimol, a γ-aminobutyric acid (GABA) receptor type A agonist, into the dorsal hippocampus immediately after training in an object-place recognition task or immediately following training in a NOR task. Consistent with previous studies (Save et al. 1992; Galani et al. 1998; Mumby et al. 2002; Stupien et al. 2003; Aggleton and Brown 2005), we observed that hippocampal inactivation impairs object-place recognition memory. Interestingly, we observed that the degree of contextual familiarity can influence NOR memory formation. We found that when shorter periods of habituation to the experimental environment were used, hippocampal inactivation enhances long-term NOR memory. In contrast, after extended periods of contextual habituation, long-term recognition memory was unaltered by hippocampal inactivation. Together these results suggest that if familiarization with objects occurs at a stage in which the contextual environment is relatively novel, the hippocampus plays an inhibitory role on the consolidation of object recognition memory. Supporting this view, we observed that object recognition memory is unaffected by hippocampal inactivation when initial exploration of the objects occurred in a familiar environment.     

The Soul of Trans‐Humanism

Abstract: This article tackles the question: how should Christian theologians think about the human soul in light of the challenges posed by the new emphasis in brain‐mind identity in neuroscience and trasn‐humanism? Ways of improving human nature through medical therapy, genetic enhancement, and trans‐human cybernetic immortality are explored; and their assumptions are correlated with a spectrum of Christian theories of the soul such as substance dualism, emergent dualism, nonreductive physicalism, and materialism. Finally, the article concludes that the human person should be thought of relationally, and the dimension that is decisive for resurrection is the relation of the soul to God.     

On being a living contradiction: the struggle of an elite intercollegiate Christian coach

While some research has been conducted on the manner in which Christian athletes utilize their faith to cope with the dominant culture of winning, there appears to be a relative paucity of investigation on the manner in which elite coaches function in this environment. The purpose of this study was to describe an elite intercollegiate coach’s response to the dominant culture of sport as it related to his spiritual life. We attempted to examine the thought processes and behaviors of an individual held in high esteem by his peers, and report his solutions to some of the dilemmas reported in the previous work by S. J. Hoffman and C. L. Stevenson. This elite intercollegiate coach was extremely committed to his relationship with Christ, but he was likewise heavily involved with the dominant culture of sport.     

THE CHARACTER OF VIRTUE: ANSWERING THE SITUATIONIST CHALLENGE TO VIRTUE ETHICS

Neo‐Aristotelian virtue ethics makes essential reference to the notion of a stable, robust character‐trait. It also claims to be constrained by at least a minimal degree of psychological realism. Recent developments in empirical psychology have drawn into question the evidence for the existence of such robust traits, arguing that it rests on what has been called a ‘fundamental attribution error’. Virtue ethics has thus seemingly been made vulnerable to criticisms that it is essentially dependent on an erroneous, folk‐psychological, notion of character and, so, must either abandon their characteristic notion of virtue or forego any pretensions to psychological realism. I develop a two‐pronged response to this objection. First, I argue that there is reason to question much of the empirical evidence and that such evidence as does exist can easily be accommodated by virtue ethics. Next, I argue that even if we allow that neo‐Aristotelian virtue ethical theories does sometimes presuppose a stronger conception of character‐traits than is warranted by the evidence, this does not significantly undermine the virtue ethicist's project.     

The Astounding Assumption of Infinite Life

The multimillennial philosophical discussion about life after death has received a recent boost in the prospect of immortality attained via technologies. In this newer version, humans generally are considered mortal but may develop means of making themselves immortal. If “immortal” means not mortal, thus existing for infinity, and if the proposed infinite‐existing entity is material, it must inhabit an infinite material universe. If the proposed entity is not material, there must be means by which it can shed its material substance and exist nonmaterially. The article examines arguments for how an infinite life would be possible given current physical understanding. The paper considers a Pascalian‐style wager weighing the likelihood of adjusting to existence wholly within a finite universe versus betting on there being some way to construe the universe(s) as a viable medium for infinite beings. Conclusion: the case for a finite being to exist infinitely has little viable support.     

Constitutive activation of the G-protein subunit Galphas within forebrain neurons causes PKA-dependent alterations in fear conditioning and cortical Arc mRNA expression

Memory formation requires cAMP signaling; thus, this cascade has been of great interest in the search for cognitive enhancers. Given that medications are administered long-term, we determined the effects of chronically increasing cAMP synthesis in the brain by expressing a constitutively active isoform of the G-protein subunit Galphas (Galphas*) in postnatal forebrain neurons of mice. Previously, we showed that Galphas* mice exhibit increased adenylyl cyclase activity but decreased cAMP levels in cortex and hippocampus due to a PKA-dependent increase in total cAMP phosphodiesterase (PDE) activity. Here, we extend previous findings by determining if Galphas* mice show increased activity of specific PDE families that are regulated by PKA, if Galphas* mice show PKA-dependent deficits in fear memory, and if these memory deficits are associated with PKA-dependent alterations in neuronal activity as mapped by Arc mRNA expression. Consistent with previous findings, we show here that Galphas* mice exhibit a significant compensatory increase in cAMP PDE1 activity and a trend toward increased cAMP PDE4 activity. Further, inhibiting the presumably elevated PKA activity in Galphas* mice fully rescues short- and long-term memory deficits in a fear-conditioning task, while extending the training session from one to four CS-US pairings partially rescues these deficits. Mapping of Arc mRNA levels suggests these PKA-dependent memory deficits may be related to decreased neuronal activity specifically within the cortex. Galphas* mice show decreased Arc mRNA expression in CA1, orbital cortex, and cortical regions surrounding the hippocampus; however, only the deficits in cortical regions surrounding the hippocampus are PKA dependent. Our results imply that chronically stimulating targets upstream of cAMP may detrimentally affect cognition.     

Identifying two potential mechanisms for changes in alcohol use among college-attending and non-college-attending emerging adults

This study tested whether pro-alcohol peer influences and prosocial involvement account for increases in drinking during the transition into emerging adulthood and whether these mechanisms differ depending on college attendance and/or moving away from home. The authors used structural equation modeling of prospective data from 825 young men and women. For 4 groups defined by college and residential status, more drinking in the spring of 12th grade predicted more pro-alcohol peer influences the following fall, and more pro-alcohol peer influences in the fall predicted increases in drinking the following spring. Going to college while living at home was a protective factor against increases in drinking and selection of pro-alcohol peer involvements. Prosocial involvement (measured by involvement in religious activities and volunteer work) was not significantly related to post-high school drinking except among college students living away from home. Prevention efforts should focus on (a) reducing opportunities for heavy drinking for college and noncollege emerging adults as they leave home and (b) increasing prosocial involvement among college students not living at home.