Intersecting Dimensions of Cognitive and Neuropsychiatric Symptoms: Embarking on a New Era of Clinical Neuropsychological Research

Neuropsychology Review -     

Surviving,to some degree

Philosophical Studies - In this paper we argue that reflection on the patterns of practical concern that agents like us exhibit strongly suggests that the same person relation comes in continuous...     

Contributions of glucocorticoid receptors in cortical astrocytes to memory recall

Dysfunctions in memory recall lead to pathological fear; a hallmark of trauma-related disorders, like posttraumatic stress disorder (PTSD). Both, heightened recall of an association between a cue and trauma, as well as impoverished recall that a previously trauma-related cue is no longer a threat, result in a debilitating fear toward the cue. Glucocorticoid-mediated action via the glucocorticoid receptor (GR) influences memory recall. This literature has primarily focused on GRs expressed in neurons or ignored cell-type specific contributions. To ask how GR action in nonneuronal cells influences memory recall, we combined auditory fear conditioning in mice and the knockout of GRs in astrocytes in the prefrontal cortex (PFC), a brain region implicated in memory recall. We found that knocking out GRs in astrocytes of the PFC disrupted memory recall. Specifically, we found that knocking out GRs in astrocytes in the PFC (AstroGRKO) after fear conditioning resulted in higher levels of freezing to the CS+ tone when compared with controls (AstroGRintact). While we did not find any differences in extinction of fear toward the CS+ between these groups, AstroGRKO female but not male mice showed impaired recall of extinction training. These results suggest that GRs in cortical astrocytes contribute to memory recall. These data demonstrate the need to examine GR action in cortical astrocytes to elucidate the basic neurobiology underlying memory recall and potential mechanisms that underlie female-specific biases in the incidence of PTSD.

Recalling important information about salient environmental cues is an integral part of how we navigate our world. Recalling too much, or too little, information about salient environmental cues is a part of the psychopathology of posttraumatic stress disorder (PTSD) (Milad and Quirk 2012). More specifically, the augmented recall of an association between an environmental cue and a traumatic event results in debilitating fear toward the cue, even in the absence of any threat. In contrast, impoverished recall of information that a cue, previously associated with trauma, is no longer a threat also results in debilitating fear toward the cue after it is no longer dangerous. Therefore, one way to mitigate debilitating fear that characterizes PTSD is to understand the neurobiological mechanisms underlying memory recall.Among many mechanisms, glucocorticoid action via signaling through glucocorticoid receptors (GRs) is an important neurobiological pathway that underlies the recall of salient information. When trauma-associated cues are encountered, the hypothalamic-pituitary-adrenal axis is activated and GR signaling is consequently triggered (McEwen et al. 1988; McEwen 1992; Lupien et al. 2009). Existing literature demonstrates that glucocorticoids and GRs do in fact influence learning, memory, and the recall of learning (Pugh et al. 1997; de Quervain et al. 1998, 2009, 2011, 2017, 2019; Roozendaal 2002, 2003; Conrad et al. 2004; Hui et al. 2004; Donley et al. 2005; Roozendaal and de Quervain 2005; Cai et al. 2006; Soravia et al. 2006; Yang et al. 2006; Roozendaal et al. 2009; Bentz et al. 2010; Blundell et al. 2011; Clay et al. 2011; Nikzad et al. 2011; Roesler 2012; Liao et al. 2013; Wislowska-Stanek et al. 2013; Arp et al. 2016; Reis et al. 2016; Dadkhah et al. 2018; Inoue et al. 2018; Scheimann et al. 2019; Lin et al. 2020). The relationship between glucocorticoids, GRs, learning and memory is complicated and within the literature cited above, one can find examples of GR action being facilitatory as well as inhibitory to learning and memory recall. As expansive as this research is, the influence of GRs on learning, memory, and recall of learning has mostly focused only on GR action in neurons or has ignored cell type specific contributions. While glia are approximately as common as neurons in the nervous system (von Bartheld et al. 2016; von Bartheld 2018), the role of GRs in glial cells on the recall of salient environmental cues has been neglected. More specifically, while astrocytes comprise a significant proportion of the glial cell population (von Bartheld et al. 2016) and express GRs (Vielkind et al. 1990; Bohn et al. 1991), the influence of GRs in astrocytes on memory recall remains largely unappreciated (for one exception, see the Discussion).Our goal in this study was to determine the influence of GRs in astrocytes on memory recall. To do so, we combined the robust and reliable experimental framework of classical fear conditioning in rodents (Santini et al. 2008; Dias et al. 2014; Bukalo et al. 2015; Keiser et al. 2017; Giustino and Maren 2018; Greiner et al. 2019; Gunduz-Cinar et al. 2019; Venkataraman et al. 2019) with molecular genetic manipulations in the prefrontal cortex (PFC), a brain region critical for the recall of memory (Morgan and LeDoux 1995; Quirk et al. 2000; Mueller et al. 2008; Quirk and Mueller 2008; Giustino and Maren 2015; Rozeske et al. 2015; Maren and Holmes 2016). We first trained mice to associate tone presentations with mild footshocks. After this auditory fear conditioning, we used a CRE-loxP strategy to specifically knock out GRs in astrocytes in the PFC (hereafter termed cortical astrocytes) of these trained mice. We then exposed animals to extinction training: 30 presentations of the tone in the absence of any footshocks. Finally, 1 d after the extinction training, we exposed animals to two presentations of the tone. This experimental timeline allowed us to ask how a lack of GRs in cortical astrocytes influences (1) the recall of the previous aversive association of the tone presentation with the footshock, (2) the extinction of fear that would typically occur during extinction training, and (3) the recall of extinction training allowing us to measure the influence of GRs in cortical astrocytes on the recall of extinction training. Broadly, our results demonstrate that knocking out GRs in cortical astrocytes disrupts fear memory recall in both male and female mice, while only disrupting extinction recall in female mice.     

Temporal Fictionalism for a Timeless World

Current debate in the metaphysics of time ordinarily assumes that we should be realists about time. Recently, however, a number of physicists and philosophers of physics have proposed that time will play no role in a completed theory of quantum gravity. This paper defends fictionalism about temporal thought, on the supposition that our world is timeless. We argue that, in the face of timeless physical theories, realism about temporal thought is unsustainable: some kind of anti-realism must be adopted. We go on to provide an argument against eliminativism about temporal thought. While it doesn't follow from this argument that fictionalism about temporal thought is true, we suggest that this nonetheless shows that fictionalism should be regarded as the preferred view.     

Belief in robust temporal passage (probably) does not explain future-bias

Philosophical Studies - Empirical work has lately confirmed what many philosophers have taken to be true: people are ‘biased toward the future’. All else being equal, we usually prefer...