Pre-attentive Visual Processing in Alzheimer's Disease: An Event-related Potential Study

INTRODUCTION

While identifying Alzheimer's Disease (AD) in its early stages is crucial, traditional neuropsychological tests tend to lack sensitivity and specificity for its diagnosis. Neuropsychological studies have reported visual processing deficits of AD, and event-related potentials (ERPs) are suitable to investigate pre-attentive processing with superior temporal resolution.

OBJECTIVE

This study aimed to investigate visual attentional characteristics of adults with AD, from pre-attentive to attentive processing, using a visual oddball task and ERPs.

METHODS

Cognitively normal elderly controls (CN) and patients with probable AD (AD) were recruited. Participants performed a three-stimulus visual oddball task and were asked to press a designated button in response to the target stimuli. The amplitudes of 4 ERPs were analyzed. Mismatchnegativity (vMMN) was analyzed around the parieto-occipital and temporo-occipital regions. P3a was analyzed around the fronto-central regions, whereas P3b was analyzed around the centro-parietal regions.

RESULTS

Late vMMN amplitudes of the AD group were significantly smaller than those of the CN group, while early vMMN amplitudes were comparable. Compared to the CN group, P3a amplitudes of the AD group were significantly smaller for the infrequent deviant stimuli, but the amplitudes for the standard stimuli were comparable. Lastly, the AD group had significantly smaller P3b amplitudes for the target stimuli compared to the CN group.

CONCLUSION

Our findings imply that AD patients exhibit pre-attentive visual processing deficits, known to affect later higher-order brain functions. In a clinical setting, the visual oddball paradigm could be used to provide helpful diagnostic information since pre-attentive ERPs can be induced by passive exposure to infrequent stimuli.

Novel effects of Foxo3a on immune system and cardiac remodeling after myocardial infarction

Background

Fibroblast/myofibroblast transdifferentiation following acute cardiac injury (MI) is a major mechanism of scar formation and adverse remodeling regulated by TGFβ/SMAD3 signaling. Myofibroblasts represent phenotypically modulated cells characterized by α-smooth muscle actin (α-SMA) and constitute the main source of extracellular matrix proteins such as collagen type I in the healing infarct wound. Moreover, the recruitment of a specific monocyte/macrophages subset (Ly6Chigh and Ly6Clow) control the healing process in the infarcted wound. The forkhead transcription factor FOXO3a has recently been shown to inhibit cardiac hypertrophy by different stressors and is involved in the immune response following injury.

Purpose

We hypothesized that FOXO3a, a key regulator of cell differentiation, cell cycle and size as well as the stress response, might inhibit matricellular remodeling following myocardial infarction by regulating transdifferentiation of fibroblasts into myofibroblasts. Moreover, we hypothesized that Foxo3a−/− mice favor the recruitment of monocytes of the type Ly6Clow leading to an anti-inflammatory profile and thus the remodeling after injury.

Methods

Acute myocardial infarction was induced in FOXO3−/− and WT mice (FVB background) by permanent LAD ligation. The myocardial infarction size was determined via ECHO. Myofibroblast trans-differentiation and fibrosis markers were analyzed by QT-PCR and protein analysis. The differentiation of macrophages studied via FACS. IP/IF and Western blotting were used to test for a direct interaction between FOXO3a and SMAD3 in vitro.

Results

FOXO3a−/− mice showed significantly higher survival rates compared to WT littermates. Myocardial inflammation (Mac-1, LFA, CD3, CD45), injury markers such as Troponin T were similar in both groups on day 4 post-MI. Myocardial expression of alpha smooth muscle actin (ASMA) and Collagen1A1 (Col1A1), as well as numbers of cardiac CD11b+/F4–80+/Ly6clow macrophages was significantly enhanced in FOXO3a−/− mice 15 days post infarction. Moreover, Foxo3a−/− mice showed larger fibrotic areas following MI. Mechanistically, immunoprecipitation showed direct interaction of FOXO3a with SMAD3a that was enhanced following activation of the transcription factor leading to diminished SMAD3 downstream gene expression.

Conclusion

Our results indicate that FOXO3a acts as a direct inhibitor of TGF-β regulated myofibroblast differentiation and matrix remodeling via FOXO3a-SMAD3 interaction following MI. Moreover, a Foxo3a deficiency might lead to the recruitment of monocytes type Ly6Clow leading to an anti-inflammatory profile in the infarct wound. Therefore, FOXO3a collectively regulates cardiac hypertrophy and fibrosis/scar formation following MI. Thus, targeting the FOXO3a-SMAD3 signaling axis might be of future therapeutic interest.

Funding Acknowledgement

Type of funding source: Foundation. Main funding source(s): German Resaerch Foundation

An Event-Related Potential Study of Decision-Making and Feedback Utilization in Female College Students Who Binge Drink

This study investigated the ability to use feedback for decision-making in female college students who binge drink (BD) using the iowa gambling task (IGT) and event-related potentials (ERPs). Twenty-seven binge drinkers and 23 non-binge drinkers (non-BD) were identified based on scores on the Korean version of the Alcohol Use Disorder Test and the Alcohol Use Questionnaire. The IGT consists of four cards, including two cards that result in a net loss, with large immediate gains but greater losses in the long term, and two cards that result in a net gain, with small immediate gains but reduced losses in the long term. Participants were required to choose one card at a time to maximize profit until the end of the task while avoiding losses. The BD group showed a significantly lower total net score than the non-BD group, indicating that the BD group chose more disadvantageous cards. The BD group showed significantly smaller ΔFRN amplitudes [difference in amplitudes of feedback-related negativity (FRN) between gain and loss feedback] but not in P3 amplitudes. Additionally, ΔFRN amplitudes in the fronto-central area were positively correlated with the total net score and net scores for sectors 4 and 5. Thus, total net scores and later performance on the IGT increased as ΔFRN amplitudes from the fronto-central area increased. FRN is known to reflect early feedback evaluation employing a bottom-up mechanism, whereas P3 is known to reflect late feedback processing and allocation of attentional resources using a top-down mechanism. These results indicate that college students who binge drink have deficits in early evaluation of positive or negative feedback and that this deficit may be related to decision-making deficits.

Decision-Making Deficits Are Associated With Learning Impairments in Female College Students at High Risk for Anorexia Nervosa: Iowa Gambling Task and Prospect Valence Learning Model

This study investigated deficits in decision-making ability in female college students at high risk for anorexia nervosa (AN) using the Iowa Gambling Task (IGT) and the prospect valence learning (PVL) model. Based on scores on the Korean version of the Eating Attitude Test-26 (KEAT-26), participants were assigned to either the high risk for AN group (n = 42) or the control group (n = 43). The high risk for AN group exhibited significantly lower total net scores and block net scores on the third, fourth, and fifth blocks of the IGT than the control group did. The high risk for AN group selected cards significantly more often from the disadvantageous A and B decks and less often from the advantageous D deck than the control group did. In addition, the block net scores of the high risk for AN group did not differ across the five blocks, whereas those of the control group increased as the trials progressed. There was a significant negative correlation between IGT total net score and total score on the KEAT-26. The high risk for AN group had significantly lower values than the control group on the learning and response consistency parameters of the PVL model. These results indicate that female college students at high risk for AN have deficits in decision-making ability, and that these deficits are related to difficulties in remembering experience obtained from earlier trials and applying it to later trials. These difficulties further lead them to make decisions randomly.

Kisspeptin is involved in ovarian follicular development during aging in rats

We have previously reported that kisspeptin (KP) may be under the control of the sympathetic innervation of the ovary. Considering that the sympathetic activity of the ovary increases with aging, it is possible that ovarian KP also increases during this period and participates in follicular development. To evaluate this possibility, we determined ovarian KP expression and its action on follicular development during reproductive aging in rats. We measured ovarian KP mRNA and protein levels in 6-, 8-, 10- and 12-month-old rats. To evaluate follicular developmental changes, intraovarian administration of KP or its antagonist, peptide 234 (P234), was performed using a mini-osmotic pump, and to evaluate FSH receptor (FSHR) changes in the senescent ovary, we stimulated cultured ovaries with KP, P234 and isoproterenol (ISO). Our results shows that KP expression in the ovary was increased in 10- and 12-month-old rats compared with 6-month-old rats, and this increase in KP was strongly correlated with the increase in ovarian norepinephrine observed with aging. The administration of KP produced an increase in corpora lutea and type III follicles in 6- and 10-month-old rats, which was reversed by P234 administration at 10 months. In addition, KP decreased the number and size of antral follicles in 6- and 10-month-old rats, while P234 administration produced an increase in these structures at the same ages. In ovarian cultures KP prevented the induction of FSHR by ISO. These results suggest that intraovarian KP negatively participates in the acquisition of FSHR, indicating a local role in the regulation of follicular development and ovulation during reproductive aging.

Altered ADAR 2 equilibrium and 5HT(2C) R editing in the prefrontal cortex of ADAR 2 transgenic mice

Modulation of serotonin signaling by RNA editing of the serotonin 2C receptor (5HT(2C) R) may be relevant to affective disorder as serotonin functions regulate mood and behavior. Previously, we observed enhanced endogenous behavioral despair in ADAR2 transgenic mice. As the transcript of the 5HT(2C) R is a substrate of ADAR2, we hypothesized that perturbed ADAR2 equilibrium in the prefrontal cortex of ADAR2 transgenic mice alters the normal distribution of edited amino acid isoforms of the 5HT(2C) R and modifies the receptor function in downstream basal extracellular signal-regulated kinase (ERK) signaling. We examined groups of naive control and ADAR2 transgenic mice and found significantly increased ADAR2 expression, increased RNA editing at A, C, D and E sites and significantly altered normal distribution of edited amino acid isoforms of the 5HT(2C) R with increased proportions of valine asparagine valine, valine serine valine, valine asparagine isoleucine, isoleucine asparagine valine and decreased isoleucine asparagine isoleucine amino acid isoforms of the 5HT(2C) R in ADAR2 transgenic mice. Localized serotonin levels (5-HT) were unchanged and perturbed ADAR2 equilibrium coincides with dysregulated edited amino acid isoforms of the 5HT(2C) R and reduced basal ERK signaling. These results altogether suggest that altered 5HT(2C) R function could be contributing to enhanced depression-like behavior of ADAR2 transgenic mice and further implicate ADAR2 as a contributing factor in cases of affective disorder.

Identification of ubiquitin ligases required for skeletal muscle atrophy

Skeletal muscle adapts to decreases in activity and load by undergoing atrophy. To identify candidate molecular mediators of muscle atrophy, we performed transcript profiling. Although many genes were up-regulated in a single rat model of atrophy, only a small subset was universal in all atrophy models. Two of these genes encode ubiquitin ligases: Muscle RING Finger 1 (MuRF1), and a gene we designate Muscle Atrophy F-box (MAFbx), the latter being a member of the SCF family of E3 ubiquitin ligases. Overexpression of MAFbx in myotubes produced atrophy, whereas mice deficient in either MAFbx or MuRF1 were found to be resistant to atrophy. These proteins are potential drug targets for the treatment of muscle atrophy.

Calcium-dependent adhesion is necessary for the maintenance of prosomeres

Cell adhesion has been suggested to function in the establishment and maintenance of the segmental organization of the central nervous system. Here we tested the role of different classes of adhesion molecules in prosencephalic segmentation. Specifically, we examined the ability of progenitors from different prosomeres to reintegrate and differentiate within various brain regions after selective maintenance or removal of different classes of calcium-dependent versus -independent surface molecules. This analysis implicates calcium-dependent adhesion molecules as central to the maintenance of prosomeres. Only conditions that spared calcium-dependent adhesion systems but ablated more general (calcium-independent) adhesion systems resulted in prosomere-specific integration after transplantation. Among the members of this class of adhesion molecules, R-cadherin shows a striking pattern of prosomeric expression during development. To test whether expression of this molecule was sufficient to direct progenitor integration to prosomeres expressing R-cadherin, we used a retroviral-mediated gain-of-function approach. We found that progenitors originally isolated from prosomere P2 (a region which does not express R-cadherin), when forced to express this molecule, can now integrate more readily into R-cadherin-expressing regions, such as the cortex, the ventral thalamus, and the hypothalamus. Nonetheless, our analysis suggests that while calcium-dependent molecules are able to direct prosomere-specific integration, they are not sufficient to induce progenitors to change their regional identity. While diencephalic progenitors from R-cadherin-expressing regions of prosomere 5 could integrate into R-cadherin-expressing regions of the cortex, they did not express the cortex-specific gene Emx1 or the telencephalic-specific gene Bf-1. Furthermore, diencephalic progenitors that integrate heterotopically into the cortex do not persist postnatally, whereas the same progenitors survive and differentiate when they integrate homotopically into the diencephalon. Together our results implicate calcium-dependent adhesion molecules as key mediators of prosomeric organization but suggest that they are not sufficient to bestow regional identities.

Telencephalic progenitors maintain anteroposterior identities cell autonomously

Grafting experiments have demonstrated that determination of anteroposterior (AP) identity is an early step in neural patterning that precedes dorsoventral (DV) specification [1,2]. These studies used pieces of tissue, however, rather than individual cells to address this question. It thus remains unclear whether the maintenance of AP identity is a cell-autonomous property or a result of signaling between cells within the grafted tissue. Previously, we and others [3-5] have used transplants of dissociated brain cells to show that individual telencephalic precursor cells can adopt host-specific DV identities when they integrate within novel regions of the telencephalon. We have now undertaken a set of transplantations during the same mid-neurogenic period used in the previous studies to assess the ability of telencephalic progenitors to integrate and differentiate into more posterior regions of the neuraxis. We observed that telencephalic progenitors were capable of integrating and migrating within different AP levels of the central nervous system (CNS). Despite this, we found that telencephalic progenitors that integrated within the diencephalon and the mesencephalon continued to express a telencephalic marker until adulthood. We speculate that during neurogenesis individual progenitors are determined in terms of their AP but not their DV identity. Hence, AP identity is maintained cell autonomously within individual progenitors.

Identification of sequence-tagged transcripts differentially expressed within the human hematopoietic hierarchy

Hematopoiesis is regulated by a complex gene expression program. To gain further insight into the molecular mechanisms underlying this process in humans, we sampled the transcriptional activity of the CD34+ hematopoietic progenitor line KG1a by single-pass sequencing the 5' ends of 1018 clones from a unidirectional cDNA library. Searches of public databases with the resulting expressed sequence tags (ESTs) identified 101 clones that showed no sequence similarity to any of the existing entries and that were therefore considered to derive from previously undescribed genes. Of the remaining 917 ESTs, 553 (a total of 485 distinct transcripts) corresponded to known genes. A further 279 KG1a ESTs matched or exhibited sequence similarity to ESTs or genomic sequences from humans and other species. Among the latter were putative human orthologs of developmental and cell cycle control genes from Caenorhabditis elegans, Drosophila, and yeast, as well as genes whose predicted amino acid sequences showed similarity to mammalian transcription factors. Hybridization of selected novel KG1a ESTs to globally amplified cDNAs prepared from single primary human hematopoietic precursors and homogeneous populations of terminally maturing hematopoietic cells revealed transcripts that are expressed preferentially at a specific stage or in a particular lineage within the hematopoietic hierarchy. Thus, included in the KG1a EST dataset are candidates for new human genes that may play roles in hematopoietic differentiative progression and lineage commitment.