It's In My Eyes, but It Doesn't Look that Way to Me

In this issue of Neuron, Hannula and Ranganath provide striking evidence that hippocampal activity predicts eye movements that reveal memory for the past even when participants' overt memory decisions are in error. Their findings bear on an ongoing debate about the relationship between mnemonic awareness and hippocampal function

Interactions Between Forms of Memory: When Priming Hinders New Episodic Learning

Human memory consists of multiple forms, including priming and explicit memory. Although considerable evidence indicates that priming and explicit memory are functionally and neuroanatomically distinct, little is know about when and how these different forms of memory interact. Here, behavioral and functional magnetic resonance imaging (fMRI) methods were used to examine a novel and counterintuitive hypothesis: Priming during episodic encoding may be negatively associated with subsequent explicit memory. Using an experimental design that exploited known properties of spacing or lag effects, the magnitudes of behavioral and neural priming during a second study episode were varied and the relation between these magnitudes of priming during re-encoding and performance on a subsequent explicit memory test was examined. Results revealed that greater behavioral priming (reduced reaction times) and neural priming (reduced left inferior prefrontal brain activation) during re-encoding were associated with lower levels of subsequent explicit memory. Moreover, those subjects who demonstrated greater behavioral and neural priming effects during re-encoding following a long lag tended to demonstrate the least benefit in subsequent explicit memory due to this second study episode. These findings suggest that priming for past experiences can hinder new episodic encoding.Physic

Neural Priming in Human Prefrontal Cortex: Multiple Forms of Learning Reduce Demands on the Prefrontal Executive System.

Past experience is hypothesized to reduce computational demands in PFC by providing bottom-up predictive information that informs subsequent stimulus-action mapping. The present fMRI study measured cortical activity reductions ("neural priming"/"repetition suppression") during repeated stimulus classification to investigate the mechanisms through which learning from the past decreases demands on the prefrontal executive system. Manipulation of learning at three levels of representation-stimulus, decision, and response-revealed dissociable neural priming effects in distinct frontotemporal regions, supporting a multiprocess model of neural priming. Critically, three distinct patterns of neural priming were identified in lateral frontal cortex, indicating that frontal computational demands are reduced by three forms of learning: (a) cortical tuning of stimulus-specific representations, (b) retrieval of learned stimulus-decision mappings, and (c) retrieval of learned stimulus-response mappings. The topographic distribution of these neural priming effects suggests a rostrocaudal organization of executive function in lateral frontal cortex

Knowledge Acquisition During Exam Preparation Improves Memory and Modulates Memory Formation

According to the schema-relatedness hypothesis, new experiences that make contact with existing schematic knowledge are more easily encoded and remembered than new experiences that do not. Here we investigate how real-life gains in schematic knowledge affect the neural correlates of episodic encoding, assessing medical students 3 months before and immediately after their final exams. Human participants were scanned with functional magnetic resonance imaging while encoding associative information that varied in relatedness to medical knowledge (face–diagnosis vs face–name pairs). As predicted, improvements in memory performance over time were greater for face–diagnosis pairs (high knowledge-relevance) than for face–name pairs (low knowledge-relevance). Improved memory for face–diagnosis pairs was associated with smaller subsequent memory effects in the anterior hippocampus, along with increased functional connectivity between the anterior hippocampus and left middle temporal gyrus, a region important for the retrieval of stored conceptual knowledge. The decrease in the anterior hippocampus subsequent memory effect correlated with knowledge accumulation, as independently assessed by a web-based learning platform with which participants studied for their final exam. These findings suggest that knowledge accumulation sculpts the neural networks associated with successful memory formation, and highlight close links between knowledge acquired during studying and basic neurocognitive processes that establish durable memories.  SIGNIFICANCE STATEMENT In a sample of medical students, we tracked knowledge accumulation via a web-based learning platform and investigated its effects on memory formation before and after participants' final medical exam. Knowledge accumulation led to significant gains in memory for knowledge-related events and predicted a selective decrease in hippocampal activation for successful memory formation. Furthermore, enhanced functional connectivity was found between hippocampus and semantic processing regions. These findings (1) demonstrate that knowledge facilitates binding in the hippocampus by enhancing its communication with the association cortices, (2) highlight close links between knowledge induced in the real world and basic neurocognitive processes that establish durable memories, and (3) exemplify the utility of combining laboratory-based cognitive neuroscience research with real-world educational technology for the study of memory

Functional MRI-Based Lie Detection: Scientific and Societal Challenges

Functional MRI (fMRI)-based lie detection has been marketed as a tool for enhancing personnel selection, strengthening national security and protecting personal reputations, and at least three US courts have been asked to admit the results of lie detection scans as evidence during trials. How well does fMRI-based lie detection perform, and how should the courts, and society more generally, respond? Here, we address various questions — some of which are based on a meta-analysis of published studies — concerning the scientific state of the art in fMRI-based lie detection and its legal status, and discuss broader ethical and societal implications. We close with three general policy recommendations

CNTRICS Final Task Selection: Long-term Memory

Long-term memory (LTM) is a multifactorial construct, composed of different stages of information processing and different cognitive operations that are mediated by distinct neural systems, some of which may be more responsible for the marked memory problems that limit the daily function of individuals with schizophrenia. From the outset of the CNTRICS initiative, this multidimensionality was appreciated, and an effort was made to identify the specific memory constructs and task paradigms that hold the most promise for immediate translational development. During the second CNTRICS meeting, the LTM group identified item encoding and retrieval and relational encoding and retrieval as key constructs. This article describes the process that the LTM group went through in the third and final CNTRICS meeting to select nominated tasks within the 2 LTM constructs and within a reinforcement learning construct that were judged most promising for immediate development. This discussion is followed by each nominating authors' description of their selected task paradigm, ending with some thoughts about future directions.Psycholog

DNA methylation pattern changes upon long-term culture and aging of human mesenchymal stromal cells

Within 2–3 months of in vitro culture-expansion, mesenchymal stromal cells (MSC) undergo replicative senescence characterized by cell enlargement, loss of differentiation potential and ultimate growth arrest. In this study, we have analyzed DNA methylation changes upon long-term culture of MSC by using the HumanMethylation27 BeadChip microarray assessing 27 578 unique CpG sites. Furthermore, we have compared MSC from young and elderly donors. Overall, methylation patterns were maintained throughout both long-term culture and aging but highly significant differences were observed at specific CpG sites. Many of these differences were observed in homeobox genes and genes involved in cell differentiation. Methylation changes were verified by pyrosequencing after bisulfite conversion and compared to gene expression data. Notably, methylation changes in MSC were overlapping in long-term culture and aging in vivo. This supports the notion that replicative senescence and aging represent developmental processes that are regulated by specific epigenetic modifications

Fv antibodies to aflatoxin B1 derived from a pre-immunized antibody phage display library system

The production and characterization of recombinant antibodies to aflatoxin B[SUB1] (AFB[SUB1]), a potent mycotoxin and carcinogen is described. The antibody fragments produced were then applied for use in a surface plasmon resonance-based biosensor (BIAcore), which measures biomolecular interactions in 'real-time'. Single chain Fv (scFv) antibodies were generated to aflatoxin B1 from an established phage display system, which incorporated a range of different plasmids for efficient scFv expression. The scFv's were used in the development of a competitive ELISA, and also for the development of surface plasmon resonance (SPR)-based inhibition immunoassays. They were found to be suitable for the detection of AFB[SUB1], in this format, with the assays being sensitive and reproducible