Brice A. Kuhl

Bio: Brice A. Kuhl is an academic researcher from University of Oregon. The author has contributed to research in topics: Forgetting & Posterior parietal cortex. The author has an hindex of 24, co-authored 51 publications receiving 3283 citations. Previous affiliations of Brice A. Kuhl include New York University & Stanford University.

Neural Systems Underlying the Suppression of Unwanted Memories

Abstract: Over a century ago, Freud proposed that unwanted memories can be excluded from awareness, a process called repression. It is unknown, however, how repression occurs in the brain. We used functional magnetic resonance imaging to identify the neural systems involved in keeping unwanted memories out of awareness. Controlling unwanted memories was associated with increased dorsolateral prefrontal activation, reduced hippocampal activation, and impaired retention of those memories. Both prefrontal cortical and right hippocampal activations predicted the magnitude of forgetting. These results confirm the existence of an active forgetting process and establish a neurobiological model for guiding inquiry into motivated forgetting.

Variability in the analysis of a single neuroimaging dataset by many teams

Abstract: Data analysis workflows in many scientific domains have become increasingly complex and flexible. Here we assess the effect of this flexibility on the results of functional magnetic resonance imaging by asking 70 independent teams to analyse the same dataset, testing the same 9 ex-ante hypotheses1. The flexibility of analytical approaches is exemplified by the fact that no two teams chose identical workflows to analyse the data. This flexibility resulted in sizeable variation in the results of hypothesis tests, even for teams whose statistical maps were highly correlated at intermediate stages of the analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Notably, a meta-analytical approach that aggregated information across teams yielded a significant consensus in activated regions. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset2-5. Our findings show that analytical flexibility can have substantial effects on scientific conclusions, and identify factors that may be related to variability in the analysis of functional magnetic resonance imaging. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for performing and reporting multiple analyses of the same data. Potential approaches that could be used to mitigate issues related to analytical variability are discussed.

Variability in the analysis of a single neuroimaging dataset by many teams (Preprint)

Abstract: Summary Data analysis workflows in many scientific domains have become increasingly complex and flexible. To assess the impact of this flexibility on functional magnetic resonance imaging (fMRI) results, the same dataset was independently analyzed by 70 teams, testing nine ex-ante hypotheses. The flexibility of analytic approaches is exemplified by the fact that no two teams chose identical workflows to analyze the data. This flexibility resulted in sizeable variation in hypothesis test results, even for teams whose statistical maps were highly correlated at intermediate stages of their analysis pipeline. Variation in reported results was related to several aspects of analysis methodology. Importantly, meta-analytic approaches that aggregated information across teams yielded significant consensus in activated regions across teams. Furthermore, prediction markets of researchers in the field revealed an overestimation of the likelihood of significant findings, even by researchers with direct knowledge of the dataset. Our findings show that analytic flexibility can have substantial effects on scientific conclusions, and demonstrate factors related to variability in fMRI. The results emphasize the importance of validating and sharing complex analysis workflows, and demonstrate the need for multiple analyses of the same data. Potential approaches to mitigate issues related to analytical variability are discussed.

Decreased demands on cognitive control reveal the neural processing benefits of forgetting

Abstract: Remembering often requires the selection of goal-relevant memories in the face of competition from irrelevant memories. Although there is a cost of selecting target memories over competing memories (increased forgetting of the competing memories), here we report neural evidence for the adaptive benefits of forgetting—namely, reduced demands on cognitive control during future acts of remembering. Functional magnetic resonance imaging during selective retrieval showed that repeated retrieval of target memories was accompanied by dynamic reductions in the engagement of functionally coupled cognitive control mechanisms that detect (anterior cingulate cortex) and resolve (dorsolateral and ventrolateral prefrontal cortex) mnemonic competition. Strikingly, regression analyses revealed that this prefrontal disengagement tracked the extent to which competing memories were forgotten; greater forgetting of competing memories was associated with a greater decline in demands on prefrontal cortex during target remembering. These findings indicate that, although forgetting can be frustrating, memory might be adaptive because forgetting confers neural processing benefits. Remembering the past is fraught with competition. Given the associative nature of memory, remembering a goal-relevant memory often involves selecting it against several competing memories, placing demands on effortful cognitive control mechanisms that detect and resolve competition 1–3 . Fortunately, memory can be adaptive 4–7 , as acts of selective remembering seem to regulate mnemonic competition. Specifically, although selective remembering facilitates future retrieval of the same target memories 8,9 , it also produces a cost—forgetting—for selected-against competing memories (a phenomenon termed ‘retrievalinduced forgetting’) 1,10,11 . Such forgetting of competing memories is hypothesized to reflect their weakening (or suppression) 1,5,10,12 . A crucial question is whether forgetting is indeed adaptive, such that it confers processing benefits precisely because it reduces competition during future attempts to retrieve target memories 4,5 . To the extent that this is the case, it predicts that the forgetting (suppression) of competing memories will be associated with a beneficial decline in demands on the cognitive control mechanisms that are typically required for remembering in the face of competition. Our functional magnetic resonance imaging (fMRI) experiment tested this hypothesis by examining the relationship between the engagement of prefrontal cognitive control mechanisms during repeated acts of selective retrieval and later behavioral evidence that competing memories were forgotten. The experiment was divided into three phases: study, selective retrieval practice and test (Fig.1a). During the study phase, participants encoded a series of cue-associate word pairs, encoding multiple associates of each cue word. Next, participants engaged in selective retrieval practice, repeatedly retrieving some of the associates of some of the cues. Crucially, of the associates that were not practiced, some competed during retrieval practice (that is, they shared cues with practiced associates) whereas others did not. Finally, about 15 min after retrieval practice, memory for all of the initially encoded cue-associate pairs was tested to assess the consequences of selective retrieval practice for both practiced and unpracticed memories. To test our hypothesis, we examined the relationship between fMRI measures of prefrontal cortical (PFC) activation during repeated selective retrieval practice and a behavioral measure of competitor forgetting. First, we predicted that unpracticed memories that competed with targets during selective retrieval practice would suffer a greater rate of forgetting than would unpracticed memories that did not compete 10 . Second, we predicted that repeated selective retrieval would yield benefits for practiced memories, reflected in both behavioral measures of retrieval efficiency and neural measures of reduced demands on PFC-mediated cognitive control mechanisms during repeated retrieval. Finally, and most important, we predicted that the behavioral measure of long-term competitor forgetting (which putatively reflects memory suppression) would correlate with fMRI measures of reduced demands on PFC-mediated control mechanisms during repeated selective retrieval. The data support each of these predictions, providing functional neurobiological evidence that mnemonic suppression occurs when competing memories conflict with target memories during retrieval, and that the successful suppression of competing memories yields immediate benefits—namely, reduced demands on neural mechanisms that detect conflict (in the anterior cingulate cortex; ACC) 13–15 and overcome competition through selection and inhibition (right dorsolateral and ventrolateral PFC) 2,3,16–24 .

Resistance to forgetting associated with hippocampus-mediated reactivation during new learning

Abstract: The authors find that during the encoding of new memories, responses in the human hippocampus are predictive of the retention of memories for previously experienced, overlapping events. They report that this is accomplished by reactivating the neural representation of older memories as new memories are formed.

疟原虫var基因转换速率变化导致抗原变异[英]／Paul H, Robert P, Christodoulou Z, et al//Proc Natl Acad Sci U S A

Abstract: 抗原变异可使得多种致病微生物易于逃避宿主免疫应答。表达在感染红细胞表面的恶性疟原虫红细胞表面蛋白1（PfPMP1）与感染红细胞、内皮细胞、树突状细胞以及胎盘的单个或多个受体作用，在黏附及免疫逃避中起关键的作用。每个单倍体基因组var基因家族编码约60种成员，通过启动转录不同的var基因变异体为抗原变异提供了分子基础。

About sleep's role in memory

Abstract: Over more than a century of research has established the fact that sleep benefits the retention of memory. In this review we aim to comprehensively cover the field of "sleep and memory" research by providing a historical perspective on concepts and a discussion of more recent key findings. Whereas initial theories posed a passive role for sleep enhancing memories by protecting them from interfering stimuli, current theories highlight an active role for sleep in which memories undergo a process of system consolidation during sleep. Whereas older research concentrated on the role of rapid-eye-movement (REM) sleep, recent work has revealed the importance of slow-wave sleep (SWS) for memory consolidation and also enlightened some of the underlying electrophysiological, neurochemical, and genetic mechanisms, as well as developmental aspects in these processes. Specifically, newer findings characterize sleep as a brain state optimizing memory consolidation, in opposition to the waking brain being optimized for encoding of memories. Consolidation originates from reactivation of recently encoded neuronal memory representations, which occur during SWS and transform respective representations for integration into long-term memory. Ensuing REM sleep may stabilize transformed memories. While elaborated with respect to hippocampus-dependent memories, the concept of an active redistribution of memory representations from networks serving as temporary store into long-term stores might hold also for non-hippocampus-dependent memory, and even for nonneuronal, i.e., immunological memories, giving rise to the idea that the offline consolidation of memory during sleep represents a principle of long-term memory formation established in quite different physiological systems.