The Functional and Structural Neuroanatomy of Systems Consolidation for Autobiographical and Semantic Memory

The Retrograde Memory for News Events Test (RM-NET) and the relationship between news event memory and performance on standard neuropsychological tests

Novel tests of semantic memory (SM)-for example, memory for news events (NE; news facts) or famous personalities-are useful for estimating the severity of retrograde amnesia. Individuals with mild cognitive impairment exhibit relatively intact SM/language on traditional neuropsychological tests but exhibit consistent impairment on novel tests of SM, suggesting novel SM tests are dissimilar from traditional SM tests. To identify the relationship between NE memory and traditional cognitive measures, older adults (N = 51) completed a traditional neuropsychological battery and the Retrograde Memory News Events Test (RM-NET; a new test that robustly measures NE memory across the adult life span with high temporal resolution), and the relationship between performance on these tests was examined. Total RM-NET scores were more closely aligned with episodic memory scores than SM scores. The strength of the association between NE scores and episodic memory scores decreased as the age of NE memory increased. Tests of news events appear to reflect performance on traditional tests of episodic memory rather than SM, especially when recent news events are tested.

An initial preparation for human cadaveric dissection ameliorates the associated mental distress in students

It is universally recognized that cadaveric dissection is an essential part of anatomy training. However, it has been reported to induce mental distress in some students and impair their intrinsic motivation (IM) to study. One of the postulated reasons for this behavior is the lack of adequate information and preparation of students for cadaveric dissection. Therefore, it is hypothesized that providing relevant information prior to cadaveric dissection will ameliorate the mental distress, enhance the IM of students, and improve their academic performance. A cohort of occupational therapy students enrolled in an anatomy course were psychologically prepared for cadaveric dissection. Students were provided with a curated list of YouTube videos and peer-reviewed journal articles related to cadaveric dissection prior to the commencement of the anatomy course. All students were also required to attend an oral presentation immediately before commencing dissection. The control group included students who had not been provided with any resources in preparation for cadaveric dissection. Compared to the control group, students who had been prepared demonstrated better quality of cadaveric dissection, improved academic performance, reported less mental distress and greater IM. Moreover, students reported the oral presentation to be most relevant and journal articles to be least useful in their preparation. Therefore, this is an effective approach in the amelioration of mental distress and improvement of performance in anatomy students. Consequently, this study represents a paradigm shift in the pedagogy of anatomy, and could represent a vital element in the evolution of a revitalized anatomy curriculum.

Intra- and inter-regional dynamics in cortical-striatal-tegmental networks

It is increasingly recognized that networks of brain areas work together to accomplish computational goals. However, functional connectivity networks are not often compared between different behavioral states and across different frequencies of electrical oscillatory signals. In addition, connectivity is always defined as the strength of signal relatedness between two atlas-based anatomical locations. Here, we performed an exploratory analysis using data collectected from high density arrays in the prefrontal cortex (PFC), striatum (STR), and ventral tegmental area (VTA) of male rats. These areas have all been implicated in a wide range of different tasks and computations including various types of memory as well as reward valuation, habit formation and execution, and skill learning. Novel intra-regional clustering analyses identified patterns of spatially restricted, temporally coherent, and frequency specific signals that were reproducible across days and were modulated by behavioral states. Multiple clusters were identified within each anatomical region, indicating a mesoscopic scale of organization. Generalized eigendecomposition (GED) was used to dimension-reduce each cluster to a single component time series. Dense inter-cluster connectivity was modulated by behavioral state, with connectivity becoming reduced when the animals were exposed to a novel object, compared to a baseline condition. Behavior-modulated connectivity changes were seen across the spectrum, with delta, theta, and gamma all being modulated. These results demonstrate the brain's ability to reorganize functionally at both the intra- and inter-regional levels during different behavioral states.

Characterizing memory loss in patients with autoimmune limbic encephalitis hippocampal lesions

Since the publication of Scoville and Milner's (1957) seminal paper, the precise functional role played by the hippocampus in support of human memory has been fiercely debated. For instance, the single question of whether the hippocampus plays a time-limited or an indelible role in the recollection of personal memories led to a deep and tenacious schism within the field. Similar polarizations arose between those who debated the precise nature of the role played by the hippocampus in support of semantic relative to episodic memories and in recall/recollection relative to familiarity-based recognition. At the epicenter of these divisions lies conflicting neuropsychological findings. These differences likely arise due to the consistent use of heterogeneous patient populations to adjudicate between these positions. Here we utilized traditional neuropsychological measures in a homogenous patient population with a highly discrete hippocampal lesion (i.e., VGKCC-Ab related autoimmune limbic encephalitis patients). We observed consistent impairment of recent episodic memories, a present but less striking impairment of remote episodic memories, preservation of personal semantic memory, and recall but not recognition memory deficits. We conclude that this increasingly well-characterized patient group may represent an important homogeneous population in which the functional role played by the hippocampus may be more precisely delineated.

A contextual binding theory of episodic memory: systems consolidation reconsidered

Episodic memory reflects the ability to recollect the temporal and spatial context of past experiences. Episodic memories depend on the hippocampus but have been proposed to undergo rapid forgetting unless consolidated during offline periods such as sleep to neocortical areas for long-term storage. Here, we propose an alternative to this standard systems consolidation theory (SSCT) - a contextual binding account - in which the hippocampus binds item-related and context-related information. We compare these accounts in light of behavioural, lesion, neuroimaging and sleep studies of episodic memory and contend that forgetting is largely due to contextual interference, episodic memory remains dependent on the hippocampus across time, contextual drift produces post-encoding activity and sleep benefits memory by reducing contextual interference.

Neuropsychological Investigations of Human Amnesia: Insights Into the Role of the Medial Temporal Lobes in Cognition

The past 30 years of research on human amnesia has yielded important changes in our understanding of the role of the medial temporal lobes (MTL) in memory. On the one hand, this body of evidence has highlighted that not all types of memory are impaired in patients with MTL lesions. On the other hand, this research has made apparent that the role of the MTL extends beyond the domain of long-term memory, to include working memory, perception, and future thinking. In this article, we review the discoveries and controversies that have characterized this literature and that set the stage for a new conceptualization of the role of the MTL in cognition. This shift toward a more nuanced understanding of MTL function has direct relevance for a range of clinical disorders in which the MTL is implicated, potentially shaping not only theoretical understanding but also clinical practice. (JINS, 2017, 23, 732-740).