A virtual reality paradigm with dynamic scene stimuli for use in memory research.

Episodic memory may essentially be memory for one's place within a temporally unfolding scene from a first-person perspective. Given this, pervasively used static stimuli may only capture one small part of episodic memory. A promising approach for advancing the study of episodic memory is immersing participants within varying scenes from a first-person perspective. We present a pool of distinct scene stimuli for use in virtual environments and a paradigm that is implementable across varying levels of immersion on multiple virtual reality (VR) platforms and adaptable to studying various aspects of scene and episodic memory. In our task, participants are placed within a series of virtual environments from a first-person perspective and guided through a virtual tour of scenes during a study phase and a test phase. In the test phase, some scenes share a spatial layout with studied scenes; others are completely novel. In three experiments with varying degrees of immersion, we measure scene recall, scene familiarity-detection during recall failure, the subjective experience of déjà vu, the ability to predict the next turn on a tour, the subjective sense of being able to predict the next turn on a tour, and the factors that influence memory search and the inclination to generate candidate recollective information. The level of first-person immersion mattered to multiple facets of episodic memory. The paradigm presents a useful means of advancing mechanistic understanding of how memory operates in realistic dynamic scene environments, including in combination with cognitive neuroscience methods such as functional magnetic resonance imaging and electrophysiology.

Factor analysis of the virtual reality Stroop task.

INTRODUCTION: Virtual reality (VR) offers neuropsychologists high dimensional (3D) platforms for administering cognitive tasks that balance experimental control with simulations of naturalistic activities. A virtual reality version of the Stroop task, the Virtual Reality Stroop Task (VRST), was developed that leverages technological advances to enhance the ecological validity of neuropsychological assessments. The high mobility multipurpose wheeled vehicle (HMMWV) version of the VRST includes high arousal (ambush) and low arousal (safe) zones was employed in this study. This version of the VRST contains both cognitive (Stroop) and affective (arousal) components. While the VRST has been shown to have good construct validity, the factor structure has yet to be explored. This study aimed to examine the factor structure of the VRST and compare the results with a lower dimensional (2D) computer-automated Stroop task (i.e., the Automated Neuropsychological Assessment Metrics - ANAM). METHOD: Data was drawn from college-aged students who completed the VRST and ANAM Stroop tasks (N = 115). Factor analyses utilized principal axis factoring (PAF), and output variables included percent of correct responses and response times the VRST and ANAM Stroop tasks. RESULTS: Results indicated that both Stroop tasks had two-factor solutions. Factor one measured response times and factor two measured accuracy. While factors respective of speed and accuracy factors were correlated across assessment modalities, within assessment factor correlations were low. CONCLUSIONS: The factors possibly indicated participants response styles in that they either focus on responding accurately or responding quickly to stimuli. Therefore, including throughput in future research examining either the ANAM Stroop task or VRST may provide useful insight into participant performance. Finally, because similar factor structures were observed for both the VRST and ANAM Stroop task this study provided additional support for the construct validity of a higher dimensional Stroop task, the VRST.

Subjective distinguishability of seizure and non-seizure Déjà Vu: A case report, brief literature review, and research prospects.

Roughly two-thirds of all people report having experienced déjà vu-the odd feeling that a current experience is both novel and a repeat or replay of a previous, unrecalled experience. Reports of an association between déjà vu and seizure aura symptomatology have accumulated for over a century, and frequent déjà vu is also now known to be associated with focal seizures, particularly those of a medial temporal lobe (MTL) origin. A longstanding question is whether seizure-related déjà vu has the same basis and is the same subjective experience as non-seizure déjà vu. Survey research suggests that people who experience both seizure-related and non-seizure déjà vu can often subjectively distinguish between the two. We present a case of a person with a history of focal MTL seizures who reports having experienced both seizure-related and non-seizure common déjà vu, though the non-seizure type was more frequent during this person's youth than it is currently. The patient was studied with a virtual tour paradigm that has previously been shown to elicit déjà vu among non-clinical, young adult participants. The patient reported experiencing déjà vu of the common non-seizure type during the virtual tour paradigm, without associated abnormalities of the intracranial EEG. We situate this work in the context of broader ongoing projects examining the subjective correlates of seizures. The importance for memory research of virtual scenes, spatial tasks, virtual reality (VR), and this paradigm for isolating familiarity in the context of recall failure are discussed.

Translation initiation factors GleIF4E2 and GleIF4A can interact directly with the components of the pre-initiation complex to facilitate translation initiation in Giardia lamblia.

Translation initiation factor eIF4F is essential for cap-dependent translation initiation in eukaryotes. eIF4F is a trimeric complex consisting of a scaffold protein eIF4G, cap-binding protein eIF4E and DEAD-box RNA helicase eIF4A. eIF4F binds to the 5' cap structure of the mRNA through eIF4E and facilitates the binding of the preinitiation complex (PIC) via protein-protein interactions of eIF4G with eIF3 in mammals or with eIF5 in yeast. Initiation factor eIF4A is known to unwind the secondary structures of the 5'UTRs encountered by the PIC during its initial binding to the mRNA and while scanning for the initiation codon. In Giardia, homologs for eIF4E (GleIF4E2) and eIF4A (GleIF4A) have been identified but not for eIF4G. To address how PIC is recruited to the 5' end of mRNA in the absence of eIF4G homolog, we have used yeast two-hybrid assays to identify potential interactions of GleIF4E2 with the components of the PIC. The results show that GleIF4E2 can interact with the ß subunit of the initiation factor GleIF2, a component of the PIC. ZDOCK modeling of the GleIF4E2-GleIF2ß complex revealed that the dorsal side of GleIF4E2 is likely involved in binding to GleIF2ß, which mimics the interaction of mammalian eIF4E with eIF4G, and with eIF4E binding proteins. These results suggest that GleIF4E2 can facilitate the recruitment of the PIC to the 5'end of the mRNA by binding directly to the components of the PIC. The role of GleIF4A in translation initiation in Giardia is not clearly understood as the short 5' UTRs of the mRNA are unlikely to form secondary structures. Interestingly, Pateamine A, a specific inhibitor of human eIF4A, inhibited the growth of Giardia in a dose-dependent manner, suggesting that the activity of GleIF4A is probably required for translation. Using yeast two-hybrid assays, we have identified a novel interaction of GleIF4A with i subunit of the initiation factor GleIF3 (GleIF3i), another component of the PIC. These results indicate that the GleIF4A can also interact directly with the components of the PIC. ZDOCK modeling of the GleIF3i-GleIF4A complex suggests that GleIF3i could serve as a stimulator of GleIF4A activity.

Practice parameters facilitating adoption of advanced technologies for enhancing neuropsychological assessment paradigms.

OBJECTIVE: Clinical neuropsychologists have long underutilized computer technologies for neuropsychological assessment. Given the rapid advances in technology (e.g. virtual reality; tablets; iPhones) and the increased accessibility in the past decade, there is an on-going need to identify optimal specifications for advanced technologies while minimizing potential sources of error. Herein, we discuss concerns raised by a joint American Academy of Clinical Neuropsychology/National Academy of Neuropsychology position paper. Moreover, we proffer parameters for the development and use of advanced technologies in neuropsychological assessments. METHOD: We aim to first describe software and hardware configurations that can impact a computerized neuropsychological assessment. This is followed by a description of best practices for developers and practicing neuropsychologists to minimize error in neuropsychological assessments using advanced technologies. We also discuss the relevance of weighing potential computer error in light of possible errors associated with traditional testing. Throughout there is an emphasis on the need for developers to provide bench test results for their software's performance on various devices and minimum specifications (documented in manuals) for the hardware (e.g. computer, monitor, input devices) in the neuropsychologist's practice. CONCLUSION: Advances in computerized assessment platforms offer both opportunities and challenges. The challenges can appear daunting but are a manageable and require informed consumers who can appreciate the issues and ask pertinent questions in evaluating their options.

An initial validation of the Virtual Environment Grocery Store.

BACKGROUND: Virtual reality-based neuropsychological assessments proffer the potential to address the limited ecological validity of pen-and-paper measures of memory. NEW METHOD: To investigate the construct validity of a newly developed virtual reality-based multiple errands task, the Virtual Environment Grocery Store (VEGS), two studies were performed. COMPARISON WITH EXISTING METHOD(S): In Study 1, we explored construct validity via comparison of traditional neuropsychological measures of memory and executive functioning with a low distraction condition of the VEGS. In Study 2, a new sample was used to compare traditional neuropsychological measures of memory and executive functioning with a high distraction condition of the VEGS. RESULTS: Performances on the VEGS memory tasks (in Study 1: low distraction condition) and the traditional neuropsychological assessments of memory were positively correlated, indicating that memory for VEGS content was similar to memory for traditional paper-and-pencil measures. Again, in Study 2, performances on the VEGS memory tasks correlated with the traditional neuropsychological assessments of memory, indicating that memory for VEGS content was similar to memory for traditional paper-and-pencil measures. As expected, though, the addition of distractors into the virtual environment resulted in significant correlations with traditional measures of inhibitory control. CONCLUSIONS: The VEGS has the advantage over traditional measures of providing objective measurement of individual components of memory in simulations of everyday activities.