Boosting Memory Through Magnetic Brain Stimulation

When you think back to a past birthday party, you can probably remember who was there and what you ate. This might seem easy to you, but memory is a complicated process that scientists are still trying to understand. Memory takes place in the brain, which is made up of billions of cells called neurons. Recent research has shown that memory can be improved safely using a tool called transcranial magnetic stimulation (TMS). TMS works by sending a very strong magnetic field through the skull and into the brain, where it changes the activity of neurons, causing changes in behavior. In this article, we will discuss how the brain remembers, how we can make the brain remember better using TMS, and how TMS could be used in the future to help people with memory problems

Neural similarity between overlapping events at learning differentially affects reinstatement across the cortex

Episodic memory often involves high overlap between the actors, locations, and objects of everyday events. Under some circumstances, it may be beneficial to distinguish, or differentiate, neural representations of similar events to avoid interference at recall. Alternatively, forming overlapping representations of similar events, or integration, may aid recall by linking shared information between memories. It is currently unclear how the brain supports these seemingly conflicting functions of differentiation and integration. We used multivoxel pattern similarity analysis (MVPA) of fMRI data and neural-network analysis of visual similarity to examine how highly overlapping naturalistic events are encoded in patterns of cortical activity, and how the degree of differentiation versus integration at encoding affects later retrieval. Participants performed an episodic memory task in which they learned and recalled naturalistic video stimuli with high feature overlap. Visually similar videos were encoded in overlapping patterns of neural activity in temporal, parietal, and occipital regions, suggesting integration. We further found that encoding processes differentially predicted later reinstatement across the cortex. In visual processing regions in occipital cortex, greater differentiation at encoding predicted later reinstatement. Higher-level sensory processing regions in temporal and parietal lobes showed the opposite pattern, whereby highly integrated stimuli showed greater reinstatement. Moreover, integration in high-level sensory processing regions during encoding predicted greater accuracy and vividness at recall. These findings provide novel evidence that encoding-related differentiation and integration processes across the cortex have divergent effects on later recall of highly similar naturalistic events

Spatial Information Modulates the Neurocognitive Dynamics of Episodic Autobiographical Memory Retrieval

Episodic autobiographical memory (EAM) enables reliving past experiences, recalling the sensory information associated with that event. Spatial information is thought to play an early and important role in EAM, contributing to the dynamics of retrieval. Using a combination of behavioural, neuroimaging, and neurostimulation approaches, this dissertation aimed to examine the temporal dynamics of EAM and the role spatial information plays in its retrieval. Chapter 2 demonstrated a temporal precedence for spatial information at the behavioural level, but importantly found high individual variability in early recall of spatial information. Further, individual differences in spatial aspects of EAM were reflected in hippocampal and precuneus grey matter volumes. Chapter 3 examined the temporal dynamics of EAM at the neural level using magnetoencephalography (MEG). While cueing individuals with familiar locations altered the dynamics of retrieval, it did not confer an early neural advantage. Together with the findings from Chapter 2, these results indicate that early spatial information alters the dynamics of EAM retrieval, but does not play a ubiquitous or automatic role in EAM. This study also found that spatial perspective during EAM retrieval was associated with a well-established neural component of episodic memory recollection. Transcranial magnetic stimulation (TMS) administered to the precuneus disrupted this association, demonstrating that this region is crucially involved in neural processing of spatial perspective during EAM. In Chapter 4, I assessed how regions representing spatial information, such as the precuneus and medial temporal lobe (MTL), interact dynamically during EAM retrieval. Using MEG to measure oscillatory activity, this study found that theta (3-7 Hz) and high gamma (65-85 Hz) oscillations underlie MTL-parietal communication, demonstrating the importance of coupling between theta and gamma oscillations in EAM. TMS to the precuneus disrupted this oscillatory activity, suggesting that this region plays a causal role in network-wide theta and gamma oscillatory activity. Together, these studies elucidate the behavioural and neural dynamics of EAM retrieval, as well as spatial contributions to EAM. Future research is needed to further clarify the key contributions of specific regions and the dynamic activity underlying widespread neural communication during EAM.Ph.D.2019-11-19 00:00:0

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Phase coupling and phase-amplitude coupling script

Does Spatial Context Come First? Examining the Temporal Dynamics of Episodic Autobiographical Memory

This study examined the temporal dynamics of episodic autobiographical memory (EAM) and the role spatial information plays in retrieval. We cued participants with familiar items consisting of locations and non-locations, and assessed the time taken to recall a memory, the first thing that came to mind when recalling the event, and the vividness of the memory. We found that location cued memories were recalled more quickly than non-location cued memories and that participants were more likely to select a location as the first thing that came to mind. Furthermore, the likelihood of selecting a location as the first thing that came to mind was associated with better self-reported trait memory functioning, as measured by the survey of autobiographical memory (SAM). The current study demonstrates that spatial information plays an early and fundamental role in memory retrieval and recollection, and that the experience of remembering can be manipulated by using different cues.M.A.2018-03-01 00:00:0

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Preprocessed MEG datasets and anatomical dat

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