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At first glance: How saccades drive communication between the visual system and the hippocampus during memory formation

Periodic Reporting for period 1 - VisHipMem (At first glance: How saccades drive communication between the visual system and the hippocampus during memory formation)

Reporting period: 2015-05-01 to 2017-04-30

We constantly move our eyes to gather information about our visual environment. Thereby, the uptake of visual information is restricted to discrete periods during which we fixate. Additionally, information sampling is restricted by ongoing brain processes. Rhythmic fluctuations in neuronal activity define brain states during which information processing is favorable. In order to be encoded into memory, information has to flow from sensory areas to memory related areas. To make the encoding of visual information into memory efficient, our eye movements need to be coordinated with the brain dynamics underlying the communication between brain areas.
The project’s aim is to understand how eye movements and brain activity are coordinated, to enable efficient memory encoding of visual information. We investigated this by simultaneously recording brain activity and eye movements from participants performing a memory task. Experiment 1 provided evidence for the memory-related coordination of brain oscillations and eye movements, indicating a mechanistic role of brain oscillations in coordinating the encoding of visual information during natural viewing. Experiment 2 revealed the impact of eye movements on brain metabolism in the hippocampus in relation to memory formation, as well as on the communication between task-relevant brain areas. Together, the findings answer basic questions about the interplay between eye movements and brain activity during memory formation.
The results of the project close a gap in understanding how visual information is processed during natural viewing and how information is transferred in the brain from the visual to the memory domain. Crucially, they provide insight into how these processes affect memory formation. Human memory is a topic of major public interest due to its core function in the human mind. Demographic change and aging, intimately related to the complex of dementia and Alzheimer’s disease, are one of the biggest challenges to today’s society. The findings of the present project advance the comprehension of the biological foundations of human memory, by investigating the neuronal basis of information processing and memory formation.
Work completed:
-Implementation of experimental paradigm, assembling stimuli and coding procedures for Experiment 1 and 2.
-Acquisition of pilot data ( Experiment 1 and 2).
-Acquisition of participants for data collection ( Experiment 1 and 2).
-MEG/fMRI data acquisition and recordings.
-MEG/fMRI data and joint analyses and results.
-Preparation for publication, publication, and presentation of results at international conferences.
Main results:
Experiment 1 showed that that eye movements are locked to the phase of ongoing brain oscillations prior to a saccade. Importantly, this coordination predicted successful memory encoding. Engagement of task-relevant brain areas reflected effective vision to memory mapping. Experiment 2 revealed that eye movements modulated the memory-related brain activity in the hippocampus. Moreover, saccade-related functional connectivity between visual cortex and the hippocampus modulated subsequent memory performance.
Exploitation and dissemination
Conference Presentations:
Saccade-triggered MEG activity during memory formation. Tübingen MEG Symposium 2015, Tübingen, Germany
Saccadic eye movements are phase-locked to posterior alpha oscillations during successful memory formation – evidence from MEG and intracranial data. Biomag 2016, Seoul, South Korea
Saccadic eye movements are phase-locked to posterior alpha oscillations during successful memory formation – evidence from MEG, fMRI and intracranial data. SfN 2016, San Diego, USA
Saccadic eye movements are phase-locked to posterior alpha oscillations and modulate neural communication during memory formation – evidence from MEG, fMRI and intracranial data. CNS 2017, San Francisco, USA
Papers:
Saccades phase-locked to alpha oscillations in the occipital and medial temporal lobe enhance memory encoding. T. Staudigl, E. Hartl, S. Noachtar, C. F. Doeller, O. Jensen. bioRxiv 158758; doi: https://doi.org/10.1101/158758
Saccades phase-locked to alpha oscillations in the occipital and medial temporal lobe enhance memory encoding (under review). T. Staudigl, E. Hartl, S. Noachtar, C. F. Doeller, O. Jensen.
Hexadirectional signals during exploration of visual space in human MEG data (in prep.). T. Staudigl, et al.
Saccade-triggered fMRI reveals effective communication during memory formation (in prep). T. Staudigl et al.
The researcher was trained in acquiring and analyzing fMRI and eye tracker data under expert supervision, enabling him to successfully apply and exploit these new techniques. He profited from the diversity of the institute’s workgroups, allowing him to gain broad insight into the field’s theoretical and methodological advances. This advanced the researcher’s opportunities in conducting multi-modal research, his independent research profile and career perspectives. The researcher actively participated in weekly group meetings and the institute’s cross-group journal clubs, interdisciplinary discussions and center-wide lectures. In addition to the direct exchange with Prof. Jensen and Prof. Doeller, these interactions fostered his independent thinking, maturity and interdisciplinary skills. The researcher supervised students and mentored colleagues, and organized lab meetings and retreats, which advanced his teamwork and leadership skills. He also organized and participated in the center’s social events. The researcher established multiple collaborations, providing a network for sustained scientific exchange and collaborations. He presented his work at international conferences, which consolidated his communication skills, strengthened his analytic and independent thinking and his abilities in establishing scientific networks. The researcher developed new multi-modal data analyses and contributed to FieldTrip, an open source toolbox for advanced data analyses, developed at the institute. He shared his knowledge with students and trainees by giving a course on the fundamentals and applications of MEG at the Radboud University, Nijmegen, and training students as a tutor at FieldTrip workshops. This advanced his teaching skills and eligibility for obtaining a permanent academic position. The researcher established international collaborations at the host institute, thereby contributing to its international visibility and amenity. He published work on an open-access preprint server (bioRxiv) and submitted his work to an open-access journal, guaranteeing free public access to the project’s findings. After publication, the researcher will further disseminate the results via different media, sharing knowledge publicly. Data will be made available on online depositories after publication. The researcher has shared his research and dissemination activities on social media (twitter), and maintains internet presences. Human memory is a topic of general interest to the public. In particular, because one of today’s society’s biggest challenges is demographic change and aging, bringing about the urgent need to understand the age-related cognitive decline, dementia and Alzheimer’s disease. The outcome of this project contributes to a better understanding of the underlying memory mechanisms, which will ultimately contribute to tackling these challenges.
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