Community Research and Development Information Service - CORDIS

Periodic Report Summary 1 - MEM_DISTRACTION (On the neural basis of working memory:How the brain retains information in the face of distraction.)

Project objectives:
The main goal of this project is to unravel the neural mechanisms supporting visual working memory in the face of distraction. This main objective was broken down into 5 different experiments that sought to answer this question in a structured fashion. Visual working memory was proposed to be investigated using functional Magnetic Resonance Imaging (fMRI) and Transcranial Magnetic Stimulation (TMS). The researcher had the training objectives of acquiring expertise in the use of forward modeling in fMRI, using TMS, expanding knowledge on neural signatures of visual working memory, and building up an international network and collaborations. Below, the work performed in the two outgoing years of the Marie Curie fellowship is outlined.

Work performed & results over the last 2 years:
The researcher has performed 3 main experiments and has collaborated on 2 additional projects.
In the first project, the researcher set out to investigate how visual working memory items are maintained by the brain when attention is not focused on the particular item. During this project, the researcher learned how to use forward modeling and what the optimal data collection for these types of visual working memory experiments is. During the piloting phase of the experiment the researcher found that, congruent with literature that was published during that same year (Ester et al., 2015), in stead of collecting a small amount of data from a large group of subjects, the forward modeling required a large amount of data from a small group of subjects. Due to these unexpected findings and this change in paradigm, the project was delayed by 4 months. After this delay, data collection and analyses were finished successfully. The main findings of the study are that when a visual working memory item is not attended, it is not represented in an active manner in visual cortex. However, an item that is discarded from working memory is suppressed in visual cortex. This has not been shown before, and these results imply that the visual system is actively involved in suppressing unwanted information. In addition, the neural representation of unattended working memory items is different from discarded working memory items. These findings have been presented in multiple labs (UC Berkeley, Donders Institute Nijmegen, Free University Amsterdam) and at the international conference of the Society for Neuroscience in Chicago, 2015. This project is being finalized and will be submitted to a high-ranking journal shortly.
The second project was designed to test what the influence of TMS is on the neural representation of the visual stimuli that are used in the visual working memory task. This project involved multiple sessions of fMRI combined with TMS to elucidate how the tuning to orientation in V1 changed after ThetaBurst Stimulation to V1 or to a control region. The results so far indicate that the amplitude of the tuning in V1 is lowered after ThetaBurst Stimulation to V1, but not after stimulation to a control region. However, results are not conclusive yet, since with the number of participants that are currently tested, the results hinge on significance. Bayesian statistics will be used to assess whether there is substantial evidence for the current hypothesis of lower amplitude after stimulation and whether further data collection is necessary. This project has been presented at the annual meeting of the Cognitive Neuroscience Society in New York, 2016. Since there was a delay in the first project, and data analyses now seems inconclusive towards the hypotheses of this project, there is a delay in this project of about 1 year.
The third project is based on the outcome of the first project and is aimed to evoke fMRI responses to the unattended visual working memory representation. The design of this study is based on very recent findings from the field (Wolff et al., 2015) and is the first to incorporate this using fMRI. Since the first and second project were delayed, there is a delay in this project as well of about 1 year. Data collection is ongoing and the first results will be presented at the annual meeting of the Cognitive Neuroscience Society 2017, in San Francisco.
The collaboration on the 2 additional projects has focused on visual working memory and the effect of intervening distractors on the main visual working memory item, as well as the general implications and methods of using the forward modelling approach. The first project has been presented at the annual meeting of the Soeciety for Neuroscience 2015 in Chicago, and the annual meeting of the Vision Science Society 2016 in Naples, Florida. The second project will be presented at the annual meeting of the Society for Neuroscience 2016 in San Diego.
Over the first 2 years of the project, the researcher has met all the 4 objectives described in the proposal. She is now an expert in using forward modelling in fMRI and the use of TMS by using these techniques for multiple studies. She has gained an extensive amount of knowledge on the neural substrates of visual working memory by additionally attending working memory journal clubs in which the most recent visual working memory papers were discussed. Her international network has been expanded by attending to multiple conferences, and building long-term collaborations between researchers in the D’Esposito lab that now have faculty positions at for example Florida State and GeorgeTech. The collaborations with UC Berkeley are ongoing and will continue to exist even after the current project has been finalized.

Expected final results and impact:
By the end of this project, the researcher expects to have elucidated how unattended visual working memory items are maintained by the brain, and how visual cortex is involved in representing different types of visual working memory information. In addition, unexpected findings have led to new knowledge about how the brain deals with unwanted information. These findings have implications for how we deal with memory in daily life situations, and how we should present new information to humans for them to be able to process and remember as much as possible. More fundamentally, the project will shed light on how the visual system represents low-level information and how such information can be altered by stimulation.

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Life Sciences
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