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Combining fMRI neurofeedback with an event-related paradigm to investigate inhibitory memory control

Tibor Auer1*, Ana Catarino2, Davide Stramaccia2 and Michael Anderson2
  • 1 MRC Cognition and Brain Sciences Unit, Methods Group, United Kingdom
  • 2 MRC Cognition and Brain Sciences Unit, Memory and Perception Group, United Kingdom

Introduction In this study we used fMRI neurofeedback to train people to self-regulate their hippocampal activity, by either retrieving or suppressing memories for previously learnt word pairs. This is a key first step in an effort to build an innovative new intervention for improving control over intrusive memories, and will provide a test for the viability of neural feedback as an intervention of clinical significance. A growing body of literature suggests that people are capable of engaging active control processes to suppress the representation and accessibility of unwanted experiences in memory (1-3). Neuroimaging research shows that this suppression effect is supported by an increase in dorsolateral prefrontal cortex (DLPFC) activation, which in turn down-regulates activity in the hippocampus (4). In the present study, we focused on the hippocampus to maximise the specificity of the training. Methods When setting up the experiment, we took several methodological issues into consideration. First, we chose to implement the self-regulation in a framework of a cognitive task to ensure specificity. We employed the Think/No-Think (TNT) paradigm (1), which has been proven effective in training participants to suppress retrieval of an unwanted memory. Second, we decided to uncouple the self-regulation phase from the feedback appraisal phase to reduce cognitive load of multi-tasking, to allow for regulation of a region which is itself potentially involved in feedback appraisal, and to be able to investigate the different phases (5). Therefore we have adapted the TNT paradigm by forming mini-blocks of trials followed by self-assessment of performance and then the presentation of the feedback for the bilateral activation of the hippocampi. We chose the rest of the grey matter to monitor the global signal, which can be potentially influenced by arousal. We have determined the number of trials within a mini-block by means of a behavioural pilot. For the sham group (not measured yet), feedback will be calculated based on the participants’ own self-assessment of performance to ensure that feedback will mirror subjective task performance, circumventing the confounding factor of participant frustration. Self-assessment scores will be confounded with white noise, introducing the necessary signal variability to make it comparable to that of the feedback signal for the training group. All subjects underwent six MRI examinations: 1 pre-training session and 5 training sessions. The pre-training session consisted of an anatomical T1W MRI measurement which allowed for the manual segmentation of the hippocampi, and a single scan of the T2*W EPI MRI measurement with the same geometry (field-of-view, spatial resolution and slice positions) and sequence parameters employed for the real-time fMRI. This EPI scan allow for the registration of the segmented regions-of-interest (ROIs) to the fMRI native space. The five training sessions were spread over three to six weeks and consisted of 4 runs of neurofeedback training. Magnetic resonance imaging was conducted at 3-T (Prisma, Siemens Healthcare, Erlangen, Germany) using a 32-channel head coil for signal reception. Structural whole-brain T1W MRI involved a non-selective inversion-recovery 3D FLASH sequence (TR = 2250 ms, TE = 3.02 ms, flip angle 9°, TI = 900 ms) at a nominal resolution of 1 mm isotropic. All fMRI measurements were based on a gradient-echo EPI sequence (TR = 1390 ms, TE = 25 ms, flip angle 78°, GRAPPA = 2) with 3 mm isotropic spatial resolution (28 slices in descending order with 0.75 mm slice gap). We have prioritised temporal over spatial resolution so that 1) higher number of scans within a mini-block increases statistical power; 2) higher voxel size ensures higher SNR in our ROIs with limited signal. For each session, a gradient-echo field mapping sequence with the same geometry as the fMRI measurements was obtained (TR/TE1/TE2 = 400/5.19/7.65 ms, flip angle 60°) to allow correction of the distortions caused by the inhomogeneities of the magnetic field. The individual geometry of the different fMRI measurements of the pre-training session were stored and re-applied in all subsequent sessions (AutoAlign Scout, Siemens) to minimize the spatial difference between datasets. Real-time analysis and neurofeedback presentation were accomplished using an in-house neurofeedback toolbox implemented in MatLab (6). The toolbox has been further developed to allow communication between the real-time analysis and the feedback presenter computers via UDP instead of file transfer. UDP has a minimum overhead thus minimising communication delays. Results As a result of the extensive methodological development, we have successfully combined fMRI-based neurofeedback with a randomised event-related paradigm to investigate the effect of neurofeedback on cognition. So far, we have measured 15 participants (all training group) each comprising 20 runs of ca. 10 min long trainings (total ca. 60 hours not including the pilots).

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Acknowledgements

T.A. and A.C. contributed equally and share first authorship

T.A. was supported by the Medical Research Council (United Kingdom) [MC-A060-53114]. A.C., D.S. and M.A. were supported by the Medical Research Council (United Kingdom) [MC-A060-5PR00].

References

1. Anderson MC, Green C. Suppressing unwanted memories by executive control. Nature (2001) 410(6826):366-9. Epub 2001/03/27. doi: 10.1038/35066572. PubMed PMID: 11268212.
2. Gagnepain P, Henson RN, Anderson MC. Suppressing unwanted memories reduces their unconscious influence via targeted cortical inhibition. P Natl Acad Sci USA (2014) 111(13):E1310-E9. doi: 10.1073/pnas.1311468111. PubMed PMID: WOS:000333579700023.
3. Kupper CS, Benoit RG, Dalgleish T, Anderson MC. Direct suppression as a mechanism for controlling unpleasant memories in daily life. Journal of experimental psychology General (2014) 143(4):1443-9. Epub 2014/04/23. doi: 10.1037/a0036518. PubMed PMID: 24749897; PubMed Central PMCID: PMCPMC4113301.
4. Benoit RG, Anderson MC. Opposing mechanisms support the voluntary forgetting of unwanted memories. Neuron (2012) 76(2):450-60. Epub 2012/10/23. doi: 10.1016/j.neuron.2012.07.025. PubMed PMID: 23083745; PubMed Central PMCID: PMC3480638.
5. Dewiputri W. An exploration of real-time functional magnetic resonance imaging neurofeedback in cognition. Göttingen: Georg-August-Universität Göttingen (2014).
6. Auer T, Schweizer R, Frahm J. Training Efficiency and Transfer Success in an Extended Real-Time Functional MRI Neurofeedback Training of the Somatomotor Cortex of Healthy Subjects. Front Hum Neurosci (2015) 9:547. Epub 2015/10/27. doi: 10.3389/fnhum.2015.00547. PubMed PMID: 26500521; PubMed Central PMCID: PMC4598802.

Keywords: functional magnetic resonance imaging (fMRI), neurofeedback (NF), think/no-think, event-related paradigm, Hippocampus, Memory control

Conference: SAN2016 Meeting, Corfu, Greece, 6 Oct - 9 Oct, 2016.

Presentation Type: Poster Presentation in SAN2016 Conference

Topic: Posters

Citation: Auer T, Catarino A, Stramaccia D and Anderson M (2016). Combining fMRI neurofeedback with an event-related paradigm to investigate inhibitory memory control. Conference Abstract: SAN2016 Meeting. doi: 10.3389/conf.fnhum.2016.220.00057

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Received: 29 Jul 2016; Published Online: 01 Aug 2016.

* Correspondence: MD, PhD. Tibor Auer, MRC Cognition and Brain Sciences Unit, Methods Group, Cambridge, United Kingdom, tibor.auer@gmail.com