Department of Medicine, Surgery and Dentistry, Scuola Medica Salernitana, University of Salerno, Baronissi, SA, Italy.
Department of Advanced Medical and Surgical Sciences, School of Medicine and Surgery, University of Campania 'Luigi Vanvitelli', Naples, Italy.
J Neural Eng. 2022 May 30;19(3). doi: 10.1088/1741-2552/ac6f81.
Real-time functional magnetic resonance imaging neurofeedback (rt-fMRI-NF) is a non-invasive procedure allowing the self-regulation of brain functions via enhanced self-control of fMRI based neural activation. In semantic rt-fMRI-NF, an estimated relation between multivariate fMRI activation patterns and abstract mental states is exploited for a multi-dimensional feedback stimulus via real-time representational similarity analysis (rt-RSA). Here, we assessed the performances of this framework in a multi-subject multi-session study on a 3 T MRI clinical scanner.Eighteen healthy volunteers underwent two semantic rt-fMRI-NF sessions on two different days. In each session, participants were first requested to engage in specific mental states while local fMRI patterns of brain activity were recorded during stimulated mental imagery of concrete objects (pattern generation). The obtained neural representations were to be replicated and modulated by the participants in subsequent runs of the same session under the guidance of a rt-RSA generated visual feedback (pattern modulation). Performance indicators were derived from the rt-RSA output to assess individual abilities in replicating (and maintaining over time) a target pattern. Simulations were carried out to assess the impact of the geometric distortions implied by the low-dimensional representation of patterns' dissimilarities in the visual feedback.Sixteen subjects successfully completed both semantic rt-fMRI-NF sessions. Considering some performance indicators, a significant improvement between the first and the second runs, and within run increasing modulation performances were observed, whereas no improvements were found between sessions. Simulations confirmed that in a small percentage of cases visual feedback could be affected by metric distortions due to dimensionality reduction implicit to the rt-RSA approach.Our results proved the feasibility of the semantic rt-fMRI-NF at 3 T, showing that subjects can successfully modulate and maintain a target mental state when guided by rt-RSA derived feedback. Further development is needed to encourage future clinical applications.
实时功能磁共振成像神经反馈（rt-fMRI-NF）是一种非侵入性程序，通过增强基于 fMRI 的神经激活的自我控制，允许大脑功能的自我调节。在语义 rt-fMRI-NF 中，利用多元 fMRI 激活模式与抽象心理状态之间的估计关系，通过实时表示相似性分析（rt-RSA）为多维反馈刺激提供信息。在这里，我们在一项使用 3T MRI 临床扫描仪的多主体多会话研究中评估了该框架的性能。18 名健康志愿者在两天的两个不同日子里接受了两次语义 rt-fMRI-NF 会话。在每次会话中，参与者首先被要求在特定的心理状态下进行操作，同时在对具体物体的刺激性心理意象（模式生成）期间记录大脑活动的局部 fMRI 模式。参与者在同一会话的后续运行中根据 rt-RSA 生成的视觉反馈（模式调制）来复制和调节所获得的神经表示。性能指标源自 rt-RSA 输出，用于评估个体复制（并随着时间的推移保持）目标模式的能力。进行了模拟以评估视觉反馈中模式相似性的低维表示所隐含的几何变形的影响。16 名受试者成功完成了两次语义 rt-fMRI-NF 会话。考虑到一些性能指标，在第一次和第二次运行之间观察到了显著的改善，并且在运行内的调制性能也有所提高，而在会话之间没有发现改善。模拟结果证实，在极少数情况下，由于 rt-RSA 方法隐含的降维，视觉反馈可能会受到度量变形的影响。
我们的结果证明了 3T 时语义 rt-fMRI-NF 的可行性，表明当受到 rt-RSA 衍生的反馈指导时，受试者可以成功地调节和维持目标心理状态。需要进一步的发展来鼓励未来的临床应用。
