Rangaprakash D, Tadayonnejad Reza, Deshpande Gopikrishna, O'Neill Joseph, Feusner Jamie D
Department of Psychiatry and Biobehavioral Sciences, University of California Los Angeles, Los Angeles, CA, 90095, USA.
Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School and Harvard-MIT Health Sciences and Technology, Cambridge, MA, 02129, USA.
Brain Imaging Behav. 2021 Jun;15(3):1622-1640. doi: 10.1007/s11682-020-00358-8.
The hemodynamic response function (HRF) represents the transfer function linking neural activity with the functional MRI (fMRI) signal, modeling neurovascular coupling. Since HRF is influenced by non-neural factors, to date it has largely been considered as a confound or has been ignored in many analyses. However, underlying biophysics suggests that the HRF may contain meaningful correlates of neural activity, which might be unavailable through conventional fMRI metrics. Here, we estimated the HRF by performing deconvolution on resting-state fMRI data from a longitudinal sample of 25 healthy controls scanned twice and 44 adults with obsessive-compulsive disorder (OCD) before and after 4-weeks of intensive cognitive-behavioral therapy (CBT). HRF response height, time-to-peak and full-width at half-maximum (FWHM) in OCD were abnormal before treatment and normalized after treatment in regions including the caudate. Pre-treatment HRF predicted treatment outcome (OCD symptom reduction) with 86.4% accuracy, using machine learning. Pre-treatment HRF response height in the caudate head and time-to-peak in the caudate tail were top-predictors of treatment response. Time-to-peak in the caudate tail, a region not typically identified in OCD studies using conventional fMRI activation or connectivity measures, may carry novel importance. Additionally, pre-treatment response height in caudate head predicted post-treatment OCD severity (R = -0.48, P = 0.001), and was associated with treatment-related OCD severity changes (R = -0.44, P = 0.0028), underscoring its relevance. With HRF being a reliable marker sensitive to brain function, OCD pathology, and intervention-related changes, these results could guide future studies towards novel discoveries not possible through conventional fMRI approaches like standard BOLD activation or connectivity.
血流动力学响应函数（HRF）代表了将神经活动与功能磁共振成像（fMRI）信号联系起来的传递函数，对神经血管耦合进行建模。由于HRF受非神经因素影响，迄今为止在许多分析中它大多被视为一种干扰因素或被忽略。然而，基础生物物理学表明HRF可能包含神经活动的有意义关联信息，而这些信息可能无法通过传统的fMRI指标获得。在此，我们通过对25名健康对照者的纵向样本（扫描两次）以及44名患有强迫症（OCD）的成年人在强化认知行为疗法（CBT）前后的静息态fMRI数据进行反卷积来估计HRF。OCD患者在治疗前尾状核等区域的HRF响应高度、峰值时间和半高宽（FWHM）异常，治疗后恢复正常。使用机器学习，治疗前的HRF以86.4%的准确率预测治疗结果（OCD症状减轻）。尾状核头部的治疗前HRF响应高度和尾状核尾部的峰值时间是治疗反应的顶级预测指标。尾状核尾部的峰值时间，这一在使用传统fMRI激活或连接性测量的OCD研究中通常未被识别的区域，可能具有新的重要性。此外，尾状核头部的治疗前响应高度预测了治疗后的OCD严重程度（R = -0.48，P = 0.001），并与治疗相关的OCD严重程度变化相关（R = -0.44，P = 0.0028），突出了其相关性。由于HRF是对脑功能、OCD病理学及干预相关变化敏感的可靠标志物，这些结果可为未来研究指引方向，以实现通过标准BOLD激活或连接性等传统fMRI方法无法达成的新发现。
