Nelson Wilf, Mayhew Stephen D
Centre for Human Brain Health (CHBH), School of Psychology, University of Birmingham, Birmingham, UK.
Institute of Health and Neurodevelopment (IHN) and School of Psychology, Aston University, Birmingham, UK.
Hum Brain Mapp. 2025 Mar;46(4):e70177. doi: 10.1002/hbm.70177.
Negative BOLD fMRI responses (NBR) occur commonly in sensory cortex and default mode network regions but remain poorly utilized as a marker of brain function due to an incomplete understanding. To better understand how NBR manifest across the brain, compare between different sensory stimuli and how they are modulated by changes in task demand, we recorded fMRI during trials of visual, auditory, or somatosensory stimulation, delivered either alone or in concurrent pairs. Twenty young-adult participants were cued to attend to a single modality and detect targets in each trial. We found that NBR were consistently induced in all non-task-relevant primary sensory cortices and default mode regions during all stimuli. NBR were observed within the stimulated modality, in the cortex ipsilateral to the stimulus; as well as cross-modal responses bilaterally within the cortex of an unstimulated sensory modality. The NBR regions showed high spatial overlap with the primary sensory positive BOLD response (PBR) of the stimulated modality. The NBR occurred in spatially comparable regions across different modality stimuli such that the peak voxel location and spatial extent were comparable between within and cross-modal NBRs. Some specific differences were seen, such as stronger magnitude sensorimotor NBR to somatosensory stimuli than to visual or auditory. No significant relationships were found between subjects' PBR and NBR magnitude, but significant linear correlations were observed between NBRs indicating that subjects with high magnitude NBR within one sensory modality also displayed high magnitude cross-modal NBR in a different modality. These findings suggest that cortical NBR are largely consistent between different sensory stimuli but also contain stimulus-specific variability in magnitude and spatial extent. Finally, positive BOLD responses were stronger to dual stimuli in all contralateral primary sensory regions, whilst NBR were slightly increased in specific regions of ipsilateral visual and sensorimotor cortex. This finding suggests a strong contribution to NBR from bottom-up stimulus input that was further modulated by attention during dual conditions and that NBR is driven by a combination of bottom-up and top-down influences whereby contributions to its generation arise from both feed-forward signals from subcortical or activated sensory regions and feedback mechanisms such as higher-level attentional control.
负性血氧水平依赖性功能磁共振成像反应（NBR）常见于感觉皮层和默认模式网络区域，但由于理解不完整，其作为脑功能标志物的应用仍不充分。为了更好地理解NBR在全脑的表现、比较不同感觉刺激之间的差异以及它们如何受到任务需求变化的调节，我们在视觉、听觉或体感刺激试验期间记录了功能磁共振成像，这些刺激单独或成对同时呈现。20名年轻成年参与者被提示关注单一模态并在每次试验中检测目标。我们发现，在所有刺激过程中，所有与任务无关的初级感觉皮层和默认模式区域均持续诱发NBR。在受刺激的模态内、刺激同侧的皮层中观察到NBR；以及在未受刺激的感觉模态皮层内双侧的跨模态反应。NBR区域与受刺激模态的初级感觉正性血氧水平依赖性功能磁共振成像反应（PBR）表现出高度的空间重叠。不同模态刺激下的NBR出现在空间上可比的区域，使得峰值体素位置和空间范围在模态内和跨模态NBR之间具有可比性。观察到一些特定差异，例如体感刺激引起的感觉运动NBR幅度比视觉或听觉刺激更强。未发现受试者的PBR与NBR幅度之间存在显著关系，但在NBR之间观察到显著的线性相关性，表明在一种感觉模态中NBR幅度高的受试者在另一种不同模态中也表现出高幅度的跨模态NBR。这些发现表明，皮层NBR在不同感觉刺激之间在很大程度上是一致的，但在幅度和空间范围上也存在刺激特异性的变异性。最后，在所有对侧初级感觉区域中，双刺激引起的正性血氧水平依赖性功能磁共振成像反应更强，而在同侧视觉和感觉运动皮层的特定区域中NBR略有增加。这一发现表明，自下而上的刺激输入对NBR有很大贡献，在双刺激条件下注意力对其有进一步调节作用，并且NBR由自下而上和自上而下的影响共同驱动，其产生的贡献既来自皮层下或激活的感觉区域的前馈信号以及诸如高级注意力控制等反馈机制。
