Beresniewicz Justyna, Riemer Frank, Kazimierczak Katarzyna, Ersland Lars, Craven Alexander R, Hugdahl Kenneth, Grüner Renate
Department of Biological and Medical Psychology, University of Bergen, Bergen, Norway.
Mohn Medical Imaging and Visualization Centre, Department of Radiology, Haukeland University Hospital, Bergen, Norway.
Front Hum Neurosci. 2023 Aug 3;17:1238888. doi: 10.3389/fnhum.2023.1238888. eCollection 2023.
Functional Magnetic Resonance Imaging (fMRI) block-design experiments typically include active ON-blocks with presentation of cognitive tasks which are contrasted with OFF- blocks with no tasks presented. OFF-blocks in between ON-blocks can however, also be seen as a proxy for intermittent periods of resting, inducing temporary resting-states. We still do not know if brain activity during such intermittent periods reflects the same kind of resting-state activity as that obtained during a continuous period, as is typically the case in studies of the classic Default Mode Network (DMN). The purpose of the current study was therefore to investigate both similarities and differences in brain activity between intermittent and continuous resting conditions.
There were 47 healthy participants in the 3T fMRI experiment. Data for the intermittent resting-state condition were acquired from resting-periods in between active task-processing periods in a standard ON-OFF block design, with three different cognitive tasks presented during ON-blocks. Data for the continuous resting-state condition were acquired during a 5 min resting period after the task-design had been presented.
The results showed that activity was overall similar in the two conditions, but with some differences. These differences were within the DMN network, and for the interaction of DMN with other brain networks. DMN maps showed weak overlap between conditions in the medial prefrontal cortex (MPFC), and in particular for the intermittent compared to the continuous resting-state condition. Moreover, DMN showed strong connectivity with the salience network (SN) in the intermittent resting-state condition, particularly in the anterior insula and the supramarginal gyrus. The observed differences may reflect a "carry-over" effect from task-processing to the next resting-state period, not present in the continuous resting-state condition, causing interference from the ON-blocks. Further research is needed to fully understand the extent of differences between intermittent and continuous resting-state conditions.
功能磁共振成像（fMRI）的组块设计实验通常包括呈现认知任务的激活“开”组块，将其与不呈现任务的“关”组块进行对比。然而，“开”组块之间的“关”组块也可被视为间歇性静息期的替代，从而诱发临时静息状态。我们仍然不知道在这种间歇性静息期的大脑活动是否反映了与连续静息期相同类型的静息状态活动，就像经典默认模式网络（DMN）研究中通常的情况那样。因此，本研究的目的是调查间歇性和连续性静息条件下大脑活动的异同。
3T fMRI实验中有47名健康参与者。间歇性静息状态条件的数据是从标准“开-关”组块设计中活跃任务处理期之间的静息期采集的，“开”组块期间呈现三种不同的认知任务。连续性静息状态条件的数据是在呈现任务设计后的5分钟静息期采集的。
结果表明，两种条件下的活动总体相似，但存在一些差异。这些差异存在于DMN网络内，以及DMN与其他脑网络的相互作用中。DMN图谱显示内侧前额叶皮质（MPFC）在两种条件下的重叠较弱，特别是间歇性静息状态条件与连续性静息状态条件相比。此外，在间歇性静息状态条件下，DMN与突显网络（SN）有很强的连接，特别是在前岛叶和缘上回。观察到的差异可能反映了从任务处理到下一个静息状态期的“遗留”效应，而在连续性静息状态条件下不存在这种效应，从而导致“开”组块的干扰。需要进一步研究以充分了解间歇性和连续性静息状态条件之间差异的程度。
