Data_Sheet_1_Magnetoencephalography Responses to Unpredictable and Predictable Rare Somatosensory Stimuli in Healthy Adult Humans.pdf

Mismatch brain responses to unpredicted rare stimuli are suggested to be a neural indicator of prediction error, but this has rarely been studied in the somatosensory modality. Here, we investigated how the brain responds to unpredictable and predictable rare events. Magnetoencephalography responses were measured in adults frequently presented with somatosensory stimuli (FRE) that were occasionally replaced by two consecutively presented rare stimuli [unpredictable rare stimulus (UR) and predictable rare stimulus (PR); p = 0.1 for each]. The FRE and PR were electrical stimulations administered to either the little finger or the forefinger in a counterbalanced manner between the two conditions. The UR was a simultaneous electrical stimulation to both the forefinger and the little finger (for a smaller subgroup, the UR and FRE were counterbalanced for the stimulus properties). The grand-averaged responses were characterized by two main components: one at 30–100 ms (M55) and the other at 130–230 ms (M150) latency. Source-level analysis was conducted for the primary somatosensory cortex (SI) and the secondary somatosensory cortex (SII). The M55 responses were larger for the UR and PR than for the FRE in both the SI and the SII areas and were larger for the UR than for the PR. For M150, both investigated areas showed increased activity for the UR and the PR compared to the FRE. Interestingly, although the UR was larger in stimulus energy (stimulation of two fingers at the same time) and had a larger prediction error potential than the PR, the M150 responses to these two rare stimuli did not differ in source strength in either the SI or the SII area. The results suggest that M55, but not M150, can possibly be associated with prediction error signals. These findings highlight the need for disentangling prediction error and rareness-related effects in future studies investigating prediction error signals.

对意外罕见刺激的脑部反应差异被认为是一种预测错误的神经指标，然而，在躯体感觉模态中，这一现象的研究却鲜有涉及。本研究旨在探讨大脑对不可预测与可预测的罕见事件的反应机制。通过测量频繁接受躯体感觉刺激（FRE）的成年人在偶尔替换为两种连续呈现的罕见刺激（不可预测罕见刺激（UR）和可预测罕见刺激（PR）；两种刺激的p值均为0.1）时的磁脑电图（MEG）反应。FRE和PR是通过在两种条件下对食指或拇指进行电刺激（两种条件间以平衡方式呈现）来实现的。UR是对食指和小指同时进行的电刺激（对于较小的一部分受试者，UR和FRE在刺激特性上进行了平衡）。在源级别分析中，主要针对初级躯体感觉皮层（SI）和次级躯体感觉皮层（SII）。在SI和SII区域，M55反应对于UR和PR均大于FRE，且UR大于PR。对于M150，两个研究区域在UR和PR与FRE相比均表现出活动增加。有趣的是，尽管UR在刺激能量（同时刺激两个手指）和预测错误潜力上大于PR，但这两个罕见刺激在SI或SII区域的源强度反应在M150上并无差异。结果表明，M55而非M150可能与预测错误信号相关。这些发现突显了在未来的研究中，有必要区分预测错误信号与罕见性相关效应的必要性。