Data_Sheet_2_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.

脑对不可预测的罕见刺激的反应被认为是一种神经预测误差的指标，然而，此类研究在躯体感觉模态中鲜有涉及。本研究旨在探究大脑对不可预测与可预测的罕见事件的反应。通过对经常接受躯体感觉刺激的成年人（FRE）进行磁脑电图测量，发现偶尔会以两种连续出现的罕见刺激（不可预测罕见刺激（UR）和可预测罕见刺激（PR），两刺激的p值均为0.1）替代FRE。FRE和PR通过电刺激在两种条件下以平衡方式作用于小指或食指。UR是对食指和小指同时进行的电刺激（对于较小的子样本组，UR和FRE在刺激特性上进行了平衡）。大平均值反应由两个主要成分组成：一个在30-100毫秒（M55）之间，另一个在130-230毫秒（M150）之间。对初级躯体感觉皮层（SI）和次级躯体感觉皮层（SII）进行了源级分析。在SI和SII区域，M55反应在UR和PR上均大于FRE，且UR大于PR。对于M150，两个研究区域对UR和PR的活动均高于FRE。有趣的是，尽管UR在刺激能量（同时刺激两个手指）和预测误差潜力上大于PR，但在SI或SII区域，这两种罕见刺激的M150反应在源强度上并未显示出差异。结果表明，M55而非M150可能与预测误差信号相关。这些发现强调了在未来的研究中，区分预测误差与罕见性相关效应的必要性。