Commentary: Probing the Neural Mechanisms for Distractor Filtering and Their History-Contingent Modulation by Means of TMS

Abstract

The ability to suppress irrelevant but attention grabbing stimuli in our environment is critical for maintaining goal-directed control during many daily activities, such as avoiding junk foods while dieting or ignoring distractions while driving. Although we know much about the properties of environmental cues that make them susceptible to attentional capture (e.g., bright lights, loud sounds, fast movements), we know far less about how to disengage from such distractions, particularly the neural mechanisms involved in these processes.In a recent paper by Lega et al. (2019), the authors examined whether non-invasive brain stimulation, using transcranial magnetic stimulation (TMS), could be used to modulate distractor filtering when applied over the dorsal frontoparietal attentional networks, specifically the frontal eye field (FEF) and the intraparietal sulcus (IPS). The authors used a visual search task in which participants had to identify a target within a four-item array. Critically, on half of the trials, the array also included a salient distractor in a pop-out color (e.g., displayed in red while all other items in the array, including the target, were displayed in green). On distractor-absent trials, participants were fast to find the target, and as expected, on distractor-present trials, participants were slow; their attention was effectively captured by the pop-out color, slowing their search and identification of the target in the array.Interestingly, the authors showed that delivering triple-pulse 10 Hz TMS at 100% of resting motor threshold to the right FEF 100 ms after the presentation of the search array reduced the slowing of reaction times (RTs) on distractor-present trials compared to stimulation over a control (sham) location. Notably, this reduction to the RT interference effect on distractor-present trials following FEF stimulation was specific to the right hemisphere and did not have the same effect over the left hemisphere. Moreover, right IPS stimulation generated a similar reduction in RT slowing on distractor-present trials compared to the sham stimulation, but this difference was not statistically significant and numerically smaller than the difference produced by right FEF stimulation. Although no discussion was provided about the TMS parameters selected and how this may affect the selectivity of the effect, the results indicate that targeting the right FEF produced the largest modulatory effects on distractor processing. This is a fascinating and highly relevant finding because it suggests that non-invasive brain stimulation may have the potential to train or improve attentional control over task-irrelevant, salient distractors.