Tracking dynamic adjustments to decision making and performance monitoring processes in conflict tasks

Abstract

How we exert control over our decision making has been investigated using conflict tasks, which involve stimuli containing elements that are either congruent or incongruent. In these tasks, participants adapt their decision making strategies following exposure to incongruent stimuli. According to conflict monitoring accounts, conflicting stimulus features are detected in medial frontal cortex, and the extent of experienced conflict scales with response time (RT) and frontal theta--band activity in the electroencephalogram (EEG). However, the consequent adjustments to decision processes following response conflict are not well--specified. To characterise these adjustments and their neural implementation we recorded EEG during a Flanker task. We traced the time--courses of performance monitoring processes (frontal theta) and multiple processes related to perceptual decision making. In each trial participants judged which of two overlaid gratings forming a plaid stimulus (termed the S1 target) was of higher contrast. The stimulus was divided into two sections, which each contained higher contrast gratings in either congruent or incongruent directions. Shortly after responding to the S1 target, an additional S2 target was presented, which was always congruent. Our EEG results suggest enhanced sensory evidence representations in visual cortex and reduced evidence accumulation rates for S2 targets following incongruent S1 stimuli. Frontal theta amplitudes positively correlated with RT following S1 targets (in line with conflict monitoring accounts). Following S2 targets there was no such correlation, and theta amplitude profiles instead resembled decision evidence accumulation trajectories. Based on these differing amplitude profiles across S1 and S2 we formulated a novel theory of frontal theta and performance monitoring, which accounts for differing theta amplitude profiles previously observed across tasks that do and do not involve conflict. We propose that frontal theta does not actually index conflict detection but instead reflects a more general performance monitoring process related to decision confidence and rapid error detection.

Electrophysiological correlates of confidence differ across correct and erroneous perceptual decisions

“…We additionally note that, in the CSD-ERPs, there were apparent differences between higher/lower confidence ratings prior to the CPP measurement window (Figures 4B, 4C, left panels). These ERP effects reflect differences in the CPP build-up rate across subsets of trials with faster and slower RTs, as typically observed in similar perceptual decision tasks (e.g., O’Connell et al, 2012; Kelly & O’Connell, 2013; Twomey et al, 2015; Feuerriegel et al, 2021a). The build-up rate of the CPP is thought to index the rate of evidence accumulation, known as the drift rate in evidence accumulation models (O’Connell et al, 2012; Kelly et al, 2021).…”

“…For analyses of CSD-transformed data we selected slightly different sets of electrodes to better isolate localised effects that become apparent when using this data transformation. We measured the CPP at CPz and Pz, consistent with electrodes used in previous work (e.g., O’Connell et al, 2012; Kelly & O’Connell, 2013; Steinemann et al, 2018; Feuerriegel et al, 2021a). Based on correlations between stimulus discriminability (which correlates with confidence) and fronto-central electrode amplitudes reported by Kelly and O’Connell (2013), we additionally measured amplitudes of a frontal component at channel FCz during the time window used to measure the CPP.…”

“…For analyses of CSD-transformed data we selected slightly different sets of electrodes to better isolate localised effects that become apparent when using this data transformation. We measured the CPP at CPz and Pz, consistent with electrodes used in previous work (e.g., O’Connell et al, 2012; Kelly & O’Connell, 2013; Steinemann et al, 2018; Feuerriegel et al, 2021a). We selected these electrodes because the CPP component shows a very focal distribution over Pz and CPz in CSD-transformed data, with amplitudes that can be markedly diminished at neighbouring channels (e.g., Kelly & O’Connell, 2013; Murphy et al, 2015; Feuerriegel et al, 2021).…”

“…The critical stimuli consisted of two overlaid diagonal gratings within a circular aperture, presented against a grey background (similar to Steinemann et al, 2018; Feuerriegel et al, 2021a). The two gratings were oriented 45° to the left and right of vertical, respectively.…”

“…We measured mean ERP amplitudes of the pre-response CPP between -130 to - 70 ms relative to the response at parietal electrodes Pz, P1, P2, CPz, and POz (same time window as Steinemann et al, 2018; Feuerriegel et al, 2021a). For these analyses we used a pre-stimulus baseline (i.e., the -200 to 0 ms pre-target interval).…”