Abstract and Effector-Selective Decision Signals Exhibit Qualitatively Distinct Dynamics before Delayed Perceptual Reports

Abstract

Electrophysiological research has isolated neural signatures of decision formation in a variety of brain regions. Studies in rodents and monkeys have focused primarily on effector-selective signals that translate the emerging decision into a specific motor plan, but, more recently, research on the human brain has identified an abstract signature of evidence accumulation that does not appear to play any direct role in action preparation. The functional dissociations between these distinct signal types have only begun to be characterized, and their dynamics during decisions with deferred actions with or without foreknowledge of stimulus-effector mapping, a commonly studied task scenario in single-unit and functional imaging investigations, have not been established. Here we traced the dynamics of distinct abstract and effector-selective decision signals in the form of the broad-band centro-parietal positivity (CPP) and limb-selective ␤-band (8 -16 and 18 -30 Hz) EEG activity, respectively, during delayed-reported motion direction decisions with and without foreknowledge of direction-response mapping. With foreknowledge, the CPP and ␤-band signals exhibited a similar gradual build-up following evidence onset, but whereas choice-predictive ␤-band activity persisted up until the delayed response, the CPP dropped toward baseline after peaking. Without foreknowledge, the CPP exhibited identical dynamics, whereas choice-selective ␤-band activity was eliminated. These findings highlight qualitative functional distinctions between effector-selective and abstract decision signals and are of relevance to the assumptions founding functional neuroimaging investigations of decision-making.

Neurodynamic Evidence Supports a Forced-Excursion Model of Decision-Making under Speed/Accuracy Instructions

“…Experiment 1 used transcranial magnetic stimulation (TMS) to track corticospinal excitability, a downstream signal presumed to be under continuous influence from the decision variable (Bestmann et al, 2008; Duque et al, 2010; Hadar et al, 2016; Klein-Flugge and Bestmann, 2012). In experiment 2, we recorded the event-related potential (ERP) centroparietal positivity (CPP; O’Connell et al, 2012; Kelly and O’Connell, 2013; Twomey et al, 2016), a large, late positivity recorded over parietal regions. Importantly, this ERP has been suggested to reflect decision-related accumulation directly, independently of associated motor responses.…”

Stimulus reliability automatically biases temporal integration of discrete perceptual targets

“…In addition, we recorded brain activity using EEG. To characterise the temporal dynamics of individual perceptual decisions, we quantified a well-documented neural correlate of decisionmaking (11,12,41), the centro-parietal positivity (CPP), time-locked to the onsets of both coloursaturation modulation and coherent motion signals (see Methods and Fig. 1a).…”

“…To characterise the time-course of evidence accumulation in the motion-averaging task, we next analysed the CPP (Fig. 3), a positive deflection over centro-parietal electrodes that has been shown to closely mimic temporal dynamics of evidence accumulation (11,12,41). Visual inspection of the ERP topographies ( Fig.…”

“…The recorded signal was pre-processed using the FASTER algorithm for automated artefact rejection (56). The pre-processed signal was down-sampled to 256 Hz, proportional to stimulus quality, and it is observed even in the absence of overt responses (11,12,41). To recover feature-specific information about motion signals from the EEG signals ( Fig.…”

The Role of Premature Evidence Accumulation in Making Difficult Perceptual Decisions under Temporal Uncertainty

“…Each of these signals builds gradually during decision formation at a rate proportional to evidence strength, peaks around the time of a decision-reporting movement, predicts choice accuracy and RT across trials and exhibits amplitude modulations consistent with decision bound adjustments (Kelly & O'Connell, 2013;O'Connell et al, 2012;Steinemann et al, 2018;Loughnane et al, 2016;Murphy et al, 2015). Unlike the decision signals observed in premotor regions of the human and non-human brain, the CPP provides a domain-general or abstract representation of an emerging decision, tracing evidence accumulation even in conditions where no overt action is required and motor preparation is absent (O'Connell et al, 2012;Twomey, Kelly & O'Connell, 2016).…”