Psychophysiological Mechanisms of Interindividual Differences in Goal Activation Modes During Action Cascading

Abstract

Our daily life is characterized by multiple response options that need to be cascaded in order to avoid overstrain of restricted response selection resources. While response selection and goal activation in action cascading are likely driven by a process varying from serial to parallel processing, little is known about the underlying neural mechanisms that may underlie interindividual differences in these modes of response selection. To investigate these mechanisms, we used a stop-change paradigm for the recording of event-related potentials and standardized low resolution brain electromagnetic tomography source localizations in healthy subjects. Systematically varying the stimulus onset asynchrony (the temporal spacing of "stop" and "change" signals), we applied mathematical constraints to classify subjects in more parallel or more serial goal activators during action cascading. On that basis, the electrophysiological data show that processes linking stimulus processing and response execution, but not attentional processes, underlie interindividual differences in either serial or parallel response selection modes during action cascading. On a systems level, these processes were mediated via a distributed fronto-parietal network, including the anterior cingulate cortex (Brodman area 32, BA32) and the temporo-parietal junction (BA40). There was a linear relation between the individual degree of overlap in activated task goals and electrophysiological processes.

A causal role of the right inferior frontal cortex in implementing strategies for multi-component behaviour

“…Such coordination requires the organization of individual actions into a hierarchical structure that can be flexibly interrupted and altered to achieve a goal whenever necessary. A number of previous studies have demonstrated that people apply different strategies when coordinating complex motor plans [1][2][3] in situations requiring a chaining of different actions to achieve a goal; however, the neuronal mechanisms underlying the strategy that links individual actions in multi-component behaviour have remained elusive.…”

“…However, an alternative strategy in which different task goals are activated with some temporal overlap (that is, parallel processing) hampers the efficient unfolding of multi-component behaviour, possibly because different actions interfere with each other and overstrain response selection capacities [1][2][3][4] .…”

“…To examine multi-component behaviour, we applied a stopchange paradigm 1,3 (Fig. 1) in which subjects were required to make rapid responses to stimuli presented on a screen.…”

“…The CHANGE stimulus was presented either simultaneously with the STOP stimulus at a stop-change delay (SCD) of 0 ms or following the STOP stimulus at an SCD of 300 ms. For simultaneous STOP and CHANGE signals (SCD ¼ 0 ms), subjects could process the two actions either serially or in parallel; at an SCD of 300 ms, it was only possible to process the two actions in a step-by-step (that is, serial) manner 3 . As parallel strategies for individual action activation are related to inefficient unfolding behaviour 1,3,4 , they typically result in longer reaction times (RTs) on the CHANGE signal (RT2). Using these SCD manipulations and applying mathematical constraints to the RT2 data allows inferences regarding the underlying processing strategy 3 .…”

“…In the present study, we examined to what extent the neural dynamics in the rIFG, as modulated via iTBS or cTBS, are related to the inferred strategy and efficiency of multi-component behaviour. Moreover, by recorded event-related potentials (ERPs), we were able to identify associated alterations in cognitive processes on the attentional and response selection levels, both of which may contribute to shifts in multi-component processing strategies 1,14,15 . cTBS applied to the rIFG results in a less efficient action cascading strategy, whereas iTBS results in a more efficient strategy, compared with a shamTBS control condition.…”