Modelling appetitive-disinhibition in modified stop-signal task: A computational model of associative memory initiated going (disinhibition) system
Background: Studies employing modified Stop-signal tasks (MSST) have demonstrated that response-inhibition, a key executive-function, severely impairs in appetitive environments. These studies demonstrate that presence of appetitive-cues results in disinhibited response and slow-stopping latencies (i.e., Stop-Signal Reaction-Times or SSRT’s). Theoretical-frameworks propose that retrieval of appetitive-cue approach/going-response associations (developed during appetitive-conditioning) from one's associative-memory traces, biases the inhibitory system such that it produces approach/going (i.e., disinhibited-response) post-exposure to appetitive-cues. Aims: The aim of the current study was to develop a computational model of response-disinhibition i.e., a going-system. In developing this model, we introduced a new free-parameter ‘λ’ which instantiated associative-memory recall. We augmented λ to the Interactive Race Model (IRM) of action suppression to model the interaction between the associative-memory (i.e., λ) and inhibitory-system (i.e., IRM) with an aim to simulate disinhibited-responses (indicated by slow SSRT’s) observed in MSST studies. Methods: We tested three model types that differed in how λ affected go-process and stop-process in IRM formalism. In the first model (Associative-Memory Interactive Disinhibition-Model–AMI) the λ parameters affected the mutual inhibitory-interaction between go-process and stop-process. In the second model (Associative-Memory Race Disinhibition-Model–AMR) λ parameters affected the mean growth-rate of go-process and stop-process. In the final model (AssociativeMemory Interactive Race Disinhibition-Model–AMIR) λ parameters affected both mean growth-rate and mutual inhibitory-interaction between go-process and stop-process simultaneously. Results: The modeling results indicated that out of the three models, only the first model–AMI, produced slow SSRT’s observed in appetitive-cue conditions in MSST studies. Conclusion: The current study validated the theoretical propositions that associative memory and inhibitory-system interact with each other in producing appetitive-cue initiated disinhibition. It specifically highlighted that associative-memory affects the mutual inhibitory interaction (between go-process and stop-process) aspect of the inhibitory-system in giving rise to appetitive-cue initiated disinhibited-responses observed in MSST studies.