Suppression-induced forgetting of motor sequences

Brain mechanisms underlying the inhibitory control of thought

Controlling action and thought requires the capacity to stop mental processes. Over the past two decades, evidence has grown that a domain-general inhibitory control mechanism supported by the right lateral prefrontal cortex achieves these functions. However, current views of the neural mechanisms of inhibitory control derive largely from research into the stopping of action. Whereas action stopping is a convenient empirical model, it does not invoke thought inhibition and cannot be used to identify the unique features of this process. Here, we review research that addresses how organisms stop a key process that drives thoughts: memory retrieval. This work has shown that retrieval stopping shares right dorsolateral and ventrolateral prefrontal mechanisms with action stopping, consistent with a domain-general inhibitory control mechanism, but also recruits a distinct fronto-temporal pathway that determines the success of mental control. As part of this pathway, GABAergic inhibition within the hippocampus influences the efficacy of prefrontal control over thought. These unique elements of mental control suggest that hippocampal disinhibition is a transdiagnostic factor underlying intrusive thinking, linking the fronto-temporal control pathway to preclinical models of psychiatric disorders and fear extinction. We suggest that retrieval-stopping deficits may underlie the intrusive thinking that is common across many psychiatric disorders.

Subliminal priming modulates motor sequence learning

Sequential behaviour is underpinned by the selection and inhibition of movement at appropriate points in space and time. Sequences embedded among movement patterns must be learnt, yet the contribution of response selection and inhibition to the acquisition of motor sequences remains poorly understood. We addressed this issue by overlaying the serial reaction time task (SRTT) with subliminal masked primes that differentially weighed response tendencies. In Experiment 1, twenty-four healthy young adults, and in Experiment 2, thirty-six participants, performed the SRTT with congruent (same position), incongruent (different position), or neutral (no prime) subliminal masked primes. Each condition featured an embedded eight-digit (Experiment 1) or ten-digit (Experiment 2) second-order sequence, with conditions presented in counterbalanced order during a single session. Sequence specific learning was observed under neutral and congruent prime conditions. Independent of sequence awareness, congruent primes reduced initial response latency and led to greater sequence specific learning compared with neutral primes. However, incongruent primes appeared to attenuate learning (Experiment 1). These results demonstrate that prime congruency modulates sequence specific learning below the threshold of conscious awareness. Congruent primes may elevate the salience of stimulus-response compounds and accentuate learning, but at the cost of increased awareness. Incongruent primes, and the induction of response conflict, attenuate sequence specific learning (Experiment 1) and may prevent the formation of cross-temporal contingencies necessary for implicit motor sequence learning.

Tackling addictive behaviors through memory suppression: A scoping review and perspective

Forgetting is often viewed as a human frailty. However, over the years, it has been considered an adaptive process that allows people to avoid retrieval of undesirable memories, preventing them from suffering and discomfort. Evidence shows that the ability to suppress memories is affected by several psychopathological conditions characterized by persistent unwanted thoughts, including anxiety and posttraumatic stress disorders. Nevertheless, memory suppression (MS) mechanisms in addiction-a clinical condition characterized by recurrent drug-related thoughts that contribute to repeated drug use-have received little attention so far. Addiction theories reveal that drugs change behavior by working on memory systems, particularly on declarative memory, which is related to the retrieval and encoding of drug-related memories. In this review, the main behavioral and neurofunctional findings concerning the Think/No-Think task-an adaptation of the classical Go/No-Go tasks typically used to evaluate the suppression of motor response-are presented. We then show how the memory system can be involved in the craving or anticipation/preoccupation stage of the addiction cycle. Subsequently, the study of MS in the context of addictive behaviors is highlighted as a promising approach for gaining knowledge about the mechanisms contributing to the continuation of addiction. Finally, we discuss how interventions aiming to strengthen this ability could impact the anticipation/preoccupation stage by (i) reducing the accessibility of drug-related memories, (ii) decreasing craving and attention toward drug-related stimuli, and (iii) improving overall inhibition abilities. In conclusion, this review aims to illustrate how the study of MS may be a valuable approach to enhance our understanding of substance use disorders by unveiling the underlying cognitive and neural mechanisms involved, which could have important implications for addiction treatment.