The ability to inhibit an inappropriate response and to flexibly adjust to a changing environment is a key factor for efficient adaptation and survival. Inhibitory control is recognized as the core underlying function of a) the ability to suppress interference from an irrelevant task during rapid task switching (cognitive-behavioral flexibility); b) the ability to inhibit unwanted emotional thoughts (cognitive-emotional flexibility); and c) the ability of the vagus nerve to inhibit sympathetic arousal (physiological flexibility). Whereas existing studies separately investigated each of these factors, to date there is lack of knowledge on their reciprocal interplay. Also, most research in this field is correlational, precluding inferences on the direction of effects. We aim to fill this gap, by investigating whether the experimental manipulation of inhibitory control via non-invasive brain stimulation techniques has effects on cognitive, behavioral, and emotional inflexibility. We plan to do so by using transcranial direct current stimulation (tDCS) to enhance excitability of the most widely recognized source of inhibitory control, the dorsolateral prefrontal cortex (dlPFC). The hypothesis is that tDCS over dlPFC will boost inhibitory control, and this will in turn enhance flexibility at all the examined levels, as indexed by post-stimulation reduced reaction times during task switching, increased heart rate variability, and decreased ruminative thinking outside the laboratory (via ecological momentary assessment) compared to pre-stimulation and sham conditions. We expect these effects to be mediated by individual differences in emotion regulation capacity. This proposal integrates cognitive and experimental psychology with affective and autonomic neuroscience to advance our understanding of the interplay between neurobiological, emotional, and cognitive factors during maladaptive ruminative thinking, potentially yielding to more effective treatment strategies.
Heightened concerns are resulting from the growing awareness of the high prevalence of mental illness, the quality of life for afflicted people and the direct and indirect costs to society. Lifetime prevalence rates in Europe for the main mental disorders are around 10% for depression and 11% for anxiety. The economic consequences of mental illness are various and long-lasting, involving costs to the individual, the family, and society. The expectation here is that clarifying the relation between a transdiagnostic factor for the development of psychopathological disorders and the individual effectiveness of executive functions-related processes (inhibitory control and emotion regulation strategies) will (1) contribute to develop effective prevention programs to clinical conditions and to improve the efficacy of existing treatments; (2) from a basic research perspective, it will advance the knowledge of the neurophysiological and cognitive mechanisms that mediate the relation between potential non-clinical predictors and clinical disorders. Indeed, high levels of rumination are associated with less therapeutic responsiveness to both antidepressant and cognitive-behavioral interventions (Ciesla and Roberts, 2002; Schmaling et al., 2002)
On this ground, it is fundamental to investigate effectiveness of alternative non-invasive neuro-cognitive modulatory methods interventions. tDCS-based interventions program have recently received increased attention, on the idea that tDCS may improve cognitive treatment of many psychological disorders. For instance, tDCS has been suggested as an option to improve extinction learning, which is a main functional factor of exposure-based therapy for anxiety disorders (Dittert et al., 2018). Evidence also indicates that tDCS may be efficacious for treatment of major depression (Meron et al., 2015). Importantly, multiple sessions of tDCS, combined with cognitive-based treatments have been shown to enhance reading abilities in adolescents with dyslexia (Costanzo et al., 2016). The relevance of the present study is based on the idea that testing the efficacy of tDCS on the individual ability to suppress intrusive thoughts will open new rehabilitative perspective for remediation of clinical syndromes associated to perseverative cognition, such as depression and anxiety.
Considering that both reduced HRV and impaired inhibitory control are characteristics of several somatic and psychopathological conditions (e.g., Makovac et al., 2016), it is important that future studies clarify the direction of effects to target the best predictor.
References
Ciesla, J.A., Roberts, J.E., (2002). J. Cogn. Psychother. Int. Q. 16, 435-453.
Costanzo F, Varuzza C, Rossi S, Sdoia S, Varvara P, Oliveri M, Giacomo K, Vicari S, Menghini D. (2016). Restorative Neurology and Neuroscience, 34, 2, 215-226.
Dittert N, Hüttner S, Polak T, Herrmann MJ. (2018). Front Behav Neurosci. 25;12:76.
E. Makovac, F. Meeten, D.R. Watson, A. Herman, S.N. Garfinkel, H.D. Critchley, C. Ottaviani (2016). Biol. Psychiatry, 80 786-795.
Ferdek MA, van Rijn CM, Wyczesany M.. (2016) Cogn Affect Behav Neurosci 16: 1099-1113.
Garnefski, N., Kraaij, V. & Spinhoven, Ph. (2002). Leiderdorp, The Netherlands: DATEC.
Joormann, J., & Gotlib, I. H. (2010). Cognition & Emotion, 24(2), 281-298.
Makovac, E., Thayer, J.F., Ottaviani, C. (2017). Neuroscience & Biobehavioral Reviews, 74, 330-341.
Mansouri, et al. (2009). Nat. Rev. Neurosci., 10.
Mayr U, Keele SW. J Exp Psy- chol Gen. (2000); 129: 4-26.
Meron D, Hedger N, Garner M, Baldwin DS (2015). Neurosci Biobehav Rev. Oct;57:46-62.
Ottaviani C, Thayer JF, Verkuil B, Lonigro A, Medea B, Couyoumdjian A, Brosschot JF. Psychol Bull. (2016);142(3):231-59.
Ottaviani, C., Medea, B., Lonigro, A., Tarvainen, M., Couyoumdjian, A. (2015). Biological Psychology, 107, 24-30.
Priori, A., Berardelli, A., Rona, S., Accornero, N. & Manfredi, M. (1998). NeuroReport 9, 2257-2260.
Schmaling, K.B., Dimidjian, S., Katon, W., Sullivan, M., (2002). J. Abnorm. Psychol. 111, 350-356.
Spinhoven P, Drost J, van Hemert B, Penninx BW. (2015) J Anxiety Disord;33:45-52.
Thayer, J.F., Ahs, F., Fredrikson, M., Sollers 3rd, J.J., Wager, T.D., (2012). Neurosci. Biobehav. Rev. 36, 747-756.
Yang Y, Cao S, Shields GS, Teng Z, Liu Y. (2017) Depress Anxiety. Jan;34(1):37-50.
Zelazo PD, Craik FI, Booth L (2004) Acta Psychologica 115:167-183.