Rappresentazioni stimolanti: Esplorazione delle basi neurali del Representational Momentum attraverso l'utilizzo di Stimolazione Transcranica a Corrente Alternata (tACS) nelle bande Beta e Theta

How does the brain predict the motion of a moving object? If a stimulus suddenly disappears in its smooth trajectory, the perceived vanishing point is displaced forward in the direction of motion. Such displacement has been referred to as Representational Momentum (RM) because it is thought that such displacement reflects the intrinsic momentum of the representations of real-world objects (Freyd and Finke, 1984; Hubbard, 2005, 2014). There are many variables related to this phenomenon, many types of RM, many paradigms to study this effect, various brain areas related to RM and motion perception and different theoretical approaches; all of this will be reviewed in the present work. In a recent study, Di Dona et al. (in preparation) found a correlation between beta-band activity (BBA) and the forward tilt of a rotating bar in a RM task. In this study, we used the same paradigm and stimuli as Di Dona et al., and we attempted to find a causal link between beta oscillations and RM with the use of transcranial alternating current stimulation (tACS). It has been found that tACS can entrain cortical neurons (Helfrich et al., 2014), that is it can align neuronal activity to an external frequency. We administered three different types of stimulation (beta-tACS, theta-tACS and sham) while participants performed an RM task. Contrary to expectation, the results showed no effect of stimulation on the RM effect and that beta-tACS lowered task accuracy. This can still demonstrate a functional specificity of BBA for motion perception. Future studies should try to use different motion perception tasks in order to understand the relationship between BBA and motion perception more deeply.