Effects of Transcranial Direct Current Stimulation on Episodic Memory Related to Emotional Visual Stimuli

Abstract

The present study investigated emotional memory following bilateral transcranial electrical stimulation (direct current of 1 mA, for 20 minutes) over fronto-temporal cortical areas of healthy participants during the encoding of images that differed in affective arousal and valence. The main result was a significant interaction between the side of anodal stimulation and image emotional valence. Specifically, right anodal/left cathodal stimulation selectively facilitated the recall of pleasant images with respect to both unpleasant and neutral images whereas left anodal/right cathodal stimulation selectively facilitated the recall of unpleasant images with respect to both pleasant and neutral images. From a theoretical perspective, this double dissociation between the side of anodal stimulation and the advantage in the memory performance for a specific type of stimulus depending on its pleasantness supported the specific-valence hypothesis of emotional processes, which assumes a specialization of the right hemisphere in processing unpleasant stimuli and a specialization of the left hemisphere in processing pleasant stimuli. From a methodological point of view, first we found tDCS effects strictly dependent on the stimulus category, and second a pattern of results in line with an interfering and inhibitory account of anodal stimulation on memory performance. These findings need to be carefully considered in applied contexts, such as the rehabilitation of altered emotional processing or eye-witness memory, and deserve to be further investigated in order to understand their underlying mechanisms of action.

The Perils of Using Electrical Stimulation to Change Human Brains

“…3.1). A similar situation holds when we examined cathodal stimulation to the left DLPFC; investigators have reported decreased verbal fluency, increase in safe choices (Fecteau et al, 2007), impaired declarative memory , selectively facilitated pleasant image recall (Penolazzi et al, 2010), and impaired verbal memory . Finally, Iuculano and Cohen Kadosh have recently demonstrated that a tDCS protocol, which enhanced numerical learning, impaired automaticity for the learned material, while a different protocol that enhanced automaticity impaired numerical learning (Iuculano & Cohen Kadosh, 2013).…”

“…Given its potential, investigators have explored tDCS for: motor learning (Boros, Poreisz, Mü nchau, Paulus, & Nitsche, 2008;Nitsche, Fricke, et al, 2003;Nitsche et al, 2007;Reis et al, 2008), numerical ability (Cohen Kadosh, Soskic, Iuculano, Kanai, & Walsh, 2010), episodic memory (Penolazzi et al, 2010), working memory (Fregni et al, 2005;Ohn et al, 2008), motor memory (Galea & Celnik, 2009), sleep-dependent consolidation of declarative memory (Marshall, 2004), learning and memory writ large (Brasil-Neto, 2012), attention (Coffman, Trumbo, & Clark, 2012), decision-making and risk (Coricelli & Rusconi, 2011;Fecteau et al, 2007), planning ability (Dockery, Hueckel-Weng, Birbaumer, & Plewnia, 2009), complex and creative problem-solving (Cerruti & Schlaug, 2009;Chi & Snyder 2012;Snyder, 2009), grammar (de Vries et al, 2010;Floel, Rö sser, Michka, Knecht, & Breitenstein, 2008), object naming (Fertonani, Rosini, Cotelli, Rossini, & Miniussi, 2010;Sparing, Dafotakis, & Meister 2008), word retrieval (Fiori et al, 2011), verbal fluency (Iyer et al, 2005), reading efficiency (Turkeltaub et al, 2011), lying Priori et al, 2007), and the likelihood of utilitarian judgments , to name but the most prominent applications of this exciting technique.…”

“…Numerous experiments have investigated applying anodal stimulation to the left DLPFC and have found similar stimulation paradigms to result in reduction of risk-taking behavior (Fecteau et al, 2007), reduction in smoking craving (Fregni et al, 2008), facilitated recall of unpleasant images (Penolazzi et al, 2010), enhanced verbal fluency (Iyer et al, 2005), and decrease in sleep efficiency (Roizenblatt et al, 2007; see also Fig. 3.1).…”

The effect of the interval-between-sessions on prefrontal transcranial direct current stimulation (tDCS) on cognitive outcomes: a systematic review and meta-analysis

“…The dorsolateral prefrontal cortex (DLPFC) is one of the most frequently targeted stimulation sites in tDCS studies. Studies have shown that tDCS has modulatory effects on attention (Gladwin et al 2012b;Kang et al 2009;Kang et al 2012;Nelson et al 2014;Nozari and Thompson-Schill 2013), memory and verbal processing (Fertonani et al 2010;Fertonani et al 2014;Metuki et al 2012;Sela et al 2012;Vannorsdall et al 2012;Wirth et al 2011), and executive functioning (including working memory; Andrews et al 2011;Berryhill and Jones 2012;Boggio and Khoury 2009;Boggio et al 2006;Dockery et al 2009;Filmer et al 2013;Fregni et al 2005;Gladwin et al 2012a;Hammer and Mohammadi 2011;Harty et al 2014;Hoy et al 2014;Jo et al 2009;Keshvari et al 2013;Leite et al 2011;Leite et al 2013;Mulquiney and Hoy 2011;Penolazzi et al 2010;Plewnia et al 2013;Saidmanesh et al 2012;Vanderhasselt et al 2013a;Vanderhasselt et al 2013b;Wu et al 2014;Zmigrod et al 2014); for a meta-analysis of the effects of tDCS on working memory, see Brunoni and Vanderhasselt (2014), among others.…”

Effects of Brain Stimulation on Declarative and Procedural Memories

“…Regarding visual materials, a recent study investigated the effects of bilateral tDCS (i.e., left cathodal and right anodal, left anodal and right cathodal, or sham) over fronto-temporal cortical areas during the encoding of images characterized by different levels of affective arousal and valence (Penolazzi et al, 2010). The results indicated that left cathodal and right anodal stimulation facilitated the recall of pleasant images, whereas the opposite pattern of stimulation facilitated the recall of unpleasant images.…”