Parameter-Based Evaluation of Attentional Impairments in Schizophrenia and Their Modulation by Prefrontal Transcranial Direct Current Stimulation

Abstract

BackgroundAttentional dysfunctions constitute core cognitive symptoms in schizophrenia, but the precise underlying neurocognitive mechanisms remain to be elucidated.MethodsIn this randomized, double-blind, sham-controlled study, we applied, for the first time, a theoretically grounded modeling approach based on Bundesen’s Theory of Visual Attention (TVA) to (i) identify specific visual attentional parameters affected in schizophrenia and (ii) assess, as a proof of concept, the potential of single-dose anodal transcranial direct current stimulation (tDCS; 20 min, 2 mA) to the left dorsolateral prefrontal cortex to modulate these attentional parameters. To that end, attentional parameters were measured before (baseline), immediately after, and 24 h after the tDCS intervention in 20 schizophrenia patients and 20 healthy controls.ResultsAt baseline, analyses revealed significantly reduced visual processing speed and visual short-term memory storage capacity in schizophrenia. A significant stimulation condition × time point interaction in the schizophrenia patient group indicated improved processing speed at the follow-up session only in the sham condition (a practice effect), whereas performance remained stable across the three time points in patients receiving verum stimulation. In healthy controls, anodal tDCS did not result in a significant change in attentional performance.ConclusionWith regard to question (i) above, these findings are indicative of a processing speed and short-term memory deficit as primary sources of attentional deficits in schizophrenia. With regard to question (ii), the efficacy of single-dose anodal tDCS for improving (speed aspects of visual) cognition, it appears that prefrontal tDCS (at the settings used in the present study), rather than ameliorating the processing speed deficit in schizophrenia, actually may interfere with practice-dependent improvements in the rate of visual information uptake. Such potentially unexpected effects of tDCS ought to be taken into consideration when discussing its applicability in psychiatric populations. The study was registered at .

Distinctive Correspondence Between Separable Visual Attention Functions and Intrinsic Brain Networks

“…For example, the TVA parameters (Finke et al, 2010 ; Vangkilde et al, 2012 ) are influenced by certain pharmacological substances. Also, visual processing speed is enhanced by appropriate computerized training regimens (Schubert et al, 2015 ), whereas special populations such as patients with dyslexia (Stenneken et al, 2011 ), depression (Gögler et al, 2016 ), and schizophrenia (Gögler et al, 2017 ), exhibit reductions in visual processing speed. Furthermore, changes in attentional variability also occur during normal and pathological aging: healthy aging involves a slowing of visual processing (McAvinue et al, 2012 ; Habekost et al, 2013 ; Espeseth et al, 2014 ), and patients with mild cognitive impairment and the beginning of Alzheimer's disease reveal a staged decline of both visual processing speed (Bublak et al, 2011 ; Ruiz-Rizzo et al, 2017 ) and top-down control (Redel et al, 2012 ).…”

Transcranial Direct Current Stimulation and Cognition in Neuropsychiatric Disorders: Systematic Review of the Evidence and Future Directions

“…Full-text versions of the remaining 55 records were then screened for eligibility, and this process excluded a further 14 studies. In the time period until January 2020, 41 studies (Bennabi and others 2015; Bersani and others 2017; Boggio and others 2009, 2012, Brunoni and others 2014; Brunoni and others 2016; Bystad and others 2016; Cotelli and others 2014; Ferrucci and others 2008; Fregni and others 2006; Gögler and others 2017; Hoy and others 2014; Khedr and others 2014; Knechtel and others 2014; Loo and others 2010; Loo and others 2012; Loo and others 2018; Martin and others 2015; Meinzer and others 2015; Mellin and others 2018; Moreno and others 2015; Nienow and others 2016; Oliveira and others 2013; Orlov and others 2017a; Orlov and others 2017b; Palm and others 2012, 2016; Papazova and others 2018; Pavlova and others 2018; Powell and others 2014; Rassovsky and others 2015, 2018; Reinhart and others 2015a; Roncero and others 2017; Schwippel and others 2018; Segrave and others 2014; Smith and others 2015; Suemoto and others 2014; Vercammen and others 2011; Wolkenstein and Plewnia, 2013; Yun and others 2016), published between 2006 and 2018, met all inclusion criteria and were included in the current systematic review. See Supplemental Material for PRISMA flow diagram, and further description of included and excluded studies.…”

“…The neuromodulatory effect of tDCS on the attentional domain has been evaluated in three studies using high voltage anodal tDCS over the DLPFC. None of the three studies evidenced any effect on attentional capacity in MDD evaluated using the Stroop Test (Brunoni and others 2016), or in schizophrenia-spectrum disorder patients using other attentional tasks, both with multiple online tDCS sessions associated with cognitive training (Orlov and others 2017b) and with a single session of off-line stimulation (Gögler and others 2017) (Table 3).…”

Acute effects of a single dose of 2 mA of anodal transcranial direct current stimulation over the left dorsolateral prefrontal cortex on executive functions in patients with schizophrenia—A randomized controlled trial

“…As response inhibition is generally considered to be a cognitive function that is neuroanatomically largely based on the right inferior frontal cortex [31], our results suggest that the placement of the cathode electrode on FP2 might have exerted an excitatory diminishing effect that ultimately impaired response inhibition performance. Interestingly, detrimental effects of the same stimulation configuration of tDCS in patients with schizophrenia were recently also shown for performance in visual attention albeit 24 h after stimulation [42], as well as on verbal working memory within 100 minutes after stimulation [27]. Taken together these findings suggest that tDCS does not essentially always improve cognition but might also further impair cognitive functions in patients with schizophrenia depending on electrode configuration and placement.…”