Cross-cortical implementation of spatial-numerical associations revealed by transcranial direct current stimulation and near-infrared-spectroscopy

• Applicant: Dr. Philipp Schroeder
• Subject Area: Biological Psychology and Cognitive Neuroscience ; Human Cognitive and Systems Neuroscience
• Term: from 2019 to 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 418004780

• Final Report Year: 2024

Final Report Abstract

Fronto-parietal networks are critically involved in numerical cognition in general and spatialnumerical associations specifically. The modulation of numerical processing by transcranial direct current stimulation (tDCS) over different cortical regions provides insights into their shared and distinct neurocognitive causal networks. Previous neuromodulation studies were apparently specific to cathodal tDCS of the left prefrontal cortex (PFC) for spatial-numerical associations, but the regional specificity of tDCS was not clear. The present project systematically disentangles effects of different electrode configurations and varies both target and return electrode positions to obtain regional specificity. WP1 investigated the causal contributions of different network sites involved in numerical magnitude (distance effect) and spatial-numerical processing (SNARC effect) in magnitude classification tasks. Results are compared to neuromodulation effects on response inhibition functions (control task). In WP2, concurrent neuroimaging of cortical hemodynamic activity with near-infrared spectroscopy (NIRS) concurrent to tDCS monitored the immediate physiological effects of tDCS interactions with spatial-numerical associations. The hemodynamic measurements were anticipated to demonstrate cross-cortical responses to prefrontal tDCS in posterior parietal cortex due to the fronto-parietal numerical processing network. Results corroborate the neuronal implementation of numerical magnitude processing and spatial-numerical associations in humans, and basic principles of tDCS effects in numerical cognition. The results from WP1 yielded more insights into the regional specificity of tDCS and electrode positions. In total, six unilateral, two high-definition and one bipolar electrode configurations were examined. Across studies, the findings indicated a relevance of the induced electric field due to the placement of the return electrode, i.e., different effects for unilateral tDCS compared to other placements of the same cortical region. Moreover, a timing-dependent modulation of response inhibition was observed. In WP2, concurrent imaging of activity in the parietal cortex replicated a neural signature in oxygenated hemoglobin, established a response in deoxygenated hemoglobin, and a modulation of the neural signature in the parietal cortex by prefrontal tDCS. Overall, the mixed results demonstrate the interplay of cross-cortical networks in the SNARC effect, but they also indicate several technical limitations of cathodal tDCS that need to be considered in future research.

Publications

• Regional specificity of cathodal transcranial direct current stimulation (tDCS) effects on spatial‐numerical associations: Comparison of four stimulation sites. Journal of Neuroscience Research, 98(4), 655-667.
  Schroeder, Philipp A.; Artemenko, Christina; Cipora, Krzysztof & Svaldi, Jennifer
  
• Meta-analysis of the effects of transcranial direct current stimulation on inhibitory control. Brain Stimulation, 13(5), 1159-1167.
  Schroeder, Philipp A.; Schwippel, Tobias; Wolz, Ines & Svaldi, Jennifer
  
• More focal, less heterogeneous? Multi-level meta-analysis of cathodal high-definition transcranial direct current stimulation effects on language and cognition. Journal of Neural Transmission, 129(7), 861-878.
  Ostrowski, Jan; Svaldi, Jennifer & Schroeder, Philipp A.
  
• Spotlight on the Left Frontal Cortex: No Evidence for Response Inhibition from Cathodal High-Definition transcranial Direct Current Stimulation over Left Inferior Frontal Gyrus or Left Dorsolateral Prefrontal Cortex. Journal of Cognitive Neuroscience, 34(6), 1090-1102.
  Schroeder, Philipp A.; Seewald, Anna & Svaldi, Jennifer
  
• High‐definition turns timing‐dependent: Different behavioural consequences during and following cathodal high‐definition transcranial direct current stimulation (HD tDCS) in a magnitude classification task. European Journal of Neuroscience, 59(11), 2967-2978.
  Schroeder, Philipp A.; Nuerk, Hans‐Christoph & Svaldi, Jennifer
  
• Regional specificity of cathodal transcranial direct current stimulation effects on spatial–numerical associations: Comparison of four stimulation sites. Journal of Neuroscience Research, 102(2).
  Farshad, Maryam; Artemenko, Christina; Cipora, Krzysztof; Svaldi, Jennifer & Schroeder, Philipp A.