scholarly journals High-definition transcranial direct current stimulation of the lateral occipital cortex influences figure-ground perception

2021 ◽  
Vol 155 ◽  
pp. 107792
Author(s):  
Brooke Sasia ◽  
Laura Cacciamani
2018 ◽  
Vol 119 (4) ◽  
pp. 1266-1272 ◽  
Author(s):  
Vincent Cabibel ◽  
Makii Muthalib ◽  
Wei-Peng Teo ◽  
Stephane Perrey

The crossed-facilitation (CF) effect refers to when motor-evoked potentials (MEPs) evoked in the relaxed muscles of one arm are facilitated by contraction of the opposite arm. The aim of this study was to determine whether high-definition transcranial direct-current stimulation (HD-tDCS) applied to the right primary motor cortex (M1) controlling the left contracting arm [50% maximum voluntary isometric contraction (MVIC)] would further facilitate CF toward the relaxed right arm. Seventeen healthy right-handed subjects participated in an anodal and cathodal or sham HD-tDCS session of the right M1 (2 mA for 20 min) separated by at least 48 h. Single-pulse transcranial magnetic stimulation (TMS) was used to elicit MEPs and cortical silent periods (CSPs) from the left M1 at baseline and 10 min into and after right M1 HD-tDCS. At baseline, compared with resting, CF (i.e., right arm resting, left arm 50% MVIC) increased left M1 MEP amplitudes (+97%) and decreased CSPs (−11%). The main novel finding was that right M1 HD-tDCS further increased left M1 excitability (+28.3%) and inhibition (+21%) from baseline levels during CF of the left M1, with no difference between anodal and cathodal HD-tDCS sessions. No modulation of CSP or MEP was observed during sham HD-tDCS sessions. Our findings suggest that CF of the left M1 combined with right M1 anodal or cathodal HD-tDCS further facilitated interhemispheric interactions during CF from the right M1 (contracting left arm) toward the left M1 (relaxed right arm), with effects on both excitatory and inhibitory processing. NEW & NOTEWORTHY This study shows modulation of the nonstimulated left M1 by right M1 HD-tDCS combined with crossed facilitation, which was probably achieved through modulation of interhemispheric interactions.


2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Evangelia G. Chrysikou ◽  
Hannah M. Morrow ◽  
Austin Flohrschutz ◽  
Lauryn Denney

AbstractNeuroimaging and transcranial direct current stimulation (tDCS) research has revealed that generating novel ideas is associated with both reductions and increases in prefrontal cortex (PFC) activity, and engagement of posterior occipital cortex, among other regions. However, there is substantial variability in the robustness of these tDCS‐induced effects due to heterogeneous sample sizes, different creativity measures, and methodological diversity in the application of tDCS across laboratories. To address these shortcomings, we used twelve different montages within a standardized tDCS protocol to investigate how altering activity in frontotemporal and occipital cortex impacts creative thinking. Across four experiments, 246 participants generated either the common or an uncommon use for 60 object pictures while undergoing tDCS. Participants also completed a control short-term memory task. We applied active tDCS for 20 min at 1.5 mA through two 5 cm × 5 cm electrodes over left or right ventrolateral prefrontal (areas F7, F8) or occipital (areas O1, O2) cortex, concurrent bilateral stimulation of these regions across polarities, or sham stimulation. Cathodal stimulation of the left, but not right, ventrolateral PFC improved fluency in creative idea generation, but had no effects on originality, as approximated by measures of semantic distance. No effects were obtained for the control tasks. Concurrent bilateral stimulation of the ventrolateral PFC regardless of polarity direction, and excitatory stimulation of occipital cortex did not alter task performance. Highlighting the importance of cross-experimental methodological consistency, these results extend our past findings and contribute to our understanding of the role of left PFC in creative thinking.


2018 ◽  
Vol 120 (1) ◽  
pp. 4-6
Author(s):  
Clayton W. Swanson ◽  
Felix Proessl

Cabibel et al. (J Neurophysiol 119: 1266–1272, 2018) report non-polarity-specific effects of high-definition direct current stimulation (HD-tDCS) on crossed facilitation (CF), demonstrated by complex excitatory and inhibitory interhemispheric interactions coupled with HD-tDCS. Choosing a variety of stimulation and muscle contraction parameters and having all participants undergo anodal, cathodal, and sham stimulation may increase the current understanding of HD-tDCS on CF. Furthermore, complementary metrics like the ipsilateral silent period may provide more clarity regarding the polarity-specific enhancement of HD-tDCS on CF.


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