Neuromodulatory effects of parietal high-definition transcranial direct-current stimulation on network-level activity serving fluid intelligence. Erker, T. D., Arif, Y., John, J. A., Embury, C. M., Kress, K. A., Springer, S. D., Okelberry, H. J., McDonald, K. M., Picci, G., Wiesman, A. I., & Wilson, T. W. The Journal of physiology, 602(12):2917–2930, June, 2024. Place: England
doi  abstract   bibtex   
Fluid intelligence (Gf) involves rational thinking skills and requires the integration of information from different cortical regions to resolve novel complex problems. The effects of non-invasive brain stimulation on Gf have been studied in attempts to improve Gf, but such studies are rare and the few existing have reached conflicting conclusions. The parieto-frontal integration theory of intelligence (P-FIT) postulates that the parietal and frontal lobes play a critical role in Gf. To investigate the suggested role of parietal cortices, we applied high-definition transcranial direct current stimulation (HD-tDCS) to the left and right parietal cortices of 39 healthy adults (age 19-33 years) for 20 min in three separate sessions (left active, right active and sham). After completing the stimulation session, the participants completed a logical reasoning task based on Raven's Progressive Matrices during magnetoencephalography. Significant neural responses at the sensor level across all stimulation conditions were imaged using a beamformer. Whole-brain, spectrally constrained functional connectivity was then computed to examine the network-level activity. Behaviourally, we found that participants were significantly more accurate following left compared to right parietal stimulation. Regarding neural findings, we found significant HD-tDCS montage-related effects in brain networks thought to be critical for P-FIT, including parieto-occipital, fronto-occipital, fronto-parietal and occipito-cerebellar connectivity during task performance. In conclusion, our findings showed that left parietal stimulation improved abstract reasoning abilities relative to right parietal stimulation and support both P-FIT and the neural efficiency hypothesis. KEY POINTS: Abstract reasoning is a critical component of fluid intelligence and is known to be served by multispectral oscillatory activity in the fronto-parietal cortices. Recent studies have aimed to improve abstract reasoning abilities and fluid intelligence overall through behavioural training, but the results have been mixed. High-definition transcranial direct-current stimulation (HD-tDCS) applied to the parietal cortices modulated task performance and neural oscillations during abstract reasoning. Left parietal stimulation resulted in increased accuracy and decreased functional connectivity between occipital regions and frontal, parietal, and cerebellar regions. Future studies should investigate whether HD-tDCS alters abstract reasoning abilities in those who exhibit declines in performance, such as healthy ageing populations.
@article{erker_neuromodulatory_2024,
	title = {Neuromodulatory effects of parietal high-definition transcranial direct-current stimulation on network-level activity serving fluid intelligence.},
	volume = {602},
	copyright = {© 2024 The Authors. The Journal of Physiology © 2024 The Physiological Society.},
	issn = {1469-7793 0022-3751},
	doi = {10.1113/JP286004},
	abstract = {Fluid intelligence (Gf) involves rational thinking skills and requires the integration of information from different cortical regions to resolve novel  complex problems. The effects of non-invasive brain stimulation on Gf have been  studied in attempts to improve Gf, but such studies are rare and the few existing  have reached conflicting conclusions. The parieto-frontal integration theory of  intelligence (P-FIT) postulates that the parietal and frontal lobes play a  critical role in Gf. To investigate the suggested role of parietal cortices, we  applied high-definition transcranial direct current stimulation (HD-tDCS) to the  left and right parietal cortices of 39 healthy adults (age 19-33 years) for  20 min in three separate sessions (left active, right active and sham). After  completing the stimulation session, the participants completed a logical  reasoning task based on Raven's Progressive Matrices during  magnetoencephalography. Significant neural responses at the sensor level across  all stimulation conditions were imaged using a beamformer. Whole-brain,  spectrally constrained functional connectivity was then computed to examine the  network-level activity. Behaviourally, we found that participants were  significantly more accurate following left compared to right parietal  stimulation. Regarding neural findings, we found significant HD-tDCS  montage-related effects in brain networks thought to be critical for P-FIT,  including parieto-occipital, fronto-occipital, fronto-parietal and  occipito-cerebellar connectivity during task performance. In conclusion, our  findings showed that left parietal stimulation improved abstract reasoning  abilities relative to right parietal stimulation and support both P-FIT and the  neural efficiency hypothesis. KEY POINTS: Abstract reasoning is a critical  component of fluid intelligence and is known to be served by multispectral  oscillatory activity in the fronto-parietal cortices. Recent studies have aimed  to improve abstract reasoning abilities and fluid intelligence overall through  behavioural training, but the results have been mixed. High-definition  transcranial direct-current stimulation (HD-tDCS) applied to the parietal  cortices modulated task performance and neural oscillations during abstract  reasoning. Left parietal stimulation resulted in increased accuracy and decreased  functional connectivity between occipital regions and frontal, parietal, and  cerebellar regions. Future studies should investigate whether HD-tDCS alters  abstract reasoning abilities in those who exhibit declines in performance, such  as healthy ageing populations.},
	language = {eng},
	number = {12},
	journal = {The Journal of physiology},
	author = {Erker, Tara D. and Arif, Yasra and John, Jason A. and Embury, Christine M. and Kress, Kennedy A. and Springer, Seth D. and Okelberry, Hannah J. and McDonald, Kellen M. and Picci, Giorgia and Wiesman, Alex I. and Wilson, Tony W.},
	month = jun,
	year = {2024},
	pmid = {38758592},
	pmcid = {PMC11178466},
	note = {Place: England},
	keywords = {*Intelligence/physiology, *Parietal Lobe/physiology, *Transcranial Direct Current Stimulation/methods, Adult, Female, Humans, Magnetoencephalography/methods, Male, Nerve Net/physiology, Young Adult, abstract reasoning, connectivity, magnetoencephalography (MEG), oscillations},
	pages = {2917--2930},
}

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