P2. Mechanisms of tES

Transcranial Electrical Stimulation Projects

Project 1: Origin of tACS-induced phosphenes in humans


Status: Completed

Background:  We applied tACS over visual cortex with a reference electrode on the vertex; and measured current thresholds for the detection of phosphenes with a Bayesian adaptive method. Then, we shifted the stimulating electrode over to the temporal lobe; away from visual cortex and towards the retina. This simple manipulation enhanced the efficacy of the stimulation as measured by lower current thresholds. This suggests that stimulation of the retina plays a significant part in the generation of phosphenes by tACS. Read more…

Publication: Journal of Neurophysiology (2012).Link
Conference: Journal of Vision 2011, VSS Abstracts. Abstract, Poster

Project 2: Effects of tACS on human motion detection


Status: Completed

Background: Healthy human volunteers showed a surprising improvement in motion sensitivity when visual stimuli were paired with 10 Hz tACS. In addition, tACS reduced the motion-after
effect, and this reduction was correlated with the improvement in motion sensitivity. Electrical stimulation had no consistent effect when applied before presenting a visual stimulus or during recovery from motion adaptation. Together,these findings suggest that perceptual effects of tACS result from an attenuation of adaptation. Read more…

Publication: Journal of Neuroscience (2014).  Link
Conference: Journal of Vision 2012, VSS Abstracts. AbstractPoster

Project 3: Effects of tACS on macaque MT neurons

Status: Completed

Background: Tuning curve estimates of macaque MT Figure2neurons showed that tACS attenuated the effects of motion adaptation on tuning amplitude and width. In addition to single cell  measures, tACS  also mitigated adaptation-induced changes in evoked LFP responses.

Publication: Journal of Neuroscience (2017). Link
Conference: Brain Stimulation 7.2 (2014): e12. AbstractPoster, Neuroscience (2013) Abstracts. San Diego, CA: Society for Neuroscience, (2013). AbstractPosterRhythmic Dynamics and Cognition Conference, (2013). Abstract, PosterJournal of Vision (2013), VSS abstracts.Abstract, Poster

Project 4: Effects of tACS on human BOLD signal

Status: Completed.

Background: We performed combined tACS and fMRI to investigate the BOLD signal changes across the entire brain with and without motion adaptation. Read more …

Publication: Biorxiv preprint
Conference: OHBM’s 2015 Annual Meeting. AbstractPoster,Brain Stimulation and Imaging Meeting 2015 Poster

Project 5: Effects of tDCS on macaque V1 neurons

Status: On going

Background: We recorded neural activity from area V1, with chronically implanted floating microelectrode arrays before and after applying tDCS. During each experimental session, we first mapped visual responses and orientation, spatial frequency, and contrast tuning using full field grating stimuli . Second, we applied tDCS for 20 minutes; either cathodal (-1 mA), anodal (+1 mA), or sham (0 mA). One (active) tDCS electrode was placed on the occipital pole of the monkey while the other (reference) was placed near the vertex. Third, we mapped the visual responses and tuning properties again, using the same stimuli.  We compared the multiunit activity (MUA) before and after stimulation.

Conference: Neuroscience 2015 Abstracts. Chicago, IL: Society for Neuroscience, 2015. Poster

Project 6: Effects of tACS at multiple frequencies on macaque V1 neuronal adaptation

Status: On going

Background:  Given that we found tACS-induced attenuation of MT neuronal adaptation, we wanted to test how generalizable is this tACS effect across the visual cortex.   In addition, we also want to understand whether there is any specific frequency tuning of this effect. So we recorded neural activity from area V1, with chronically implanted floating micro electrode arrays, while the animals fixated a dot, and full field grating stimuli were shown on the screen. We are currently analyzing the recorded data.

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