We work on a variety of topics related the perception of natural stimuli, which we study with electro-encephalography (EEG). We are also trying to understand basic mechanisms of transcranial electric stimulation (TES) of the brain, as well as develop tools for targeting TES.

Neural processing of natural stimuli

We are interested in how people process natural stimuli and use EEG to measure stimulus-evoked neural activity. In our experience with EEG, small changes in the task can have large effects on the resulting brain signals. We therefore emphasize analysis of EEG in the most natural setting possible. Video and audio narratives provide a good balance between reproducibility and natural dynamics. We have also started to look at video games, and different study populations. The workhorse for the analysis of these natural stimuli has been inter-subject correlation (ISC) which does not require any kind of labeling of the stimulus.

Current projects:

  • Attention to online educational videos: Samantha Cohen, Gad Touchan
  • Attention to speech in minimally contious patients: Ivan Iotzos, in collaboration with Brian Fidali, Nico Shiff
  • fMRI correlates of ISC of EEG: Samantha Cohen
  • Speech comprehension for noisy speech: Evan Owen
Engagement with video | Cohen et al. 2017 | Dmochowski et al. 2014 | Dmochowski et al. 2012 | Burleson-Lesser et al. 2017

ISC of EEG and eyes movements appears to be a marker of engagement with a video stimulus. It is therefore predictive of the behavior of large audiences, including tweeting, viewership size and preference ratings. Engaging narratives synchronize not just our brains, but also our perception of time.

Attention and memory for narratives | Ki, Kelly, Parra 2016 | Cohen, Parra 2016

ISC of EEG is dramatically modulated by attention.

Video games | Dmochowski et al. 2016

For the case of unique experience we find that correlation with the actual stimulus also captures attention. Surprisingly, we find a strong coupling of the stimulus with a supramodal component of the EEG.

Videos in the classroom | Poulsen et al. 2016

ISC of EEG during videos can be measured simultansously in the classroom.

Mechanisms of TES

Transcranial electrical stimulation (TES) applies weak electric currents at the scalp in order to improve brain function. While this has shown a great deal of promise in clinical and cognitive studies,there is very limited knowledge of the underlying cellular mechanisms. We aim to understand how stimulation modifies information processing and storage in individual neurons and networks. In the past we have demonstrated that stimulation acutely modifies firing rate, spike timing, excitability, synaptic efficacy, and network oscillations. More recently we have focused on how these acute effects translate into long-term strorage through synaptic plasticity.

Current projects:

  • Modulation of hippocampal synaptic plasticity with direct current stimulation: Greg Kronberg
Acute effects of tDCS | Reato et al. 2010 | Rahman et al. 2013 | Lafon et al. 2016

Acute effects of tACS | Reato et al. 2013

Long-term effects of tDCS | Reato et al. 2015 | Kronberg et al. 2017

Targeting of TES with electrode arrays

TES is applied often using simple sponge electrodes. We have advocated the use "high-definition" stimulation using arrays of small electrodes (comparable to what is done with EEG). To this end we have developed methods to steer currents with these arrays, as well as build individualized head models in particular to account for altered anatomies in stroke patients. We have been the first to thoroughly validate the corresponding current-flow models in human.

Current projects:

  • Automated brain segmentation in the presence of lesions
  • Multifocal targeting: Yu (Andy) Huang
Automated whole-head segmentation | Huang et al. 2013 | Huang, Parra 2015

Model validation | Huang, Liu, et al. 2017 |

TES targeting | Dmochowski et al. 2011 | Dmochowski et al. 2016