Basil Preisig: Selective modulation of interhemispheric connectivity by TACS stimulation influences auditory perception  

Hi,

interesting poster! May I ask you more specific info on the type of DCM you used? For example, was it a one-state deterministic model? Did you perform DCM on each individual and then performed traditional group statistics afterwards?

Thanks!

Hi, nice poster. I have two short questions.

1) Did you find any significant BOLD modulation due to tACS beyond your auditory ROIs? 

2) In figure 5B, is the correlation between tACS induced connectivity changes and the behavioral changes referring to tACS 180°?

Hi @yuranny-cabral-calderin,

Thank you for your interest.

1) The whole-brain analysis did not reveal significant modulation outside the ROIs

2) Yes that is correct, the color code is blue=tACS 180° and red= tACS 0°

Hi @sara-calzolari,

Thank you for your interest. We computed first level DCM models and DCM with parametric empirical bayes (PEB) with bayesian model reduction and bayesian model averaging at the second level as described in this publication ( http://www.sciencedirect.com/science/article/pii/S1053811919305233).

Hi @basil,

thanks for the reply. Did you find any correlation between tACS 0° induced connectivity changes and the behavioral changes? (Since tACS 0° was the condition showing the significant modulation in the behavior)

thanks again

Hi @yuranny-cabral-calderin,

Good question. Yes we did. The negative modulation of the intra-hemispheric connections was also correlated with binaural integration. The feedward connections (HG->pSTS) were positively correlated (the larger the perturbation, the larger the reduction in binaural integration). For the feedback connections (pSTS->HG) the correlation was in the opposite direction.

Hi @sara-calzolari,

After checking your poster I noticed that you are a DCM expert and I feel that I may not carefully addressed your question.

You asked whether we used a one-state deterministic model?

Yes exactly, the PEB approach assumes that all subjects have the same basic architecture

You asked whether we preformed DCM on each individual and then performed traditional group statistics afterwards?

May I ask for clarification: Is your question whether we used PEB on models of single participants to estimate the connecitivity parameters individually? What did you mean with a traditional group statistics? Subsequent ANOVA or t-tests?

Hi @basil,

thanks for the additional info. You answered my question when you replied you employed PEB, because I was precisely wondering whether you used PEB for the group analysis or if you performed frequentist stats like anova, so all good.
I do not consider myself a DCM expert at all, I'm fairly new to it so I am always glad to find other people who use it!

Hi @basil,

thanks for the reply. In your discussion you mentioned that both tACS 180° and 0° were detrimental for performance since one reduces inter-hemispheric while the other reduces intra-hemispheric connectivity. Do you think that there might be another optimal phase-lag that could contribute to improving performance?, or maybe different frequency, tACS-stimulus lag, stimulation montage? or maybe tACS is just inducing noise in the brain and the effect for binaural integration will always be negative regardless or the stimulation protocol? 

Thanks again, I really enjoyed your poster

Hi @yuranny-cabral-calderin,

You ask a very important question. I believe that there are small inter-individual differences in the optimal lags for interhemispheric communication. However, I am not sure, if we would be able to increase performance, or at least not in young healthy participants, even if we could a priori identify the inherent interhemispheric phase lag. I think the reason is that young healthy participants already performs at an optimal level and that they show an optimal level of gamma band oscillatory activity, reflecting a high neural signal-to-noise ratio. In this case, TACS may simply add noise that makes performance worse. 

Thank you for the question. I really enjoy this discussion

Hi @basil,

yes, that's a good point. Maybe we might be able to see improvements in conditions where binaural integration and/or gamma band activity are compromised or in more difficult tasks where performance is not at ceiling. 

Thanks again for the nice discussion