I'm interested in administering 10-15 minutes of tACS to participants before a visual short term memory task. I'd like to keep my participants entertained with eyes open (better for increasing the alpha power with my 10 Hz tACS) during this time, but I'm not sure what the best method of doing so might be as the literature often doesn't mention what the participants do during the stimulation period when the task is not being performed during stimulation.
I currently think if I show them all the same 10-15 min nature documentary clip, any differences caused by watching might be standardized throughout the sample. However, as my visual task involves recalling color, I'm wondering if a black and white film clip might be a better choice.
Any advice or insight into what to show participants to keep them entertained during offline tACS?
One possibility is to minimize visual stimulation or imagery by showing something abstract that nevertheless catches the person's attention, such as an out-of-focus grey image of a person reading poetry.
Personally, I will stick with a black and white movie. However, the choice of movie might be an issue as some participants might find the movie boring if it does not interest them. I was also thinking of music as this will not interfere with your visual memory task. Some evidence show that certain music generate alpha rhythm (see: http://jrm.sagepub.com/content/23/1/3.short). However, this also has the same issue as a movie.
Hmmm... Based on your answers, perhaps I should also consider an audio book.
I would be really inclined to make sure whatever you do end up choosing has minimal impact in adding additional variation due to subjective differences in perception of whatever is presented to them during the 10-15 mins.
Out of curiosity, is there a rationale for providing stimulation before the task and not during the task ? The tDCS literature seems to vary but mostly suggests during may be more beneficial than before, at least for a motor learning task (Stagg et al., Neuropsychologia 2011 - link attached below). Does the literature vary for tACS and/or cognitive tasks ?
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3083512/
Thanks for the paper Rohan! I have however, already considered that aspect of online vs offline stimulation. For the particular experiment I am running, the point is to run an offline tACS protocol prior to an online tDCS protocol.
Offline tACS followed by online tDCS, got it ! Maybe neutral valence pictures (black and white) from the IAPS set ? I was thinking a fixation cross for 10-15 mins but that might too long !
Wouldn't it be better to have the eyes closed (dark; higher alpha) and having them listen to an interesting audio book (better control because you are not messing with the visual cortex too much) ?
According to Neuling, T. et al (2013), I would expect a weak after effect in an eyes closed paradigm as my alpha power would approach a ceiling.
Hi,
Fascinating question. Considering the wealth of research showing how important (and the impact on what tDCS does) is what you do before/during/and after tDCS and it's impact I would be extremely cautious with regards to presenting any visual stimuli to subjects while receiving tDCS who are going to be tested on a task that involves the visual system.
My preference would be not to present any visual stimuli, other than those stimuli that you have in your testing room (which I would suggest is the same and does not change during the duration of your study).
Best regards,
Fidel
Several considerations come to mind. First, CES has shown to be effective whether the subject reads or watches TV or listens to music during the CES session. If you are loking to augment the CES session, it could be augmented via synchronized light and sound. Binaural beat entrainment during the CES session may augment the effects. if augmentation is desirable, and you are not interested in isolating the CES derived effects thatare to be measured. Feel free to PM if you would like me to explore further.
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