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[Solved] Clarification hypothesis

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(@franzi)
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Joined: 10 months ago

Hi FRESH team,

I have a question regarding the hypotheses for the motor data set. What is meant by contralateral here:

"2. Left AND right hand finger tapping of 2 sec duration, conditions combined, evokes a response in the contralateral primary motor cortex."

Same question for hypotheses 3. and 4. Does this mean contralateral to the LEFT hand? 

Thanks,

Franziska

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Meryem Yücel
Posts: 191
(@mayucel)
Joined: 3 years ago

@franzi, i.e. to say: Is the response ,overall, -i.e. considering both left and right-hand finger tapping conditions- significant on the contralateral side. Contralateral side means different for each task i.e. for left-hand finger tapping, a brain activation on the right hemisphere, and for right-hand finger tapping, a brain activation on the left hemisphere. Does that answer your question?

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(@franzi)
Joined: 10 months ago

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@mayucel, thank you very much, this does indeed answer my question!

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(@dani)
Joined: 2 years ago

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Posts: 2

@mayucel My apologies, our team still doesn't quite understand the formulation of the hypothesis. Specifically, we got confused about the phrasing 'conditions combined'. Do you mean that we pool the conditions (left and right finger tapping) together in our analysis and then check for brain activation on both hemispheres (which would then be bilateral activity and not contralateral activity)

Or do you mean that we check for e.g. the left hand 2s run whether we can find contralateral activity AND for the right hand 2s run whether we can find contralateral activity separately? Which would then also mean that if we find that we need to reject the 1st hypothesis, we also automatically reject the 2nd hypothesis and 3rd hypothesis by default, since the 2nd and 3rd are dependent on 1st hypothesis?

We had quite the discussion in our team as to how to interpret the hypotheses!

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Meryem Yücel
Posts: 191
(@mayucel)
Joined: 3 years ago

Hi Danielle, 

Thanks for reaching out! I am hoping that I will not bias you re your choice of statistical test you will apply but I believe this would be the easiest way to explain it: e.g. for the hypothesis of 2 and 3 sec duration, conditions combined, think of it as a pool of all trials combined. However for the 2 and 3 sec left hand conditions, the response is coming from the right hemisphere (either a channel or an ROI or a bunch of voxels you have chosen), and similarly for the right hand, you have the response from the left hemisphere. Eventually you will have a pool of trials for all conditions, a hemodynamic response on the contralateral side for each of these trials, and you need to find, given all trials, whether this response is higher than baseline. Please let me know if this clarifies things for you.

Thanks,

Meryem

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(@dani)
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Joined: 2 years ago

Dear Meryem,

This has indeed helped us with interpreting the hypotheses. Thanks a lot for your detailed response!

Kinds regards,

Danielle

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