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Hi all,<div><br></div><div><p style="font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration-style:initial;text-decoration-color:initial;margin:0px 0px 1em;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;font-size:15px;line-height:inherit;font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;vertical-align:baseline;clear:both;color:rgb(67,70,72);text-align:left;background-color:rgb(255,255,255)">I am working with functional connectivity between different (EEG) signals. I'm calculating the connectivity strength between different brain regions and correlate the connectivity strength to a certain outcome measure. Among others, I'm using the cross spectral density (CSD) and the coherence. The CSD is not generally used as a measure of connectivity but I don't completely understand why not. Especially since the CSD correlates well with my outcome measure, while the coherence doesn't. I'm trying to undertand whether there is a fundamental reason why I can't use the CSD, and why I should use the coherence. </p><p style="font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration-style:initial;text-decoration-color:initial;margin:0px 0px 1em;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;font-size:15px;line-height:inherit;font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;vertical-align:baseline;clear:both;color:rgb(67,70,72);text-align:left;background-color:rgb(255,255,255)">So I'm trying to understand why people use coherence (the normalized version of the cross spectral density) as a measure of connectivity instead of cross spectral density (CSD). Why do you have to normalize the CSD with the autospectral densities to determine connectivity when the CSD by itself is a measure of signal similarity? Is there a fundamental reason to normalize the CSD?</p><p style="font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;text-decoration-style:initial;text-decoration-color:initial;margin:0px 0px 1em;padding:0px;border:0px;font-variant-numeric:inherit;font-variant-east-asian:inherit;font-stretch:inherit;font-size:15px;line-height:inherit;font-family:Arial,"Helvetica Neue",Helvetica,sans-serif;vertical-align:baseline;clear:both;color:rgb(67,70,72);text-align:left;background-color:rgb(255,255,255)">Jord</p><div class="gmail-yj6qo" style="color:rgb(34,34,34);font-family:arial,sans-serif;font-size:12.8px;font-style:normal;font-variant-ligatures:normal;font-variant-caps:normal;font-weight:400;letter-spacing:normal;text-align:start;text-indent:0px;text-transform:none;white-space:normal;word-spacing:0px;background-color:rgb(255,255,255);text-decoration-style:initial;text-decoration-color:initial"></div><br class="gmail-Apple-interchange-newline">

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