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--></style></head><body lang=EN-US link="#467886" vlink="#96607D" style='word-wrap:break-word'><div class=WordSection1><p class=MsoNormal><span style='font-size:14.0pt'>Hello<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'>If I calculate the PSI value between 2 channels [channels A and B], the output of ft_connectivity_psi is a 3D matrix in which the first 2 indices are the PSI values of AA [always null], AB, BA, and BB [null]. The AB and BA values are the same magnitude but opposite sign indicating causal direction. The 3<sup>rd</sup> index is frequency.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'>If I now have more than 2 channels [A1, A2, etc, B1, B2,etc], the output of the matrix is NumChannelsA X NumChannelsB X Frequency. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'>My question is how do I interpret the sign of the PSI value? Is it always correct to assume that the positive value indicates that Ax is driving Bx?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'>Thank you!<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:14.0pt'><o:p> </o:p></span></p><div><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri",sans-serif;color:black;mso-ligatures:none'>-- <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri",sans-serif;color:black;mso-ligatures:none'>Yale E. Cohen, Ph.D. <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri",sans-serif;color:black;mso-ligatures:none'>Professor<br>Associate Dean for Research Infrastructure and Strategy<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri",sans-serif;color:black;mso-ligatures:none'>Chair, Bioengineering Graduate Group<br>Department of Otorhinolaryngology:Head and Neck Surgery<br>University of Pennsylvania School of Medicine<br>3400 Spruce - <a href="x-apple-data-detectors://1" title="x-apple-data-detectors://1"><span style='color:black'>5 Ravdin</span></a><br><a href="x-apple-data-detectors://1" title="x-apple-data-detectors://1"><span style='color:black'>Philadelphia, PA 19104</span></a><br><br>Office: G12A Stemmler <o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri",sans-serif;color:black;mso-ligatures:none'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri",sans-serif;color:black;mso-ligatures:none'>E-mail: <a href="mailto:ycohen@pennmedicine.upenn.edu" title="mailto:ycohen@pennmedicine.upenn.edu"><span style='color:black'>ycohen@pennmedicine.upenn.edu</span></a><br>Phone: <a href="tel:215%20898%207504" title="tel:215%20898%207504"><span style='color:black'>215 898 7504</span></a> <br>FAX: <a href="tel:215%20898%209994" title="tel:215%20898%209994"><span style='color:black'>215 898 9994</span></a><br><a href="https://eur01.safelinks.protection.outlook.com/?url=http%3A%2F%2Fauditoryresearchlaboratory.weebly.com%2F&data=05%7C02%7Cfieldtrip%40science.ru.nl%7Cbe2befa207dd47c106d208ddc572d8aa%7C084578d9400d4a5aa7c7e76ca47af400%7C1%7C0%7C638883819256795882%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=XcqSBGJb2kfeGuLaGdJPt5z7GK3KsSyZESSPMCPe708%3D&reserved=0" originalSrc="http://auditoryresearchlaboratory.weebly.com/" title="http://auditoryresearchlaboratory.weebly.com/"><span style='color:black'>Research</span></a> <a href="https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fbe.seas.upenn.edu%2Fdoctoral%2F&data=05%7C02%7Cfieldtrip%40science.ru.nl%7Cbe2befa207dd47c106d208ddc572d8aa%7C084578d9400d4a5aa7c7e76ca47af400%7C1%7C0%7C638883819256812829%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=B%2F9eKo41gHAbM4NhwW825Teg7MWYq4vpqNcnb43X24Q%3D&reserved=0" originalSrc="https://be.seas.upenn.edu/doctoral/" title="https://be.seas.upenn.edu/doctoral/"><span style='color:black'>BE PhD Program</span></a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri",sans-serif;color:black;mso-ligatures:none'><a href="https://eur01.safelinks.protection.outlook.com/?url=https%3A%2F%2Fjoin.slack.com%2Ft%2Fpennbioengineering%2Fshared_invite%2Fzt-ftaz0sis-Lsm4UhkeBWU26i9ZtrMGVw&data=05%7C02%7Cfieldtrip%40science.ru.nl%7Cbe2befa207dd47c106d208ddc572d8aa%7C084578d9400d4a5aa7c7e76ca47af400%7C1%7C0%7C638883819256826316%7CUnknown%7CTWFpbGZsb3d8eyJFbXB0eU1hcGkiOnRydWUsIlYiOiIwLjAuMDAwMCIsIlAiOiJXaW4zMiIsIkFOIjoiTWFpbCIsIldUIjoyfQ%3D%3D%7C0%7C%7C%7C&sdata=gqyu%2FtIzvelYCjMA%2F6Fs3scL8s87O1QXI%2BYAxe8vGLs%3D&reserved=0" originalSrc="https://join.slack.com/t/pennbioengineering/shared_invite/zt-ftaz0sis-Lsm4UhkeBWU26i9ZtrMGVw" title="https://join.slack.com/t/pennbioengineering/shared_invite/zt-ftaz0sis-Lsm4UhkeBWU26i9ZtrMGVw"><span style='color:black'>Join BE Slack</span></a><o:p></o:p></span></p><p class=MsoNormal><span style='font-size:10.0pt;font-family:"Calibri",sans-serif;color:black;mso-ligatures:none'> <o:p></o:p></span></p></div><p class=MsoNormal><o:p> </o:p></p></div></body></html>