spm_hrf makes an upsampled hemodynamic response function that can be
convolved with an upsampled onset stream. The resulting regressor can be
downsampled.
Linda Seltzer
UC Davis
> <FONT face="Sans Serif
> predeterminado,Verdana,Arial,Helvetica,sans-serif" size=2><DIV><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><FONT face="Serif
> predeterminado,Times New Roman,Times,serif">Dear SPMers,
> <?xml:namespace prefix = o ns =
> "urn:schemas-microsoft-com:office:office"
> /><o:p></o:p></FONT></SPAN></P><P class=MsoNormal
> style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB style="FONT-SIZE: 14pt;
> mso-ansi-language: EN-GB"><o:p><FONT face="Serif
> predeterminado,Times New
> Roman,Times,serif"> </FONT></o:p></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><FONT face="Serif
> predeterminado,Times New Roman,Times,serif">I am interested in defining
> high-temporal resolution regressors for a block design analysis. In
> particular, I am interested in using a slice-order temporal resolution (in
> this case TR/22). This is intended to make possible the use of slice-wise
> physiological noise
> estimators.<o:p></o:p></FONT></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><o:p><FONT
> face="Serif predeterminado,Times New
> Roman,Times,serif"> </FONT></o:p></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><FONT face="Serif
> predeterminado,Times New Roman,Times,serif">As the conventional menu
> “Multiple Regressors” will not allow me to select matrices
> with more rows than volumes in the design, this is the approach I have
> arrived at:<o:p></o:p></FONT></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><o:p><FONT
> face="Serif predeterminado,Times New
> Roman,Times,serif"> </FONT></o:p></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><FONT face="Serif
> predeterminado,Times New Roman,Times,serif">-Defining the time bins to
> TR/nSlices and appropriately controlling slice timing and reference
> slice.<o:p></o:p></FONT></SPAN></P><P class=MsoNormal
> style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB style="FONT-SIZE: 14pt;
> mso-ansi-language: EN-GB"><o:p><FONT face="Serif
> predeterminado,Times New
> Roman,Times,serif"> </FONT></o:p></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><FONT face="Serif
> predeterminado,Times New Roman,Times,serif">-Adding to the model an
> event-related column with one event per slice (i.e. having
> nVolumes*nSlices onsets with 0 s duration) and modulating these events
> with my high resolution
> regressor.<o:p></o:p></FONT></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><o:p><FONT
> face="Serif predeterminado,Times New
> Roman,Times,serif"> </FONT></o:p></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><FONT face="Serif
> predeterminado,Times New Roman,Times,serif">-Switching off the HRF
> convolution and avoiding filtering to prevent the modification of the
> regressors used.<o:p></o:p></FONT></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><o:p><FONT
> face="Serif predeterminado,Times New
> Roman,Times,serif"> </FONT></o:p></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><FONT face="Serif
> predeterminado,Times New Roman,Times,serif">So my doubt
> is:<o:p></o:p></FONT></SPAN></P><P class=MsoNormal
> style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB style="FONT-SIZE: 14pt;
> mso-ansi-language: EN-GB"><o:p><FONT face="Serif
> predeterminado,Times New
> Roman,Times,serif"> </FONT></o:p></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><FONT face="Serif
> predeterminado,Times New Roman,Times,serif">By doing this, am I actually
> defining the regressors that will be used internally in the GLM model or
> they will be downsampled to match image timing prior to statistical
> processing? Is there any preferable method to define over-TR resolution
> regressors?<o:p></o:p></FONT></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><o:p><FONT
> face="Serif predeterminado,Times New
> Roman,Times,serif"> </FONT></o:p></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB
> style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><FONT face="Serif
> predeterminado,Times New Roman,Times,serif">Thanks in
> advance,<o:p></o:p></FONT></SPAN></P><P class=MsoNormal
> style="MARGIN: 0cm 0cm 0pt"><SPAN lang=EN-GB style="FONT-SIZE: 14pt;
> mso-ansi-language: EN-GB"><o:p><FONT face="Serif
> predeterminado,Times New
> Roman,Times,serif"> </FONT></o:p></SPAN></P><P
> class=MsoNormal style="MARGIN: 0cm 0cm 0pt; tab-stops: 80.25pt"><SPAN
> lang=EN-GB style="FONT-SIZE: 14pt; mso-ansi-language: EN-GB"><FONT
> face="Serif predeterminado,Times New Roman,Times,serif">Hector<SPAN
> style="mso-tab-count:
> 1">
>
</SPAN></FONT><o:p></o:p></SPAN></P><BR><DIV><BR>___________________________________________________<BR>Hector Ortiz Valencia -- Enginyer de telecomunicació<BR>Institut d'Alta Tecnologia -- Parc de Recerca Biomèdica de Barcelona<BR>IAT-PRBB <BR>====>ATENCIO: NOU TELEFON I FAX<====<BR>telf. 932212180 Fax: 932212181<BR>Pg Marítim 25-29 (Ressonancia Magnetica) 08003 Barcelona<BR><A
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