2009 Grace Tang & Kelly Hennigan - Revision history

imported>Winawer: Unprotected "2009 Grace Tang & Kelly Hennigan"

2010-03-10T01:48:16Z

Unprotected "2009 Grace Tang & Kelly Hennigan"

← Older revision	Revision as of 01:48, 10 March 2010
(No difference)

imported>Winawer: Protected "2009 Grace Tang & Kelly Hennigan" ([edit=sysop] (indefinite) [move=sysop] (indefinite))

2010-03-10T01:43:30Z

Protected "2009 Grace Tang & Kelly Hennigan" ([edit=sysop] (indefinite) [move=sysop] (indefinite))

← Older revision	Revision as of 01:43, 10 March 2010
(No difference)

imported>Psych 204: /* Smoothing */

2009-12-15T00:06:39Z

Smoothing

← Older revision		Revision as of 00:06, 15 December 2009
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	\|[[File:smoothhist_555_05_rel.jpg\|thumb\|none\|[5 5 5], 0.5]]		\|[[File:smoothhist_555_05_rel.jpg\|thumb\|none\|[5 5 5], 0.5]]
			\|}

			== Implications for functional analysis ==

			Structural malalignment introduces variance to functional group data fitted to normalized space, which increases the likelihood of false negatives (i.e., given positive results, it becomes less likely find significant activation). For example, consider an experiment that evokes a reliable and consistent increase in the BOLD signal relative to a baseline in bilateral nucleus accumbens in each of 10 participants. Assuming that the effect is equally expressed in each voxel across subjects, a voxel with an overlap index of 3 or less will not yield a significant result within that voxel (t=1.52, 9 df, p>.05), however for 4 or more participants, this effect may still be detected (t=2.02, 9 df, p<.05). Figure 8 below shows the areas of the group averaged NAc mask in which the effect (as described above) could or could not be detected in red and blue, respectively. Voxels labeled red (NAc overlap index of 4 and greater) constitute 30.3% of the total masked NAc voxels in all 10 participants, totaling 2,641 voxels. Noteably, this number is comparable to the average voxels/subject mask (2,491 voxels).

			It should be noted that this is a highly artificial estimate since it assumes a uniformly distributed effect. Nonetheless, it provides some insight about the impact of malalignment on functional analysis.

			=== Figure 8 ===

			{\|
			\| [[File:thresh_axial.jpg\|thumb\|250px\|axial plane]]
			\| [[File:thresh_sag.jpg\|thumb\|250px\|sagittal plane]]
			\| [[File:thresh_cor.jpg\|thumb\|250px\|coronal plane]]
	\|}		\|}

imported>Psych 204: /* Smoothing */

2009-12-11T23:13:04Z

Smoothing

← Older revision		Revision as of 23:13, 11 December 2009
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	The number of non-zero voxels from the summed matrix that fell inside the representative mask volume was 266 (the size of the representative mask volume is 266 - every voxel within the representative mask overlapped with at least one individual subject brain), while the number of non-zero voxels that fell outside the representative mask was 848. While this at first glance appears to show poor agreement with the representative mask, closer inspection of the index of overlap within and outside the representative mask indicates otherwise. The mean index of overlap within the representative mask was 5.0, while the mean outside the mask was 2.088. An independent samples t-test showed that the index of overlap was significantly higher within the representative mask (p<0.01).		The number of non-zero voxels from the summed matrix that fell inside the representative mask volume was 266 (the size of the representative mask volume is 266 - every voxel within the representative mask overlapped with at least one individual subject brain), while the number of non-zero voxels that fell outside the representative mask was 848. While this at first glance appears to show poor agreement with the representative mask, closer inspection of the index of overlap within and outside the representative mask indicates otherwise. The mean index of overlap within the representative mask was 5.0, while the mean outside the mask was 2.088. An independent samples t-test showed that the index of overlap was significantly higher within the representative mask (p<0.01).

	~~==Smoothing==~~

	==Smoothing==		==Smoothing==

imported>Psych 204: /* Histograms */

2009-12-11T21:08:53Z

Histograms

← Older revision		Revision as of 21:08, 11 December 2009
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	\|[[File:smoothhist_111_03.jpg\|thumb\|none\|[1 1 1], 0.3]]		\|[[File:smoothhist_111_03.jpg\|thumb\|none\|[1 1 1], 0.3]]

	\|[[File:~~smoothhist_111_05~~.jpg\|thumb\|none\|[1 1 1], 0.5]]		\|[[File:smoothhist_111_03.jpg\|thumb\|none\|[1 1 1], 0.5]]
	\|}		\|}
	{\|		{\|

imported>Psych 204: /* Histograms */

2009-12-11T21:07:02Z

Histograms

← Older revision		Revision as of 21:07, 11 December 2009
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	===Histograms===		===Histograms===
	**** CHECK... [1 1 1] 05 is a placeholder
	{\|		{\|
	\|[[File:smoothhist_111_03.jpg\|thumb\|none\|[1 1 1], 0.3]]		\|[[File:smoothhist_111_03.jpg\|thumb\|none\|[1 1 1], 0.3]]

imported>Psych 204: /* Histograms */

2009-12-11T21:06:55Z

Histograms

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	\|[[File:smoothhist_111_03.jpg\|thumb\|none\|[1 1 1], 0.3]]		\|[[File:smoothhist_111_03.jpg\|thumb\|none\|[1 1 1], 0.3]]

	\|[[File:~~smoothhist_111_03~~.jpg\|thumb\|none\|[1 1 1], 0.5]]		\|[[File:smoothhist_111_05.jpg\|thumb\|none\|[1 1 1], 0.5]]
	\|}		\|}
	{\|		{\|

imported>Wandell: /* Appendix */

2009-12-10T23:38:22Z

Appendix

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	=Appendix=		=Appendix=

			Please note: I moved your source code into a better named page. The generic title 'code' or 'more code' wouldn't work with the whole wiki.

	[[2009_Grace_Tang_%26_Kelly_Hennigan_Appendix]]		[[2009_Grace_Tang_%26_Kelly_Hennigan_Appendix]]

imported>Wandell: /* Appendix */

2009-12-10T23:34:39Z

Appendix

← Older revision		Revision as of 23:34, 10 December 2009
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	=Appendix=		=Appendix=

	* [[~~Code]]~~		[[2009_Grace_Tang_%26_Kelly_Hennigan_Appendix]]
	* [[More Code]]
	* [[Smoothing Code]]

imported>Psych 204: /* Relative Histograms */

2009-12-10T07:40:32Z

Relative Histograms

← Older revision		Revision as of 07:40, 10 December 2009
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	Relative histograms can be used to investigate changes in overlap while controlling for increases in mask size. A shift to the right (i.e. a higher proportion of voxels with higher overlap index) in relative histograms implies an improvement of overlap that is not due to an overall increase in number of voxels per mask.		Relative histograms can be used to investigate changes in overlap while controlling for increases in mask size. A shift to the right (i.e. a higher proportion of voxels with higher overlap index) in relative histograms implies an improvement of overlap that is not due to an overall increase in number of voxels per mask.

	~~Comparing the effects of different smoothing kernels...~~

	With smoothing kernels of 3x3x3 and 5x5x5, there is a shift to the right when the threshold is lowered from 0.5 to 0.3, indicating better overlap. Changing the threshold does not make a difference when using a smoothing kernel of 1x1x1.		With smoothing kernels of 3x3x3 and 5x5x5, there is a shift to the right when the threshold is lowered from 0.5 to 0.3, indicating better overlap. Changing the threshold does not make a difference when using a smoothing kernel of 1x1x1.