It is normalized. I haven't checked it without normalization, but I'm not sure how normalization would contribute to this random scattered pattern of activity...?
The other contrasts show similar activation patterns but they're not identical. I did try putting a +1 in front of my conditions and I got activity everywhere as expected.
From: Chris Watson [[log in to unmask]]
Sent: Tuesday, March 29, 2011 6:23 PM
To: Meera Paleja
Cc: [log in to unmask]
Subject: Re: [SPM] "dalmation" pattern in data
Is your data normalized? If so, have you checked to see what it looks
like without normalization?
What about other contrasts? Do they look similar? Have you tried, say, a
contrast of just a +1 over each key press? Then you should at least see
something in motor cortex.
Meera Paleja wrote:
> Attached is a figure for one subject, but this is a fairly consistent pattern across all my subjects for all contrasts.
> This was a high-resolution fMRI experiment that used a medial temporal lobe shim. The task involved seeing an image of an object on the floor of a computerized room. This was followed by the recognition phase, where subjects saw an image with two objects, one in the same location as the original and another in a different location and were asked to indicate which is in the same location using a key press.
> The image file attached here is a contrast comparing the recognition phase with a baseline letter task, where participants are asked to indicate whether a displayed letter is a vowel or consonant using a key press.
> From: Chris Watson [[log in to unmask]]
> Sent: Tuesday, March 29, 2011 5:03 PM
> To: Meera Paleja
> Cc: [log in to unmask]
> Subject: Re: [SPM] "dalmation" pattern in data
> Could you attach a screenshot? And explain the experiment?
> Meera Paleja wrote:
>> Hi SPM-ers,
>> I am seeing odd activation patterns in my data, specifically "dalmation-like" activation, where one or two voxel "clusters" are activated throughout the brain, with very few clusters larger than that. Does anyone know what might account for this? I haven't smoothed the data as I am interested in very small regions (hippocampal subregions)- could the lack of smoothing be a reason for these strange patterns?
>> Meera Paleja, B.Sc. (Hons.), M.A.
>> PhD. Student, Psychological Science
>> Brain Imaging and Memory Lab
>> Department of Psychology
>> Ryerson University
>> Phone: (416) 979-5000 ex. 2192
>> email: [log in to unmask]
>> “Perhaps the most fascinating and mysterious universe of all is the one within us.” -- Carl Sagan