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Frank Pollick, William Steel, Haodan Tan, Lukasz Piwek, Frances Crabbe, Ulf Ahlstrom; A New Action Library for Localising Brain Activity Specific to Biological Motion. Journal of Vision 2011;11(11):683. doi: https://doi.org/10.1167/11.11.683.
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Ahlstrom, Blake, and Ahlstrom (1997) introduced a point-light stimuli set for the study biological motion perception. It consisted of 25 assorted actions sampled at 20 Hz for a 1 second duration and an additional 25 scrambled versions of the same actions. We revisited this stimulus set with an aim to examine the effects of using more rapid acquisition rates and obtaining higher quality data without missing markers. Using a 12 camera Vicon system we recorded the motions of an actor to obtain an equivalent set of 25 actions at a sampling rate of 120 Hz. These data were processed into movies of 1 second duration at a display rate of 60 Hz that showed black dots on a grey background. This display set was subsequently used in an fMRI experiment that contrasted brain activity when viewing the intact displays to brain activity when viewing the scrambled displays. This was achieved using a 3T Tim Trio scanner (Siemens) with a TR of 2000 msec and a block design. Each block had either all intact or all scrambled displays and a total duration of 16 sec, made up of eight 1-second animations followed by a 1-second blank screen. Analysis of the contrast between intact and scrambled blocks was examined for activity in posterior STS (pSTS), a region implicated in biological motion processing. Preliminary results from scanning the first 8 participants showed activity in the left pSTS for 2 of 8 participants and in the right pSTS for 4 of 8 participants. The lack of consistent activition in pSTS appears in contrast to results obtained in previous studies with the original displays. Possible theoretical reasons for this difference will be discussed.
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