2013 Fiscal Year Annual Research Report
事前知識と視覚知覚 （Ｐｒｉｏｒｓ ａｎｄ ｖｉｓｕａｌ ｐｅｒｃｅｐｔｉｏｎ）
| Project/Area Number |
24300146
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| Research Institution | Institute of Physical and Chemical Research |
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Principal Investigator |
ガードナー ジャステン 独立行政法人理化学研究所, 脳科学総合研究センター, チームリーダー (70565134)
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| Project Period (FY) |
2012-04-01 – 2015-03-31
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| Keywords | 事前知識 / Priors / fMRI / Attention / Vision / Perception |
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| Research Abstract |
1.Published a main aim of this Kakenhi grant in Journal of Neuroscience. We examined a prior for slow movement and found it to be represented in human early visual cortex. As proposed in the Kakenhi grant, we used functional imaging and classification techniques to read-out representations of the speed of visual stimuli. When contrast is lowered, human observers are biased to seeing the same stimuli as moving slower and we found that cortical responses in the first stages of the visual system represent this shift. We concluded that this slow speed prior is combined with sensory evidence at the earliest stages of visual processing.
2.Developed a signal detection task in which we change the prior for whether a stimulus will appear and found that this changes signal detection bias. This can be done independently of attentional effects in that we cue subjects to respond to one of two potential locations and show that attention changes sensitivity (d’) and not criterion.
3. Developed a motion estimation task in which subjects are presented with a noisy sensory stimulus and must report the direction of motion. We can change sensory evidence by manipulating motion coherence, making it harder or easier to judge the direction of the stimulus. We manipulate the prior probability of motion directions by changing the frequency with which particular directions are shown in each block of trials. We are asking whether subjects can learn priors on a short time scale, and to what extent they use the reliability of the prior and the sensory evidence to make perceptual inferences.
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| Current Status of Research Progress |
Current Status of Research Progress
2: Research has progressed on the whole more than it was originally planned.
Reason
We have completed the first half of the objectives of the Kakenhi grant in which we set out to examine the cortical basis for priors in human speed motion perception. That work was published in Journal of Neuroscience which is a leading international journal in the field. Progress continues with the other main aim of understanding cortical processes of how changes in prior signal probability affect signal detection criterion.
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| Strategy for Future Research Activity |
We plan to develop our behavioral paradigms for studying how priors affect signal detection criterion and motion direction estimation. By analyzing the behavior we expect to differentiate different models for how subjects use prior information to affect performance. Using fMRI measurements, we can then test models for how computations involving priors are implemented in the brain.
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| Expenditure Plans for the Next FY Research Funding |
In FY2013 we concentrated on development of behavioral paradigms which used existing equipment and partial effort of personnel resulting in lower costs and carry-over budget.
In FY2014 we intend to move these behavioral projects into data collection for fMRI which will require significant costs of doing experiments and full time effort of personnel.
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