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David C Cappadocia, Michael Vesia, Patrick A Byrne, Xiaogang Yan, J Douglas Crawford; Saccade target selection in subjects cued to remember single or multiple visual features. Journal of Vision 2010;10(7):536. doi: 10.1167/10.7.536.
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© ARVO (1962-2015); The Authors (2016-present)
Most visuomotor experiments use dots or simple shapes as targets, but in the real world we act on complex objects with many visual features. Here we tested the limitation of memory in a feature detection paradigm for saccades. 6 Head-fixed subjects were shown a ‘probe’ template with a conjunction of two features (shape and texture) at central fixation for 500 ms, and instructed to remember either the shape, texture, or both features before each trial. After a delay, subjects were presented with a mask followed by stimuli at four radial locations at an eccentricity of 5° for 1 second. After stimuli were extinguished, subjects were required to saccade to the stimuli that matched the probe. In trials where only one feature was to be remembered, the three other stimuli differed from the probe only in the given feature. In trials where both features were to be remembered, the other stimuli differed in one or both features. We analysed the data with a 2(number of features)x4(locations)x6(subjects) mixed-model ANOVA, with subjects as a random factor. Results indicate that subjects performed significantly better if they only had to remember only one feature. Interestingly, a main effect of probe location was also found. Post hoc tests revealed that subjects responded significantly better if the probe was shown left of center rather than to the top right, and if shown at the top left rather than bottom right. There were also significant interactions between probe location and both number of features and subject. We are currently analyzing probability distributions of correct and incorrect saccades to one or both features within each task, and compared across both tasks. Future experiments will repeat this paradigm with transcranial magnetic stimulation over parietal cortex to examine its causal role in the integration of visual features into the motor plan.
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