Cite as:
Likova L T, Tyler C W, 2007, "Instantaneous stimulus paradigm: Perceptual organization networks and dynamics" Perception 36 ECVP Abstract Supplement

Instantaneous stimulus paradigm: Perceptual organization networks and dynamics

L T Likova, C W Tyler

To reveal the neural dynamics of the cortical networks underlying different types of perceptual organization, we developed a novel paradigm that creates distinct and prolonged percepts of spatial structures by instantaneous refreshes in random-dot fields. Three different configurations were generated by refreshing: (i) the whole stimulus field (uniform field), (ii) the ground region only (negative-figure or hole), and (iii) the figure and ground regions in brief temporal asynchrony (figure - ground). fMRI responses were measured throughout the brain. The uniform-field refresh activated the posterior part of the brain only, but the figure - ground and the negative-figure conditions activated two distinct networks extending beyond the occipital lobe toward the frontal cortex. For each of the three brief stimulus types, a wide variety of BOLD waveforms was found even within the same regions of cortex. Such expressly different responses within identical cortical regions ensure that the differences could be securely attributed to the neural dynamics, not to spatial variations in the hemodynamic response function. Even where activations are partially overlapping, an integrated analysis of the temporal properties of the BOLD response enables the functional specificity of the cortical areas to be distinguished.

[Supported by NIH EY 13025 and The Pacific Vision Foundation.]

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