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Abstract
How the brain constructs a coherent representation of the environment from noisy visual input remains poorly understood. Here, we explored whether awareness of the stimulus plays a role in the integration of local features into a representation of global shape. Participants were primed with a shape defined either by position or orientation cues, and performed a shape-discrimination task on a subsequently presented probe shape. Crucially, the probe could either be defined by the same or different cues as the prime, which allowed us to distinguish the effect of priming by local features and global shape. We found a robust priming benefit for visible primes, with response times being faster when the probe and prime were the same shape, regardless of the defining cue. However, rendering the prime invisible uncovered a dissociation: position-defined primes produced behavioural benefit only for probes of the same cue type. Surprisingly, orientation-defined primes afforded an enhancement only for probes of the opposite cue. In further experiments, we showed that the effect of priming was confined to retinotopic coordinates and that there was no priming effect by invisible orientation cues in an orientation-discrimination task. This explains the absence of priming by the same cue in our shape-discrimination task. In summary, our findings show that while in the absence of awareness orientation signals can recruit retinotopic circuits (e.g. intrinsic lateral connections), conscious processing is necessary to interpret local features as global shape.
Highlights
One of the key functions of the visual system is to construct a coherent representation of the environment
In this study, we used a priming paradigm to address two previously unresolved questions about how the brain processes information about a visual scene: First, how are discrete, local features of the input from the retina integrated into a representation about global shape? Second, in what way do these processes depend on whether we are consciously aware of the stimulus? We found that invisible prime shapes could exert an influence on participants’ performance in a simple shape-discrimination task, as participants’ response times were faster when the probe was the same shape as the prime
We found that while position information is not integrated into a representation of global form in the absence of awareness, orientation information is
Summary
One of the key functions of the visual system is to construct a coherent representation of the environment. It must identify the local features belonging to the same object, such as edges, corners and surfaces, and bind them together into a global percept. One question has not been explored in this context: to what extent does this process of perceptual integration depend on conscious awareness of the visual stimulus? Previous research exploring the differences between conscious and unconscious processing suggested that a great deal of information about a stimulus is present in the visual system even when participants are unaware of it. Extrastriate brain regions contain a representation of complex visual
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