Community Research and Development Information Service - CORDIS

How the brain perceives the world

Researchers have revealed how the human brain perceives objects among countless sensory signals that create noise.
How the brain perceives the world
The human brain deals with so much sensory input from the external world that it needs to prioritise what it perceives to avoid being overwhelmed. For this reason, it filters out irrelevant information while making us aware of what is deemed important, such as an object or a face. This is known as attention.

How the brain does this is hotly debated among neuroscientists and psychologists. Some theories rely on a bottom-up approach, according to which the eye takes in visual information that the brain pieces together to construct an entire scene. A top-down approach, meanwhile, maintains that the brain uses prior memories and information to construct a scene, and then derives the details to support it.

The EU-funded project PREPARING TO SEE (Neural mechanisms of top-down preparation and their influence on visual awareness of real-world objects) used cutting-edge psychophysical techniques to see whether attention, and therefore top-down processing, is required to perceive natural objects.

Researchers first demonstrated that prior information about an object before being presented as a visual stimulus makes people more aware of the object. This proved that top-down preparation can turn noisy stimuli into focused awareness.

Building on this finding, they tested the influence of top-down expectations on how people consciously perceive objects in photographs of natural scenes. As before, prior information about categories (for example, animals or vehicles) improved their detection in cluttered natural scenes.

Researchers showed that even when the brain processes information contained in bottom-up sensory signals, it uses a top-down approach to make sense of it. When asked to look for faces or houses in images that contained pure noise, people's brains processed them as if they contained actual visual stimuli. This showed that our expectations can strongly influence not only what we see but even whether we see something at all.

This work has shown that conscious perception is strongly influenced by our internal goals and expectations, rather than by properties of the external world alone.

Related information


Human brain, objects, sensory signals, attention, PREPARING TO SEE
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