Disentangling visual imagery and perception of real-world objects

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Visual Perception and Imagery

Background:

• Mental imagery involves creating visual representations without direct sensory input.
• Previous research shows overlapping neural substrates for imagery and perception, but neuropsychological studies reveal a double dissociation, indicating distinct mechanisms.
• The apparent contradiction between neuroimaging and patient studies necessitates further investigation into the neural basis of visual imagery and perception.

Purpose of the Study:

• To investigate the specificity, distribution, and similarity of neural information for seen versus imagined objects using fMRI.
• To resolve the apparent contradiction between neuroimaging and neuropsychological findings regarding the neural substrates of visual imagery and perception.
• To elucidate the differences in network dynamics between visual perception and mental imagery.

Main Methods:

• Functional magnetic resonance imaging (fMRI) with multi-voxel pattern analysis (MVPA).
• An event-related design where participants viewed or imagined trained object images.
• Decoding object identity from patterns of brain activity in the ventral visual processing stream.

Main Results:

• Object identity for both seen and imagined objects was decodable from the ventral visual processing stream.
• A significant correspondence between imagery and perception allowed discrimination of imagined objects based on perception responses.
• Strikingly different distributions of object information were observed: a posterior-to-anterior gradient for seen objects and an opposite gradient for imagined objects.
• Representational structure (similarity patterns) was more similar across visual regions during imagery than perception.

Conclusions:

• Visual imagery and perception share common neural substrates within the ventral visual stream.
• Despite shared substrates, imagery and perception exhibit distinct network dynamics, evidenced by differing information distribution gradients.
• These findings reconcile previous neuroimaging and neuropsychological data, suggesting that differences in network dynamics underlie the apparent dissociation between visual perception and mental imagery.