Sensory representations in primary visual cortex are not sufficient for subjective imagery

Area of Science:

• Cognitive Neuroscience
• Neuroimaging
• Psychology

Background:

• Mental imagery is defined by sensory representations and subjective experience.
• Neuroimaging shows imagery-related sensory representations in primary visual cortex (V1) similar to perception.
• It is unclear if V1 representations always correlate with subjective experience.

Purpose of the Study:

• To investigate whether sensory representations in V1 can be dissociated from subjective visual imagery.
• To compare visualizers and aphantasics (individuals with impaired imagery ability).
• To examine spontaneous and voluntary imagery to decouple representations from generation ability.

Main Methods:

• Multivariate functional magnetic resonance imaging (fMRI) was used to decode sensory representations in V1.
• Participants included visualizers and aphantasics.
• Brain activity was analyzed during spontaneous (passive listening) and voluntary (instructed) imagery tasks while blindfolded.

Main Results:

• V1 decoding of sound content was successful in aphantasics during passive listening, despite no reported imagery, but at chance during voluntary imagery.
• In visualizers, V1 decoding was higher for voluntary than spontaneous imagery and correlated with vividness.
• Precuneus decoding was successful in visualizers but not in aphantasics for both conditions.

Conclusions:

• Primary visual cortex (V1) representations can be dissociated from subjective mental imagery.
• The precuneus plays a crucial role in subjective visual imagery.
• Findings challenge the notion that sensory representations invariably accompany conscious imagery.