The functional anatomy of imagining and perceiving colour

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Neuroimaging

Background:

• Understanding the neural basis of visual perception and mental imagery is crucial for cognitive neuroscience.
• Previous research suggests overlapping but distinct brain regions are involved in processing visual stimuli and generating internal representations.
• Investigating the visual submodality of color offers a focused approach to differentiate these networks.

Purpose of the Study:

• To investigate the similarities and differences between neural networks supporting color perception and color imagery.
• To identify specific brain regions activated during visual perception of color versus mental generation of color images.
• To reconcile neuroimaging findings with clinical observations of dissociations between color perception and imagery.

Main Methods:

• Two functional magnetic resonance imaging (fMRI) experiments were conducted.
• Experiment 1: Contrasted viewing of colored versus grayscale Mondrian displays.
• Experiment 2: Contrasted a relative color judgment task with a spatial task requiring mental image generation.

Main Results:

• Color perception activated bilateral posterior fusiform gyrus (area V4), right anterior fusiform and lingual gyri, striate cortex (V1), and bilateral insula.
• Color imagery activated right anterior fusiform gyrus, left insula, right hippocampus, and parahippocampal gyrus.
• Crucially, V4 and V1 were not activated during color imagery.

Conclusions:

• The findings demonstrate a double dissociation between color perception and color imagery networks.
• This reconciles neurological case studies reporting deficits in one but not the other.
• The study implicates the anterior fusiform gyrus, parahippocampal gyrus, and hippocampus in the storage of colored object representations.