"What"-Then-Where" in visual working memory: an event-related fMRI study

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Functional Magnetic Resonance Imaging (fMRI)

Background:

• Behavioral evidence suggests distinct neural systems for spatial and object working memory.
• Understanding the neural basis of working memory is crucial for cognitive function.

Purpose of the Study:

• To investigate the neural substrates underlying the dissociation between spatial and object working memory.
• To directly assess delay-period activity in the brain using fMRI, free from trial confounds.

Main Methods:

• Utilized a "what"-then-"where" fMRI task design to probe object and spatial working memory.
• Employed whole-brain fMRI with a novel analysis to isolate delay-period activity.
• Balanced the within-trial order of object and spatial delay conditions across scans.

Main Results:

• No evidence for anatomically segregated frontal cortex regions for spatial versus object working memory.
• Caudate nucleus activity showed trial-order sensitivity in spatial, but not object, memory.
• Spatial working memory engaged extrastriate visual areas (Brodmann's area 19) and superior parietal lobule.
• Object working memory primarily involved ventral posterior cortex with greater inter-subject variability.

Conclusions:

• Spatial and object working memory rely on dissociable posterior neural substrates.
• The frontal cortex does not appear to anatomically segregate these two working memory types.
• Neural representations for object working memory exhibit greater topographic variability than spatial working memory.