Category-specific modulation of inferior temporal activity during working memory encoding and maintenance.

Area of Science:

• Neuroscience
• Cognitive Neuroscience

Background:

• Neurophysiological findings suggest visual working memory (WM) relies on modulating neuronal activity in object-selective populations within the inferior temporal cortex.
• This study investigates whether similar mechanisms support encoding and maintenance in human visual working memory.

Purpose of the Study:

• To examine if category-specific regions in the inferior temporal cortex (ITC) are modulated by active encoding and maintenance demands in visual working memory.
• To compare the activity patterns in ITC with those in the dorsolateral prefrontal cortex (PFC) during visual working memory tasks.

Main Methods:

• Event-related functional magnetic resonance imaging (fMRI) was employed to measure brain activity.
• Regions of interest, including the fusiform face area (FFA) and parahippocampal place area (PPA), were identified based on category-specific responses to faces and scenes.
• Activity in FFA and PPA was analyzed in relation to the task relevance of faces and scenes during encoding and maintenance phases.

Main Results:

• The FFA and PPA showed increased encoding- and maintenance-related activity when their preferred stimulus category (faces or scenes) was relevant to the recognition task, irrespective of perceptual stimulation.
• In contrast, dorsolateral prefrontal cortex (PFC) exhibited maintenance-related activity that was influenced by memory load, independent of the specific stimulus type.

Conclusions:

• The findings support the model where visual working memory encoding and maintenance are achieved through prefrontal cortex modulation of inferior temporal cortex activity.
• This suggests a hierarchical processing mechanism where PFC exerts top-down control over specialized visual areas for memory representation.