Object and spatial mnemonic interference differentially engage lateral and medial entorhinal cortex in humans

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Human Neuroimaging

Background:

• Episodic memory models suggest medial temporal lobe (MTL) cortices specialize in object/item versus spatial/contextual information.
• A functional division between perirhinal cortex (object) and parahippocampal cortex (spatial) is established in humans.
• However, a similar domain-selective division within the human entorhinal cortex remains elusive.

Purpose of the Study:

• To investigate domain-specific information processing within human medial temporal lobe cortices, specifically the entorhinal cortex.
• To examine the contributions of MTL cortices to downstream hippocampal computations, particularly pattern separation.
• To test for a functional dissociation between lateral and medial entorhinal cortex in humans during memory tasks.

Main Methods:

• High-resolution functional magnetic resonance imaging (fMRI) was employed.
• Participants performed a mnemonic discrimination task designed to tax object identity versus spatial location memory.
• Task design aimed to differentially engage object-related (perirhinal/lateral entorhinal) and spatial-related (parahippocampal/medial entorhinal) pathways.

Main Results:

• Novel evidence for a domain-selective dissociation between lateral entorhinal cortex (object information) and medial entorhinal cortex (spatial information) in humans.
• A similar domain dissociation was observed between perirhinal cortex and parahippocampal cortex, aligning with information content.
• The hippocampal dentate gyrus/CA3 showed activity consistent with mnemonic interference resolution across both object and spatial domains.

Conclusions:

• These findings support domain-specialized processing within human medial entorhinal cortex subregions, mirroring animal models.
• The results highlight a hierarchical system for interference resolution within the human medial temporal lobe.
• This study advances our understanding of the functional architecture supporting episodic memory in the human brain.