The Perirhinal Cortex Engages in Area and Layer-Specific Encoding of Item Dimensions

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Memory Systems

Background:

• The perirhinal cortex (PRC), comprising areas 35 and 36, is crucial for sensory processing and object recognition.
• Previous research suggested area 35's caudal part is involved in large-scale object encoding.
• The PRC's diverse connections imply varied functional roles across its regions and layers.

Purpose of the Study:

• To differentiate the roles of PRC areas 35 and 36, and their layers/compartments, in processing objects of varying dimensions.
• To investigate how the PRC encodes microscale (subtle) versus macroscale (prominent) object information.

Main Methods:

• Compared immediate early gene Arc expression in response to learning about microscale and macroscale objects.
• Utilized fluorescence in situ hybridization to quantify nuclear Arc expression in specific PRC areas and layers.
• Examined rostro-caudal and area-specific differences in neuronal activity.

Main Results:

• Area 35 (middle and caudal parts, layers III-VI) showed increased Arc expression for both microscale and macroscale objects.
• Area 36 exhibited increased Arc expression exclusively in response to microscale objects.
• These findings suggest distinct dimensional processing roles within the PRC.

Conclusions:

• Area 36 is specifically implicated in encoding small, less visible (microscale) objects.
• Area 35 broadly participates in encoding object information, irrespective of object dimensions (microscale and macroscale).
• The study clarifies the functional specialization within the perirhinal cortex for object dimension processing.