Activating the medial temporal lobe during oddity judgment for faces and scenes

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neuroimaging

Background:

• Amnesic individuals show visual discrimination impairments linked to hippocampal and perirhinal cortex damage.
• Hippocampal lesions impair scene discrimination, while perirhinal cortex damage affects object discrimination.

Purpose of the Study:

• To investigate the neural correlates of visual oddity judgment for novel scenes and faces in healthy participants using fMRI.
• To differentiate the roles of the hippocampus and perirhinal cortex in processing different types of visual stimuli.

Main Methods:

• Functional magnetic resonance imaging (fMRI) was employed to monitor brain activity in healthy adults.
• Participants performed oddity judgment tasks involving novel, trial-unique scenes and faces.
• Brain activity was contrasted between oddity judgments for scenes, faces, and size variations.

Main Results:

• Scene oddity judgment activated the posterior hippocampus and parahippocampal cortex.
• Face oddity judgment engaged the perirhinal cortex and anterior hippocampus.
• Activity in these regions decreased with stimulus repetition, indicating habituation, with notable exceptions in the perirhinal cortex and anterior hippocampus during face tasks.

Conclusions:

• The posterior hippocampus and parahippocampal cortex are involved in scene discrimination.
• The perirhinal cortex and anterior hippocampus play a role in object (face) discrimination.
• These findings suggest that the perirhinal cortex and anterior hippocampus may have broader roles in visual processing beyond episodic memory encoding.