Hippocampal dysfunction during declarative memory encoding in schizophrenia and effects of genetic liability

Area of Science:

• Neuroscience
• Cognitive Psychology
• Psychiatry

Background:

• Declarative memory (DM) deficits are common in schizophrenia and their relatives.
• Neural mechanisms of encoding and genetic influences on DM in schizophrenia are not fully understood.

Purpose of the Study:

• To investigate neural correlates of successful and unsuccessful memory encoding in schizophrenia patients, unaffected relatives, and controls.
• To explore the impact of genetic liability on medial temporal lobe (MTL) memory system function.

Main Methods:

• Event-related functional MRI (fMRI) was used to compare brain activations during face-name associative memory encoding.
• Participants included 26 schizophrenia patients, 30 controls, and 14 unaffected relatives.
• Regions-of-interest analysis focused on hippocampal activity and hippocampal volume.

Main Results:

• Schizophrenia patients exhibited hyper-activations in visual and temporo-parietal areas during successful encoding.
• Patients showed right anterior hippocampus hyper-activation and left anterior hippocampus hypo-activation during successful encoding.
• Unaffected relatives displayed similar left anterior hippocampus hypo-activations, suggesting genetic liability. Patients had reduced hippocampal volume, but relatives did not.

Conclusions:

• DM encoding deficits in schizophrenia involve both disease-specific and genetic liability factors affecting the MTL memory system.
• Hyper-activations in temporo-occipital and parietal regions indicate disease-related influences in patients.
• Shared hippocampal hypo-activations in patients and relatives point to genetic factors influencing memory encoding.