Brain regions differentially involved in remembering what and when: a PET study

Area of Science:

• Neuroscience
• Cognitive Psychology
• Neuroimaging

Background:

• Recollection of past experiences requires recalling both event details and their temporal sequence.
• Previous research suggests distinct neural mechanisms underlie different aspects of memory retrieval.

Purpose of the Study:

• To directly contrast the neural correlates of item memory versus temporal order memory using positron emission tomography (PET).
• To investigate the brain regions involved in retrieving specific items from memory compared to their order of occurrence.

Main Methods:

• Positron emission tomography (PET) was employed to scan subjects during memory retrieval tasks.
• Participants studied a list of words and were subsequently scanned while performing two retrieval tasks: recalling list items and recalling the temporal order of items.

Main Results:

• Item retrieval activated medial temporal and basal forebrain regions.
• Temporal order retrieval showed increased activity in dorsal prefrontal, cuneus/precuneus, and right posterior parietal regions.
• A clear dissociation was observed between temporal lobe regions for item memory and frontal/posterior regions for temporal order memory.

Conclusions:

• The findings provide direct neural evidence for distinct brain networks supporting item and temporal order memory.
• The results confirm and extend previous lesion studies, highlighting the role of frontal and posterior brain regions in temporal order retrieval.
• Temporal order retrieval involves a distributed network of frontal and posterior brain regions.