Hippocampal sequences represent working memory and implicit timing.

Area of Science:

• Neuroscience
• Cognitive Science
• Animal Behavior

Background:

• Working memory (WM) and timing are crucial cognitive functions.
• Neural mechanisms underlying WM and timing share similarities, suggesting potential overlap.
• The hypothesis that WM and timing might be multiplexed requires further investigation.

Purpose of the Study:

• To investigate the potential multiplexing of working memory and timing.
• To explore how neural activity encodes temporal information within a WM task.
• To determine if WM performance is influenced by expectations of delay duration.

Main Methods:

• Development of a novel rodent task where odor identity predicts delay duration.
• Behavioral analysis of working memory performance under expected and violated delay conditions.
• In vivo calcium imaging of dorsal CA1 neuronal activity during the task.

Main Results:

• Working memory performance decreased when delay expectations were violated.
• Performance was more impaired by unexpected long delays than unexpected short delays.
• Dorsal CA1 neural activity exhibited odor-specific sequential patterns that tiled delay durations and reflected temporal expectations.

Conclusions:

• Neural sequences in the dorsal CA1 may encode both sensory cues and cue-specific elapsed time.
• Findings support the hypothesis that working memory and timing are multiplexed in the brain.
• Neural representations in dorsal CA1 dynamically track expected and actual time during a working memory task.