The intrinsic time tracker: temporal context is embedded in entorhinal and hippocampal functional connectivity...

Area of Science:

• Neuroscience
• Cognitive Neuroscience
• Functional Neuroimaging

Background:

• Task-evoked neural activity in the entorhinal cortex (EC) and hippocampus tracks temporal context.
• It is unknown if spontaneous neural signals in these regions also reflect time passage.

Purpose of the Study:

• To investigate if resting-state connectivity patterns in the EC and hippocampus exhibit spontaneous temporal drifts.
• To determine if these drifts reflect the passage of time independently of task demands.

Main Methods:

• Dense-sampling resting-state fMRI data from two individuals over 30 days.
• Analysis of whole-brain connectivity patterns in the EC and hippocampus.
• Correlation analysis between connectivity similarity and time intervals between sessions.

Main Results:

• Resting connectivity similarity in the EC and anterior hippocampus negatively correlated with the time interval between sessions.
• Hippocampal connectivity drifts showed an anterior-to-posterior gradient.
• Anterolateral EC exhibited stronger temporal drift than posteromedial EC.
• Posterior brain networks drove drifts in EC and hippocampal connectivity.

Conclusions:

• A spontaneous, slow-drifting neural signature of time exists in resting-state EC and hippocampal connectivity.
• This temporal signature is independent of task demands and other time-varying factors.
• Functional gradients along the longitudinal axis of the hippocampus and EC are involved in tracking time.