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NCT Number: NCT05910762

Human Learning of New Structured Information Across Time and Sleep

Acting adaptively requires quickly picking up on structure in the environment and storing the acquired knowledge for effective future use. Dominant theories of the hippocampus have focused on its ability to encode individual snapshots of experience, but the investigators and others have found evidence that it is also crucial for finding structure across experiences. The mechanisms of this essential form of learning have not been established. The investigators have developed a neural network model of the hippocampus instantiating the theory that one of its subfields can quickly encode structure using distributed representations, a powerful form of representation in which populations of neurons become responsive to multiple related features of the environment.

The first aim of this project is to test predictions of this model using high resolution functional magnetic resonance imaging (fMRI) in paradigms requiring integration of information across experiences. The results will clarify fundamental mechanisms of how humans learn novel structure, adjudicating between existing models of this process, and informing further model development. There are also competing theories as to the eventual fate of new hippocampal representations. One view posits that during sleep, the hippocampus replays recent information to build longer-term distributed representations in neocortex. Another view claims that memories are directly and independently formed and consolidated within the hippocampus and neocortex.

The second aim of this project is to test between these theories. The investigators will assess changes in hippocampal and cortical representations over time by re-scanning participants and tracking changes in memory at a one-week delay. Any observed changes in the brain and behavior across time, however, may be due to generic effects of time or to active processing during sleep.

The third aim is thus to assess the specific causal contributions of sleep to the consolidation of structured information. The investigators will use real-time sleep electroencephalography to play sound cues to bias memory reactivation. The investigators expect that this work will clarify the anatomical substrates and, critically, the nature of the representations that support encoding and consolidation of novel structure in the environment.

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Key information

Conditions

Learning Consolidation Humans Sleep

Age range

18 year–35 year

Sex eligibility

All sexes

Study type

Interventional

Phase

Not applicable

Primary location

University of Pennsylvania

Philadelphia, Pennsylvania, 19104, United States

Location status: Recruiting

Location contact

Rishi Krishnamurthy, BA

CONTACT

Who can participate

Healthy volunteers accepted: Yes

Only the study team can determine whether someone qualifies for participation.

Inclusion criteria

  • Between 18 and 35 years of age (all aims)
  • Not a member of a vulnerable population (all aims)
  • Normal or corrected-to-normal vision (all aims)
  • Normal hearing (all aims)
  • Able to speak English fluently (all aims)
  • No prior history of major psychiatric or neurological disorders (Aims 1 and 2; MRI-specific)
  • Not currently taking any antidepressants or sedatives (Aims 1 and 2; MRI-specific)
  • No known neurological disorders (Aim 3; EEG-specific)

Exclusion criteria

  • The investigators will exclude individuals with MR contraindications such as non-removable biomedical devices or metal in or on the body (Aims 1 and 2; MRI-specific)
  • Claustrophobia (Aims 1 and 2; MRI-specific)
  • Pregnant women will also be excluded from neuroimaging, as the effects of MR on pregnancy are not fully understood (Aims 1 and 2; MRI-specific)

Treatment and study plan

Associative Inference

Behavioral

Participants will engage in an associative inference paradigm. Memory will be assessed behaviorally and neural representations will be assessed using functional magnetic resonance imaging.

Category learning

Behavioral

Participants will engage in a category learning paradigm. Memory will be assessed behaviorally (Arms 2 and 3), and neural representations will be assessed using functional magnetic resonance imaging (Arm 2).

sleep

Behavioral

Participants will sleep after engaging in a category learning paradigm while electroencephalography data are collected, and memory will be assessed behaviorally after sleep.

Primary outcomes

  1. Changes in multivariate representations

    Time frame: Within first session (spanning 2-3 hrs.) and at approximately one week delay in second session (spanning 1-2 hrs.)

    Changes in spatial correlations between the MRI BOLD pattern associated with related objects over the course of learning and across the one-week delay.

  2. Brain-behavior correlations

    Time frame: Within first session (spanning 2-3 hrs.) and at approximately one week delay in second session (spanning 1-2 hrs.)

    Correlations between BOLD signal in the brain and participant behavior during judgments about objects.

  3. Correlations between activity across brain regions

    Time frame: Within first session (spanning 2-3 hrs.) and at approximately one week delay in second session (spanning 1-2 hrs.)

    Relationships between BOLD activity across different regions of the brain as a function of trial type and delay.

  4. Memory accuracy

    Time frame: Within single study session (spanning 4-5 hrs.)

    Change in generalization ability from before to after the nap as a function of the different conditions of object cueing during sleep.

Study contacts

Contact information is provided by the study sponsor or research team.

Anna C Schapiro, PhD

CONTACT

[email protected]

6177974555

Rishi Krishnamurthy, BA

CONTACT

[email protected]

4255050841

Sponsors and collaborators

Lead sponsor

University of Pennsylvania

Other

Collaborators

  • National Institute of Mental Health (NIMH)

Registry information

Official study title

Learning Novel Structure Across Time and Sleep

Important dates

Study start
2023
Primary completion
2028
Study completion
2028
First posted
Jun 20, 2023
Registry last updated
Aug 1, 2025

OpenTrials presents study information sourced from ClinicalTrials.gov. The official registry record should be consulted for the latest information.

View the official ClinicalTrials.gov record (opens in a new tab)

This listing is for discovery and informational purposes only. It is not medical advice, does not guarantee that a study is recruiting, and does not determine eligibility. Contact the study team and a qualified healthcare professional when considering participation.

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