The HED Task Catalog is under development. IDs are not stable until formal release. Comments are welcome at github.com/hed-standard/hed-task/issues.

Mnemonic Similarity Task

HED task ID: hedtsk_mnemonic_similarity

Family: Recall and recognition memory tests

Also known as: MST, Mnemonic Discrimination Task, Pattern Separation Task, Mnemonic Similarity

Incidental encoding of images followed by a test with old, new, and lure items; discrimination of lures from repetitions indexes pattern separation.

Description

The Mnemonic Similarity Task measures hippocampal pattern separation—the ability to distinguish similar but not identical memory representations. During encoding, participants view a series of everyday object images. At test, they classify each image as “old” (previously seen), “similar” (a different exemplar of a studied object with slight visual changes), or “new” (novel). The critical measure is the ability to correctly identify “similar” lures as similar rather than incorrectly endorsing them as old. This discrimination (lure discrimination index) is thought to rely on dentate gyrus/CA3 pattern separation processes and is impaired in early-stage Alzheimer’s disease and normal aging.

Inclusion test

An experiment is an instance of this task when its procedure matches, it manipulates at least one of the listed variables, and it records at least one of the listed measures.

Procedure

Participants study a set of images, then view old items, new items, and similar lures (items resembling studied items). They classify each as old, new, or similar.

Manipulation

Lure similarity (mnemonic similarity parameter); encoding depth; retention interval; number of items.

Measurement

Lure discrimination index (LDI: p(‘similar’|lure) − p(‘similar’|foil)); recognition d-prime; pattern separation score.

Variations

Named versions that change what the participant experiences or does. The identifier of a variation is hedvar_<task>__<variation>.

Variation

Description

Justification

Standard Object MST

hedvar_mnemonic_similarity__standard_object_mst

Indoor and outdoor objects; old/similar/new judgments.

Canonical everyday objects with lure pairs for pattern separation

Scene MST

hedvar_mnemonic_similarity__scene_mst

Indoor/outdoor scene photographs as stimuli; spatial pattern separation.

Scene stimuli instead of objects; different stimulus class

Continuous MST

hedvar_mnemonic_similarity__continuous_mst

Online recognition during a single continuous stream; no separate study/test phases.

Study and test interleaved; different trial structure

Parametric Similarity Manipulation

hedvar_mnemonic_similarity__parametric_similarity_manipulation

Lures at graded levels of similarity (high, medium, low) to the studied items.

Graded lure similarity levels; tests pattern separation threshold

MST for Faces

hedvar_mnemonic_similarity__mst_for_faces

Face stimuli to test pattern separation for social stimuli.

Face stimuli; different recognition domain

Spatial MST

hedvar_mnemonic_similarity__spatial_mst

Objects in spatial contexts; measures spatial vs. object pattern separation.

Location-based similarity; tests spatial pattern separation

Short-Delay vs. Long-Delay MST

hedvar_mnemonic_similarity__short_delay_vs_long_delay_mst

Varying retention interval between encoding and test.

Retention interval manipulation tests forgetting of pattern separation

Cognitive processes

This task is designed to engage the following processes:

Key references

  • Kirwan, C. B., & Stark, C. E. L. (2007). Overcoming interference: An fMRI investigation of pattern separation in the medial temporal lobe. Learning & Memory, 14(9), 625–633. (DOI, PubMed)

  • Stark, S. M., Yassa, M. A., Lacy, J. W., & Stark, C. E. L. (2013). A task to assess behavioral pattern separation (BPS) in humans: Data from healthy aging and mild cognitive impairment. Neuropsychologia, 51(12), 2442–2449. (DOI, PubMed)

  • Yassa, M. A., & Stark, C. E. L. (2011). Pattern separation in the hippocampus. Trends in Neurosciences, 34(10), 515–525. (DOI, PubMed)

Further references

  • Lacy, J. W., Yassa, M. A., Stark, S. M., Muftuler, L. T., & Stark, C. E. L. (2011). Distinct pattern separation related transfer functions in human CA3/dentate and CA1 revealed using high-resolution fMRI and variable mnemonic similarity. Learning & Memory, 18(1), 15–18. (DOI)

  • Bakker, A., Kirwan, C. B., Miller, M., & Stark, C. E. L. (2008). Pattern separation in the human hippocampal CA3 and dentate gyrus. Science, 319(5870), 1640–1642. (DOI, PubMed)

  • Stark, S. M., & Stark, C. E. L. (2017). Age-related deficits in the mnemonic similarity task for objects and scenes. Behavioural Brain Research, 333, 109–117. (DOI, PubMed)

  • Reagh, Z. M., & Yassa, M. A. (2014). Object and spatial mnemonic interference differentially engage lateral and medial entorhinal cortex in humans. Proceedings of the National Academy of Sciences, 111(40), E4264–E4273. (DOI, PubMed)