Teasing apart tangrams: Testing hippocampal pattern separation with a collaborative referencing paradigm

Melissa C. Duff, David E. Warren, Rupa Gupta, Juan Pablo Benabe Vidal, Daniel Tranel, Neal J. Cohen

Research output: Contribution to journalArticlepeer-review


The hippocampus and the medial temporal lobe cortex [medial temporal lobe cortices (MTLC)] both contribute to long-term memory. Although their contributions are thought to be dissociable, the nature of the representations that each region supports remains unclear. The Complementary Learning Systems (CLS) modeling approach suggests that hippocampus represents overlapping information in a sparser and therefore more separated fashion than MTLC. We tested this prediction using a collaborative referencing paradigm whereby hippocampal amnesic patients and a partner work together to develop and use unique labels for a set of abstract visual stimuli (tangrams) across extended interactions. Previously, we reported that amnesic patients demonstrate intact learning when the tangrams are conceptually dissimilar. Here, we manipulated the degree of visual similarity; half of the stimuli were dissimilar to one another (e.g., camel and giraffe), and half were similar (e.g., birds). We hypothesized that while patients would have little difficulty with the dissimiliar tangrams (quickly arriving at unique and concise labels), they would be unable to rapidly form distinct representations of highly similar visual patterns. Consistent with this prediction, patients and both healthy and brain-damaged comparison participants showed similar rates of learning for dissimilar tangrams, but the similar tangrams proved more difficult for hippocampal patients as reflected in the greater number of words they used to describe each similar card. This result supports the CLS model's central claim of hippocampal specialization for pattern separation and suggests that our collaborative referencing paradigm may be a useful tool for observing extended encoding of complex representations.

Original languageEnglish (US)
Pages (from-to)1087-1091
Number of pages5
Issue number5
StatePublished - May 2012


  • Hippocampus
  • Medial temporal lobe
  • Pattern separation

ASJC Scopus subject areas

  • Cognitive Neuroscience


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