Dissociating Hippocampal and Basal Ganglia Contribitions to Category Learning Using Stimulus Novelty and Subjective Judgements. Seger, Dennison, Lopez-Paniagua, Peterson, Roark. Neuroimage 2011.

  1. We identified factors leading to hippocampal and basal ganglia recruitment during categorization learning.”
  2. In the experiment there were alternating trial and error catergory learning, interspersed with a subjective judgement task
    1. In the subjective task, subjects categorized the stimulus, but instead of receiving feedback they also recorded the basis of their response with one of 4 options:
      1. Remember: <response is based on?> “Conscious episodic memory of previous trials.”
      2. Know-Automatic: “Automatic, rapid response accompanied by conscious awareness of category membership.”
      3. Know-Intuition: “A ‘gut feeling’ without fully conscious knowledge of category membership.”
      4. Guess: 
  3. “Categorization overall recruited both the basal ganglia and posterior hippocampus.”
    1. Use of basal ganglia showed up when making both types of “know-” based decisions
    2. Posterior hippocampus showed up with remember judgements
    3. <This distinction is a little unclear, as later they say> “First, we used subjects’ subjective judgments to dissociate trials performed on the basis of memory (and found to recruit the hippocampus), from trials performed in a subjectively automatic or intuitive way (found to recruit the basal ganglia).
    4. <But if you know something how is it not based on memory – the language seems sloppy to me>
  4. “[Analysis shows] the putamen exerting directed influence on the posterior hippocampus, which in turn exerted directed influence on the posterior caudate nucleus.
  5. Our results indicate that subjective measures may be effective in dissociating basal ganglia from hippocampal dependent learning, and that the basal ganglia are involved in both conscious and unconscious learning. They also indicate a dissociation within the hippocampus, in which the anterior regions are sensitive to novelty, and the posterior regions are involved in memory based categorization learning.”
  6. Commonly accepted that basal is important for categorization. “… they are particularly important for feedback-based categorization, in which subjects learn via trial and error.”
  7. The evidence of the role of hippocampus in categorization is less strong, although results show that anterior and posterior portions may be playing different roles

<Seems like review was incomplete>


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