The Domain Dichotomy theory: Exploring familiarity in Associative Recognition using behavioural studies and functional magnetic resonance imaging.

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Abstract

There has been a long running dispute about whether the medial temporal lobes show functional differentiation with respect to how they support recognition memory for items and associations. Most researchers believe that item recognition is supported by both recollection, a form of cued recall, and familiarity, a raw feeling of memory for an encoded stimulus that involves no recall. The Domain Dichotomy theory postulates that the parahippocampal and perirhinal cortices create memories for context and items respectively that support only familiarity, not just for their individual stimulus inputs, but also for associations between any inputs that they process (within-domain associations) into either intra-‘item’/context associations or inter-‘item’/context associations, although this distinction cannot currently be sensibly tested. In contrast, the hippocampus supports recollection for associations between inputs that only converge within its borders for binding into memories (between-domain associations). This view is fiercely disputed. In this thesis, behavioural experiments are described that find that, apparently, between- as well as well as within-domain associations show high levels of familiarity support at test. This conflicts with the Domain view’s behavioural account of what within- and between-domain associations are, but not necessarily its neural definition of these concepts. Levels of recognition for different kinds of auditory association were extremely low and it was hard to compare these with visual associations without major confounding factors interfering. A functional magnetic resonance study was used in order to investigate continuous recognition for twice presented visual stimuli in six different categories (scenes, faces, words, animal pictures, tool pictures, and abstract art) with familiarity memory being assessed via a familiarity only procedure. This study found that familiarity for each of the categories of stimuli activated overlapping extra-medial temporal lobe regions very similar to those that Montaldi et al., (2006) found in a different familiarity only study of scene memory. Most importantly, there was an overlapping perirhinal cortex region deactivated by familiarity (relative to novelty) for stimuli from all six categories studied. It is predicted that associations between any combination of these stimuli will be supported by familiarity, which will deactivate a similar region of the perirhinal cortex. Future work needs to improve the design of similar imaging studies and to examine associations also between items and their temporal and spatial features, as well as looking at associations for inputs of different sensory modalities.

Keyword(s)

Associative Recognition Memory; Domain Dichotomy

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