Sadil at Cognitive Brown Bag Weds. 2/11 at noon

Patrick Sadil (lab manager of Rosie Cowell’s Computational Memory and Perception Lab) will be presenting Visual Recollection in the Cognitive Brown Bag series in Tobin 521 at noon Wednesday, February 11. Everyone is welcome – the abstract is below.

Abstract: It is widely agreed that two processes – ‘recollection’ and ‘familiarity’ – contribute to performance on episodic recognition. Furthermore, these processes have been related to separate brain structures within MTL (e.g., Brown and Aggleton, 2001). However, we and others have proposed that both processes are carried out by multiple MTL sub-regions (Cowell et al., 2010; Diana et al. 2007) and what determines engagement of a given MTL region by either recollection or familiarity is the representational content of the memory (e.g., item/context/associations or spatial information). The Representational-Hierarchical (RH) view (Cowell et al. 2010) makes a novel prediction: recollection is a pattern completion process that may be computed by any brain region containing representations that could be used in the service of memory. We tested this prediction as applied to different kinds of visual representations (object, scenes, and object in scenes). For instance, if a subject encodes a visual object at study and is cued with part of the object at test, the RH view predicts that a pattern-completion process of recollecting the object (generating the whole from the part) should be carried out in object-representing regions (e.g., perirhinal cortex) without requiring hippocampal involvement. Behaviorally, this would amount to recollection in a non-associative memory task. We examined the behavioral effects of visual pattern completion using the process dissociation procedure (PDP) of Jacoby (1991). Following study, subjects were presented with a part of the studied item (an object part, a scene part, or an object that had been embedded in a scene): a visual analog of the word-stem completion task. They named the studied object or scene either by using (inclusion) or disallowing (exclusion) their memory of the study list. To avoid well-known aggregation biases with this procedure, we used the Bayesian hierarchical model of Rouder et al. (2008) to measure recollection and familiarity. Selective influence of an experimental manipulation was used to validate the use of the PDP; we found that recollection was greater for objects studied twice rather than once, whereas familiarity was unaffected by study frequency. These results provide evidence of visual recollection for objects. Future work will use these stimuli in an fMRI experiment to determine the brain locus of visual recollection for different kinds of visual stimuli.

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