Relational and conjunctive binding functions dissociate in short-term memory

Abstract

Remembering complex events requires binding features within unified objects (conjunctions) and holding associations between objects (relations). Recent studies suggest that the two functions dissociate in long-term memory (LTM). Less is known about their functional organization in short-term memory (STM). The present study investigated this issue in patient AE affected by a stroke which caused damage to brain regions known to be relevant for relational functions both in LTM and in STM (i.e., the hippocampus). The assessment involved a battery of standard neuropsychological tasks and STM binding tasks. One STM binding task (Experiment 1) presented common objects and common colors forming either pairs (relations) or integrated objects (conjunctions). Free recall of relations or conjunctions was assessed. A second STM binding task used random polygons and non-primary colors instead (Experiment 2). Memory was assessed by selecting the features that made up the relations or the conjunctions from a set of single polygons and a set of single colors. The neuropsychological assessment revealed impaired delayed memory in AE. AE's pronounced relational STM binding deficits contrasted with his completely preserved conjunctive binding functions in both Experiments 1 and 2. Only 2.35% and 1.14% of the population were expected to have a discrepancy more extreme than that presented by AE in Experiments 1 and 2, respectively. Processing relations and conjunctions of very elementary nonspatial features in STM led to dissociating performances in AE. These findings may inform current theories of memory decline such as those linked to cognitive aging.

Evaluating the developmental trajectory of the episodic buffer component of working memory and its relation to word recognition in children

“…Supporting evidence also comes from the observation that younger children produced a higher rate of inappropriate feature pairings in the presence of correct feature memory. Unlike tasks used in previous research, the binding between visual form and novel auditory-verbal information explored in the current study likely reflects a particular form of extrinsic or relational binding (Ecker et al, 2013;Parra et al, 2013) that relies more heavily on the active formation of new associations between modalities within a working memory storage component such as the episodic buffer (Baddeley, 2000(Baddeley, , 2012Baddeley et al, 2011). The current findings that these processes show a particular developmental trajectory and are separable from those shown in working memory for the constituent visual and auditory-verbal elements therefore provides novel evidence for maturation of processes associated with the episodic buffer.…”

“…of shape and color within an object) may be relatively low-level and perceptual in nature, possibly accomplished by specialized visuospatial processing before being consciously retained within the episodic buffer. In contrast, relational or extrinsic binding (Ecker, Maybery, & Zimmer, 2013;Parra et al, 2013) of elements from different domains or modalities may particularly require the episodic buffer for their formation and retention, as implied by BaddeleyÕs original (2000) proposal. Therefore, for current purposes, episodic buffer capacity was indexed by a task in which temporary creation and maintenance of bound visual and phonological information were needed.…”

Differential age-related effects on conjunctive and relational visual short-term memory binding

“…Neuroimaging studies have also demonstrated that the hippocampus is activated during relational binding in short-term memory tasks Piekema, Kessels, Rijpkema, & Fernandez, 2009;Piekema, Kessels, Mars, Petersson, & Fernández, 2006;Piekema, Rijpkema, Fernandez, & Kessels, 2010). Neuropsychological evidence additionally pointed to a crucial role of the hippocampus for relational short-term binding (Hannula et al, 2015;Olson, Page, Moore, Chatterjee, & Verfaellie, 2006;Parra et al, 2015;van Geldorp, Bouman, Hendriks, & Kessels, 2014). So, it is likely that age-related changes to the hippocampus explain at least partly the decrease in relational short-term binding.…”

“…The same kind of materials (objects and colours, after Parra et al (2015)) were used in two short-term memory tasks; the only difference between the tasks being how objects and colours were linked. In the conjunctive task, colour was integrated as a feature of the object.…”

The formation of novel social category conjunctions in working memory: A possible role for the episodic buffer?

“…Ecker et al, 2013;Parra et al, 2013;Zimmer et al, 2006). Thus, the integration of elements for different types of social category conjunction might represent one example of a wider set of differences between automatic and more effortful binding processes.…”