The right parahippocampal gyrus contributes to the formation and maintenance of bound information in working memory
ABSTRACT Working memory is devoted to the temporary storage and on-line manipulation of information. Recently, an integrative system termed the episodic buffer has been proposed to integrate and hold information being entered or retrieved from episodic memory. Although the brain system supporting such an integrative buffer is still in debate, the medial temporal lobe appears to be a promising candidate for the maintenance of bound information. In the current work, binding was assessed by comparing two conditions in which participants had to retain three letters and three spatial locations presented either bound or separate. At the behavioral level, lower performance was found for bound information than for separate information. When contrasting the two conditions, activation in the right parahippocampal gyrus was greater for the encoding and maintenance of bound information. No activation was observed in the medial temporal lobe during the retrieval of bound information. Together, our results suggest that the parahippocampal gyrus may underlie the integrative and maintenance functions of the episodic buffer.
[Show abstract] [Hide abstract]
- "These deficits may be related to damage to extrahippocampal MTL structures, since patients with lesions limited to the hippocampus proper do not show deficits on working memory binding tasks (see, e.g., Allen, Vargha-Khadem, & Baddeley, 2014). In addition, neuroimaging studies found activation in the MTL, when assessing working memory binding (Hannula & Ranganath, 2008; Luck et al., 2010; Mitchell, Johnson, Raye, & D'Esposito, 2000; Piekema, Kessels, Mars, Petersson, & Fernández, 2006; Piekema, Kessels, Rijpkema, & Fernández, 2009; Piekema, Rijpkema, Fernández, & Kessels, 2010). "
ABSTRACT: Recent studies indicate that in both normal and pathological aging working memory (WM) performance deteriorates, especially when associations have to be maintained. However, most studies typically do not assess the relationship between WM and episodic memory formation. In the present study, we examined WM and episodic memory formation in normal aging and in patients with early Alzheimer's disease (mild cognitive impairment, MCI; and Alzheimer's dementia, AD). In the first study, 26 young adults (mean age 29.6 years) were compared to 18 middle-aged adults (mean age 52.2 years) and 25 older adults (mean age 72.8 years). We used an associative delayed-match-to-sample WM task, which requires participants to maintain two pairs of faces and houses presented on a computer screen for short (3 s) or long (6 s) maintenance intervals. After the WM task, an unexpected subsequent associative memory task was administered (two-alternative forced choice). In the second study, 27 patients with AD and 19 patients with MCI were compared to 25 older controls, using the same paradigm as that in Experiment 1. Older adults performed worse than both middle-aged and young adults. No effect of delay was observed in the healthy adults, and pairs that were processed during long maintenance intervals were not better remembered in the subsequent memory task. In the MCI and AD patients, longer maintenance intervals hampered the task performance. Also, both patient groups performed significantly worse than controls on the episodic memory task as well as the associative WM task. Aging and AD present with a decline in WM binding, a finding that extends similar results in episodic memory. Longer delays in the WM task did not affect episodic memory formation. We conclude that WM deficits are found when WM capacity is exceeded, which may occur during associative processing.Journal of Clinical and Experimental Neuropsychology 05/2015; 37(5):1-11. DOI:10.1080/13803395.2015.1037722 · 2.08 Impact Factor
[Show abstract] [Hide abstract]
- "In Baddeley's revised working memory model (2000), separate STM and LTM representations interact through an episodic buffer that links different representational formats. Although it has been proposed that the integrative functions of the episodic buffer may be supported by MTL regions such as the hippocampus (Berlingeri et al., 2008; Luck et al., 2010), Baddeley cautions against linking the buffer to a single brain region and instead argues that memory integration likely results from interactions between distributed neural regions (Baddeley, 2000; Baddeley et al., 2010, 2011). In state-based models of STM, interactions between STM and LTM occur naturally through a shared representational system in which the contents of STM represent a temporarily activated subset of LTM (Cowan, 1999; Postle, 2006; Ranganath and Blumenfeld, 2005; Zhou et al., 2007). "
ABSTRACT: Short-term memory (STM) and long-term memory (LTM) have traditionally been considered cognitively distinct. However, it is known that STM can improve when to-be-remembered information appears in contexts that make contact with prior knowledge, suggesting a more interactive relationship between STM and LTM. The current study investigated whether the ability to leverage LTM in support of STM critically depends on the integrity of the hippocampus. Specifically, we investigated whether the hippocampus differentially supports between-domain versus within-domain STM-LTM integration given prior evidence that the representational domain of the elements being integrated in memory is a critical determinant of whether memory performance depends on the hippocampus. In Experiment 1, we investigated hippocampal contributions to within-domain STM-LTM integration by testing whether immediate verbal recall of words improves in MTL amnesic patients when words are presented in familiar verbal contexts (meaningful sentences) compared to unfamiliar verbal contexts (random word lists). Patients demonstrated a robust sentence superiority effect, whereby verbal STM performance improved in familiar compared to unfamiliar verbal contexts, and the magnitude of this effect did not differ from that in controls. In Experiment 2, we investigated hippocampal contributions to between-domain STM-LTM integration by testing whether immediate verbal recall of digits improves in MTL amnesic patients when digits are presented in a familiar visuospatial context (a typical keypad layout) compared to an unfamiliar visuospatial context (a random keypad layout). Immediate verbal recall improved in both patients and controls when digits were presented in the familiar compared to the unfamiliar keypad array, indicating a preserved ability to integrate activated verbal information with stored visuospatial knowledge. Together, these results demonstrate that immediate verbal recall in amnesia can benefit from two distinct types of semantic support, verbal and visuospatial, and that the hippocampus is not critical for leveraging stored semantic knowledge to improve memory performance. Copyright © 2015 Elsevier Ltd. All rights reserved.Neuropsychologia 03/2015; DOI:10.1016/j.neuropsychologia.2015.02.004 · 3.30 Impact Factor
[Show abstract] [Hide abstract]
- "In line with this, Schon et al. (2004); see also Axmacheret al., 2008) demonstrated that MTL involvement in working memory predicts later long-term memory formation. More recently, Piekema and colleagues failed to observe increased MTL activation in facelocation binding (Piekema, Rijpkema, Fernánde, & Kessel 2010), instead identifying parietal and prefrontal areas as being critical (though see Luck et al. 2010). Jeneson and Squire (2012) have recently developed further the argument that evidence for a hippocampal contribution to binding in working memory may actually reflect LTM involvement. "
ABSTRACT: A general consensus is emerging that the hippocampus has an important and active role in the creation of new long-term memory representations of associations or bindings between elements. However, it is less clear whether this contribution can be extended to the creation of temporary bound representations in working memory, involving the retention of small numbers of items over short delays. We examined this by administering a series of recognition and recall tests of working memory for color-location binding and object-location binding to a patient with highly selective hippocampal damage (Jon), and groups of control participants. Jon achieved high levels of accuracy in all working memory tests of recognition and recall binding across retention intervals of up to 10 seconds. In contrast, Jon performed at chance on an unexpected delayed test of the same object-location binding information. These findings indicate a clear dissociation between working memory and long-term memory, with no evidence for a critical hippocampal contribution to item-location binding in working memory.Neuropsychologia 07/2014; 59(1). DOI:10.1016/j.neuropsychologia.2014.04.013 · 3.30 Impact Factor