Reduced short-term memory span in aphasia and susceptibility to interference: Contribution of material-specific maintenance deficits

Abstract

Semantic short-term memory (STM) deficits have been traditionally defined as an inability to maintain semantic representations over a delay (R. Martin, Shelton & Yaffee, 1994). Yet some patients with semantic STM deficits make numerous intrusions of items from previously presented lists, thus presenting an interesting paradox: Why should an inability to maintain semantic representations produce an increase in intrusions from earlier lists? In this study, we investigated the relationship between maintenance deficits and susceptibility to interference in a group of 20 aphasic patients characterized with weak semantic or weak phonological STM. Patients and matched control participants performed a modified item-recognition task designed to elicit semantic or phonological interference from list items located one, two, or three trials back (Hamilton & R. Martin, 2007). Controls demonstrated significant effects of interference in both versions of the task. Interference in patients was predicted by the type and severity of their STM deficit; that is, shorter semantic spans were associated with greater semantic interference and shorter phonological spans were associated with greater phonological interference. We interpret these results through a new perspective, the reactivation hypothesis, and we discuss their importance for accounts emphasizing the contribution of maintenance mechanisms for STM impairments in aphasia as well as susceptibility to interference. Keywords WORKING-MEMORY; RECENT-NEGATIVES; INHIBITION; SEMANTIC; PHONOLOGICALThough it is uncontroversial to state that short-term memory (STM) deficits are common in acquired aphasia (N. Martin & Ayala, 2004), a debate is currently in progress regarding the root of these patients' limited capacity to temporarily hold linguistic information in mind. The lightning rod in the discussion is a patient called ML; following a left fronto-parietal stroke, his performance on standard delayed-probe and immediate serial recall tasks was found to be dramatically deficient compared to age-and education-matched controls (Freedman & R. Martin, 2001; R. Martin & He, 2004; R. Martin & Lesch, 1996). Notably, his STM deficit was Corresponding author: Laura H.F. Barde, Ph.D., Department of Pediatrics, Stanford University School of Medicine, 300 Pasteur Drive, Grant Building, Suite S224, Palo Alto, CA lbarde@stanford.edu,. Publisher's Disclaimer: This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. NIH Public Access Author ManuscriptNeuropsychologia. Author manuscript; available in PMC 2011 March 1. NIH-PA Author ManuscriptNIH-PA Author Manuscript NIH-PA Author...

Type-specific proactive interference in patients with semantic and phonological STM deficits

“…Notably there was no effect of word length, consistent with a phonological STM impairment. As is the case in other reports of phonological and semantic STM patients (e.g., Barde et al, 2010;patient GR in Freedman & Martin, 2001), patterns of performance were not unequivocal. Figure 3.…”

“…A modified item recognition task, based on the task used in Barde et al (2010), was used to create phonological and semantic interference (Figure 8). Phonological interference was produced when probes rhymed with one of the words in the list, and semantic interference was produced when probes matched the category of one of the list words.…”

“…Most of the verbal tasks used to explore proactive interference in STM-impaired patients have employed word stimuli and manipulated phonological and semantic relatedness between the words to elicit PI (e.g., Barde et al, 2010;Hamilton & Martin, 2007). There may be problems with using word stimuli to study typespecific PI, as words possess both semantic and phonological features.…”

“…To investigate patterns of PI across word and nonword stimuli in both patients, we contrasted interference under conditions of recurring word stimuli (where encoding based on both semantic and phonological properties was possible, Experiment 1a) and nonword stimuli (where encoding of only phonological features is possible, Experiment 1b). To provide comparison with similar patients in previous studies, Experiment 2 tested interference from phonological and semantic relatedness between word stimuli (using a similar paradigm to that employed by Barde et al, 2010). Three hypotheses were identified: type-specific STM patients might show (i) exaggerated interference effects in tests tapping the impaired information type (owing to reduced distinction between similar previously seen items, as in Barde et al, 2010); (ii) reduced interference from the impaired information type (due to inability to maintain information in STM); and (iii) increased interference from both types of information for the semantic STM patient, but no elevated effects for the pSTM patient (because of impaired control processes in sSTM but not pSTM patients; Hamilton & Martin, 2007).…”

Working memory treatment in aphasia: A theoretical and quantitative review

“…Finally, there seem to be no intervention methods that would target WM impairment resulting from excessive interference at the level of semantic or phonological item representations. The development of treatment strategies for serial order retention deficits and control of semantic/phonological interference deficits is important given the growing number of patients that have been identified to show these types of WM impairment (Barde et al, 2010;Majerus et al, 2015;Ralph et al, 2017). There may also be other important distinctions in WM components such as the distinction between recall and recognition tasks and the use of verbal rehearsal strategies.…”