Semantic Short-term Memory Research Articles

Memory functioning in developmental dyslexia: an analysis using two clinical memory measures.

The goals of this project were threefold: to determine the nature of the memory deficit in children/adolescents with dyslexia, to utilize clinical memory measures in this endeavor, and to determine the extent to which semantic short-term memory (STM) is related to basic reading performance. Two studies were conducted using different samples, one incorporating the Wide Range Assessment of Memory and Learning and the other incorporating the California Verbal Learning Test-Children's Version. Results suggest that phonological STM is deficient in children with dyslexia, but semantic STM and visual-spatial STM are intact. Long-term memory (LTM) for both visual and verbal material also is intact. Regarding reading performance, semantic STM had small correlations with word identification and pseudoword decoding across studies despite phonological STM being moderately to strongly related to both basic reading skills. Overall, results are consistent with the phonological core deficit model of dyslexia as only phonological STM was affected in dyslexia and related to basic reading skill.

Selective short-term memory deficits arise from impaired domain-general semantic control mechanisms.

Semantic short-term memory (STM) patients have a reduced ability to retain semantic information over brief delays but perform well on other semantic tasks; this pattern suggests damage to a dedicated buffer for semantic information. Alternatively, these difficulties may arise from mild disruption to domain-general semantic processes that have their greatest impact on demanding STM tasks. In this study, mild semantic processing impairments were demonstrated in 2 semantic STM patients. They performed well on untimed semantic tasks but were deficient in accuracy and reaction times on speeded tasks. Demanding semantic production tasks were also affected. These patients were compared with a case series of individuals with semantic aphasia whose multimodal semantic difficulties stemmed from poor cognitive control. STM and semantic performance were more impaired in this group, but there were qualitative similarities to the semantic STM patients. The difference between the 2 patient types may be a matter of degree. In semantic aphasia, severe disruption to semantic control leads to global semantic impairments, whereas in semantic STM milder disruption might impact mainly on STM tests because of the high control demands of these tasks.

Non-verbal auditory cognition in patients with temporal epilepsy before and after anterior temporal lobectomy

For patients with pharmaco-resistant temporal epilepsy, unilateral anterior temporal lobectomy (ATL) – i.e. the surgical resection of the hippocampus, the amygdala, the temporal pole and the most anterior part of the temporal gyri – is an efficient treatment. There is growing evidence that anterior regions of the temporal lobe are involved in the integration and short-term memorization of object-related sound properties. However, non-verbal auditory processing in patients with temporal lobe epilepsy (TLE) has raised little attention. To assess non-verbal auditory cognition in patients with temporal epilepsy both before and after unilateral ATL, we developed a set of non-verbal auditory tests, including environmental sounds. We could evaluate auditory semantic identification, acoustic and object-related short-term memory, and sound extraction from a sound mixture. The performances of 26 TLE patients before and/or after ATL were compared to those of 18 healthy subjects. Patients before and after ATL were found to present with similar deficits in pitch retention, and in identification and short-term memorisation of environmental sounds, whereas not being impaired in basic acoustic processing compared to healthy subjects. It is most likely that the deficits observed before and after ATL are related to epileptic neuropathological processes. Therefore, in patients with drug-resistant TLE, ATL seems to significantly improve seizure control without producing additional auditory deficits.

The relationship between semantic short-term memory and immediate serial recall of known and unknown words and nonwords: Data from two Chinese individuals with aphasia.

The present study investigated verbal recall of semantically preserved and degraded words and nonwords by taking into consideration the status of one's semantic short-term memory (STM). Two experiments were conducted on 2 Chinese individuals with aphasia. The first experiment showed that they had largely preserved phonological processing abilities accompanied by mild but comparable semantic processing deficits; however, their performance on STM tasks revealed a double dissociation. The second experiment found that the participant with more preserved semantic STM had better recall of known words and nonwords than of their unknown counterparts, whereas such effects were absent in the patient with severe semantic STM deficit. The results are compatible with models that assume separate phonological and semantic STM components, such as that of R. C. Martin, M. Lesch, and M. Bartha (1999). In addition, the distribution of error types was different from previous studies. This is discussed in terms of the methodology of the authors' experiments and current views regarding the nature of semantic STM and representations in the Chinese mental lexicon.

An investigation of lexical-semantic access and decay for a patient with a semantic short-term memory deficit

An investigation of lexical-semantic access and decay for a patient with a semantic short-term memory deficit

Impaired vs. preserved inhibitory processes in a patient with a semantic short-term memory deficit

Impaired vs. preserved inhibitory processes in a patient with a semantic short-term memory deficit

Proactive Interference in a Semantic Short-Term Memory Deficit: Role of Semantic and Phonological Relatedness

Previous research has indicated that patients with semantic short-term memory (STM) deficits demonstrate unusual intrusions of previously presented material during serial recall tasks (Martin and Lesch, 1996). These intrusions suggest excessive proactive interference (PI) from previous lists. Here, we explore one such patient's susceptibility to PI. Experiment 1 demonstrated patient M.L.'s extreme susceptibility to PI using a probe recognition task that manipulates the recency of negative probes (the recent negatives task). When stimuli consisted of letters, M.L. showed greatly exaggerated effects of PI, well outside of the range of healthy control participants. Experiment 2 used a variation of the recent negatives task to examine the relative contribution of semantic and phonological relatedness in PI. This task manipulated semantic and phonological relatedness of probes and recently presented list items. Relative to healthy control participants, patient M.L. showed exaggerated interference effects for both phonological and semantically related probes, both for probes related to the current list and for probes related to the previous list. These data have important implications for theories of semantic STM deficits. Specifically, these data suggest that it is not the rapid decay of semantic representations that is responsible for difficulties in short-term recall, but rather the abnormal persistence of previously presented material. We propose that this susceptibility to PI is the result of a deficit in control processes acting on STM.

The role of left inferior frontal gyrus (LIFG) in semantic short-term memory: A comparison of two case studies

The role of left inferior frontal gyrus (LIFG) in semantic short-term memory: A comparison of two case studies

Dissociations among tasks involving inhibition: A single-case study

Recent theories of working memory have emphasized the role of inhibition in suppressing irrelevant information. Moreover, psychometric studies have reported that several inhibition tasks with very diverse requirements load on a single inhibition factor. A patient with left inferior frontal damage, Patient M.L., previously reported to have a semantic short-term memory deficit (R. C. Martin & He, 2004), showed evidence of difficulty with inhibition on short-term memory tasks. We investigated whether he would show evidence of inhibition difficulty on two verbal tasks (a Stroop task and a recent-negatives task) and two nonverbal tasks (a nonverbal spatial Stroop task and an antisaccade task). M.L. was impaired on both verbal tasks but performed normally on the nonverbal tasks. M.L.'s data also represent a dissociation between Stroop and antisaccade performance, two tasks that load on a single factor in factor-analytic studies. The implications of these data for theories of inhibition and executive function are discussed.

Age-Related Declines in Context Maintenance and Semantic Short-Term Memory

This study reports age-related declines in context maintenance (Braver et al., 2001) and semantic short-term memory (STM) and evidencc for a relation between the two. A group of younger and older adults completed a context maintenance task (AX-CPT), a semantically oriented STM task (conceptual span), a phonologically oriented STM task (digit span), and a meaning integration task (semantic anomaly judgement). In the AX-CPT task, a target response is required to the probe letter "X" but only when it is preceded by the letter "A" (the context). Either three (short interference) or six distractor letters (long interference) were presented between the cue and the probe. Results indicated an age-related deficit in context maintenance. Age-related declines were also observed for conceptual span and semantic anomaly judgement but not for digit span. Context maintenance was correlated with conceptual span and semantic anomaly judgement but not with digit span. These correlations were largely mediated by age differences, which also explained variance that was unique to (and not shared among) context maintenance, conceptual span, and semantic anomaly judgement.

Complex sentence comprehension in a patient with a semantic short-term memory deficit

Complex sentence comprehension in a patient with a semantic short-term memory deficit

Semantic relatedness effects in conjoined noun phrase production: implications for the role of short-term memory

Speech error data and empirical studies suggest that the scope of planning is larger for semantic than for phonological form representations in speech production. Previous results have demonstrated that some patients show dissociable impairments in the retention of semantic and phonological codes. The effect of these STM deficits on speech production was investigated using a phrase production paradigm that manipulated the semantic relatedness of the words in the phrase. Subjects produced a conjoined noun phrase to describe two pictures (e.g., "ball and hat") or produced the same phrases in response to pairs of written words. For the picture naming condition, control subjects showed an interference effect for semantically related pictures relative to unrelated pictures. This interference effect was greatly exaggerated for two patients with semantic short-term memory deficits but not for a patient with a phonological STM deficit. For the written words, control subjects showed a small facilitatory effect for the onset of phrases containing semantically related words. One of the patients with a semantic STM deficit who was tested on picture naming was also tested on these materials and showed a small facilitatory effect within the range of controls. The findings support the contention that speech planning is carried out at a phrasal level at the lexical-semantic level and that the capacities that support semantic retention in list recall support speech production planning.

Semantic short-term memory and its role in sentence processing: A replication

Previous studies have shown that an aphasic patient (AB) with a semantic short-term memory deficit (STM) had difficulties comprehending and producing sentences with structures that demanded the simultaneous retention of several individual word meanings ( Martin & Freedman, 2001a, 2001b; Martin & Romani, 1994; Martin, Shelton, & Yaffee, 1994). The present study provides a replication of these findings with an additional case (ML) who shows a striking dissociation between preserved semantic knowledge and disrupted semantic STM. ML performed poorly on comprehension tasks for sentences that required the retention of single word meanings across several intervening words. In contrast, he did not show an effect of intervening words on processing grammatical relations. ML had difficulty producing adjective–noun phrases, though able to produce the individual nouns and adjectives. These findings support the contention that there is a semantic retention capacity, involved in both comprehension and production, that is separate from semantic knowledge representations.

An event-related fMRI investigation of phonological versus semantic short-term memory

Studies with normal and brain damaged subjects have indicated that there are semantic as well as phonological contributions to verbal short-term memory. An event-related functional MRI study was carried out to determine if different brain regions would be activated during the delay period in a phonological vs. a semantic retention task. A recognition probe procedure was used in which memory load and task (i.e. rhyme judgment vs. synonym judgment) were manipulated. A left inferior parietal region overlapping the supramarginal gyrus was more activated in the phonological than the semantic task. A large left inferior and mid-frontal region and another left parietal region showed a load effect that was common to the phonological and semantic tasks. No region showed significantly greater activation in the semantic than the phonological task, though there was a trend towards a more anterior localization of the frontal load effect in the semantic task compared to the phonological task.

Individual differences in semantic short-term memory capacity and reading comprehension

We report three correlation studies, which investigate the hypothesis that individual differences in the capacity of a semantic short-term memory (STM) component in working memory (WM) predict performance on complex language tasks. To measure the capacity of semantic STM, we devised a storage-only measure, the conceptual span, which makes use of a category-cued recall procedure. In the first two studies, where the conceptual span was administered with randomized words (not blocked by categories), we found that conceptual span predicted single-sentence and text comprehension, semantic anomaly detection and verbal problem solving, explaining unique variance beyond non-word and word span. In some cases, the conceptual span explained unique variance beyond the reading span. Conceptual span correlated better with verbal problem solving than reading span, suggesting that a storage-only measure can outperform a storage-plus-processing measure. In Study 3, the conceptual span was administered with semantically clustered lists. The clustered span correlated with the comprehension measures as well as the non-clustered span, indicating that the critical process is memory maintenance and not semantic clustering. Moreover, we found an interaction between subjects’ performance on the conceptual span and the effect of the distance between critical words in anomaly detection, supporting the proposal that semantic STM maintains unintegrated word meanings.

Dissociable components of short-term memory and their relation to long-term learning

Short-term memory (STM) includes dissociable phonological and semantic components (R.C. Martin, 1993). Previous findings indicate that phonological STM capacity supports learning of novel phonological forms, such as new vocabulary (e.g., Baddeley, Gathercole, & Papagno, 1998). It was hypothesised that semantic STM capacity would support the learning of novel semantic information. Five aphasic patients were tested who demonstrated deficits in the short-term retention of either phonological or semantic information. Four of the five patients demonstrated learning deficits in a paired associate paradigm that corresponded to their STM deficits. One patient with a severe deficit in phonological STM but a better-preserved ability to retain semantic information showed better learning of new semantic information than new phonological information. Three patients with a greater deficit in semantic than phonological STM showed the reverse. A fifth patient with a severe semantic STM deficit failed to show learning for either type of material. Results suggest that the semantic and phonological components of STM are essential for the long-term learning of corresponding representations in long-term memory.

Dissociable components of short-term memory and their relation to long-term learning

Short-term memory (STM) includes dissociable phonological and semantic components (R.C. Martin, 1993). Previous findings indicate that phonological STM capacity supports learning of novel phonological forms, such as new vocabulary (e.g., Baddeley, Gathercole, & Papagno, 1998). It was hypothesised that semantic STM capacity would support the learning of novel semantic information. Five aphasic patients were tested who demonstrated deficits in the short-term retention of either phonological or semantic information. Four of the five patients demonstrated learning deficits in a paired associate paradigm that corresponded to their STM deficits. One patient with a severe deficit in phonological STM but a better-preserved ability to retain semantic information showed better learning of new semantic information than new phonological information. Three patients with a greater deficit in semantic than phonological STM showed the reverse. A fifth patient with a severe semantic STM deficit failed to show learning for either type of material. Results suggest that the semantic and phonological components of STM are essential for the long-term learning of corresponding representations in long-term memory.

Short-term Memory and Language Processing: Further Evidence for the Existence of Separate Phonological and Semantic Short-term Memory Components

Short-term Memory and Language Processing: Further Evidence for the Existence of Separate Phonological and Semantic Short-term Memory Components

Contributions of Phonological and Semantic Short-Term Memory to Sentence Processing: Evidence from Two Cases of Closed Head Injury in Children

This paper reports the short-term memory and sentence processing performance of two head-injured children who were approximately 10 years of age at the time of test. The two children were found to have similarly reduced memory span on a variety of short-term memory tasks relative to age-matched control children, but differing patterns of performance. One child showed reduced (or absent) effects of phonological variables, and the other showed reduced effects of semantic variables. A dissociation in their performance on sentence processing tasks was also observed, with one child showing preserved comprehension but impaired repetition, and the other child showing the reverse. The results are consistent with previous findings from brain-damaged adults supporting a multiple-components model of short-term memory in which phonological and semantic components play different roles in sentence processing. Contrary to our initial hypothesis, the phonological component did not appear to play a more important role in sentence comprehension for children than for adults.