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Two case studies are presented of the short-term memory performance of patients with semantic dementia. The first case showed a pervasive pattern of semantic effects in his auditory verbal short-term memory performance, in particular a marked superiority in serial recall for sequences of " known " words over " unknown " words—words which he no long...
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Overabundance is the situation where two or more distinct word forms fill the same cell in an inflectional paradigm (Thornton 2011). While this topic has received renewed attention in recent years, there are still several open questions regarding its properties and status. In this paper we present a new take on the matter. On the basis of a case st...
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... Furthermore, although number names are of course words, they are relatively protected for a long time by their extremely high frequency/familiarity: success in immediate serial recall (ISR) of non-number words for SD patients, and indeed controls, is strongly affected by word frequency. SD patients provide an even more striking demonstration of the impact of semantic knowledge on ISR: if words are selected for each individual SD case as items that are still 'known' or now 'unknown' to that patienton the basis of whether he or she still uses the word in spontaneous speech or (if it is a picture-able word) can name or comprehend the corresponding picturea number of studies have demonstrated a significant advantage in ISR for 'known' words (Jefferies et al., 2004(Jefferies et al., , 2005Knott et al., 1997;Patterson et al., 1994). The patients' many errors in this task consist mainly of 'Spoonerisms', i.e. exchange of the onsets of two consecutive words in the sequence. ...
Semantic Dementia (SD) is a neurodegenerative disease characterised by progressive deterioration of semantic knowledge, resulting in diminished understanding of concepts, whether encountered in verbal or non-verbal form. Over the past three decades, a number of studies employing a range of treatment techniques and learning methods have examined whether patients with SD can relearn previously known concepts or learn and retain new information. In this article, we review this research, addressing two main questions: a) Can aspects of semantic knowledge that are ‘lost’ due to degeneration be re-acquired? b) How much do other memory systems (working and episodic memory) interact with and depend on semantic memory? Several studies demonstrate successful relearning of previously known words and concepts in SD, particularly after regular, prolonged practice; but this success tends to diminish once practice ceases, and furthermore often fails to generalise to other instances of the same object/concept. This pattern suggests that, with impaired semantic knowledge, learning relies to an abnormal extent on perceptual factors, making it difficult to abstract away from the specific visual or other perceptual format in which a given concept has been trained. Furthermore, the impact of semantic ‘status’ of a word or object on both working and episodic memory indicates pervasive interaction of these other memory systems with conceptual knowledge.
... These response patterns suggest that, with degeneration of the anterior temporal lobe, patients might be encoding information phonetically rather than lexically (Papagno, Vernice, & Cecchetto, 2013) (for a review of this distinction see Snowling, Chiat, & Hulme, 1991;Gathercole, 1995). This leads to poorer recall performance for words that are no longer understood (Knott, Patterson, & Hodges, 1997;Patterson et al., 1994), as patients lose the normal recall benefit for real words over nonwords that is observed in healthy participants (Hulme, Maughan, & Brown, 1991). Indeed, there is evidence that in SD, the brain processing of real words and word-like nonwords becomes increasingly similar. ...
... When a real word like FRUIT with rather atypical spelling was paired with a more typically spelled non-word homophone (FRUTE) and the patients were asked to choose the real word, all 22 SD patients had abnormal accuracy, and the more advanced cases tended to prefer the typical non-word to the atypical word as 'the real thing'. Patterson et al. (1994) and Knott et al. (1997) studied immediate serial recall of short word sequences by SD patients, under three conditions: real words that each patient still 'knew' or understood; real words that he or she no longer understood; and word-like non-words. Successful recall of the real-but-'unknown' words was at a level intermediate between real-"known" words and nonwords. ...
In the healthy human brain, the processing of language is strongly lateralised, usually to the left hemisphere, while the processing of complex non-linguistic sounds recruits brain regions bilaterally. Here we asked whether the anterior temporal lobes, strongly implicated in semantic processing, are critical to this special treatment of spoken words. Nine patients with semantic dementia (SD) and fourteen age-matched controls underwent magnetoencephalography and structural MRI. Voxel based morphometry demonstrated the stereotypical pattern of SD: severe grey matter loss restricted to the anterior temporal lobes, with the left side more affected. During magnetoencephalography, participants listened to word sets in which identity and meaning were ambiguous until word completion, for example PLAYED versus PLATE. Whereas left-hemispheric responses were similar across groups, patients demonstrated increased right hemisphere activity 174-294 msec after stimulus disambiguation. Source reconstructions confirmed recruitment of right-sided analogues of language regions in SD: atrophy of anterior temporal lobes was associated with increased activity in right temporal pole, middle temporal gyrus, inferior frontal gyrus and supramarginal gyrus. Overall, the results indicate that anterior temporal lobes are necessary for normal and efficient lateralised processing of word identity by the language network.
... These response patterns suggest that, with degeneration of the anterior temporal lobe, patients might be encoding information phonologically rather than lexically (Snowling et al, 1991, Gathercole, 1995. This leads to poorer recall performance for words that are no longer understood (Patterson et al, 1994, Knott et al, 1997, as patients lose the normal recall benefit for real words over non-words that is observed in healthy participants . ...
... doi: bioRxiv preprint first posted online Jan. 2, 2019; tended to prefer the typical non-word to the atypical word as 'the real thing'. Patterson et al (1994) and Knott et al (1997) studied immediate serial recall of short word sequences by SD patients, under three conditions: real words that each patient still 'knew' or understood; real words that he or she no longer understood; and word-like non-words. Successful recall of the real-but-'unknown' words was at a level intermediate between real-"known" words and nonwords. ...
In the healthy human brain, the processing of spoken words is strongly left-lateralised, while the processing of complex non-linguistic sounds recruits brain regions bilaterally. Here we asked whether the left anterior temporal lobe, strongly implicated in semantic processing, is critical to this special treatment of linguistic stimuli. Nine patients with semantic dementia (SD) and fourteen age-matched controls underwent magnetoencephalography and structural MRI. Voxel based morphometry demonstrated the stereotypical pattern of SD: severe grey matter loss restricted to the left anterior temporal lobe. During magnetoencephalography, participants listened to word sets in which identity and meaning were ambiguous until utterance completion, for example played vs plate. Whereas left-hemispheric responses were similar across groups, patients demonstrated increased right hemisphere activity 174-294ms after stimulus disambiguation. Source reconstructions confirmed recruitment of right-sided analogues of language regions in SD: atrophy of left anterior temporal lobe was associated with increased activity in right temporal pole, middle temporal gyrus, inferior frontal gyrus and supramarginal gyrus. Moreover only healthy controls had differential responses to words versus non-words in right auditory cortex and planum temporale. Overall, the results indicate that anterior temporal lobe is necessary for normal and efficient processing of word identity in the rest of the language network.
... The primacy of phonology in STM is challenged by evidence that conceptual information can directly influence the stability of the phonological trace from studies of patients with semantic dementia (Patterson, Graham, & Hodges, 1994) and broadly by theoretical perspectives which posit direct involvement of lexical-semantic processing/knowledge in STM capacities (e.g., Acheson & MacDonald, 2009; R.C. Martin, Lesch & Bartha, 1999;N. Martin & Gupta, 2004;Knott, Patterson & Hodges, 1997). One such perspective suggests that semantic information directly impacts the Running head: SEMANTIC AND PHONOLOGICAL COHERENCE stability of phonological information in short-term memory: According to the "semantic binding" account (Patterson, Graham, & Hodges, 1994), sequenced speech sounds processed by the phonological system interact with representations of word meaning whenever we comprehend or produce language, allowing conceptual knowledge to scaffold evolving phonological processing in STM. ...
... Patients with semantic dementia show progressive degradation of conceptual knowledge, but possess relatively preserved language skills, including fluent, well-formed speech and normal digit span (Jefferies, Jones, Bateman, & Lambon Ralph, 2005). When asked to repeat lists of words that they understand poorly, these patients make frequent phonological errors, characterised by phoneme migrations between the items (e.g., "cat, dog" might be recalled as "dat, cog"; Hoffman, Jefferies, Ehsan, Jones, & Lambon Ralph, 2009;Jefferies, Crisp, & Lambon Ralph, 2006;Jefferies, Hoffman, Jones, & Lambon Ralph, 2008;Knott, Patterson, & Hodges, 1997;Majerus, Norris, & Patterson, 2007;Patterson, Graham, & Hodges, 1994). Although this evidence emphasises the importance of semantic knowledge in STM that cannot be readily explained by a retrieval-based process, it is controversial since the neurodegeneration in semantic dementia may affect lexical-phonological as well as semantic knowledge (Papagno, Vernice, & Cecchetto, 2013). ...
Our ability to hold a sequence of speech sounds in mind, in the correct configuration, supports many aspects of communication, but the contribution of conceptual information to this basic phonological capacity remains controversial. Previous research has shown modest and inconsistent benefits of meaning on phonological stability in short-term memory, but these studies were based on sets of unrelated words. Using a novel design, we examined the immediate recall of sentence-like sequences with coherent meaning, alongside both standard word lists and mixed lists containing words and nonwords. We found, and replicated, substantial effects of coherent meaning on phoneme-level accuracy: The phonemes of both words and nonwords within conceptually coherent sequences were more likely to be produced together and in the correct order. Since nonwords do not exist as items in long-term memory, the semantic enhancement of phoneme-level recall for both item types cannot be explained by a lexically based item reconstruction process employed at the point of retrieval (“redintegration”). Instead, our data show, for naturalistic input, that when meaning emerges from the combination of words, the phonological traces that support language are reinforced by a semantic-binding process that has been largely overlooked by past short-term memory research.
... Furthermore, the reverse pattern of impairment, that is, an association between prevalent disruption of non-verbal representation and greater atrophy of the right ATLs was also reported by several authors (e.g. Knott et al. 1997;Gorno-Tempini et al. 2004;Ikeda et al. 2006;Acres et al. 2009;Butler et al. 2009;Mion et al. 2010). ...
This paper reviews some controversies concerning the original and revised versions of the 'hub-and-spoke' model of conceptual representations and their implication for abstraction capacity levels. The 'hub-and-spoke' model, which is based on data gathered in patients with semantic dementia (SD), is the most authoritative model of conceptual knowledge. Patterson et al.'s (Nature Reviews Neuroscience, 8(12), 976-987, 2007) classical version of this model maintained that conceptual representations are stored in a unitary 'amodal' format in the right and left anterior temporal lobes (ATLs), because in SD the semantic disorder cuts across modalities and categories. Several authors questioned the unitary nature of these representations. They showed that the semantic impairment is 'multi-modal'only in the advanced stages of SD, when atrophy affects the ATLs bilaterally, but that impariments can be modality-specific in lateralised (early) stages of the disease. In these cases, SD mainly affects lexical-semantic knowledge when atrophy predominates on the left side and pictorial representations when atrophy prevails on the right side. Some aspects of the model (i.e. the importance of spokes, the multimodal format of representations and the graded convergence of modalities within the ATLs), which had already been outlined by Rogers et al. (Psychological Review, 111(1), 205-235, 2004) in a computational model of SD, were strengthened by these results. The relevance of these theoretical problems and of empirical data concerning the neural substrate of concrete and abstract words is discussed critically. The conclusion of the review is that the highest levels of abstraction are due more to the structuring influence of language than to the format of representations.
... When participants reproduce a sequence of items in order, as in immediate serial recall (ISR), performance is better for lists of words that are higher in imageability/concreteness (Acheson, Postle, & MacDonald, 2010;Allen & Hulme, 2006;Caza & Belleville, 1999;Hoffman, Jefferies, Ehsan, Jones, & Lambon Ralph, 2009;Jefferies, Frankish, & Lambon Ralph, 2006a;Majerus & van der Linden, 2003;Roche, Tolan, & Tehan, 2011;Romani, McAlpine, & Martin, 2008;Walker & Hulme, 1999;Wilshire, Keall, & O'Donnell, 2010), related in meaning (Poirier & Saint-Aubin, 1995;Saint-Aubin et al., 2013;Wilshire et al., 2010), or when word meaning has been emphasised at encoding (Campoy & Baddeley, 2008;Savill, Metcalfe, Ellis, & Jefferies, 2015). Knott, Patterson, & Hodges, 1997;Majerus, Norris, & Patterson, 2007;Patterson, Graham, & Hodges, 1994). As first noticed by Patterson et al. (1994), these patients frequently recombine the phonological elements of different items in ISR, particularly when repeating words with more degraded meanings, despite fluent speech production and generally intact phonological performance. ...
... Studies that have examined phoneme-level recall have largely failed to separate these factors. The semantic binding hypothesis was originally proposed to explain the tendency of patients with semantic dementia to recombine phonemes across different items in immediate serial recall for semantically-degraded words (Hoffman et al., 2009;Jefferies et al., 2004;Knott et al., 1997;Majerus et al., 2007;Patterson et al., 1994). This phoneme error pattern is also seen for nonwords compared to words in healthy individuals (Hoffman et al., 2009;Jefferies, Frankish, et al., 2006a;Jefferies, Frankish, & Lambon Ralph, 2006b;). ...
... These effects are likely to be particularly important for the maintenance of multiple items in STM, since in this situation, the phonemes of different items can be recombined. We (and others) have previously shown that when STM is challenged, and it is necessary to hold on to several fragile phonological representations, the task will strongly tap the ability of people to keep the phonemes from the same item together (Jefferies, Frankish, et al., 2006a;Jefferies, Frankish, & Noble, 2011;Jefferies, Grogan, Mapelli, & Isella, 2012;Jefferies et al., 2008;Knott et al., 1997;Majerus et al., 2007;Patterson et al., 1994;Savill, Ashton, et al., 2015;Savill, Metcalfe, Ellis & Jefferies, 2015). By this token, the semantic binding account would also anticipate that the availability of semantic representations at the familiarisation phase would influence acquisition of the phonological forms, since phonological learning requires phonological maintenance, and this would be more veridical when there is an associated meaning. ...
Verbal short-term memory (STM) is a crucial cognitive function central to language learning, comprehension and reasoning, yet the processes that underlie this capacity are not fully understood. In particular, although STM primarily draws on a phonological code, interactions between long-term phonological and semantic representations might help to stabilise the phonological trace for words (“semantic binding hypothesis”). This idea was first proposed to explain the frequent phoneme recombination errors made by patients with semantic dementia when recalling words that are no longer fully understood. However, converging evidence in support of semantic binding is scant: it is unusual for studies of healthy participants to examine serial recall at the phoneme level and also it is difficult to separate the contribution of phonological-lexical knowledge from effects of word meaning. We used a new method to disentangle these influences in healthy individuals by training new ‘words’ with or without associated semantic information. We examined phonological coherence in immediate serial recall (ISR), both immediately and the day after training. Trained items were more likely to be recalled than novel nonwords, confirming the importance of phonological-lexical knowledge, and items with semantic associations were also produced more accurately than those with no meaning, at both time points. For semantically-trained items, there were fewer phoneme ordering and identity errors, and consequently more complete target items were produced in both correct and incorrect list positions. These data show that lexical-semantic knowledge improves the robustness of verbal STM at the sub-item level, even when the effect of phonological familiarity is taken into account.
... In addition to verbatim encoding, the listening span task requires participants to integrate the presented items based on syntactic and semantic information. In other words, the listening span task relies on processes that serve language comprehension (Hulme et al., 1997;Knott, Patterson, & Hodges, 1997;Walker & Hulme, 1999). Semantic working memory tasks have been shown to be better predictors of reading comprehension than working memory tasks that mainly tap phonological processing (Cain et al., 2004a, b;Daneman & Merikle, 1996;Oakhill, Cain, & Bryant, 2003;Seigneuric, Ehrlich, Oakhill, & Yuill, 2000) and non-verbal working memory tasks (Shah & Miyake, 1996) in both typically developing children and adults. ...
Working memory is considered a well-established predictor of individual variation in reading comprehension in children and adults. However, how storage and processing capacities of working memory in both the phonological and semantic domain relate to reading comprehension is still unclear. In the current study, we investigated the contribution of phonological and semantic storage, and phonological and semantic processing to reading comprehension in 123 Dutch children in fifth grade. We conducted regression and mediation analyses to find out to what extent variation in reading comprehension could be explained by storage and processing capacities in both the phonological and the semantic domain, while controlling for children’s decoding and vocabulary. The analyses included tasks that reflect storage only, and working memory tasks that assess processing in addition to storage. Regression analysis including only storage tasks as predictor measures, revealed semantic storage to be a better predictor of reading comprehension than phonological storage. Adding phonological and semantic working memory tasks as additional predictors to the model showed that semantic working memory explained individual variation in reading comprehension over and above all other memory measures. Additional mediation analysis made it clear that semantic storage contributed indirectly to reading comprehension via semantic working memory, indicating that semantic storage tapped by working memory, in addition to processing capacities, explains individual variation in reading comprehension. It can thus be concluded that semantic storage plays a more important role in children’s reading comprehension than previously thought.
... In the immediate serial recall task, results concerning imageability effects have been inconsistent across cases. Knott et al. (1997) reported a significant standard imageability effect in one SD case, that was most pronounced for longer lists of four items, similar to the effects seen in normal participants (Walker and Hulme, 1999). This aligns with the results of Jefferies et al., (2008), who reported enhanced imageability effects in immediate serial recall of five word lists relative to controls in a case series of five semantic dementia patients. ...
... This comparison establishes whether limited exposure to phonological forms 24 hours earlier is sufficient to yield better (i.e., more phonologically coherent) ISR performance. This is an important addition to the literature since previous studies comparing words and nonwords have only established a recall advantage for well-established phonological-lexical representations that have been acquired over long periods of time, and which, in the case of real words, may further benefit from independent support from those words' corresponding semantic representations (Bourassa & Besner, 1994;Patterson et al., 1994;Poirier & Saint-Aubin, 1995;Knott & Patterson, 1997;Saint-Aubin & Poirier, 1999;Walker & Hulme, 1999;Jefferies, Jones, Bateman, & Lambon Ralph, 2005;Hoffman et al., 2009). ...
Research has shown that direct current stimulation (tDCS) over left temporoparietal cortex – a region implicated in phonological processing – aids new word learning. The locus of this effect remains unclear since (i) experiments have not empirically separated the acquisition of phonological forms from lexical-semantic links and (ii) outcome measures have focused on learnt associations with a referent rather than phonological stability. We tested the hypothesis that left temporoparietal tDCS would strengthen the acquisition of phonological forms, even in the absence of the opportunity to acquire lexical-semantic associations. Participants were familiarised with nonwords paired with (i) photographs of concrete referents or (ii) blurred images where no clear features were visible. Nonword familiarisation proceeded under conditions of anodal tDCS and sham stimulation in different sessions. We examined the impact of these manipulations on the stability of the phonological trace in an immediate serial recall (ISR) task the following day, ensuring that any effects were due to the influence of tDCS on long-term learning and not a direct consequence of short-term changes in neural excitability. We found that only a few exposures to the phonological forms of nonwords were sufficient to enhance nonword ISR overall compared to entirely novel items. Anodal tDCS during familiarisation further enhanced the acquisition of phonological forms, producing a specific reduction in the frequency of phoneme migrations when sequences of nonwords were maintained in verbal short-term memory. More of the phonemes that were recalled were bound together as a whole correct nonword following tDCS. These data show that tDCS to left temporoparietal cortex can facilitate word learning by strengthening the acquisition of long-term phonological forms, irrespective of the availability of a concrete referent, and that the consequences of this learning can be seen beyond the learning task as strengthened phonological coherence in verbal short-term memory.
... The motivation behind this analysis was the possibility that semantic damage could exert its effects on reading aloud through disruption of phonological processing. This notion is supported by a body of literature demonstrating poorer repetition by SD patients of short sequences of words whose meanings they no longer know than of words with meanings that are still known (Knott, Patterson, & Hodges, 1997Patterson, Graham, & Hodges, 1994). This poorer performance is characterized by phoneme migration errors (e.g., mint, rug will be reproduced as rint, mug), suggesting that semantic activation helps to bind together phonological elements. ...
Exaggerated effects of word length upon reading-aloud performance define pure alexia, but have also been observed in semantic dementia. Some researchers have proposed a reading-specific account, whereby performance in these two disorders reflects the same cause: impaired orthographic processing. In contrast, according to the primary systems view of acquired reading disorders, pure alexia results from a basic visual processing deficit, whereas degraded semantic knowledge undermines reading performance in semantic dementia. To explore the source of reading deficits in these two disorders, we compared the reading performance of 10 pure alexic and 10 semantic dementia patients, matched in terms of overall severity of reading deficit. The results revealed comparable frequency effects on reading accuracy, but weaker effects of regularity in pure alexia than in semantic dementia. Analysis of error types revealed a higher rate of letter-based errors and a lower rate of regularization responses in pure alexia than in semantic dementia. Error responses were most often words in pure alexia but most often nonwords in semantic dementia. Although all patients made some letter substitution errors, these were characterized by visual similarity in pure alexia and phonological similarity in semantic dementia. Overall, the data indicate that the reading deficits in pure alexia and semantic dementia arise from impairments of visual processing and knowledge of word meaning, respectively. The locus and mechanisms of these impairments are placed within the context of current connectionist models of reading.
