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According to the semantic binding hypothesis, long-term stored semantic information helps to stabilise lexical-phonological forms in verbal short-term memory (vSTM). A stronger reliance on semantic knowledge in short-term memory has been implicated when phonological abilities are weak (Savill, Cornelissen, Whiteley, Woollams, & Jefferies, 2018; in line with a primary systems perspective, e.g. Ueno et al., 2011). Since learning new phonological forms draws upon vSTM and the quality of underlying phonological representations, we examine whether providing new semantic information supports the acquisition and maintenance of novel phonological forms in vSTM in dyslexia. The present project is a partial online replication of a previous study (in prep) whereby healthy adults and dyslexic participants were exposed to new spoken nonwords with or without novel semantic information, before completing tasks assessing immediate serial recall (ISR) and word learning of these items. Data from our previous study did not provide evidence for a benefit of semantic representations in learning for adults with a diagnosis of dyslexia. It also appeared that semantic representations did not stabilise phonological forms in verbal short-term memory in healthy adults and adults with dyslexia. These results were somewhat surprising since previous studies found a positive impact of meaning on verbal short-term memory (Jefferies, Frankish, & Lambon Ralph, 2006; Savill, Cornelissen, Whiteley, Woollams, & Jefferies, 2018; Savill, Ellis, & Jefferies, 2017) and word learning (Hawkins, Astle, & Rastle, 2015). We expected to find a compensatory role of associated semantic representations on maintenance processes in dyslexic participants who have an identified phonological processing impairment. In this study we seek to address several concerns related to the potential sensitivity of the previous study design – namely related to the effectiveness of the training tasks underpinning our semantic manipulation and concerns about initial quality of learning: the large number of to-be-learned nonwords, the type of semantic training used (i.e. nonwords associated with an unusual object-image and three descriptions of its functions), and the strength of memory traces after training. The purpose of the present study is to re-examine whether semantic knowledge stabilises phonological maintenance of newly-learnt nonwords for participants with and without dyslexia, having implemented changes to the training tasks to ensure a baseline level of learning. A number of methodological adjustments will be undertaken: First, the experiment will run online, which will allow us to access large samples that would be impossible to get in a laboratory environment. This will increase sensitivity of our measures. Two experiments with different versions of the training task will be used with a between-subject design. The first training version will be similar to our previous study, yet a reduced number of nonwords will be trained. This change will allow more repetitions of the nonwords during training and should thus increase the learning strength of the nonwords and their associated meaning. In the second training version, nonwords will be associated to existing words varying in their imageability rating (the extent to which a word evokes a mental image, commonly used as a proxy of semantic representations). If results of our previous study were due to the artificial aspect of the semantic representation, semantic binding should be observable in the second experiment. Participants will also repeat the nonwords each time they encounter them during the training phase, on account of the significant role of temporary phonological storage that supports word learning (i.e., to facilitate acquistion; Avons, Wragg, Cupples, & Lovegrove, 1998; Gathercole, 2006). Furthermore, a minimum training percentage accuracy criterion for continuation to the tasks comprising our outcome measures will be added to provide a baseline standard of learning (an addition to enable more confidence in evaluation of the impact of added semantic associations, i.e. to support assumptions of construct validity).

To capture the EEG-correlates (i.e. ERPs) underpinning the distinct characteristics of involuntary memories at encoding and retrieval, we propose a study based on a paradigm previously used by Hall et al. (2014). At encoding, participants will encode pairs of sounds and images, and will listen to control sounds. At retrieval, participants will hear some sounds in an involuntary memory condition, and some in a voluntary retrieval task. A post-retrieval task will determine which pairs were remembered and forgotten. We can use this design to examine the ERPs associated with a 'successfully encoded' versus forgotten involuntary memory, as well as examining the ERPs associated with involuntary and voluntary retrieval. It is hoped this will allow insight into the cognitive processes at play when humans experience involuntary memories of their personal life (I.e., involuntary autobiographical memories).

There are well-established links between long-term language knowledge and verbal short-term memory (vSTM) with varied evidence that available semantic information either directly or indirectly supports phonological maintenance (e.g. Savill et al., 2018). Furthermore, a relatively stronger influence on semantic knowledge in short-term memory has been observed when phonological abilities are relatively weak (Savill, Cornelissen, Whiteley, Woollams, & Jefferies, 2019; in line with a primary systems perspective, e.g. Ueno et al., 2014). In Kowialiewski and Majerus (2018), long-term linguistic effects on vSTM are mostly non-strategic as they arise in a fast encoding running span procedure that prevented strategic processes. However, when examining the semantic effect of imageability, researchers found that it only appeared under slower presentation rates that would therefore allow for strategic encoding of the words. Imageability effects have been found in relation to phonological skills under standard immediate serial recall conditions (lists presented at a rate of one item per second) (Savill et al., 2019). Considering that the typical verbal short-term memory deficit observed in dyslexic individuals has been suggested to be related to less efficient encoding strategies (Kramer, Knee, & Delis, 2000), the present study will investigate the nature of lexical-semantic effects under speeded conditions in dyslexic and non-dyslexic individuals, and will assess ISR performance under different semantic and lexical manipulations across two experiments (words imageability, semantic relatedness, lexicality). The first experiment will assess short-term recall performance in an immediate serial recall (ISR) task with lists of high and low imageability words as well as nonwords lists presented under slow and fast presentation rates. In the second experiment, ISR lists will either be semantically related or unrelated.

Distinct neural processes are thought to support the retrieval of semantic information that is (i) coherent with strongly-encoded aspects of knowledge, and (ii) non-dominant yet relevant for the current task or context. While the brain regions that support readily coherent and more controlled patterns of semantic retrieval are relatively well-characterised, the temporal dynamics of these processes are not well-understood. This study used magnetoencephalography (MEG) and dual-pulse chronometric transcranial magnetic stimulation (cTMS) in two separate experiments to examine temporal dynamics during the retrieval of strong and weak associations. MEG results revealed a dissociation within left temporal cortex: anterior temporal lobe (ATL) showed greater oscillatory response for strong than weak associations, while posterior middle temporal gyrus (pMTG) showed the reverse pattern. Left inferior frontal gyrus (IFG), a site associated with semantic control and retrieval, showed both patterns at different time points. In the cTMS experiment, stimulation of ATL at ∼150 msec disrupted the efficient retrieval of strong associations, indicating a necessary role for ATL in coherent conceptual activations. Stimulation of pMTG at the onset of the second word disrupted the retrieval of weak associations, suggesting this site may maintain information about semantic context from the first word, allowing efficient engagement of semantic control. Together these studies provide converging evidence for a functional dissociation within the temporal lobe, across both tasks and time.

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 found modest and inconsistent benefits of meaning on phonological stability in short-term memory but these studies presented sets of unrelated words. Using a novel design, we examined the immediate recall of sentence-like sequences with coherent meaning, alongside 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, 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, 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.