Substantial behavioral evidence implies the existence of separable working memory (WM) components... more Substantial behavioral evidence implies the existence of separable working memory (WM) components for maintaining phonological and semantic information. In contrast, only a few studies have addressed the neural basis of phonological vs. semantic WM using functional neuroimaging and none has used a lesion-symptom mapping (LSM) approach. Here we address this gap, reporting a multivariate LSM study of phonological and semantic WM for 94 individuals at the acute stage of left hemisphere stroke. Testing at the acute stage avoids issues of brain reorganization and the adoption of patient strategies for task performance. The LSM analyses for each WM component controlled for the other WM component and semantic and phonological knowledge at the single word level. For phonological WM, the regions uncovered included the supramarginal gyrus, argued to be the site of phonological storage, and several cortical and subcortical regions plausibly related to inner rehearsal. For semantic WM, inferior frontal regions and the angular gyrus were uncovered. The findings thus provide converging evidence for separable systems for phonological and semantic WM that are distinguished from the systems supporting longterm knowledge representations in those domains.
The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or i... more The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleed-through, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion.
Prior behavioral and neuroimaging evidence supports a separation between working memory capacitie... more Prior behavioral and neuroimaging evidence supports a separation between working memory capacities in the phonological and orthographic domains. Although these data indicate distinct buffers for orthographic and phonological information, prior neural evidence does indicate that nearby left inferior parietal regions support both of these working memory capacities. Given that no study has directly compared their neural substrates based on data from the same individuals, it is possible that there is a common left inferior parietal region shared by both working memory capacities. In fact, those endorsing an embedded processes account of working memory might suggest that parietal involvement reflects a domain-general attentional system that directs attention to long-term memory representations in the two domains, implying that the same neural region supports the two capacities. Thus, in this work, a multivariate lesion-symptom mapping approach was used to assess the neural basis of phono...
Sentence comprehension involves maintaining and continuously integrating linguistic information a... more Sentence comprehension involves maintaining and continuously integrating linguistic information and, thus, makes demands on working memory (WM). Past research has demonstrated that semantic WM, but not phonological WM, is critical for integrating word meanings across some distance and resolving semantic interference in sentence comprehension. Here, we examined the relation between phonological and semantic WM and the comprehension of center-embedded relative clause sentences, often argued to make heavy demands on WM. Additionally, we examined the relation between phonological and semantic WM and the comprehension of transitive and dative active and passive sentences, which may also draw on WM resources depending on the number of propositions that must be maintained and the difficulty of processing passive clauses. In a large sample of individuals with aphasia (N = 56), we assessed whether comprehension performance on more complex vs. simpler active-passive or embedded relative claus...
Proceedings of the Annual Meeting of the Cognitive Science Society, 2021
Representational Similarity Analysis (RSA) is a powerful tool for linking brain activity patterns... more Representational Similarity Analysis (RSA) is a powerful tool for linking brain activity patterns to cognitive processes via similarity, allowing researchers to identify the neural substrates of different cognitive levels of representation. However, the ability to map between levels of representation and brain activity using similarity depends on underlying assumptions about the dynamics of cognitive processing. To demonstrate this point, we present three toy models that make different assumptions about the interactivity within the reading system, (1) discrete, feedforward, (2) cascading, feedforward and (3) fully interactive. With the temporal resolution of fMRI, only the discrete, feedforward model provides a straightforward mapping between activation similarity and level of representation. These simulations indicate the need for a cautious interpretation of RSA results, especially with processes that are highly interactive and with neuroimaging methods that have low temporal resolution. The study further suggests a role for fully-fleshed out computational models in RSA analyses.
Representational Similarity Analysis (RSA) is a powerful tool for linking brain activity patterns... more Representational Similarity Analysis (RSA) is a powerful tool for linking brain activity patterns to cognitive processes via similarity, allowing researchers to identify the neural substrates of different cognitive levels of representation. However, the ability to map between levels of representation and brain activity using similarity depends on underlying assumptions about the dynamics of cognitive processing. To demonstrate this point, we present three toy models that make different assumptions about the interactivity within the reading system, (1) discrete, feedforward, (2) cascading, feedforward and (3) fully interactive. With the temporal resolution of fMRI, only the discrete, feedforward model provides a straightforward mapping between activation similarity and level of representation. These simulations indicate the need for a cautious interpretation of RSA results, especially with processes that are highly interactive and with neuroimaging methods that have low temporal reso...
The neural basis of phonological working memory (WM) was investigated through an examination of t... more The neural basis of phonological working memory (WM) was investigated through an examination of the effects of irrelevant speech distractors and disruptive neural stimulation from transcranial magnetic stimulation (TMS). Embedded processes models argue that the same regions involved in speech perception are used to support phonological WM whereas buffer models assume that a region separate from speech perception regions is used to support WM. Thus, according to the embedded processes approach but not the buffer approach, irrelevant speech and TMS to the speech perception region should disrupt the decoding of phonological WM representations. According to the buffer account, decoding of WM items should be possible in the buffer region despite distraction and should be disrupted with TMS to this region. Experiment 1 used fMRI and representational similarity analyses (RSA) with a delayed recognition memory paradigm using nonword stimuli. Results showed that decoding of memory items in t...
Theories of semantic memory based on neuropsychological findings have posited a distinction betwe... more Theories of semantic memory based on neuropsychological findings have posited a distinction between stored semantic representations and the mechanisms used to access and manipulate them (e.g., Lambon Ralph, Jefferies, Patterson, & Rogers, 2017; Warrington & Cipolotti, 1996). The most recent instantiation of this view, the controlled semantic cognition theory (Lambon Ralph et al., 2017), is supported by findings suggesting that multimodal (i.e., both verbal and nonverbal) semantic deficits may result from qualitatively different impairments: on the one hand, damage to a semantic access mechanism related to executive control, which is observed in semantic aphasia (SA), and on the other, damage to semantic representations, which is observed in semantic dementia (SD) (Jefferies & Lambon Ralph, 2006). In this study we compared SA and SD patients on several phenomena previously used to support these distinctions. Contrary to the prior results, we found that (1) overall, cross-task consistency was equivalent for the two groups; (2) neither patient group showed consistency driven by item identity across different semantic tasks; (3) correlations among task performance were not obviously driven by the semantic control demands of different tasks; (4) both groups showed executive function deficits; and (5) both groups showed strong effects of distractor interference in a synonym judgment task. Furthermore, we investigated the components of executive ability that could underlie semantic control deficits by correlating performance on updating, shifting, and inhibition tasks with performance on tasks testing semantic abilities. We found that updating was related to semantic processing generally, whereas shifting and inhibition were not. These results also suggest that complex executive function tasks relate to semantic tasks through their shared relationship with language abilities. Overall, evidence from SA and SD patients does not differentiate representations and access mechanisms in the semantic system, as has previously been suggested. Implications for the storage-access distinction are discussed.
Verbal Working Memory Capacities in Sentence Comprehension: Evidence from Aphasia
Successful sentence comprehension often requires the ability to link non-adjacent constituents. R... more Successful sentence comprehension often requires the ability to link non-adjacent constituents. Recent studies implicate that readers link non-adjacent constituents through an associative, direct-access mechanism, while working memory (WM) or short-term memory (STM) may not play an important role in this operation because only 1- 2 items could be maintained in the focus of attention (Van Dyke, 2007). However, prior studies with aphasic patients have supported a role for semantic STM and executive control in sentence processing (Martin et al., 2004; Vuong et al., 2011). Recently, a study with healthy subjects also demonstrated a role for semantic STM in resolving semantic interference, and a role for attentional control in resolving syntactic interference during sentence comprehension (Tan et al., 2011). These results suggested that semantic STM and attentional control are involved in semantic and syntactic aspects of sentence processing, respectively. This study further examined semantic and syntactic interference resolution in aphasic patients, who show dramatic variation in their WM/STM capacities. Semantic and syntactic interference were manipulated in a 2 x 2 design by varying the semantic plausibility of the intervening noun as the subject of the main verb and varying the syntactic role of the intervening noun (subj vs. obj). Both manipulations have been shown to increase difficulty in linking the head noun to the main verb. Example: Low-Syn: The student who was tired of the demanding assignment/coach yesterday was leaving. High-Syn: The student who said that the assignment/coach was demanding yesterday was leaving. Ten aphasic patients with good single word comprehension abilities but deficits on STM tasks were assessed on whole sentence RTs and on time and accuracy to answer comprehension questions (e.g. Was the student leaving?“). Interference effects were calculated by computing difference scores for RT and accuracy for low vs. high interference conditions. For RTs, the semantic and syntactic interference effects for most patients were within the range of controls. However, most of the patients showed exaggerated sensitivity to either semantic or syntactic interference for comprehension questions accuracy. Moreover, patients with relative better semantic STM made fewer errors in semantic interference resolution (r = -.77, p = .04), while patient with better attentional control made fewer errors in syntactic interference resolution (r = -.93, p < .001). However, neither phonological STM nor vocabulary was related to sentence processing. Our current results are consistent with the previous findings that WM and attentional control are critical for sentence processing. Poor maintenance of semantic information and deficits in attentional control lead to difficulties in semantic and syntactic processing. Reference Martin, R. C., & He, T. (2004). Semantic STM and its role in sentence processing: A replication. Brain & Lang, 89, 76-82. Tan, Y., Martin, R.C., & Van Dyke, J.A. (2011). Interference and WM in sentence comprehension. CUNY, Palo Alto, CA. Van Dyke, J.A. (2007). Interference effects from grammatically unavailable constituents during sentence processing. JEP:LMC, 33, 407-430. Vuong, L. C., & Martin, R. C. (2011). LIFG-based attentional control and the resolution of lexical ambiguities in sentence context. Brain & Lang, 116, 22-32
This study examined the role of verbal short-term memory (STM) and executive function (EF) underl... more This study examined the role of verbal short-term memory (STM) and executive function (EF) underlying semantic and syntactic interference resolution during sentence comprehension for persons with aphasia (PWA) with varying degrees of STM and EF deficits. Semantic interference was manipulated by varying the semantic plausibility of the intervening NP as subject of the verb and syntactic interference was manipulated by varying whether the NP was another subject or an object. Nine PWA were assessed on sentence reading times and on comprehension question performance. PWA showed exaggerated semantic and syntactic interference effects relative to healthy age-matched control subjects. Importantly, correlational analyses showed that while answering comprehension questions, PWA' semantic STM capacity related to their ability to resolve semantic but not syntactic interference. In contrast, PWA' EF abilities related to their ability to resolve syntactic but not semantic interference. Phonological STM deficits were not related to the ability to resolve either type of interference. The results for semantic interference are consistent with prior findings indicating a role for semantic but not phonological STM in sentence comprehension, specifically with regard to maintaining semantic information prior to integration. The results for syntactic interference are consistent with the recent findings suggesting that EF is critical for syntactic processing.
Several studies have reported that aphasic patients may perform substantially better on 2 lexical... more Several studies have reported that aphasic patients may perform substantially better on 2 lexical than sublexical perception tasks (e.g., Miceli, Gainotti, Caltagirone, & Masullo, 3 1980). These findings challenge claims made by models of speech perception which 4 assume obligatory sublexical processing (e.g., McClelland & Elman, 1986; Norris, 1994). 5 However, prior studies have not closely matched the phonological similarity of targets 6 and distractors or task demands of the sublexical and lexical perception tasks. The 7 current study addressed shortcomings of these prior studies, testing 13 aphasic patients 8 on sublexical and lexical tasks matched in phonological similarity of stimuli and task 9 demands. When the lexical and sublexical tasks were not matched (Experiment 1a), as 10 in prior studies (e.g., Miceli et al., 1980), several patients with impaired sublexical 11 perception were within the control range on tasks tapping lexical perception. In contrast, 12 when the lexical and sublexical tasks (sublexical: syllable discrimination, auditory-written 13 syllable matching (AWSM); lexical: word discrimination, lexical decision, and picture-14 word matching (PWM)) were matched on these factors (Experiments 1b and 2), in most 15 instances, patients were impaired on both sublexical and lexical tasks relative to controls 16 and performance on the lexical tasks was not significantly greater than that on the 17 sublexical tasks. For two patients, performance on one lexical task was statistically 18 better than that on one sublexical task, but the advantage was not replicated across 19 other task comparisons. The current study is consistent with models of speech 20 perception which assume obligatory sublexical processing and fails to support models 21 that do not require successful sublexical perception in order to access lexical levels 22
Increasing evidence supports dissociable short-term memory (STM) capacities for semantic and phon... more Increasing evidence supports dissociable short-term memory (STM) capacities for semantic and phonological representations. Cognitive neuropsychological data suggest that damage to the left inferior and middle frontal gyri are associated with deficits of semantic STM, while damage to inferior parietal areas is associated with deficits of phonological STM. Patients identified as having semantic STM deficits are also impaired on a number of language comprehension and production paradigms. We used one such comprehension task derived from cognitive neuropsychological data to test predictions with functional magnetic resonance imaging (fMRI) using healthy participants. Using a task that required participants to make semantic anomaly judgements, we found significantly greater activation in areas of the left inferior frontal and middle frontal gyri for phrases that required maintenance of multiple words for eventual integration with a subsequent noun or verb. These data are consistent with our previous patient studies (Hanten & Martin, 2000; R. C. Martin & He, 2004; R. C. Martin & Romani, 1994) that suggest that semantic STM is associated with the left inferior and middle frontal gyri and that deficits of semantic STM have particular consequences for comprehension tasks that require maintenance of several word meanings in unintegrated form.
A shared serial order system for verbal working memory and language production: Evidence from aphasia
Serial order information is critical in our daily life, as in recalling a phone number, producing... more Serial order information is critical in our daily life, as in recalling a phone number, producing a sequence of phonemes when saying a word out loud, or writing down a sequence of letters when spelling. In the current study, we use a multiple case study approach to investigate the extent to which a common serial order system is shared in these daily activities. Three individuals with brain damage due to stroke completed a series of working memory (WM) tasks in both verbal and nonverbal (visuospatial) domains to assess whether they had a WM impairment specific to the capacity to maintain serial order. In addition, participants were administered a series of spoken production and spelling tasks, and the error corpus produced by these three individuals was analyzed to assess whether there was a tendency to produce the correct phonemes/letters in the wrong order. M.B. showed a serial order impairment with verbal but not visuospatial stimuli in WM tasks, whereas the other two participants did not exhibit any serial order impairment in either domain. This dissociation between verbal and nonverbal serial order WM systems provides clear evidence for the domain-specific nature of serial order WM. In both spoken and written production tasks, M.B. had a tendency to make errors that involved producing serial order errors, or errors in which the right segments were produced in the wrong order, whereas the other two participants did not produce serial order errors at rates different than would be expected by chance. The association between M.B.’s serial order impairments in verbal WM, spoken production, and spelling, along with the other two patients’ preserved serial order performance, supports a shared system for processing serial order information in verbal WM and language production.
Uploads
Papers by Randi Martin