Articulatory Rehearsal Processes Research Articles

Dissociable Mechanisms of Verbal Working Memory Revealed through Multivariate Lesion Mapping.

Two maintenance mechanisms with separate neural systems have been suggested for verbal working memory: articulatory-rehearsal and non-articulatory maintenance. Although lesion data would be key to understanding the essential neural substrates of these systems, there is little evidence from lesion studies that the two proposed mechanisms crucially rely on different neuroanatomical substrates. We examined 39 healthy adults and 71 individuals with chronic left-hemisphere stroke to determine if verbal working memory tasks with varying demands would rely on dissociable brain structures. Multivariate lesion-symptom mapping was used to identify the brain regions involved in each task, controlling for spatial working memory scores. Maintenance of verbal information relied on distinct brain regions depending on task demands: sensorimotor cortex under higher demands and superior temporal gyrus (STG) under lower demands. Inferior parietal cortex and posterior STG were involved under both low and high demands. These results suggest that maintenance of auditory information preferentially relies on auditory-phonological storage in the STG via a nonarticulatory maintenance when demands are low. Under higher demands, sensorimotor regions are crucial for the articulatory rehearsal process, which reduces the reliance on STG for maintenance. Lesions to either of these regions impair maintenance of verbal information preferentially under the appropriate task conditions.

Right and left perisylvian cortex and left inferior frontal cortex mediate sentence‐level rhyme detection in spoken language as revealed by sparse fMRI

In this study, we used functional magnetic resonance imaging to investigate the neural basis of auditory rhyme processing at the sentence level in healthy adults. In an explicit rhyme detection task, participants were required to decide whether the ending syllable of a metrically spoken pseudosentence rhymed or not. Participants performing this task revealed bilateral activation in posterior-superior temporal gyri with a much more extended cluster of activation in the right hemisphere. These findings suggest that the right hemisphere primarily supports suprasegmental tasks, such as the segmentation of speech into syllables; thus, our findings are in line with the "asymmetric sampling in time" model suggested by Poeppel (: Speech Commun 41:245-255). The direct contrast between rhymed and nonrhymed trials revealed a stronger BOLD response for rhymed trials in the frontal operculum and the anterior insula of the left hemisphere. Our results suggest an involvement of these frontal regions not only in articulatory rehearsal processes, but especially in the detection of a matching syllable, as well as in the execution of rhyme judgment.

Understanding Phonological Memory Deficits in Boys with Attention-Deficit/Hyperactivity Disorder (ADHD): Dissociation of Short-term Storage and Articulatory Rehearsal Processes

The current study dissociated and examined the two primary components of the phonological working memory subsystem--the short-term store and articulatory rehearsal mechanism--in boys with ADHD (n = 18) relative to typically developing boys (n = 15). Word lists of increasing length (2, 4, and 6 words per trial) were presented to and recalled by children following a brief (3 s) interval to assess their phonological short-term storage capacity. Children's ability to utilize the articulatory rehearsal mechanism to actively maintain information in the phonological short-term store was assessed using word lists at their established memory span but with extended rehearsal times (12 s and 21 s delays). Results indicate that both phonological shortterm storage capacity and articulatory rehearsal are impaired or underdeveloped to a significant extent in boys with ADHD relative to typically developing boys, even after controlling for age, SES, IQ, and reading speed. Larger magnitude deficits, however, were apparent in short-term storage capacity (ES = 1.15 to 1.98) relative to articulatory rehearsal (ES = 0.47 to 1.02). These findings are consistent with previous reports of deficient phonological short-term memory in boys with ADHD, and suggest that future attempts to develop remedial cognitive interventions for children with ADHD will need to include active components that require children to hold increasingly more information over longer time intervals.

The role of inferior parietal and inferior frontal cortex in working memory.

Verbal working memory involves two major components: a phonological store that holds auditory-verbal information very briefly and an articulatory rehearsal process that allows that information to be refreshed and thus held longer in short-term memory (A. Baddeley, 1996, 2000; A. Baddeley & G. Hitch, 1974). In the current study, the authors tested two groups of patients who were chosen on the basis of their relatively focal lesions in the inferior parietal (IP) cortex or inferior frontal (IF) cortex. Patients were tested on a series of tasks that have been previously shown to tap phonological storage (span, auditory rhyming, and repetition) and articulatory rehearsal (visual rhyming and a 2-back task). As predicted, IP patients were disproportionately impaired on the span, rhyming, and repetition tasks and thus demonstrated a phonological storage deficit. IF patients, however, did not show impairment on these storage tasks but did exhibit impairment on the visual rhyming task, which requires articulatory rehearsal. These findings lend further support to the working memory model and provide evidence of the roles of IP and IF cortex in separable working memory processes.

Duration estimation and the phonological loop: Articulatory suppression and irrelevant sounds

Clock-based theories of time estimation propose that clock pulses are accumulated in working memory. Although these theories do not constrain the form of the memory trace, evidence reported in the literature suggests that active manipulation of a verbal trace may be involved. Four experiments are reported in which participants reproduced or verbally estimated short durations (up to a few seconds) either in a single-task condition or in a condition with a phonological load. Experiments 1, 2 and 4 showed that both interval reproduction and verbal estimation were impaired under concurrent articulatory suppression in comparison to a timing only control condition. Neither irrelevant speech (Experiments 1-3) nor irrelevant tones and music (Experiment 3) impaired timing performance. These findings are taken to show that time estimation is mediated by phonological working memory and the involvement of an active articulatory rehearsal process.

Disruption of verbal STM by irrelevant speech, articulatory suppression, and manual tapping: do they have a common source?

Under appropriate conditions, immediate serial verbal recall is impaired by irrelevant speech, articulatory suppression, and syncopated tapping. Interpretation of these variables in terms of the phonological loop component of working memory assumes separate phonological storage and articulatory rehearsal processes. In contrast, the Object-Oriented Episodic Record (O-OER) of Jones and the feature theory of Neath interpret these and other phenomena in terms of a unitary multimodal system. Three experiments investigate these disrupting tasks, with each experiment emphasizing one parameter. In each case, recall of phonologically similar and dissimilar letter sequences is compared as a marker of the presence or absence of phonological coding. In Experiment 1, subjects heard or articulated a single item, or tapped a single key at equal intervals. Only articulatory suppression impaired performance; it also abolished the effects of phonological similarity. Experiment 2 was identical, except that items were heard, or generated in a syncopated rhythm. Both suppression and tapping impaired performance to an equivalent extent and obliterated the effect of phonological similarity. Syncopated irrelevant speech caused a modest but significant impairment in performance. Experiment 3 was identical to Experiment 1, except that six tokens were used. Irrelevant speech and tapping had a clear impact on recall, but neither removed the phonological similarity effect. Again articulatory suppression had a major impact on performance and removed the effect of phonological similarity. We conclude that the pattern of results readily fits the phonological loop hypothesis, provided one accepts Saitos proposal that generating syncopated sequences uses common processes with speech production. It is not clear how the results can be explained by either the O-OER or the feature hypothesis.

The Inner Voice in Writing

This study explores the connection between writing and working memory, specifically the role of the subvocal articulatory rehearsal process (or inner voice). The authors asked the 18 participants to type sentences describing 24 multipanel cartoons. In some conditions, the participants were required to repeat a syllable continuously while writing. This activity, called articulatory suppression, interferes with the articulatory rehearsal process. Results indicated that interfering with the articulatory rehearsal process (or inner voice) interferes with writing by slowing the rate of writing, increasing mechanical errors, changing the temporal microstructure of text production, and increasing the perceived difficulty of the writing task. The authors applied their model of written text production to provide a theoretical account for these results.

A Phonological Account For The Cross-Language Variation In Working Memory Processing

This study examines the relationship between immediate serial recall and word articulation rate with Cantonese and English materials. Using bilingual subjects, Experiment 1 reported a steeper regression function relating recall to word articulation rate for Cantonese than for English items. The effect of language on regression slopes was shown to hold both with and without concurrent articulation (i.e., subjects repeating irrelevant digits during list learning and recall, thus blocking any articulatory mechanisms), although it was significantly more pronounced in the latter condition. In Experiment 2, the effect of language on slopes was replicated in monolingual English speakers, using pseudowords that preserved the consonant-vowel structures of the Experiment 1 items. These findings indicate that (1) both articulatory and nonarticulatory processes contribute to the cross-language variation in regression slopes and (2) the language effect is attributable to a difference in consonant-vowel structures of the items from the two languages. It is concluded that the phonological loop model (Baddeley, 1986), which specifies an articulatory rehearsal process and a nonarticulatory phonological store, is applicable to cross-language working memory processing.

On the Structure of Verbal Short-term Memory and its Functional Role in Sentence Comprehension: Evidence from Neuropsychology

Abstract We present a case of a patient with a disorder of short-term memory. BO has a reduced span (2 to 3 items), no recency effect in free recall, and rapid forgetting in Brown-Peterson tasks, establishing her as a patient with impaired short-term verbal memory functions. She shows no effect of either phonological similarity or word length in recall of auditory or written word lists, but some recency effect under recall-from-end conditions and better performance on Brown-Peterson tasks in an unfilled than in a filled condition. This pattern of performance is interpreted as being consistent with a primary disturbance of the articulatory rehearsal processes of S.T.M. and possibly some impairment of the phonological store (using Baddeley's 1986 terminology). Her aphasic disturbance—apraxia of speech—is also consistent with a disturbance of articulatory rehearsal. BO shows a retained ability to extract phonology from print, including an ability to apply sublexical grapheme-phoneme correspondences, thus ind...

Articulatory rehearsal in Alzheimer type dementia

This study investigated the relationship between articulation rate and memory span in a sample of 21 patients with early Alzheimer type dementia (AD), comparing their performance with 21 matched controls. Memory span was measured using auditorily and visually presented digits. The AD patients were moderately impaired in both conditions. Articulation rate was measured either by requiring subjects to read lists of random digits or repeatedly count from 1 to 10. The AD patients were able to read the digits as fast as the controls but were slower in the counting task. The measures of memory span and articulation rate correlated significantly for the controls but not for the AD patients, indicating that the normal association between articulation and memory span is disrupted. These results are discussed in relation to previous results and suggest that articulatory rehearsal processes in primary memory are unimpaired at the early stages of AD.

Exploring the Articulatory Loop

A series of five experiments explore the influence of articulatory suppression on immediate memory for auditorily presented items with a view to testing the revised concept of an articulatory loop. Experiments 1, 2 and 3 demonstrate that the phonological similarity effect is not abolished by articulatory suppression, whether this occurs only at input or at both input and recall. Experiments 4 and 5 show that the tendency for long words to be less well remembered than short is abolished by articulatory suppression, even when presentation is auditory, provided suppression occurs during both input and recall. These results are consistent with the concept of a loop comprising a phonological store, which is responsible for the phonological similarity effect, coupled with an articulatory rehearsal process that gives rise to the word length effect.