A narrative review of the anatomy and function of the white matter tracts in language production and comprehension

Much is known about the role of cortical areas in language processing. The shift towards network approaches in recent years has highlighted the importance of uncovering the role of white matter in connecting these areas. However, despite a large body of research, many of these tracts’ functions are not well-understood. We present a comprehensive review of the empirical evidence on the role of eight major tracts that are hypothesized to be involved in language processing (inferior longitudinal fasciculus, inferior fronto-occipital fasciculus, uncinate fasciculus, extreme capsule, middle longitudinal fasciculus, superior longitudinal fasciculus, arcuate fasciculus, and frontal aslant tract). For each tract, we hypothesize its role based on the function of the cortical regions it connects. We then evaluate these hypotheses with data from three sources: studies in neurotypical individuals, neuropsychological data, and intraoperative stimulation studies. Finally, we summarize the conclusions supported by the data and highlight the areas needing further investigation

Different electrophysiological signatures of similarity-induced and Stroop-like interference in language production

Published: August 01 2023Contextual similarity between targets and competitors, whether semantic or phonological, often leads to behavioral interference in language production. It has been assumed that resolving such interference relies on control processes similar to those involved in tasks such as Stroop. This article tests this assumption by comparing the electrophysiological signatures of interference resulting from a contextual similarity versus a Stroop-like manipulation. In blocks containing two items, participants repeatedly named pictures that were semantically related, phonologically related, or unrelated (contextual similarity manipulation). In straight blocks, the pictures were named by their canonical names. In reverse blocks, participants had to reverse the names (Stroop-like manipulation). Both manipulations led to behavioral interference, but with different electrophysiological profiles. Whole-scalp stimulus-locked and response-locked analyses of semantic and phonological similarity pointed to a system with global modularity with some degree of cascading and interactivity, whereas the effect of phase reversal was sustained and of the opposite polarity. More strikingly, a representational similarity analysis showed a biphasic pattern for Stroop-like reversal, with earlier higher similarity scores for the reverse phase flipping into lower scores ~500 msec poststimulus onset. In contrast, contextual similarity induced higher similarity scores up to articulation. Finally, response-locked mediofrontal components indexing performance monitoring differed between manipulations. Correct response negativity's amplitude was lower in the phonological blocks, whereas a pre-correct response negativity component had higher amplitude in reverse versus straight blocks. These results argue against the involvement of Stroop-like control mechanisms in resolving interference from contextual similarity in language production.This work was supported in part by the Therapeutic Cognitive Neuroscience Fund at Johns Hopkins Universit

Correction Without Consciousness in Complex Tasks: Evidence from Typing

Published: 07 January 2022It has been demonstrated that with practice, complex tasks can become independent of conscious control, but even in those cases, repairing errors is thought to remain dependent on conscious control. This paper reports two studies probing conscious awareness over repairs in nearly 15,000 typing errors collected from 145 participants in a single-word typing-to-dictation task. We provide evidence for subconscious repairs by ruling out alternative accounts, and report two sets of analyses showing that a) such repairs are not confined to a specific stage of processing and b) that they are sensitive to the final outcome of repair. A third set of analyses provides a detailed comparison of the timeline of trials with conscious and subconscious repairs, revealing that the difference is confined to the repair process itself. We propose an account of repair processing that accommodates these empirical findings.This project was supported by the Therapeutic Cognitive Neurology Fund to Johns Hopkins School of Medicine, Department of Neurology, Division of Cognitive Neurology

Behavioral interference or facilitation does not distinguish between competitive and noncompetitive accounts of lexical selection in word production.

One of the major debates in the field of word production is whether lexical selection is competitive or not. For nearly half a century, semantic interference effects in picture naming latencies have been claimed as evidence for competitive (relative threshold) models of lexical selection, while semantic facilitation effects have been claimed as evidence for non-competitive (simple threshold) models instead. In this paper, we use a computational modeling approach to compare the consequences of competitive and noncompetitive selection algorithms for blocked cyclic picture naming latencies, combined with two approaches to representing taxonomic and thematic semantic features. We show that although our simple model can capture both semantic interference and facilitation, the presence or absence of competition in the selection mechanism is unrelated to the polarity of these semantic effects. These results question the validity of prior assumptions and offer new perspectives on the origins of interference and facilitation in language production

Language control in bilingual production: Insights from error rate and error type in sentence production

First published online: 16 October 2020Most research showing that cognates are named faster than non-cognates has focused on isolated word production which might not realistically reflect cognitive demands in sentence production. Here, we explored whether cognates elicit interference by examining error rates during sentence production, and how this interference is resolved by language control mechanisms. Twenty highly proficient Spanish–English bilinguals described visual scenes with sentence structures ‘NP1-verb-NP2’ (NP = noun-phrase). Half the nouns and half the verbs were cognates and two manipulations created high control demands. Both situations that demanded higher inhibitory control pushed the cognate effect from facilitation towards interference. These findings suggest that cognates, similar to phonologically similar words within a language, can induce not only facilitation but robust interference.We thank Michael Freund and Nicholas McCloskey for their help with data collection. This work was supported in part by the Therapeutic Cognitive Neuroscience Fund endowed to the Cognitive Neurology division of the Neurology Department at Johns Hopkins University. C.D. Martin was supported by the Spanish Ministry of Economy and Competitiveness (SEV-2015-490; PSI2017-82941-P; Europa-Excelencia ERC2018-092833), the Basque Government (PIBA18-29), and the European Research Council (ERC-2018-COG-819093). N. Nozari was also supported by a NSF grant (NSF BCS-1949631)

The effects of utterance timing and stimulation of left prefrontal cortex on the production of referential expressions

We examined the relationship between the timing of utterance initiation and the choice of referring expressions, e.g., pronouns (it), zeros (…and went down), or descriptive NPs (the pink pentagon). We examined language production in healthy adults, and used anodal transcranial direct current stimulation (tDCS) to test the involvement of the left prefrontal cortex (PFC) on the timing of utterance production and the selection of reference forms in a discourse context. Twenty-two subjects (11 anodal, 11 sham) described fast-paced actions, e.g. The gray oval flashes, then it moves right 2 blocks. We only examined trials in contexts that supported pronoun/zero use. For sham participants, pronouns/zeros increased on trials with longer latencies to initiate the target utterance, and trials where the previous trial was short. We argue that both of these conditions enabled greater message pre-planning and greater discourse connectedness: The strongest predictor of pronoun/zero usage was the presence of a connector word like and or then, which was also tended to occur on trials with longer latencies. For the anodal participants, the latency effect disappeared. PFC stimulation appeared to enable participants to produce utterances with greater discourse connectedness, even while planning incrementally

Is repairing speech errors an automatic or a controlled process? Insights from the relationship between error and repair probabilities in English and Spanish

Published online: 02 Jul 2019Speakers can correct their speech errors, but the mechanisms behind repairs are still unclear. Some findings, such as the speed of repairs and speakers’ occasional unawareness of them, point to an automatic repair process. This paper reports a finding that challenges a purely automatic repair process. Specifically, we show that as error rate increases, so does the proportion of repairs. Twenty highly-proficient English-Spanish bilinguals described dynamic visual events in real time (e.g. “The blue bottle disappears behind the brown curtain”) in English and Spanish blocks. Both error rates and proportion of corrected errors were higher on (a) noun phrase (NP)2 vs. NP1, and (b) word1 (adjective in English and noun in Spanish) vs. word2 within the NP. These results show a consistent relationship between error and repair probabilities, disentangled from position, compatible with a model in which greater control is recruited in error-prone situations to enhance the effectiveness of repair.This work was supported in part by the NSF grant 1631993 awarded to N.N., and in part by the Therapeutic Cognitive Neuroscience Fund endowed to the Cognitive Neurology division of the Neurology Department at Johns Hopkins University. C.D. Martin was supported by the Spanish Ministry of Economy and Competitiveness (SEV-2015-490; PSI2017-82941-P; Europa-Excelencia ERC2018-092833) and the Basque Government (PIBA18-29)

Did I say dog or cat? A study of semantic error detection and correction in children

While naturalistic studies of spontaneous speech suggest that young children can monitor their speech, the mechanisms for detection and correction of speech errors in children are not well understood. In particular, there is little research on monitoring semantic errors in this population. This study provides a systematic investigation of detection and correction of semantic errors in children between the ages of 5 and 8, as they produced sentences to describe simple visual events involving nine highly familiar animals (the moving animals task). Results showed that older children made fewer errors and corrected a larger proportion of the errors that they made than younger children. We then tested the prediction of a production-based account of error monitoring that the strength of the language production system, and specifically its semantic-lexical component, should be correlated with the ability to detect and repair semantic errors. Strength of semantic-lexical mapping, as well as lexical-phonological mapping, was estimated individually for children by fitting their error patterns, obtained from an independent picture naming task, to a computational model of language production (Foygel & Dell, 2000). Children’s picture naming performance was predictive of their ability to monitor their semantic errors, above and beyond age. This relationship was specific to the strength of the semantic-lexical part of the system, as predicted by the production-based monitor

The Effects of Anodal Stimulation of the Left Prefrontal Cortex on Sentence Production

Most studies in which Anodal Transcranial Direct Current Stimulation (A-tDCS) has been used to improve language production have focused on single words. Yet sentence production requires more than lexical retrieval. For example, successful suppression of the past and careful planning of the future are two critical requirements for producing a correct sentence. Can A-tDCS improves those, and by extension, production at the sentence level

Did I say dog or cat? A study of semantic error detection and correction in children

Although naturalistic studies of spontaneous speech suggest that young children can monitor their speech, the mechanisms for detection and correction of speech errors in children are not well understood. In particular, there is little research on monitoring semantic errors in this population. This study provides a systematic investigation of detection and correction of semantic errors in children between the ages of 5 and 8 years as they produced sentences to describe simple visual events involving nine highly familiar animals (the moving animals task). Results showed that older children made fewer errors and corrected a larger proportion of the errors that they made than younger children. We then tested the prediction of a production-based account of error monitoring that the strength of the language production system, and specifically its semantic–lexical component, should be correlated with the ability to detect and repair semantic errors. Strength of semantic–lexical mapping, as well as lexical–phonological mapping, was estimated individually for children by fitting their error patterns, obtained from an independent picture-naming task, to a computational model of language production. Children’s picture-naming performance was predictive of their ability to monitor their semantic errors above and beyond age. This relationship was specific to the strength of the semantic–lexical part of the system, as predicted by the production-based monitor