Speech monitoring and phonologically-mediated eye gaze in language perception and production: a comparison using printed word eye-tracking

The Perceptual Loop Theory of speech monitoring assumes that speakers routinely inspect their inner speech. In contrast, Huettig and Hartsuiker (2010) observed that listening to one's own speech during language production drives eye-movements to phonologically related printed words with a similar time-course as listening to someone else's speech does in speech perception experiments. This suggests that speakers use their speech perception system to listen to their own overt speech, but not to their inner speech. However, a direct comparison between production and perception with the same stimuli and participants is lacking so far. The current printed word eye-tracking experiment therefore used a within-subjects design, combining production and perception. Displays showed four words, of which one, the target, either had to be named or was presented auditorily. Accompanying words were phonologically related, semantically related, or unrelated to the target. There were small increases in looks to phonological competitors with a similar time-course in both production and perception. Phonological effects in perception however lasted longer and had a much larger magnitude. We conjecture that this difference is related to a difference in predictability of one's own and someone else's speech, which in turn has consequences for lexical competition in other-perception and possibly suppression of activation in self-perception

Verbal monitoring in production and perception : a cognitive neuroscience approach

The goal of this dissertation is to investigate the process of verbal monitoring. Specifically, this thesis investigates whether internal and external monitoring proceeds via the same, perception-based process, as proposed by the perceptual loop theory. We compare verbal internal and external monitoring with the use of eye-tracking, fMRI and Parkinson patient data. The data obtained suggest that verbal monitoring is not perception based, and that is a domain general process. We therefore propose the improvement of current monitoring models by describing a domain general monitoring mechanism for internal monitoring and external monitoring, by which conflict is resolved in a process-independent manner

Towards a new model of verbal monitoring

As all human activities, verbal communication is fraught with errors. It is estimated that humans produce around 16,000 words per day, but the word that is selected for production is not always correct and neither is the articulation always flawless. However, to facilitate communication, it is important to limit the number of errors. This is accomplished via the verbal monitoring mechanism. A body of research over the last century has uncovered a number of properties of the mechanisms at work during verbal monitoring. Over a dozen routes for verbal monitoring have been postulated. However, to date a complete account of verbal monitoring does not exist. In the current paper we first outline the properties of verbal monitoring that have been empirically demonstrated. This is followed by a discussion of current verbal monitoring models: the perceptual loop theory, conflict monitoring, the hierarchical state feedback control model, and the forward model theory. Each of these models is evaluated given empirical findings and theoretical considerations. We then outline lacunae of current theories, which we address with a proposal for a new model of verbal monitoring for production and perception, based on conflict monitoring models. Additionally, this novel model suggests a mechanism of how a detected error leads to a correction. The error resolution mechanism proposed in our new model is then tested in a computational model. Finally, we outline the advances and predictions of the model

Conflict monitoring in speech processing: an fMRI study of error detection in speech production and perception

To minimize the number of errors in speech, and thereby facilitate communication, speech is monitored before articulation. It is, however, unclear at which level during speech production monitoring takes place, and what mechanisms are used to detect and correct errors. The present study investigated whether internal verbal monitoring takes place through the speech perception system, as proposed by perception-based theories of speech monitoring, or whether mechanisms independent of perception are applied, as proposed by production-based theories of speech monitoring. With the use of fMRI during a tongue twister task we observed that error detection in internal speech during noise-masked overt speech production and error detection in speech perception both recruit the same neural network, which includes pre-supplementary motor area (pre-SMA), dorsal anterior cingulate cortex (dACC), anterior insula (AI), and inferior frontal gyrus (IFG). Although production and perception recruit similar areas, as proposed by perception-based accounts, we did not find activation in superior temporal areas (which are typically associated with speech perception) during internal speech monitoring in speech production as hypothesized by these accounts. On the contrary, results are highly compatible with a domain general approach to speech monitoring, by which internal speech monitoring takes place through detection of conflict between response options, which is subsequently resolved by a domain general executive center (e.g., the ACC)

Exploring a new technique for comparing bilinguals’ L1 and L2 reading speed

Is it possible to tell whether bilinguals are able to read simple text in their two languages equally fluently? Is it thus possible to distinguish balanced bilinguals from unbalanced bilinguals with respect to reading fluency in their first language (L1) and second language (L2)? In this study, we avoided making direct comparisons between L1 and L2 reading speeds, comparing, instead, the amount of inhibition caused by a nonlinguistic, external factor (degraded text visibility). In two tasks, 32 university students read 20 target sentences in L1 Dutch and L2 English, each sentence appearing both in normal and in poorly readable font. Degraded font affected reading times substantially, more so in L2 than in L1, as predicted. However, it was not found that participants with higher L2 proficiency were less affected by degraded font in L2 reading than participants with lower L2 proficiency

Internal modeling of upcoming speech: a causal role of the right posterior cerebellum in non-motor aspects of language production

International audienceSome language processing theories propose that, just as for other somatic actions, self-monitoring of language production is achieved through internal modeling. The cerebellum is the proposed center of such internal modeling in motor control, and the right cerebellum has been linked to an increasing number of language functions, including predictive processing during comprehension. Relating these findings, we tested whether the right posterior cerebellum has a causal role for self-monitoring of speech errors. Participants received 1Hz repetitive transcranial magnetic stimulation during 15 minutes to lobules Crus I and II in the right hemisphere, and, in counterbalanced orders, to the contralateral area in the left cerebellar hemisphere (control) in order to induce a temporary inactivation of one of these zones. Immediately afterwards, they engaged in a speech production task priming the production of speech errors. Language production was impaired after right compared to left hemisphere stimulation, a finding that provides evidence for a causal role of the cerebellum during language production. We interpreted this role in terms of internal modeling of upcoming speech through a verbal working memory process used to prevent errors

Visual from interference

These materials were used in an fMRI study to investigate neural correlates of Visual Form Interference in the Picture Word Interference task. Manuscript title: The shape of things to come in speech production: An fMRI study of visual form interference during lexical access. Authors: Hanna Gauvin, Katie McMahon, Marcus Meinzer and Greig de Zubicara

tDCS effects on word production: limited by design? Comment on Westwood et al. (2017)

Transcranial direct current stimulation (tDCS), has sparked enormous scientific, clinical and public interest (Dubljević, Saigle, & Racine, 2014; Riggall et al., 2015), because of its potential to modulate human brain function and behaviour without significant side effects. It thereby offers exciting prospects for clinical applications (Bikson et al., 2016). However, recent publications have highlighted substantial variability among reported stimulation effects in healthy individuals (e.g., Wiethoff, Hamada, & Rothwell, 2014) or even questioned the potential of tDCS to induce behavioural effects on cognition and motor function (Horvath, Forte, & Carter, 2015a,b). While the latter have attracted criticism for conceptual and methodological reasons (Antal, Keeser, Priori, Padberg, & Nitsche, 2015; Chhatbar & Feng, 2015), they have nonetheless motivated reflections on the use and the efficacy of tDCS and prompted urgent calls for more rigorous methodology, including replication studies (Fertonani & Miniussi, 2017). In this vein, a recent paper by Westwood, Olson, Miall, Nappo and Romani (2017) published in Cortex reported an attempt to replicate previously observed effects of tDCS on semantic interference during spoken word production using continuous and blocked cyclic naming paradigms (Damian, Vigliocco, & Levelt, 2001; Howard, Nickels, Coltheart, & Cole-Virtue, 2006). Across four experiments, active tDCS was administered to frontal and temporal cortical sites with the authors reporting null effects compared to sham stimulation, followed by far-reaching conclusions concerning the utility of tDCS to modulate cognition in healthy participants. In this commentary, we discuss a number of problems with Westwood et al.'s report, including their theoretical assumptions, choice of stimulation sites, use of reading and naming tasks in the same experiment, stimulation protocols, data analyses and interpretation of their null findings as a “test” of tDCS' efficacy. We conclude with a brief reminder concerning the proper use of the term replication, and recommend measures to be taken to ensure greater rigour in tDCS research conduct and reporting