Motor imagery is accompanied by a subjective multisensory experience. This sensory experience is thought to result from the deployment of internal models developed for the execution and monitoring of overt actions. If so, how is it that motor imagery does not lead to overt execution? It has been proposed that inhibitory mechanisms may prevent execution during imagined actions such as imagined typing. To test this hypothesis, we combined an experimental with a modelling approach. We conducted an experiment in which participants (N = 49) were asked to alternate between overt (executed) and covert (imagined) typing. We predicted that motor inhibition should lead to longer reaction and movement times when the current trial is preceded by an imagined vs. an executed trial. This prediction was borne out by movement times, but not by reaction times. We introduced and fitted an algorithmic model of motor imagery to disentangle potentially distinct inhibitory mechanisms underlying these effects. Results from this analysis suggest that motor inhibition may affect different aspects of the latent activation function (e.g., the shape of the activation function or the motor execution threshold) with distinct consequences on reaction times and movement times. Overall, these results suggest that typing imagery involves the inhibition of motor commands related to typing acts. Preregistration, complete source code, and reproducible analyses are available at https://osf.io/y9a3k/.

A vast body of research suggests that the primary motor cortex is involved in motor imagery. This raises the issue of inhibition: how is it possible for motor imagery not to lead to motor execution? Bach et al. (2022) suggest that the motor execution threshold may be ‘upregulated’ during motor imagery to prevent execution. Alternatively, it has been proposed that, in parallel to excitatory mechanisms, inhibitory mechanisms may be actively suppressing motor output during motor imagery. These theories are verbal in nature, with well-known limitations. Here, we describe a toy-model of the inhibitory mechanisms thought to be at play during motor imagery to start disentangling predictions from competing hypotheses.

Humans have the ability to mentally examine speech. This covert form of speech production is often accompanied by sensory (e.g., auditory) percepts. However, the cognitive and neural mechanisms that generate these percepts are still debated. According to a prominent proposal, inner speech has at least two distinct phenomenological components: inner speaking and inner hearing. We used transcranial magnetic stimulation to test whether these two phenomenologically distinct processes are supported by distinct neural mechanisms. We hypothesised that inner speaking relies more strongly on an online motor-to-sensory simulation that constructs a multisensory experience, whereas inner hearing relies more strongly on a memory-retrieval process, where the multisensory experience is reconstructed from stored motor-to-sensory associations. Accordingly, we predicted that the speech motor system will be involved more strongly during inner speaking than inner hearing. This would be revealed by modulations of TMS evoked responses at muscle level following stimulation of the lip primary motor cortex. Overall, data collected from 31 participants corroborated this prediction, showing that inner speaking increases the excitability of the primary motor cortex more than inner hearing. Moreover, this effect was more pronounced during the inner production of a syllable that strongly recruits the lips (vs. a syllable that recruits the lips to a lesser extent). These results are compatible with models assuming a central role of the primary motor cortex for inner speech production and contribute to clarify the neural implementation of the fundamental ability of silently speaking in one’s mind.

Short journal club about the unexpected consequences of randomisation in psychological research.

Covert speech is accompanied by a subjective multisensory experience with auditory and kinaesthetic components. An influential hypothesis states that these sensory percepts result from a simulation of the corresponding motor action that relies on the same internal models recruited for the control of overt speech. This simulationist view raises the question of how it is possible to imagine speech without executing it. In this perspective, we discuss the possible role(s) played by motor inhibition during covert speech production. We suggest that considering covert speech as an inhibited form of overt speech maps naturally to the purported progressive internalisation of overt speech during childhood. We further argue that the role of motor inhibition may differ widely across different forms of covert speech (e.g., condensed vs. expanded covert speech) and that considering this variety helps reconciling seemingly contradictory findings from the neuroimaging literature.

Inner speech is accompanied by a subjective multisensory experience. However, the origins (causes) of this subjective experience are debated. In this study, we used transcranial magnetic stimulation to disentangle the predictions of competing theoretical frameworks.

Motor imagery is accompanied by a subjective multisensory experience. This sensory experience is thought to result from internal models that control the execution of overt actions. If so, how is it that motor imagery does not to lead to overt execution?

With the aim of moving beyond mindless statistics, Wasserstein, Schirm, & Lazar (2019) formulated the ATOM guidelines: ‘Accept uncertainty. Be thoughtful, open, and modest.’ In this talk, I explore some consequences of these guidelines when applied to the analysis of empirical data, in the light of core concepts from the philosophy of statistics.

A gentle conceptual and practical primer to Bayesian multilevel models using R, brms, and Stan.

Using commonality analysis to identify unique and shared (common) variance across three or more variables.

The second part of my compiled reading notes on Meehl’s metatheory and related meta-peregrinations.

My compiled reading notes on Meehl’s metatheory and related meta-peregrinations.

An attempt to illustrate what a Bayes factor looks like, using GIFs.

Why can’t we be more idiographic in our research? It is the individual organism that is the principle unit of analysis in the science of psychology (Barlow & Nock, 2009).