In this commentary on Rieger et al., Psychological Research Psychologische Forschung, 2023, I discuss possible ways to test the hypothesis that action imagery is achieved by simulations of actions ...through an internal forward model. These include brain imaging, perturbation through TMS, and psychophysical tests of adaptation of intended reach actions.
The possibility that different neural systems are used to measure temporal durations at the sub-second and several second ranges has been supported by pharmacological manipulation, psychophysics, and ...neural network modelling. Here, we add to this literature by using fMRI to isolate differences between the brain networks which measure 0.6 and 3
s in a temporal discrimination task with visual discrimination for control. We observe activity in bilateral insula and dorsolateral prefrontal cortex, and in right hemispheric pre-supplementary motor area, frontal pole, and inferior parietal cortex during measurement of both intervals, suggesting that these regions constitute a system used in temporal discrimination at both ranges. The frontal operculum, left cerebellar hemisphere and middle and superior temporal gyri, all show significantly greater activity during measurement of the shorter interval, supporting the hypotheses that the motor system is preferentially involved in the measurement of sub-second intervals, and that auditory imagery is preferentially used during measurement of the same. Only a few voxels, falling in the left posterior cingulate and inferior parietal lobe, are more active in the 3
s condition. Overall, this study shows that although many brain regions are used for the measurement of both sub- and supra-second temporal durations, there are also differences in activation patterns, suggesting that distinct components are used for the two durations.
The principle that the standard deviation of estimates scales with the mean estimate, commonly known as the scalar property, is one of the most broadly accepted fundamentals of interval timing. This ...property is measured using the coefficient of variation (CV) calculated as the ratio between the standard deviation and the mean. In 1997, John Gibbon suggested that different time measurement mechanisms may have different levels of absolute precision, and would therefore be associated with different CVs. Here, we test this proposal by examining the CVs produced by human subjects timing a broad range of intervals (68 ms to 16.7 min). Our data reveal no evidence for multiple mechanisms, but instead show a continuous logarithmic decrease in CV as timed intervals increase. This finding joins other recent reports in demonstrating a systematic violation of the scalar property in timing data. Interestingly, the estimated CV of circadian judgements fits onto the regression of decreasing CV, suggesting a link between short interval and circadian timing mechanisms.
Two recent developments in motor neuroscience are promising the extension of theoretical concepts from motor control towards cognitive processes, including human social interactions and understanding ...the intentions of others. The first of these is the discovery of what are now called mirror neurons, which code for both observed and executed actions. The second is the concept of internal models, and in particular recent proposals that forward and inverse models operate in paired modules. These two ideas will be briefly introduced, and a recent suggestion linking between the two processes of mirroring and modelling will be described which may underlie our abilities for imitating actions, for cooperation between two actors, and possibly for communication via gesture and language.
Recent theoretical work has suggested that internal predictive signals are used for motor control and coordination. The predictive signal – proposed to be the output of a forward model – would be a ...sensory representation of action. Hence, these sensory representations could potentially influence other sensory processes. We report here how performance of hand actions assisted the visual discrimination of target hand postures presented at random times within an on-going series of hand images. Reaction times to discriminate the targets were significantly shorter when the displayed images were both sequential and congruent with the action being performed. Hence, the planning or execution of action appears to allow better prediction of a displayed series of congruent images. In further control experiments, we show that the motor–visual priming effect is unlikely to be due to differential attentional demands and it is specific to a first person perspective display; it is short lasting, being lost if a 500
ms delay is introduced between successive stimulus presentations. The data are interpreted as evidence supporting the hypothesis that forward models in the motor system provide action-specific sensory predictions that are available to cognitive processes.
To copy a natural visual image as a line drawing, visual identification and extraction of features in the image must be guided by top-down decisions, and is usually influenced by prior knowledge. In ...parallel with other behavioral studies testing the relationship between eye and hand movements when drawing, we report here a functional brain imaging study in which we compared drawing of faces and abstract objects: the former can be strongly guided by prior knowledge, the latter less so. To manipulate the difficulty in extracting features to be drawn, each original image was presented in four formats including high contrast line drawings and silhouettes, and as high and low contrast photographic images. We confirmed the detailed eye–hand interaction measures reported in our other behavioral studies by using in-scanner eye-tracking and recording of pen movements with a touch screen. We also show that the brain activation pattern reflects the changes in presentation formats. In particular, by identifying the ventral and lateral occipital areas that were more highly activated during drawing of faces than abstract objects, we found a systematic increase in differential activation for the face-drawing condition, as the presentation format made the decisions more challenging. This study therefore supports theoretical models of how prior knowledge may influence perception in untrained participants, and lead to experience-driven perceptual modulation by trained artists.
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•Drawing natural images requires feature identification and extraction.•Top-down decisions and prior knowledge e.g. of faces guide this process.•We used fMRI with concurrent eye tracking and measured drawing actions.•Ventro-lateral occipital areas were more active drawing faces than abstract objects.•There was also differential activity with more difficult stimulus formats.
A recent review of neuroimaging data on time measurement argued that the brain activity seen in association with timing is not influenced by specific characteristics of the task performed. In ...contrast, we argue that careful analysis of this literature provides evidence for separate neural timing systems associated with opposing task characteristics. The ‘automatic’ system draws mainly upon motor circuits and the ‘cognitively controlled’ system depends upon prefrontal and parietal regions.
It has been postulated recently that the cerebellum contributes the same prediction and learning functions to linguistic processing as it does towards motor control. For example, repetitive TMS over ...posterior-lateral cerebellum caused a significant loss in predictive language processing, as assessed by the latency of saccades to target items of spoken sentences, using the Visual World task. We aimed to assess the polarity-specific effects of cerebellar TDCS, hypothesising that cathodal TDCS should impair linguistic prediction, and anodal TDCS facilitate it. Our design also tested whether TDCS modulated associative learning in this task. A between groups (sham, anodal, cathodal) design was used, with concurrent stimulation during performance of a manual variation of the Visual World paradigm, and with assessment of latency reduction over repeated presentations of the spoken sentences. Mixed model ANOVA was used to analyse change in response latency. Cathodal TDCS decreased participants’ response time advantage for the predictable sentence items without change for non-predictable items, consistent with the previous TMS results. Furthermore, anodal stimulation enhanced the response time advantage for the predictable items, again without change in latencies for non-predictive items. We found a clear practice-based effect over 4 blocks. However, this difference was not significantly modulated by either anodal or cathodal stimulation. Our results therefore support the hypothesis that cerebellum contributes to predictive language processing, mirroring its predictive role in motor control, but we do not yet have evidence that the learning process was affected by cerebellar TDCS.
•Disruption of the lateral cerebellum with TMS impairs prediction in language processing.•We now report the effect of anodal and cathodal TDCS, and assess short-term learning.•Cathodal TDCS replicated the TMS effect, reducing linguistic prediction.•Anodal TDCS reversed the effect, enhancing prediction; neither affected short-term learning.•This work adds new evidence that the cerebellum contributes to predictive language processing.
Movement interference occurs when concurrently observing and executing incompatible actions and is believed to be due to co-activation of conflicting populations of mirror neurons. It has also been ...suggested that mirror neurons contribute towards the imitation of observed actions. However, the exact neural substrate of imitation may depend on task demands: a processing route for goal-directed meaningful actions may be distinct from one for non-goal-directed actions. A more controversial role proposed for these neurons is in theory of mind processing, along with the subsequent suggestion that impairment in the mirror neuron circuit can contribute to autism-spectrum disorder (ASD) where individuals have theory of mind deficits. We have therefore examined movement interference in nine ASD participants and nine matched controls while performing actions congruent and incongruent with observed meaningless arm movements. We hypothesised that if the mirror neuron system was impaired, reduced interference should be observed in the ASD group. However, control and ASD participants demonstrated an equivalent interference effect in an interpersonal condition, with greater movement variability in the incongruent compared to the congruent condition. A component of movement interference which is independent of congruency did differ between groups: ASD participants made generally more variable movements for the interpersonal task than for biological dot-motion task, while the reverse was true for the control participants. We interpret these results as evidence that the ASD participant group either rely to a greater extent on the goal-directed imitation pathway, supporting claims that they have a specific deficit of the non-goal-directed imitation pathway, or exhibit reduced visuomotor integration.
The ability to attribute mental states to others, and therefore to predict others' behavior, is particularly advanced in humans. A controversial but untested idea is that this is achieved by ...simulating the other person's mental processes in one's own mind. If this is the case, then the same neural systems activated by a mental function should re-activate when one thinks about that function performed by another. Here, using functional magnetic resonance imaging (fMRI), we tested whether the neural processes involved in preparing one's own actions are also used for predicting the future actions of others. We provide compelling evidence that areas within the action control system of the human brain are indeed activated when predicting others' actions, but a different action sub-system is activated when preparing one's own actions.
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