Real-Time Prediction of Observed Action Requires Integrity of the Dorsal Premotor Cortex: Evidence From Repetitive Transcranial Magnetic Stimulation

Predictive coding for the actions and emotions of others and its deficits in autism spectrum disorders

Traditionally, the neural basis of social perception has been studied by showing participants brief examples of the actions or emotions of others presented in randomized order to prevent participants from anticipating what others do and feel. This approach is optimal to isolate the importance of information flow from lower to higher cortical areas. The degree to which feedback connections and Bayesian hierarchical predictive coding contribute to how mammals process more complex social stimuli has been less explored, and will be the focus of this review. We illustrate paradigms that start to capture how participants predict the actions and emotions of others under more ecological conditions, and discuss the brain activity measurement methods suitable to reveal the importance of feedback connections in these predictions. Together, these efforts draw a richer picture of social cognition in which predictive coding and feedback connections play significant roles. We further discuss how the notion of predicting coding is influencing how we think of autism spectrum disorder.

TMS-induced inhibition of the left premotor cortex modulates illusory social perception

Communicative actions from one person are used to predict another person's response. However, in some cases, these predictions can outweigh the processing of sensory information and lead to illusory social perception such as seeing two people interact, although only one is present (i.e., seeing a Bayesian ghost). We applied either inhibitory brain stimulation over the left premotor cortex (i.e., real TMS) or sham TMS. Then, participants indicated the presence or absence of a masked agent that followed a communicative or individual gesture of another agent. As expected, participants had more false alarms in the communicative (i.e., Bayesian ghosts) than individual condition in the sham TMS session and this difference between conditions vanished after real TMS. In contrast to our hypothesis, the number of false alarms increased (rather than decreased) after real TMS. These pre-registered findings confirm the significance of the premotor cortex for social action predictions and illusory social perception.

Measuring the prediction of observed actions using an occlusion paradigm: Comparing autistic and non-autistic adults

Action prediction involves observing and predicting the actions of others and plays an important role in social cognition and interacting with others. It is thought to use simulation, whereby the observers use their own motor system to predict the observed actions. As individuals diagnosed with autism are characterized by difficulties understanding the actions of others and motor coordination issues, it is possible that action prediction ability is altered in this population. This study compared action prediction ability between 20 autistic and 22 non-autistic adults using an occlusion paradigm. Participants watched different videos of a female actor carrying out everyday actions. During each video, the action was transiently occluded by a gray rectangle for 1000 ms. During occlusions, the video was allowed to continue as normal or was moved forward (i.e., appearing to continue too far ahead) or moved backwards (i.e., appearing to continue too far behind). Participants were asked to indicate after each occlusion whether the action continued with the correct timing or was too far ahead/behind. Autistic individuals were less accurate than non-autistic individuals, particularly when the video was too far behind. A trend analysis suggested that autistic participants were more likely to judge too far behind occlusions as being in time. These preliminary results suggest that prediction ability may be altered in autistic adults, potentially due to slower simulation or a delayed onset of these processes. LAY SUMMARY: When we observe other people performing everyday actions, we use their movements to help us understand and predict what they are doing. In this study, we found that autistic compared to non-autistic adults were slightly less accurate at predicting other people's actions. These findings help to unpick the different ways that social understanding is affected in autism.

Effects and safety of combined rTMS and action observation for recovery of function in the upper extremities in stroke patients: A randomized controlled trial

BACKGROUND

Repetitive transcranial magnetic stimulation (rTMS) modulates cortical excitability and facilitates motor learning to improve motor recovery after stroke. Action observation (AO) therapy effectively facilitates physical training for motor memory formation.

OBJECTIVE

To compare the effectiveness of rTMS alone with that of combined rTMS and AO for the functional recovery of upper extremity function in subacute stroke patients and to verify the safety of the interventions.

METHODS

The present study was a prospective, randomized controlled trial involving subacute unilateral stroke patients. In total, 22 patients were randomly assigned to 2 groups: the trial group (rTMS with AO) and the control group (rTMS alone). Both groups received 1 Hz rTMS (intensity: 120% of resting motor threshold; rMT) over the contralesional primary motor cortex for 20 minutes on 10 consecutive days. Trial group received rTMS while watching a video of 5 different complex hand movements. The functional parameters were the Brunnstrom stage, Fugl-Meyer assessment (FMA) score of the upper extremity, Manual Function Test (MFT) score, and grip power. The following motor evoked potential (MEP) parameters were recorded from the abductor pollicis brevis muscle: rMT, latency, and amplitude. Both parameters were measured before and after the 2 week intervention.

RESULTS

After the 2 week trial, the total FMA and MFT scores were significantly improved in both groups, but the MFT subscores of hand motor function and grip power were significantly improved in the combination therapy group only. In contrast, the changes (Δ) of FMA, MFT, grip power test, and MEP outcomes were not significantly different between the 2 groups. No adverse events or complications were reported.

CONCLUSIONS

Distal upper extremity function, as measured by MFT and grip power, was improved after rTMS and AO in combination. The combination of rTMS with AO may be applied safely to improve upper extremity function after stroke.