[Paper Review] Altering sensorimotor simulation impacts early stages of facial expression processing depending on individual differences in alexithymic traits

Arianna Schiano Lomoriello, Antonio Maffei+2 more|arXiv (Cornell University)|Jun 14, 2019

Face Recognition and Perception4 citations

TL;DR

This study investigates how sensorimotor simulation—specifically facial mimicry—affects early neural processing of facial expressions, revealing that individual differences in alexithymic traits modulate this influence. Using event-related potentials (ERP), it shows that low-alexithymia individuals exhibit P1 amplitude modulation under mimicry interference, while high-alexithymia individuals show N170 modulation, suggesting compensatory visual processing and differential sensorimotor-visual connectivity.

ABSTRACT

Simulation models of facial expressions suggest that posterior visual areas and brain areas underpinning sensorimotor simulations might interact to improve facial expression processing. According to these models, facial mimicry may contribute to the visual processing of facial expressions by influencing early stages. The aim of the present study was to assess whether/how early sensorimotor simulation influences early stages of face processing. A secondary aim was to investigate the relationship between alexithymic traits and sensorimotor simulation. We monitored P1 and N170 components of the event-related potentials (ERP) in participants performing a fine discrimination task of facial expressions while implementing an animal discrimination task as control condition. In half of the experiment, participants could freely use their facial mimicry whereas in the other half, they had their facial mimicry blocked by a gel. Our results revealed that, on average, both P1 and N170 ERP components were not sensitive to mimicry manipulation. However, when taking into account alexithymic traits, a scenario corroborating sensorimotor simulation models emerged, with two dissociable temporal windows affected by mimicry manipulation as a function of alexithymia levels. Specifically, as a function of mimicry manipulation, individuals with lower alexithymic traits showed modulations of the P1 amplitude, while individuals with higher alexithymic traits showed modulations of the later N170). Furthermore, connectivity analysis at the scalp level suggested increased connectivity between sensorimotor and extrastriate visual regions in individuals with lower alexithymic traits compared to individuals with higher alexithymic traits. Overall, we interpreted these ERPs modulations as compensative visual processing under conditions of interference on the sensorimotor processing.

Motivation & Objective

• To examine whether sensorimotor simulation, particularly facial mimicry, influences early stages of facial expression processing.
• To investigate how individual differences in alexithymic traits affect the interaction between sensorimotor and visual processing during facial expression perception.
• To determine whether mimicry interference alters ERP components (P1 and N170) in a manner dependent on alexithymia levels.
• To explore the neural connectivity patterns between sensorimotor and visual regions as a function of alexithymic traits.

Proposed method

• Event-related potentials (ERP) were recorded during a fine facial expression discrimination task.
• Participants performed the task under two conditions: free facial mimicry and mimicry blocked via a gel.
• The P1 and N170 ERP components were analyzed to assess early visual and structural face processing stages.
• Alexithymic traits were measured using standardized self-report assessments to categorize participants into high and low alexithymia groups.
• Scalp-level functional connectivity was computed between sensorimotor and extrastriate visual regions to examine neural network interactions.
• A control condition involving animal discrimination was used to isolate effects specific to facial expression processing.

Experimental results

Research questions

• RQ1 Does altering sensorimotor simulation through facial mimicry blockade affect early ERP components (P1 and N170) during facial expression processing?
• RQ2 How do individual differences in alexithymic traits modulate the impact of sensorimotor simulation on early face processing stages?
• RQ3 Is there a differential pattern of neural connectivity between sensorimotor and visual regions based on alexithymia levels during facial expression perception?
• RQ4 Do individuals with high alexithymia rely more on visual processing as a compensatory mechanism when sensorimotor simulation is disrupted?

Key findings

• Participants with low alexithymic traits showed significant modulation of the P1 amplitude when facial mimicry was blocked, indicating early visual processing sensitivity to sensorimotor interference.
• Individuals with high alexithymic traits exhibited significant modulation of the N170 component under mimicry blockade, suggesting later structural face processing is affected.
• Scalp-level connectivity analysis revealed stronger functional connectivity between sensorimotor and extrastriate visual regions in low-alexithymia individuals compared to high-alexithymia individuals.
• The overall ERP patterns suggest compensatory visual processing in high-alexithymia individuals when sensorimotor simulation is disrupted.
• The absence of group-averaged ERP effects indicates that the influence of mimicry is masked when data are collapsed across alexithymia levels.
• The dissociable temporal windows (P1 vs. N170) affected by mimicry manipulation highlight a trait-dependent neural mechanism underlying facial expression processing.