Although both motor imagery (MI) and low-frequency sound listening have independently been shown to modulate brain activity, the potential synergistic effects that may arise from their combined application remains unexplored. Any further modulation derived from this combination may be relevant for motor learning and rehabilitation. We probed neurophysiological activity during these two processes, measuring alpha and beta band power amplitude by means of EEG recordings. Twenty healthy volunteers were instructed to (i) explicitly imagine right finger flexion/extension movements in a kinesthetic modality, (ii) listen to low-frequency sounds, (iii) imagine right finger movements while listening to low-frequency sounds, or (iv) stay at rest. We observed a bimodal distribution of alpha-band reactivity to the conditions, suggesting the presence of variability in brain activity across participants during both MI and low-frequency sound listening. One group of participants (12 individuals) displayed increased alpha power within contralateral sensorimotor and ipsilateral medial parieto-occipital regions during MI. Another group (eight individuals) exhibited a decrease in alpha and beta band power within sensorimotor areas. Interestingly, low-frequency sound listening elicited a similar pattern of brain activity within both groups. The combination of MI and sound listening did not result in additional changes in alpha and beta power amplitudes, regardless of group (groups based on individual alpha-band reactivity). Altogether, these findings shed significant insight into the brain activity and its variability generated during MI and low-frequency sound listening. The simultaneous engagement of MI and low-frequency sound listening did not further modulate alpha power amplitude, possibly due to concurrent cortical activation. It remains possible that sequential performance of these tasks could elicit additional modulation.

Action reading is thought to engage motor simulations, such as those involved during the generation of mental motor images. These simulations would yield modulations in activity of motor-related cortical regions and contribute to action language comprehension. To test these ideas, we measured corticospinal excitability during action reading, and reading comprehension ability, in individuals with normal and impaired imagery (i.e., phantasia and aphantasia, respectively). Thirty-four participants (17 phantasic and 17 aphantasic) were asked to read manual action sentences. By means of TMS, we triggered motor-evoked potentials in the target right index finger. Motor-evoked potential amplitude, a marker of corticospinal excitability, increased during action reading relative to rest for phantasic individuals, but not for aphantasic individuals. This result provides neurophysiological evidence that individuals living with aphantasia present a real neurophysiological deficit in motor system engagement during action reading. Furthermore, deep-level reading comprehension ability was impaired in individuals with aphantasia, who had difficulty selecting words that best fit the context of sentences. Altogether, these findings support the idea that motor simulations, along with the activation within the motor system, contribute to action language comprehension.