Attentional focus differentially modulates the corticospinal and intracortical excitability during dynamic and static exercise.

Although attentional focus affects motor performance, whether corticospinal excitability and intracortical modulations differ between focus strategies depending on the exercise patterns remains unclear. In the present study, using single- and paired-pulse transcranial magnetic stimulation and peripheral nerve stimulation, we demonstrated changes in the cortical and spinal excitability under external focus (EF) and internal focus (IF) conditions with dynamic or static exercise. Participants performed the ramp-and-hold contraction task of right index finger abduction against an object (sponge or wood) with both exercises. They were asked to concentrate on the pressure on the sponge/wood induced by finger abduction under the EF condition, and on the index finger itself under the IF condition. Motor-evoked potential (MEP) and F-wave in the premotor, phasic, or tonic phase, and short- and long-interval intracortical inhibition (SICI and LICI, respectively), and intracortical facilitation (ICF) in the premotor phase were examined by recording surface electromyographic activity in the right first dorsal interosseous muscle. Increments in the MEP amplitude were larger under the EF condition than under the IF condition in the dynamic, but not static, exercise. The F-wave, SICI, and LICI did not differ between focus conditions in both exercises. In the dynamic exercise, interestingly, ICF was greater under the EF condition than under the IF condition and positively correlated with the MEP amplitude. These results indicate that corticospinal excitability and intracortical modulations to attentional focus differ depending on exercise patterns, suggesting that attentional focus differentially affects the central nervous system responsible for diverse motor behaviors.NEW & NOTEWORTHY We investigated attentional focus-dependent corticospinal and intracortical modulations in dynamic or static exercise. The corticospinal excitability was modulated differentially depending on the focus of attention during dynamic, but not static exercise. Although the reduction of intracortical GABAergic inhibition was comparable between focus conditions in both exercises, intracortical facilitation was smaller when focusing on the internal environments in the dynamic exercise, resulting in lower activation of the corticospinal tract.

Lack of action-sentence compatibility effect in non-clinical individuals with high autistic traits.

Introduction: Patients with autism spectrum disorder (ASD) exhibit atypical responses to language use and comprehension. Recently, various degrees of primary autistic symptoms have been reported in the general population. We focused on autistic traits and examined the differences in mechanisms related to language comprehension using the action-sentence compatibility effect (ACE). ACE is a phenomenon in which response is facilitated when the action matches the behavior described in the statement. Methods: In total, 70 non-clinical individuals were divided into low autistic and high autistic groups according to their autism spectrum quotient (AQ) scores. ACEs with adverbs and onomatopoeias were examined using a stimulus set of movement-related sentences. A choice-response task helped determine the correct sentence using antonym adverbs (slow and fast) and onomatopoeia (quick and satto) related to the speed of the movement. Results: The low-AQ group showed ACEs that modulated the reaction time in antonym sentences. The high-AQ group showed less temporal modulation, and their overall reaction time was shorter. The low-AQ group showed faster reaction times for onomatopoeic words; however, the high-AQ group showed a tendency to reverse this trend. In individuals with intermediate autistic traits, the angle effect may be moderated by individual differences in motor skills and experience rather than autistic traits. The stimulus presentation involved a passive paradigm. Discussion: This study provides insight into language comprehension processes in non-clinical individuals ranging from low to high autistic idiosyncrasy and elucidates language and behavior in individuals at different locations on the autistic trait continuum.