Adopting an external focus of attention alters intracortical inhibition within the primary motor cortex

Abstract

AimAlthough it is well established that an external (EF) compared to an internal (IF) or neutral focus of attention enhances motor performance, little is known about the underlying neural mechanisms. This study aimed to clarify whether the focus of attention influences not only motor performance but also activity of the primary motor cortex (M1) when executing identical fatiguing tasks of the right index finger (first dorsal interosseous). Transcranial magnetic stimulation (TMS) at intensities below motor threshold was applied over M1 to assess and compare the excitability of intracortical inhibitory circuits.MethodsIn session 1, 14 subjects performed an isometric finger abduction at 30% of their maximal force to measure the time to task failure (TTF) with either an IF or EF. In session 2, the same task was performed with the other focus. In sessions 3 and 4, subthreshold TMS (subTMS) and paired‐pulse TMS were applied to the contralateral M1 to compare the activity of cortical inhibitory circuits within M1 during EF and IF.ResultsWith an EF, TTF was significantly prolonged (P = 0.01), subTMS‐induced electromyographical suppression enhanced (P = 0.001) and short‐interval intracortical inhibition (SICI) increased (P = 0.004).ConclusionThe level of intracortical inhibition was previously shown to influence motor performance. Our data shed new light on the ability to instantly modulate the activity of inhibitory circuits within M1 by changing the type of attentional focus. The increased inhibition with EF might contribute to the better movement efficiency, which is generally associated with focusing externally.

Individual optimal attentional strategy during implicit motor learning boosts frontoparietal neural processing efficiency: A functional near‐infrared spectroscopy study

“…Previous studies have implicated activities of motor-related areas in focus of attention (Kuhn et al, 2016;Zentgraf et al, 2009;Zimmermann et al, 2012), while our current findings indicate that the right frontoparietal network also has an important function in determining the attentional strategy most suitable for individuals during a motor learning task. The prefrontal cortex (including the frontal eye field) and the parietal cortex are strongly interconnected by fibers passing through the superior longitudinal fasciculus (Makris et al, 2005), and the frontoparietal network does contribute to attention control (Corbetta & Shulman, 2002;Dosenbach et al, 2008;Kehrer et al, 2015).…”

“…In one functional magnetic resonance imaging (fMRI) study, primary somatosensory and motor cortices exhibited greater activation under the EF condition than the IF condition during learning of a finger movement sequence (Zentgraf et al, 2009). A more recent study investigated the effect of focus of attention on the activity of the primary motor cortex by transcranial magnetic stimulation (TMS) (Kuhn, Keller, Ruffieux, & Taube, 2016). Another study demonstrated that the switch of attentional focus during a finger movement task induced neural activations in the left lateral premotor cortex, left primary somatosensory cortex, and intraparietal lobule (Zimmermann et al, 2012).…”

Focus of attention changes intracortical excitability in the primary motor cortex

“…The new findings reported by Kuhn et al . () demonstrate that we can now add the manipulation of the focus of attention to the list of neuromodulatory techniques with the potential to boost motor functions.…”

“…Although Kuhn et al . 's () results are promising, one should be cautious to conclude that attention‐induced neural plasticity underlies the beneficial effects of EF on motor learning reported in previous studies (for a review, see Wulf & Prinz ). Motor learning is a complex phenomenon and performance in different contexts and tasks may rely on different brain areas and mechanisms other than motor cortex intracortical plasticity.…”

“…Using a repeated measures design, Kuhn et al . () investigated the effects of attentional foci on SICI and electromyography (EMG) suppression. In two sessions, participants were asked to either adopt an internal focus of attention (IF) – concentrating on the muscle and finger – or external focus (EF) – concentrating on the goniometer angle.…”