Background: The dorsolateral prefrontal cortex (DLPFC) in both hemispheres have a central integrative function for motor control and behavior. Understanding the hemispheric difference between DLPFC and ipsilateral motor cortex connection in the resting-state will provide fundamental knowledge to explain the different roles DLPFC plays in motor behavior. Purpose: The current study tested the interactions between the ipsilateral DLPFC and the primary motor cortex (M1) in each hemisphere at rest. We hypothesized that left DLPFC has a greater inhibitory effect on the ipsilateral M1 compared to the right DLPFC. Methods: Fourteen right-handed subjects were tested in a dual-coil paired-pulse paradigm using transcranial magnetic stimulation. The conditioning stimulus (CS) was applied to the DLPFC and the test stimulus (TS) was applied to M1. Interstimulus intervals (ISIs) between CS and TS were 2, 4, 6, 8, 10, 15, 20, 25, and 30 ms. The result was expressed as a percentage of the mean peak-to-peak amplitude of the unconditioned test pulse. Results: There was stronger inhibitory effect for the left compared to the right hemisphere at ISIs of 2 (p = 0.045), 10 (p = 0.006), 15 (p = 0.029) and 20 (p = 0.024) ms. There was no significant inhibition or facilitation at any ISI in the right hemisphere. Conclusions: The two hemispheres have distinct DLPFC and M1 cortico-cortical connectivity at rest. Left hemisphere DLPFC is dominant in inhibiting ipsilateral M1.

Human cognition is often biased (Fiske & Taylor, 1991). Cognitive bias may lead to effective action in a given context, enabling individuals to make faster decisions and solve problems more practically (Haselton & Nettle, 2006). It is a fundamental question in psychology how cognitive bias is created and modulated in the human brain. Automatic action tendency is a typical cognitive bias and plays a crucial role in human behavior (Stacy & Wiers, 2010;Van Dessel et al., 2020). An approaching bias refers to the tendency that an individual approaches a certain type of stimuli automatically, whereas the opposite automatic tendency is referred to as an avoiding bias (Leung et al.

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Background Motor imagery (MI) improves motor skill learning, which is further enhanced when MI is paired with primary motor cortex transcranial brain stimulation or with electrical stimulation of the peripheral median nerve. Applying both stimulation types (here with 25 ms intervals) is called paired associative stimulation (PAS25). The final primary motor cortex output is determined by combined excitatory and intracortical inhibitory circuits, and reducing the latter is associated with enhanced synaptic transmission and efficacy. Indeed, short‐interval intracortical inhibition (SICI) inhibits motor evoked potentials (MEPs), and motor learning has been associated with decreased SICI and increased cortical excitability. Here, we investigated whether cortical excitability and SICI are altered by PAS25 applied after MI‐induced modulation of motor learning. Methods Peak acceleration of a hand‐grasping movement and MEPs and SICI were measured before and after MI alone, PAS25 alone, and MI followed by PAS25 in 16 healthy participants to evaluate changes in motor learning, corticospinal excitability, and intracortical inhibition. Results After PAS25 alone, MEP amplitude increased while peak acceleration was unchanged. However, PAS25 applied following MI not only significantly enhanced both peak acceleration (p = 0.011) and MEP amplitude (p = 0.004) but also decreased SICI (p = 0.011). Moreover, we found that this decrease in SICI was significantly correlated with both the peak acceleration (r = 0.49, p = 0.029) and the MEP amplitude (r = 0.56, p = 0.013). Conclusions These results indicate that brain function altered by PAS25 of the motor cortex enhances MI‐induced motor learning and corticospinal excitability and decreases SICI, suggesting that SICI underlies, at least in part, PAS25 modulation of motor learning.