The Frontal Cortex and rTMS
The human frontal cortex, particularly the dorsolateral prefrontal cortex (DLPFC), plays a vital role in regulating thought, emotion, and behavior. It supports complex processes such as decision-making, attention, emotional control, and working memory. Recent neuroscience research has shown that functional differences exist between the left and right hemispheres of the prefrontal cortex, and that stimulating these regions can change brain activity in meaningful ways (White, 2022). One of the most advanced techniques for achieving this modulation is repetitive transcranial magnetic stimulation (rTMS), a non-invasive therapy that uses magnetic fields to influence neural activity.
This article introduces the major functions of the left and right prefrontal cortices and explains how rTMS acts on these two areas. The goal is to help readers understand why targeting specific sides of the DLPFC can produce different effects on cognition, emotion, and even clinical symptoms.
1. Functions of the Left Dorsolateral Prefrontal Cortex
The left DLPFC is strongly associated with logical reasoning, language, and goal-directed thought. Studies using neuroimaging and brain stimulation have found that this region supports working memory, particularly for verbal and symbolic information (Barbey, Koenigs, & Grafman, 2012). In simple terms, it helps people plan actions, focus attention, and hold several ideas in mind while making decisions.
Physiological studies also show that the left DLPFC exerts top-down control over other brain regions, such as the motor cortex and emotional centers, allowing individuals to suppress distractions and regulate their responses (Wang, Cao, Lin, Chen, & Zhang, 2020). This explains why reduced activity in the left DLPFC has been observed in conditions like depression, where cognitive control and positive emotion are weakened.
High-frequency rTMS, which increases excitability in this region, has been widely used to enhance mood and cognitive performance. Clinical meta-analyses demonstrate that stimulating the left DLPFC with rTMS can significantly alleviate depressive symptoms and chronic pain (Zhu et al., 2022; Zhou et al., 2024). The improvement is likely due to increased neural connectivity between the prefrontal cortex and deeper emotion-related structures such as the limbic system.
2. Functions of the Right Dorsolateral Prefrontal Cortex
While the left DLPFC focuses on analytical and linguistic processes, the right DLPFC is more involved in emotional regulation, spatial attention, and social behavior. Neuropsychological studies show that this hemisphere contributes to recognizing emotional cues and managing stress responses (White, 2022).
Unlike the left side, which tends to activate during approach and goal-oriented behavior, the right DLPFC is linked to inhibitory control—the ability to pause or re-evaluate actions. This balance between both hemispheres allows the brain to maintain emotional stability and cognitive flexibility.
Brain imaging data suggest that the right DLPFC connects strongly with the thalamus, striatum, and default mode network, which are involved in emotion processing and self-referential thought (Caparelli et al., 2022). These connections explain why low-frequency rTMS (which reduces neural activity) on the right DLPFC can be used to calm hyperactive emotional circuits, such as in anxiety or post-traumatic stress disorder (PTSD).
3. rTMS Effects on the Left and Right Prefrontal Cortex
rTMS influences brain function by generating short magnetic pulses that create small electrical currents in targeted cortical areas. Depending on the stimulation frequency, rTMS can either increase or decrease brain excitability:
High-frequency (≥10 Hz) stimulation generally enhances activity.
Low-frequency (≤1 Hz) stimulation tends to reduce activity.
When applied to the left DLPFC, high-frequency rTMS increases synaptic activity and promotes greater neural communication within the prefrontal-limbic network. This leads to improved mood regulation and executive function (Zhu et al., 2022). It has been particularly effective in treating major depressive disorder (MDD), where the left side is often underactive.
Conversely, applying low-frequency rTMS to the right DLPFC helps reduce excessive arousal or anxiety by dampening overactivity in circuits linked to fear and negative emotions (Caparelli et al., 2022). The hemispheric difference in stimulation strategy—enhancing the left, calming the right—reflects the brain’s natural balance between approach and avoidance systems (White, 2022).
Furthermore, physiological research demonstrates that both hemispheres interact dynamically: stimulating one side can indirectly affect the other due to interhemispheric inhibition (Wang et al., 2020). This means that modulating one region’s excitability can restore functional symmetry in cases of mental or neurological imbalance.
4. Clinical and Cognitive Implications
Because the DLPFC is deeply involved in both emotion and cognition, rTMS has found applications beyond depression. It is being explored for treating chronic pain, addiction, anxiety disorders, and cognitive decline. According to Zhou et al. (2024), prefrontal rTMS improves pain perception not only by modulating local cortical activity but also by influencing descending pain control pathways.
In addition, cognitive neuroscience studies suggest that enhancing left DLPFC activity can improve working memory, attention, and decision-making—functions essential to daily life and mental performance (Barbey et al., 2012). On the other hand, right DLPFC stimulation has shown potential in reducing impulsivity and improving emotional regulation, which could benefit individuals with stress-related conditions (White, 2022).
These findings collectively show that rTMS is not merely a treatment for psychiatric disorders, but a precision neuromodulation tool capable of fine-tuning the brain’s balance between thought and emotion.
Conclusion
The left and right dorsolateral prefrontal cortices perform complementary functions that together maintain cognitive efficiency and emotional balance. The left side primarily supports reasoning, language, and goal-directed behavior, while the right side governs emotional restraint and stress control. rTMS acts as a powerful method to restore equilibrium between these two systems—stimulating the left DLPFC to elevate mood and motivation, and calming the right DLPFC to reduce anxiety and overactivity.
As evidence accumulates from neuroimaging and clinical research, rTMS continues to demonstrate its value not only as a therapy but as a scientific tool for understanding how the human brain organizes thought, feeling, and behavior.
References
Barbey AK, Koenigs M, Grafman J. Dorsolateral prefrontal contributions to human working memory. Cortex. 2013 May;49(5):1195-205. doi: 10.1016/j.cortex.2012.05.022. Epub 2012 Jun 16. PMID: 22789779; PMCID: PMC3495093.
Caparelli, E. C., Abulseoud, O. A., Gu, H., Zhai, T., Schleyer, B., & Yang, Y. (2022). Low frequency repetitive transcranial magnetic stimulation to the right dorsolateral prefrontal cortex engages thalamus, striatum, and the default mode network. Frontiers in Neuroscience, 16, 997259. https://doi.org/10.3389/fnins.2022.997259
Wang, Y., Cao, N., Lin, Y., Chen, R., & Zhang, J. (2020). Hemispheric differences in functional interactions between the dorsal lateral prefrontal cortex and ipsilateral motor cortex. Frontiers in Human Neuroscience, 14, 202. https://doi.org/10.3389/fnhum.2020.00202
White LK, Makhoul W, Teferi M, Sheline YI, Balderston NL. The role of dlPFC laterality in the expression and regulation of anxiety. Neuropharmacology. 2023 Feb 15;224:109355. doi: 10.1016/j.neuropharm.2022.109355. Epub 2022 Nov 26. PMID: 36442650; PMCID: PMC9790039.
Zhou, J., Wang, Y., Luo, X., et al. (2024). Revisiting the effects of rTMS over the dorsolateral prefrontal cortex on pain: An updated systematic review and meta-analysis. Brain Stimulation. https://pubmed.ncbi.nlm.nih.gov/39089648/
Zhu, Y., et al. (2022). Systematic review and meta-analysis of high-frequency rTMS on the DLPFC for chronic pain and depression. ACS Chemical Neuroscience, 13(5), 651–664. https://doi.org/10.1021/acschemneuro.2c00395
