Modulatory Effects of Modafinil on Neural Circuits Regulating Emotion and Cognition

While modafinil is widely recognized as a cognitive enhancer, its impact on the brain's emotional circuitry remains poorly understood. Unlike traditional psychostimulants like amphetamine, which are known to enhance cognitive performance but often induce anxiety and increase amygdala reactivity, the researchers sought to determine if modafinil offers a more favorable profile by simultaneously improving cognitive efficiency and reducing emotional reactivity.

In a double-blind, placebo-controlled, crossover study, 38 healthy volunteers were administered either 100 mg of modafinil or a placebo daily for seven days. Participants underwent functional MRI (fMRI) while performing three distinct tasks: a face-matching task (to assess amygdala reactivity to fearful and angry stimuli), a 2-back working memory task, and a variable attentional control (VAC) task. The researchers also monitored clinical markers, including blood pressure, heart rate, and standardized mood and anxiety questionnaires.

• Reduced Amygdala Reactivity: Modafinil significantly decreased amygdala activation in response to threatening facial expressions compared to the placebo condition. This was accompanied by increased negative functional coupling between the amygdala and the supragenual anterior cingulate cortex, suggesting enhanced top-down regulation of emotional responses.
• Increased Cognitive Efficiency: During both the working memory and attentional control tasks, modafinil reduced BOLD signal in the prefrontal cortex and anterior cingulate. Because task performance remained consistent between drug and placebo conditions, this reduction in brain activity indicates that the brain processed information more efficiently under the influence of modafinil.
• Clinical Profile: While the drug did not significantly alter blood pressure or heart rate, participants showed trends toward reduced anxiety and fatigue, along with increased vigor, suggesting a potentially unique neuropharmacological profile compared to traditional stimulants.