Activating Locus Ceruleus–Motor Cortex Circuit during Task Performance Strengthens Cortical Output
Ching-Tzu Tseng, Hailey F. Welch, Ashley L. Gi, Erica Mina Kang, Tanushree Mamidi et al.
(see article e1528232023)
The neocortex drives arousal states, attention, behavioral flexibility, and memory and impacts sensory processing and perception. Its output is modulated by noradrenaline release from the locus ceruleus (LC). When artificially stimulating the LC in parallel to an experience that activates one of the five senses, neocortical representations of that experience are strengthened, and perceptual learning is improved. In this issue, Tseng and colleagues investigated whether this effect also occurs in motor cortical regions, which underlie movement planning and action execution. They trained male and female rats in a lever pressing task that engages the motor cortex. Once trained, rats received an additional five sessions in which correct task performance was paired with artificial activation of noradrenergic LC neurons. This activation, driven by blue light, occurred at three different frequencies. The researchers found that lever pressing paired with LC stimulation at 10 Hz, but not 3 or 30 Hz, increased task-relevant motor map representations, thus demonstrating that training-paired activation of the LC drives neuroplasticity in the motor cortex in a manner dependent on the rate of LC activation. These findings posit the noradrenergic system as a potential target for patients with motor deficits and may thus be informative for future work exploring novel motor deficit treatment strategies.
Network Connectivity Changes Following Long-Term Cocaine Use and Abstinence
Li-Ming Hsu, Domenic H. Cerri, Sung-Ho Lee, Tatiana A. Shnitko, Regina M. Carelli, Yen-Yu Ian Shih
(see article e1452232023)
Quitting cocaine is difficult after long-term use because irresistible urges to seek it, driven at least in part by strong cravings, contribute to relapse. Research has revealed that abstinence following long-term cocaine use alters neurotransmitter signaling and synaptic strength within and between several important brain networks, including the default mode network (DMN), the salience network (SN), and the central executive network (CEN). But because you cannot predict if a person is going to become addicted to cocaine, what is missing from these investigations is a comparison to the strength of connectivity between these networks prior to cocaine use. Hsu et al. addressed this experimental question in male rats. They used fMRI to image their brains before cocaine self-administration (baseline) and on days 1 and 30 of forced abstinence following 10 d of cocaine. Connectivity between networks was significantly changed, with the most robust change observed between the DMN and SN on day 1 of abstinence as compared to baseline. Escalation of cocaine intake during the 10 days of self-administration was associated with stronger SN–DMN and SN–CEN connectivity changes between days 1 and 30 of abstinence. While sex differences are still unexplored, the robust changes in connectivity between the SN and DMN suggest that targeting this circuit may weaken cocaine cravings in those abstaining from use.
Data from network-based statistics analyses are depicted. Red squares indicate significantly altered connectivity between networks in the cocaine group (left) among the three conditions (baseline and 1 and 30 days of abstinence). The water control group (right) had no changes.
Footnotes
This Week in The Journal was written by Paige McKeon
