A new study published in the journal Clinical Interventions in Aging has revealed the correlation between functional connectivity and anxiety improvement in patients with Parkinson’s disease (PD) who underwent subthalamic nucleus deep brain stimulation (STN-DBS). The study found that two functional connectivity networks in the brain were significantly associated with the rate of anxiety improvement after the surgery.
What is STN-DBS and how does it help PD patients?
STN-DBS is a surgical procedure that involves implanting electrodes in a brain region called the subthalamic nucleus (STN), which is involved in motor control and movement. The electrodes are connected to a battery-powered device that delivers electrical impulses to the STN, modulating its activity and reducing the symptoms of PD, such as tremors, rigidity, and bradykinesia.
STN-DBS has also been shown to improve some non-motor symptoms of PD, such as mood disorders, cognitive impairments, and sleep problems. Anxiety is one of the most common and disturbing non-motor symptoms of PD, affecting up to 40% of patients. However, few studies have explored the relationship between functional connectivity and the rate of anxiety improvement after STN-DBS.
What is functional connectivity and how does it relate to anxiety?
Functional connectivity (FC) is a measure of how different brain regions communicate with each other during resting-state functional magnetic resonance imaging (rs-fMRI), which captures brain activity when a person is not performing any specific task. FC reflects the strength and pattern of synchronization between brain regions, which may indicate their functional integration and coordination.
Anxiety is a complex emotion that involves multiple brain regions, such as the amygdala, the prefrontal cortex, the insula, and the hippocampus. Previous studies have suggested that abnormal FC between these regions may contribute to the development and maintenance of anxiety disorders. Therefore, investigating how STN-DBS affects FC in these regions may provide insights into how it alleviates anxiety in PD patients.
What did the study find?
The study involved 62 patients with anxious PD (aPD), 68 patients with PD without anxiety (naPD), and 64 healthy controls (HCs). The researchers analyzed their rs-fMRI data before and after STN-DBS using a multi-scale factor analysis (MSFA) model, which partitions the brain into regional clusters and extracts latent factors that represent the signals within each cluster. The correlation matrix for all nodes in the network can be approximated by lower-dimensional sub-structures derived from the cluster-specific factors.
The researchers found that there were 24 significant differences in FCs between the three groups. Among them, 15 significantly different FCs were observed between the naPD and aPD groups. In addition, two FCs in patients with aPD were significantly correlated with the rate of improvement in anxiety. These two FCs were:
- Olfactory cortex and inferior frontal gyrus (IFG) pars orbitalis
- Inferior temporal gyrus and posterior orbital gyrus
The olfactory cortex is involved in processing smell information and emotional responses. The IFG pars orbitalis is part of the ventral prefrontal cortex, which is implicated in emotion regulation and decision making. The inferior temporal gyrus is involved in visual recognition and memory. The posterior orbital gyrus is part of the orbitofrontal cortex, which is involved in reward processing and social behavior.
The researchers speculated that these two FCs may reflect the emotional and cognitive aspects of anxiety, respectively. They suggested that STN-DBS may modulate these FCs by influencing the activity of the STN and its connections with other brain regions, such as the basal ganglia, the thalamus, and the cortex.
What are the implications of the study?
The study provides novel evidence for the correlation between FC and anxiety improvement after STN-DBS in PD patients. It also identifies two potential biomarkers for predicting and evaluating the outcome of STN-DBS on anxiety. The study may help us understand the underlying mechanisms by which STN-DBS improves anxiety in PD patients and identify more effective treatment strategies.
However, the study also has some limitations, such as:
- The sample size was relatively small and may not represent the general population of PD patients.
- The study did not control for other factors that may affect FC and anxiety, such as medication use, depression, personality traits, and cognitive function.
- The study did not explore the causal relationship between FC and anxiety improvement, which may require longitudinal or interventional studies.
Therefore, more research is needed to validate and extend the findings of this study.