Abstract
Tics can be associated with neurological disorders and are thought to be the result of dysfunctional basal ganglia pathways. In Tourette Syndrome (TS), excess dopamine in the striatum is thought to excite the thalamo-cortical circuits, producing tics. When external stressors activate the hypothalamic-pituitary-adrenal (HPA) axis, more dopamine is produced, furthering the excitation of tic-producing pathways. Emotional processing structures in the limbic are also activated during tics, providing further evidence of a possible emotional component in motor ticking behaviors. The purpose of this review is to better understand the relationship between emotional states and ticking behavior. We found support for the notion that premonitory sensory phenomena (PSP), sensory stimulation, and other environmental stressors that impact the HPA axis can influence tics through dopaminergic neurotransmission. Dopamine plays a vital role in cognition and motor control and is an important neurotransmitter in the pathophysiology of other disorders such as obsessive–compulsive disorder (OCD) and attention deficit hyperactivity disorder (ADHD), which tend to be comorbid with ticking disorders and are thought to use similar pathways. It is concluded that there is an emotional component to ticking behaviors. Emotions primarily involving anxiety, tension, stress, and frustration have been associated with exacerbated tics, with PSP contributing to these feelings.
Highlights
Tics are phenomena or symptoms associated with dysfunction in the pathways of the basal ganglia, which are largely of childhood onset
While HPA axis activation can exacerbate tics due to their origin in the abnormalities of the basal ganglia, these abnormalities may contribute to ticking behaviors in neurological disorders such as Sydenham’s chorea (SC) and in the controversial pediatric autoimmune neuropsychiatric disorder associated with streptococcus (PANDAS)
Because the limbic system and its structures are involved in emotional processing, it is thought that external stressors can exacerbate abnormalities along this pathway, influencing tic output
Summary
Tics are phenomena or symptoms associated with dysfunction in the pathways of the basal ganglia, which are largely of childhood onset. Hypothalamic-pituitary-adrenal (HPA) axis, and other aspects associated with emotions play into this network, it is thought that emotions can influence ticking behaviors. In addition to an increase in cytokines being associated with an overactive immune response, it is thought that streptococcal infections and autoantibodies can play a role in the immune system of individuals with tic disorders. Neuronal activity was recorded in the basal ganglia, cerebellum, and primary motor cortex (M1) in order to further investigate the relationship between the structures. Following the disinhibition of the NAc, it was found that cerebral blood flow bilaterally increased in the ACC, amygdala, and hippocampus, indicating that these structures are involved in which processes emotions, projects to the striatum, which allows these signals to affect motor behavior [39,40]. It is possible that the limbic system can affect emotional responses, in turn being related in some cases to ticking behaviors based on the neural pathways involved
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