Many people in our community suffer from severe mental illness and neurological disorders. The personal suffering is great, and there is a huge cost in terms of the burden of care on families plus the overall loss of the individual’s contribution to society. The costbenefits of early diagnosis and intervention are well established at an economic, societal and individual level but hampering early intervention is the current lack of definitive, quantitative techniques for diagnosing or measuring many of the biological, brain changes in mental illnesses. Neither are there any objective, quantitative techniques to measure the efficacy of drugs applied to the majority of these conditions. We are working towards developing a new biomarker technique that can quantify biological change in mental illness by measuring signals from well established bi-direction neural pathways between emotional centres of the brain and the vestibular (balance) system. The purpose of this literature review is to provide a background to our new technique, Electrovestibulography, which measures signals from the vestibular system. Studies identifying links between the vestibular system and emotion processing systems supports our research aims, which are to explore biomarkers derived from the vestibular system that can help differentiate and monitor different neuropsychiatric disorders. Recent literature has examined the close links between the vestibular system and emotion processing systems, with some researchers suggesting a causal relationship. In particular, the co-occurrence of dizziness and anxiety has been well documented. Studies exploring the neurological bases of the links between the vestibular and emotion processing systems have confirmed that there a number of bi-direction neural pathways that connect brain regions involved in emotional processing, to the vestibular system. Certain neurotransmitter (brain chemicals) pathways, which are clearly involved in disorders such as schizophrenia, depression and Parkinson’s disease, have also been implicated as modulators of vestibular function.
The relevance of the vestibular system is apparent in a number of psychiatric and neurological disorders:
1. The co-existence of dizziness, panic and/or anxiety has been identified in medical literature throughout history and in more recent times. As previously stated, this is thought to reflect shared neural pathways that may be compromised in both balance disturbance/dizziness (i.e. the vestibular system) and anxiety/panic. 2. Parkinson’s disease (PD), a degenerative disorder of the central nervous system that impairs movement, is related to reductions in a particular neurotransmitter called dopamine. There is evidence for interactions between the dopamine and vestibular systems. Furthermore, abnormalities in the vestibular system have been previously documented in PD.
3. Schizophrenia is a serious and debilitating psychiatric disorder, with a lifetime risk of around 1%. No single symptom is definitive for a diagnosis of schizophrenia; rather, the diagnosis encompasses a pattern of signs and symptoms, in conjunction with impaired occupational or social functioning.
Vestibular system and neuropsychiatric conditions: Lay summary 3
Characteristic symptoms include psychotic manifestations, such as hearing internal voices or experiencing other sensations not connected to an obvious source (hallucinations) and assigning unusual significance or meaning to normal events or holding fixed false personal beliefs (delusions); a profound disruption in cognition (thinking and learning abilities), emotion and behaviour; and a diminution of normal functions (lack of emotion, reduced motivation). The cause of schizophrenia remains unclear but it is widely considered to stem from interactions between genetic and environmental factors. Abnormalities of multiple brain areas and neurotransmitter systems are documented. There are also documented abnormalities of vestibular...
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