Abstract
Several lines of evidence point to a pervasive disturbance of energy balance in Parkinson's disease (PD). Weight loss, common and multifactorial, is the most observable sign of this. Bradykinesia may be best understood as an underinvestment of energy in voluntary movement. This accords with rodent experiments that emphasise the importance of dopamine in allocating motor energy expenditure. Oxygen consumption studies in PD suggest that, when activities are standardised for work performed, these inappropriate energy thrift settings are actually wasteful. That the dopaminergic deficit of PD creates a problem with energy efficiency highlights the role played by the basal ganglia, and by dopamine, in thermodynamic governance. This involves more than balancing energy, since living things maintain their internal order by controlling transformations of energy, resisting probabilistic trends to more random states. This review will also look at recent research in PD on the analysis of entropy—an information theory metric of predictability in a message—in recordings from the basal ganglia. Close relationships between energy and information converge around the concept of entropy. This is especially relevant to the motor system, which regulates energy exchange with the outside world through its flow of information. The malignant syndrome in PD, a counterpart of neuroleptic malignant syndrome, demonstrates how much thermodynamic disruption can result from breakdown of motor signalling in an extreme hypodopaminergic state. The macroenergetic disturbances of PD are consistent with a unifying hypothesis of dopamine's neurotransmitter actions—to adapt energy expenditure to prevailing economic circumstances.
Highlights
The prevalence of weight loss as a symptom suggests that many patients deviate from normal energy balance as Parkinson’s disease (PD) progresses [1]
That the dopaminergic deficit of PD creates a problem with energy efficiency highlights the role played by the basal ganglia, and by dopamine, in thermodynamic governance
PD predisposes to negative energy balance across its course
Summary
The prevalence of weight loss as a symptom suggests that many patients deviate from normal energy balance as Parkinson’s disease (PD) progresses [1]. Many patients with advanced disease have low body weight and depleted fat stores. Thermodynamics is the study of energy in transformation. Organisms achieve internal order through interactions with their environments. These are the iron laws of the physical world and even conditional suspensions turn out to be temporary. While living systems are complex, they don’t directly monitor or control their complexity. In addition to changes in energy balance, we will be looking at the role of signalling within the motor system. Energy and information have a deep relationship, which converges around the concept of entropy [2]
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have