Do different relationships among stimuli matter?
Written by Doc Irish | Aug. 26, 2026
One of the strangest things about living with Parkinson’s disease is how inconsistent it can be.
A movement that feels nearly impossible one moment can sometimes become easier a few seconds later. A person may struggle to initiate a step but then walk fluidly once they get going. A line on the floor, a rhythmic sound, a change in attention, or some other external cue can occasionally alter what the body seems capable of doing.
I keep coming back to the same question: If the machinery is completely broken, why can changing the context sometimes change the performance?
I don’t think that question has a simple answer. Parkinson’s is enormously complex, and dopamine, the basal ganglia, motor circuits, sensory processing, cognition, and many other systems are involved. I’m certainly not proposing that all of Parkinson’s can be reduced to one explanation.
But I increasingly wonder whether coordination deserves more attention as part of the picture.
We usually think about disease by asking which individual part is malfunctioning. Which molecule? Which neuron? Which brain region? Which pathway?
Those are essential questions. But there is another kind of failure that can occur even when individual parts retain some ability to function: the parts may stop working together properly.
Think about an orchestra. Every musician might still be capable of playing. But if their timing, sequencing, volume, or responsiveness to one another begins to drift, the music falls apart.
Nothing necessarily has to disappear. The relationships can fail.
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