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Apathy comes in four kinds
Behavioral apathy was the first form measured: whether someone is inert or active. Social apathy shows up in colleagues who are driven at work and want nothing to do with a party. Emotional apathy shows up in blunted responses to news that would make most people congratulate someone or feel sad. Some researchers also argue for cognitive apathy, where a person who can't be bothered to do anything physical stays curious about the world and reads the newspaper.
The domains can separate, so someone can be socially apathetic and cognitively very highly motivated. That fits how motivation signals are built. Signals for behavior, thought, social life, and emotion are formed in different parts of the brain, then funnel through the basal ganglia to the action systems of the frontal lobe, a final common pathway.
Why can apathy split into separate kinds?
In 2006, Richard Levy and Bruno Dubois proposed in Cerebral Cortex that apathy has three forms tied to different loops through the basal ganglia. Damage to the loop through the orbital and medial prefrontal cortex produces emotional-affective apathy. Damage through the dorsolateral prefrontal cortex produces cognitive apathy, and damage through the anterior cingulate and medial areas produces a loss of self-initiated action.
What does a final common pathway mean?
Charles Sherrington used the term final common path in 1906 for motor neurons, because many different inputs converge on the same neurons that command a muscle. The apathy idea borrows the same logic higher up. Many kinds of signals meet in the basal ganglia before reaching the frontal action systems, so damage at that point can affect several domains at once.
How do researchers measure the different types of apathy?
Ratings made by clinicians and caregivers can score apathy in separate domains. The Dimensional Apathy Scale, developed by Maria Radakovic and Sharon Abrahams in 2014, has three subscales: executive, emotional, and initiation. A person can therefore score high in one area and normal in another.
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