A virus has delivered a special end-of-semester gift in the form of a cold and mild fever. I know this is a common experience among teachers: our immune systems carry us through to the moment that grades are due, then dump us over the cliff, their patience finally worn to nothing.

But the point here is not to whine about minor ailments or the rhythm of the semester, but to ask why fevers mess with our minds. High fevers bring on full blown hallucinations; milder versions create a restless cacophony of strange images and thoughts, seeming to rise up through the acidic vapors of the sinuses.

The neurobiological literature is, as far as I can tell, not clear about the causes of all this confusion. For major hallucinations, it seems that an imbalance between inhibition and excitation in the brain creates sensory illusions. In other words, some parts of the brain are shooting out way too many signals which, when combined with dulling of the parts of the brain that say “stop,” creates the neural mirages we call hallucinations.

For the milder confusion of a low fever, I suspect that mistiming plays a part. All our thoughts exist as relationships among nerves. These relationships depend critically on the timing of which nerves fire when. Even a simple thought, like an imagined object, is held in a network of neural firing patterns that shifts five times per second. So, thought is like music — it depends on relationships among dozens of players and the timing of those relationships determines the nature of the melody. When we heat up the brain with a fever, chemical reactions quicken slightly, throwing off the tempo.

Taking an aspirin is therefore like switching on the metronome. Click, click, click. Back to coherence.