The human brain contains a little over 80-odd billion neurons, each joining with other cells to create trillions of connections called synapses.
The numbers are mind-boggling, but the way each individual nerve cell contributes to the brain’s functions is still an area of contention. A new study has overturned a hundred-year-old assumption on what exactly makes a neuron ‘fire’, posing new mechanisms behind certain neurological disorders.
French neuroscientist named Louis Lapicque proposed a model to describe how the voltage of a nerve cell’s membrane increases as a current is applied.
Once reaching a certain threshold, the neuron reacts with a spike of activity, after which the membrane’s voltage resets.
What this means is a neuron won’t send a message unless it collects a strong enough signal.
Lapique’s equations weren’t the last word on the matter, not by far. But the basic principle of his integrate-and-fire model has remained relatively unchallenged in subsequent descriptions, today forming the foundation of most neuronal computational schemes.