The target was reached eight weeks after Mr Aikman's death on 2 February at the age of 31.
Now the Gordon's Fightback campaign is seeking to raise £1m in his memory to fund research into the disease.
Mr Aikman was director of research for the Better Together campaign at the time of his diagnosis.
His campaign has been supported by leading figures in all of Scotland's major political parties.
Gordon's husband Joe Pike said: "I miss Gordon's voice, his eyes and his smile. I miss the in-jokes and affection and finishing each other's sentences.
"But Gordon never wanted pity, and I don't either. I want to turn a negative into a positive. Today, I want everyone to mark Gordon's birthday by giving the gift of a cure for Motor Neurone Disease.
"Gordon's real passion was finding a cure. Doctors do not know what causes Motor Neurone Disease, let alone how to cure it. But scientists in labs doing research provided him with hope. Not that he would be saved, but hope for future generations.
"A cure for MND - that would be a real gift to remember Gordon by."
The fund named after Scottish motor neurone disease (MND) campaigner Gordon Aikman has raised £600,000.