Kolb – sensitive periods  

The word sensitive period and critical period are usually interchangeable although I think historically critical meant it was really a tight period that went from time one to time two and sensitive was a bit more blurry. But today in usage we tend to use them interchangeably. 

So there are critical or sensitive periods that vary depending on where in the brain we’re looking. So, for example, in the visual system which is early on we know there’s a period where you must have input to both eyes that’s in focus or you’re going to get amblyopia, lazy eye. And that period, you only need a short window to have that normal input but if you don’t have it you’ve got a problem because the critical period closes and that region of the brain is no longer plastic and so it’s very difficult to repair. It’s possible, we now know ways that we can turn the critical period back on again but it’s a bit tricky. 

Other regions of the brain the critical period is later so for audition it’s a bit later than vision and for things in the frontal lobe, for example, it’s much later. But these, if you think about it imagine you’re on a train and you’re on the Orient Express and the windows are open and you can look out and at some point the window closes and you can’t look out anymore. So that closing window is the end of that critical period and it’s biological, there’s a lot of molecular breaks that break the period but that’s basically what it is.