Learning happens when reality doesn’t match
our expectations. If, after we make a decision, something good and unexpected happens, our
expectations will change in order to favour that same decision in the future. It has been
thought that, in the brain, only one signal is responsible for learning. This signal is
called a prediction error. If we represent it in a graph, then it would increase linearly,
going from a negative signal if something surprisingly bad happens, to no signal change
if things match our expectations, to a positive signal if something surprisingly good happens.
But traditionally, this brain signal was either studied using single cell recording, which could only
target one area at a time, or using fMRI, which is a cool brain imaging technique showing
where the brain is active, but without showing precisely when this activity occurs. In a
series of new studies, neuroscientists from the universities of Oxford and Glasgow have
combined classic fMRI simultaneously with EEG, another technique which involves recording
electrical activity from the skull, and which gives precise information about when the brain
is active. Together, these two techniques provide information about both where and when activity
occurs in the brain as we make decisions. In these new studies, the scientists were
able to show that separate brain signals are actually involved when we learn. Here are
the key points of their discovery. 1. Some brain areas signal valence, meaning whether
something is bad or good to either avoid it or approach it in the future. 2. Some other
brain areas signal surprise, regardless of how good or bad things are. The important
take home message of these studies is that multiple brain signals, occurring almost at
the same time, are at play when we are learning, rather than just one prediction error signal.
Bit by bit, we’re beginning to understand how our complex brain works, and there is
still so much more to discover!