By Adrian Galbreth
A new study has shed light on how the brain recognises certain objects that we have seen before - something that was previously a grey area for scientists.
Brown University neuroscientists have highlighted the potentially different roles that two distinct cell types may play in the process of viewing an object and then recognising it when it is seen again.
In the study, published in the journal Neuron, experts note that this kind of learning is based in the inferior temporal cortex (ITC), a brain area buried deep in the skull.
Although experts already knew the area was important for visual recognition of familiar items, they had not yet determined the steps required to move from novelty to familiarity, a process referred to as 'plasticity'.
Senior author David Sheinberg, professor of neuroscience and a member of the Brown Institute for Brain Science, explained: "We know little about that because of the level at which this plasticity is taking place. The inner workings made up of individual neurons make it very hard to actually track what's going on at that level."
In the study, the researchers monitored single neuron activity in monkeys using tiny microelectrodes and tracked the firing patterns of individual neurons in the ITC while monkeys viewed 125 objects they had been trained to recognise and 125 others that they had never seen before.
The scientists found that the two major classes of cells found in the brain, excitatory and inhibitory, responded differently depending on what the monkeys saw, with excitatory neurons especially active when the monkeys saw a preferred familiar object out of the 125 such images that the cell "liked" best.
Although the particular preferred familiar image varied across the sample of neurons, almost every excitatory cell had at least one familiar image to which it responded more robustly than its preferred novel image, the experts noted.
Dr Sheinberg said that when a familiar object has been recognised, it is a positive signal and that can cause the system to move on.
"In the absence of that signal, that means the object isn't familiar. What we think is going on is that the ongoing inhibitory activity actually promotes a learning process. It can be a signal to learn," he added.
by Martin Burns