When people see an image of a person they recognise – whether it’s their mum or famous tennis player Roger Federer – particular cells light up in the brain.
Now, a new study has found that those cells light up even when you see a familiar face but fail to notice it.
The researchers hope the findings will shed new light on the nature of conscious perception.
The researchers recorded the activity of 2,735 individual brain cells (neurons) in 21 people found that brain cells light up even when you see a familiar face but fail to notice it
Researchers from the University of Bonn looked at the brain processes that occur when we see familiar faces.
They found that the only difference in the way our cells light up when we see a face but don’t notice it is that the process is weaker and delayed than the times we do notice it.
Dr Florian Mormann, lead author of the study, said: ‘Our study finds that a “Roger Federer cell” can also become active when its owner fails to notice the image of Roger Federer rapidly flickering by in a stream of other images.
‘Thus, we find that there is highly abstract information present in neuronal activity that is inaccessible to conscious experience.’
In their study, the researchers recorded the activity of 2,735 individual brain cells (neurons) in 21 people with electrodes implanted in their brains.
Participants were shown two familiar images in quick succession – a phenomenon known as attentional blink.
As expected, the participants often failed to notice the second image, especially when it was presented soon after the first.
Participants who had electrodes (pictured next to a coin) implanted in their brains were shown two familiar images in quick succession – a phenomenon known as attentional blink
Interestingly, the researchers found that the corresponding neurons lit up either way.
But there was a noticeable difference in the strength and timing of this response.
Dr Mormann said: ‘Studying the activity of individual neurons in awake, behaving humans was key to picking up weak but informative signals from individual neurons during nonconscious perception, particularly in regions further down the processing stream, which are impossible to measure with conventional tools.
‘We were quite surprised to see that timing of neuronal responses is indicative of whether participants report having seen the image or not.’
The findings add to long-standing debates about the nature of human consciousness.
When people see an image of a person they recognise – whether it’s their mum or famous tennis player Roger Federer (pictured) – particular cells light up in the brain
For example, it hasn’t been clear whether consciousness is an all-or-nothing phenomenon or a matter of degrees.
The researchers say the observation that neurons light up in both cases, but differently, argues in favour of consciousness as a more nuanced, graded phenomenon.
The team now hopes to explore how the activity of individual neurons in one part of the brain are related to the activity in other areas.