New Scientist has a tantalising snippet reporting on a shortly to be released and potentially important new study challenging the idea of ‘mirror neurons’.
Mirror neurons fire both when we perform an action and when we see someone else doing it. The theory is that by simulating action even when watching an act, the neurons allow us to recognise and understand other people’s actions and intentions…
However, Alfonso Caramazza at Harvard University and colleagues say their research suggests this theory is flawed.
Neurons that encounter repeated stimulus reduce their successive response, a process called adaptation. If mirror neurons existed in the activated part of the brain, reasoned Caramazza, adaptation should be triggered by both observation and performance.
To test the theory, his team asked 12 volunteers to watch videos of hand gestures and, when instructed, to mimic the action. However, fMRI scans of the participants’ brains showed that the neurons only adapted when gestures were observed then enacted, but not the other way around.
Caramazza says the finding overturns the core theory of mirror neurons that activation is a precursor to recognition and understanding of an action. If after executing an act, “you need to activate the same neurons to recognise the act, then those neurons should have adapted,” he says.
The study is to appear in the Proceedings of the National Academy of Sciences and apparently is embargoed so the full text is not yet available, although it should appear here when it is.
The announcement is interesting because using adaptation is a novel way of testing ‘mirror neurons’ and the lead researcher, Alfonso Caramazza, is known for a long series of influential neuropsychology studies.
He has a reputation for being a sober and considered scientist so it will be interesting to see if the final study is really the challenge to mirror neurons as it seems.
Although the hype has subsided a little, the years following the initial reports saw these now famous neurons being used to explain everything from language, to empathy, to why we love art.
We’re now in a period where we’re taking, if you’ll excuse the pun, a somewhat more reflective look at the topic and developing more nuanced theories about how this brain system functions.
UPDATE: Grabbed from the comments. Looks like this paper might have the potential to cause a ruckus. A comment from mirror neuron researcher Marco Iacoboni:
Caramazza‚Äôs paper is seriously flawed. The technique of fMRI adaptation seemed very promising ten years ago, but careful studies on its neurophysiological correlates have demonstrated that its findings are uninterpretable. Indeed, Caramazza‚Äôs manuscript has been around for many years and nobody wanted to publish it. Caramazza managed to publish with an old trick that only PNAS allows: he handed it personally to a friend of his. The paper is basically unrefereed (this is what it means ‚ÄòEdited by…‚Äô under its title).
Link to NewSci on ‘Role of mirror neurons may need a rethink’.