Author: vaughanbell

There have been some critical commentaries recently that suggest that the hype over mirror neurons has become unbearable and a backlash is about to begin.

Mirror neurons are cells in the brain that are active both when a person is performing an action, or when they see someone else perform an action, and have been hypothesised to be involved in perceiving and comprehending others’ actions.

Worryingly, this system has been proposed as the basis of everything from empathy to appreciation of art, with very little supporting evidence.

Both Mixing Memory and Neurotopia have sceptical commentaries on mirror neurons and doubt whether they have been consistently demonstrated in humans in anything other than correlational brain scanning experiments.

This is probably a little unfair, as evidence for ‘mirror neurons’ in humans has been found using subdural (brain surface) electrodes, transcranial magnetic stimulation, fMRI, magnetoencephalography, EEG and when studying patients with action production and recognition problems after brain injury.

That’s quite a lot of converging evidence for the existence of an equivalent human system.

What is a little misleading is that the original studies measured the responses of single neurons in monkeys, whereby the human studies have all been using techniques that measured activation from a group of neurons.

This, and the fact that the recognition and generation of actions also relies on other brain areas, has led some to use the more accurate term ‘mirror system’ in preference to ‘mirror neuron’.

What most of the recent articles seem to be criticising, however, is that the concept is being used as a convenient ‘just so’ story for explaining almost any sort of complex human behaviour, usually by people with a fairly poor grasp of the existing evidence.

It’s easy to see why the idea is attractive. A system that is both involved in producing our own movements and becomes active when we see others moving leads some to infer (perhaps falsely) that we encode others’ behaviour into our brains in quite a direct way.

Even worse, in some retellings of the story, behaviour can include almost anything you care to think of.

As noted by Frontal Cortex, this concept, although flawed, is easy to grasp and user-friendly, making almost anyone an instant ‘expert’ on how the brain supports human interaction.

The reality will probably turn out to have too many qualifications to allow the media obsession with mirror neurons to continue forever, but in the mean time, don’t get put off by the hype.

The findings are fascinating and the mirror system will surely play an important role in our future understanding of human neuropsychology, even if this won’t exactly match how the media portrays it the moment.

Link to Mixing Memory article.
Link to Neurotopia article.

This week’s ABC Radio All in the Mind had an edition on auditory hallucinations that discusses the experience of ‘hearing voices’ as well as the neuroscience that might explain them.

Hallucinatory voices are still largely mysterious to science. Originally they were linked to psychotic mental illness and particularly schizophrenia, but it later became known that only about 30% of people who hear voices ever become psychiatric patients.

Furthermore, for some people who hear voices, they can seem to exist as separate conscious entities with their own personalities. Someone may experience a number of voices each with a distinct age, sex and accent.

Research has suggested some explanations for why voices occur (it is know that the auditory cortex is activated with hallucinated voices are heard, suggesting that they may be internal thoughts experienced as sound) but many of these other issues are still unresolved.

The programme discusses the current state of research, as well as talking to two voice hearers about the experience itself, including campaigner Ron Coleman who has been particularly active within the Hearing Voices Network.

The network has taken an alternative view to the medical model, which assumes that voices are a symptom of mental disturbance, and encourages hearers to understand their voices in whatever way best promotes successful living.

Link to ABC Radio All in the Mind on hearing voices.
Link to Wikipedia article on hearing voices movement.

There’s a thought-provoking piece over at Brain Ethics about the role of genetics in violence, and particularly the role of a gene that codes for a type of monoamine oxidase enzyme involved in the breakdown of certain neurotransmitters in the brain.

The post reports on recent research led by neuroscientist Andreas Meyer-Lindenberg that found that variants of the MAOA gene predicted amygdala size, and both the response of the amygdala and cingulate cortex.

Both the amygdala and the cingulate cortex have been strongly linked to emotion recognition, and the cingulate cortex to empathy and anticipation.

It may be that differences in these structures may make someone more likely to react violently in certain situations.

The full story is a little more nuanced that this, however, and you’re best visiting Brain Ethics for more comprehensive coverage and analysis.

Link to article ‘MAOA and the risk for impulsivity and violence’.

An article in last month’s American Scientist offered an interesting theory of why some people are driven to find knowledge – because of the kick of natural opioids in the brain.

Sadly, the article is not freely available online, but the theory is outlined by neuroscientist Professor Irving Biederman in a pdf file he’s put online, and in a summary from Eureka Alert.

The idea is that the moment of finally understanding something causes a release of natural endorphins in the brain, providing a response to knowledge acquisition that conditions us to want more.

In other words, intellectual curiosity may be driven by an addiction to an opioid high.

Biederman’s theory was inspired by the well-known discovery that opioid receptors increase along the ventral visual pathway in the brain – the one that is most strongly associated with recognition and meaning.

At the moment, the theory is still largely speculative, although remains an interesting take on why humans are naturally curious.

Link to summary from Eureka Alert.
pdf of talk by Biederman outlining his theory.
Link to summary of Biederman’s American Scientist article.