'Mind reading' neurones help predict behaviour of others
Friday, 27 February 2015 Clare  Pain
ABC Science
 
Scientists have discovered a group of neurones that enable one  monkey to 
predict what another monkey is about to do - the first-known instance  of 
neurones calculating another animal's behaviour.  
The discovery may be fundamental for understanding social behaviour and 
could  lead to better treatments for conditions like autism spectrum disorder. 
US neuroscientists got pairs of monkeys to play a game based on classic 
game  theory known as 'the prisoner's dilemma.'  
Their findings are published today in the journal _Cell_ 
(http://dx.doi.org/10.1016/j.cell.2015.01.045) . 
Decisions… decisions
In the game, the monkeys sit side by side facing computer screens. They can 
 choose either to cooperate (signified by pressing a hexagon on their 
screen) or  to be selfish (by pressing a triangle). 
Although they are well aware of each other's presence, neither monkey can 
see  the other's facial expressions, nor can they see the choice the other 
monkey  makes as they make it, explains study co-author neuroscientist Dr 
Keren Haroush  of _Harvard Medical School _ (http://hms.harvard.edu/) and 
_Massachusetts General Hospital_ (http://www.massgeneral.org/) , Boston,  USA. 
Their reward depends on their combined choices. If one monkey chooses to be 
 selfish and the other to cooperate, the selfish monkey wins hands down, 
getting  six drops of juice as a reward while the other (cooperative) monkey 
gets only  one drop. 
But if they both choose the selfish option they get just two drops each. 
Both  deciding to cooperate, however, wins them each four drops of juice.  
"The only follow-up was at the end of the trial: once they had both made  
their selections, they got to see what the other one chose." says Haroush.  
Not only could they see the choice the other monkey made, they could also  
hear the drops of juice that it got as a reward. 
Listening in
While the monkeys were making up their minds, the researchers were  
eavesdropping on the neurones in a brain region known as the cingulate  cortex. 
"We had small microchips inside the brains and we were able to record many  
neurones at the same time. We could basically 'listen in' on their activity 
as  the monkeys were performing this task," says co-author Associate 
Professor Ziv  Williams, also of Harvard Medical School and Massachusetts 
General 
Hospital,  Boston, USA. 
"We found some of these neurones fired differently based on what the other  
monkey's yet unknown decision was predicted to be. That was pretty 
remarkable  and surprising…we could actually tell what the first monkey thought 
the 
other  would do way before that decision was revealed," he says. 
The researchers recorded from 363 neurones during the games. Of these 32.4  
per cent appeared to be involved in predicting what the other monkey would 
do -  attempting to 'mind read' - while a (largely different) 24.3 per cent 
of  neurones seemed to be encoding the monkey's own decision.  
"Basically what's happening is these neurones are building up a predictive  
model of what the other monkey is likely to do in a situation, given their 
past  interactions," says Williams. 
Furthermore, the 'mind-reading' neurones appear to be activated more in  
social situations. When the monkeys played the game in separate rooms (and did 
 not know about each other) or played against a computer, considerably 
fewer  neurones activated by the task were 'mind-reading' ones. 
"Our best guess is that these types of neurones are likely to be found in  
other social animals including humans. However, without testing this 
hypothesis  directly, we currently do not know for certain," remarks Williams.  
Social disruption
Haroush and Williams also tried disrupting the cingulate cortex by sending  
electrical pulses to that part of the brain while the monkeys were doing 
the  task. 
They found the monkeys were much less likely to cooperate with each other,  
even if they had both cooperated on the immediately preceding trial. 
The pulses "selectively inhibited their ability to cooperate and to  
reciprocate past cooperation," says Williams. The pair thinks this demonstrates 
 
the key role of the cingulate cortex in social behaviour.  
"Ultimately we want to see if we can use some of these insights to develop  
treatment for social behavioural disorders such as autism and antisocial  
personality disorders," concludes Williams. 

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