February 2, 2014

expert reaction to brain immune cells and social behaviour

An animal study in Nature Neuroscience found that defects in an early developmental process in the brain were associated with alterations in mice’s social behaviour. 

Dr Cathy Fernandes, MRC Social, Genetic & Developmental Psychiatry Centre, Institute of Psychiatry, King’s college London, said:

“This is a well-designed and executed study which provides evidence for a link between microglia (non-neuronal cells with an immune function) and the way nerves are wired in the brain and affect behaviour. Overall, this article presents some important basic science findings regarding the role of microglia in the underlying mechanisms which mediate behaviour. It makes a valuable contribution to our understanding of basic processes in the brain and how deficits in these systems might result in behavioural dysfunction. However, the work is based on the alteration of one gene in a simple model system. Therefore, it is challenging to translate this to neurodevelopmental and psychiatric disorders in humans which are likely mediated by changes in many genes against a background of environmental risk factors.

“Previous studies have demonstrated this link so the current study is not particularly novel but it does make an important contribution to the field and supports the hypothesis that dysfunction in microglia leading to synaptic pruning can alter behaviour and cognitive function.

“The unique contribution of this work is the finding that social behaviours may be influenced by deficits in microglia. The authors report that their genetically-modified mice with dysfunctional microglia show reduced social interaction with other mice – but they did not really look at social investigation between mice, they measured the preference for a social cue as the test mice could not physically interact with the stimulus mouse. Their statements regarding social deficits would be more compelling had they assessed direct physical interaction between a test mouse and a stimulus mouse. It is surprising that this test was not performed in their mice. The other behavioural change they report, increased grooming behaviour, was at best a very weak, not statistically significant, effect.

“Another important point is that there is no specificity to their findings, something the authors do acknowledge in the discussion. One of the main problems with animal models is that we can only model simple aspects of disorders. Therefore it is hard to make a specific claim about a deficit like social interaction as these are features of several psychiatric disorders/neurodevelopmental disorders and not just autism and obsessive compulsive disorder.”

‘Deficient neuron-microglia signaling results in impaired functional brain connectivity and social behavior’ by Zhan et al. published in Nature Neuroscience on Sunday 2^nd February.