Chandelier neurons are the latest candidates for 鈥�the uniqueness of being human鈥�, the thing that gives us the edge over other mammals in our ability to think and use language.
The cells are found exclusively in the cerebral cortex 鈥� the part of the brain responsible for functions such as language, thought, sensation and spatial reasoning 鈥� and named for their resemblance to old-fashioned candlesticks.
at the University of Szeged, Hungary, and colleagues have for the first time demonstrated just how powerful chandelier cells are, by showing that a single cell can trigger a whole series of neuronal signals in human brain tissue. As this has not been seen in other mammals, it may explain why we humans are so much brighter.
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Tam谩s鈥檚 team investigated how chandelier cells make connections with other nerve cells using brain tissue removed during surgery that would otherwise have been 鈥渨asted鈥�.
鈥淲e used tissue from patients having surgery for deep brain tumours,鈥� he says. 鈥淥n the way to these deep brain tumours surgeons have to remove some healthy cortical tissue above the troubled area. We used this little piece of healthy tissue which would have otherwise been discarded.鈥�
The power of one
The researchers recorded the electrical signals produced as pairs of connected neurons fired, allowing them to determine how individual neurons affect others. They found that a single chandelier cell can trigger a cascade of firing in several pyramidal cells, the 鈥渨ork horse鈥� cells of the brain that allow communication between brain areas.
Hundreds of nerve cells usually have to send a signal to the pyramidal cell in order to kick it into action. The chandelier cell however makes a unique contact with the pyramidal cell so that a signal from just one chandelier cell produces the same effect.
鈥淭he chandelier cells are extremely potent at stimulating pyramidal cells. They are probably the most potent cell type in the brain compared to all other non-pyramidal cell types,鈥� says of University College London.
鈥淸A chandelier cell] has a much more profound impact on the ability of the pyramidal cell to fire a signal. It has a very loud voice so if it has something to say, everything will hear it,鈥� he says.
Tam谩s says chandelier cells help the cortex pass on longer sequences of information like a series of tumbling dominoes. Chandeliers are also found in other mammals such as rats, in which they are involved in touch perception. But they are much more abundant in humans, and the new work shows that the synaptic pathways they form are far stronger than in other mammals.
Journal reference:
The Human Brain 鈥� With one hundred billion nerve cells, the complexity is mind-boggling. Learn more in our cutting edge special report.
