Big brain evolution: our neurons differ from apes (Evolution)

by David Turell @, Monday, January 21, 2019, 19:07 (28 days ago) @ David Turell

Latest study comparison:

"Over the decades, neuroscientists have discovered many subtle and significant differences in the anatomy — the hardware — of the brains of humans and other primates. But the latest study looked instead at differences in brain signals.

“There is a clear difference in behaviour and psychology between humans and non-human primates,” says Mark Harnett from the Massachusetts Institute of Technology in Cambridge who studies how the biophysics of neurons affect neural computation. “Now we see this difference in the brain’s biology — it’s a tremendously valuable study.”


"The data were collected from nearly 750 neurons from the two brain regions from the five monkeys and seven humans. They comprise a long series of firing spikes or silences from single neurons recorded over several hours. The researchers searched the data for the two properties: they defined robustness as the level of synchrony, or near synchrony, in both the firing of neurons and the frequent repetition of similar patterns of spikes, and efficiency as having more combinations of patterns in the activity.

"They found that in both species, the signals in the amygdala were more robust than those in the cingulate cortex. But those in the cingulate cortex were more efficient. Both regions in humans were less robust and more efficient than those in monkeys — so humans have sacrificed some robustness for increased efficiency.

"It makes sense, says Paz. The more robust a signal, the less ambiguous or error-prone it is. “If I see a tiger, I want all of my amygdala neurons to shout, ‘Run away fast!’” But in higher species, such as primates, the brain evolved more flexible areas — the cortex — to allow for more considered responses to the animals’ environments, says Paz.


"The researchers' robustness–efficiency trade-off hypothesis is an important one that needs to be explored in further studies, says neuroscientist Christopher Petkov of Newcastle University, UK. Direct comparisons between monkey and human data sets are challenging because it is hard to know whether the two species were in comparable states of mind when the data were collected, he notes. But such comparisons are “immensely valuable”.

"Paz says that the long recording times in his current study probably ironed out any differences in mind states, but that he is planning new studies that will collect data from neurons while monkeys and humans carry out similar tasks that could track a particular state of mind, such as anxiousness."

Comment: Not only are our brains much bigger, but the neuron networks and their function is different, perhaps more efficient.

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