Contrary to expectations, primate visual cortex neurons have fewer synapses than mice

Primates are generally considered smarter than mice

In a study comparing the levels of synapses in the brains of macaques and mice, researchers found that compared with rodents, primates have much fewer synapses per neuron, whether in the primary visual cortex.

The research team is composed of scientists from the laboratory of Dr.

After reconstructing the microscope images and measuring the shapes of 107 rhesus monkey neurons and 81 mouse neurons, the researchers identified nearly 6,000 synapses in the rhesus monkey samples and more than 9,700 synapses in the mouse samples

Dr.

After discovering this amazing discovery, Freedman contacted Matt Rosen, a graduate student in Friedman's lab, hoping that Rosen could use his computer expertise to better understand the differences in the number of synapses and their possible causes

"We have always expected that the synaptic density of primates will be similar to that of rodents, and possibly even higher, because primates have more space and more neurons in their brains," Rosen said

This model considers two potential metabolic costs: one is the cost of a single electrical signal sent by a neuron, called an action potential, which is very expensive in terms of energy; the other is the establishment and maintenance of the processes between different cells.

Wildenberg said: "The brain only accounts for 2.

The researchers said that this result will help future studies of primates and mice, as well as comparisons between the two

Rosen also pointed out that understanding the differences between species can help clarify the general principles of the brain to better understand behavior

For example, understanding the density of synapses—especially the ratio of excitatory synapses to inhibitory synapses—can provide information for research on neurological diseases such as Parkinson's disease and autism

Future research will include studying similar problems during brain development, trying to understand how the number and density of synapses affect neural networks over time, as well as the developmental differences between mice and primates

Cell Reports

DOI

10.
1016/j.
celrep.
2021.
109709