An international team of 34 scientists has identified a new type of brain cell in humans not found in other well-studied species.
The discovery of “Rosehip” neurons, published today in the journal Nature Neuroscience, raises a number of questions: How does it influence human behavior and experience?
How does it differentiate us from other species? Can it be found in primates and other cognitively advanced species?
But there is one issue this discovery highlights immediately: there’s a neuron in human brains that is missing from the brains of mice and other animals used to model human brains in experiments.
Does this mean current animal models yield distorted results? “If we want to understand how the human brain works, we need to study humans or closely related species,” says Trygve Bakken, co-author of the paper and a neuroscientist at the Allen Institute for Brain Science.
The flow of info
Rosehip neurons are inhibitory neurons that form synapses with pyramidal neurons, the primary excitatory neurons in the prefrontal cortex.
“We all have inhibitory neurons and excitatory neurons,” says Bakken, “but this particular type of inhibitory neuron is what’s new in this study. It’s special based on its shape and its connections and also the genes that it expresses.”
When a traffic signal turns red it helps controls the flow of traffic. Similarly, inhibitory neurons help control the flow of electrochemical information.
The type of information rosehip neurons control, and why they appear particular to humans, is yet to be discovered. “It has these really discrete connections with [pyramidal] neurons,” says Bakken.
“It has the potential to sort of manipulate the circuit in a really targeted way, but how that influences behavior will have to come in later work.”
Found in the neocortex of human brains
The researchers identified rosehip neurons by looking at brain samples from two males who died in their 50’s and donated their bodies to science.
The brain slabs were tissue from the neocortex, a most recent evolutionary development inside our skulls responsible for higher-order thinking.
“The neocortex, the outermost layer of cells, is greatly expanded in humans–about a thousandfold compared to mice,” says Bakken.
“From neurological studies, if you have a stroke in your neocortex for example, it really impacts your ability to do these sorts of high-order cognitive processing.”
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