By Nick Fontaine
The goal of modern neuroscience is to understand the the brain on a microscopic scale in order to understand all the macro-level questions that come with being a human. This goes back to the early 20th century with Santiago Ramon y Cajal, who painstakingly drew out the microscopic intricacies of neurons by hand decades or even a full century before we knew the role of each part of his drawings. This article is not about Ramon y Cajal, but he would be proud of the findings described below (also, he’s my favorite historical scientist and you should look him up).
More contemporary neuroscientists like to think they understand the structure of the brain more fully. While this is generally the case, an article published in September’s journal Nature Neuroscience by an international group of scientists from the Hungary and the US sent ripples throughout the entire neuroscience community as they reported on the discovery of a new type of neuron, and the best part— it appears to only be present in humans.
The new neuron is called the Rosehip neuron due to its vague resemblance to the fruit part of a rose plant (see images below). These cells were determined to be unique and previously undiscovered based on their distinct shape, genetic signature, and electrical firing patterns (Boldog, et al., 2018).
It is still too early to report on the precise function of rosehip neurons. However, it is known that they act as inhibitory neurons, meaning they prevent the firing of nearby excitatory neurons in the neocortex that send signals to far away targets throughout the brain and rest of the body. Inhibitory interneurons (interneurons are those that only communicate with other neurons, such as rosehip neurons) are a vital part of nearly every neural circuit, from basic tasks such as feeling physical pain to complex decision making. These newly discovered neurons may help scientist understand more of the complex circuitry going on in our heads and elucidate the neural underpinnings of complex behaviors going forward. Researchers hope to examine if rosehip neurons are different in people with neuropsychiatric disorders in future research, and see if they are a viable avenue for treatment.
Perhaps the most interesting finding from this groundbreaking article is that rosehip neurons are not seen in the brains of rodents like mice or rats. Mice and rats are very commonly used as models for human brains and behavior. While generally good models, this finding may explain why some treatments and behaviors do not scale up from rodents to humans. It is yet to be seen if our closest primate relatives also have rosehip neurons, but as of right now they are unique to humans (Boldog, et al., 2018). If this is true, or even if rosehips are only seen in other high-intelligence primates, they may be able to explain a key evolutionary change that lead to the higher cognitive ability we enjoy.
One of the things that drew me and so many others to study neuroscience is just how little is known about the brain. It is pretty often called the “frontier” of science. I like this comparison. Studying neuroscience truly is like exploring a previously unmapped landscape. We know the basics (rivers flow to the ocean and neurons that fire together wire together), but there is still a lot left to be found out. The discovery of rosehip neurons is like the discovery of new fertile land on which to build a settlement. I imagine many neuroscientists will make their home in the study of rosehip neurons for years to come.
Boldog, E., Bakken, T., Hodge, R. D., Novotny, M., Aevermann, B. D., Baka, J., . . . Tamas, G. (2018). Transcriptomic and morphophysiological evidence for a specialized human cortical GABAergic cell type. Nature Neuroscience,21. doi:10.1101/216085