Much remains hidden in the tissues that are in our skulls. As Yasemin Saplakoglu reports in LiveScience this week, researchers have recently discovered a whole new breed of neurons that may only exist in the human brain.
The new cell type is referred to as "rosehip neuron" since the cells are shaped like the fruit of rose bushes. According to a press release from two years ago two different laboratories, one at the University of Szeged in Hungary and one at the Allen Institute for Brain Science in Seattle, discovered what appeared to be a new kind of brain cell. When they learned that they were both examining the same neuron, they decided to work on a study. With two brains donated to science by deceased men in their fifties, laboratories used various techniques to study the neurons. The Hungarian team studied the shape and electrical properties of the neuron, while the Allen team studied the genetics of the neurons. The results appear in the journal Nature Neuroscience .
Molecular Neuroscientist Trygve Bakken of the Allen Institute, a principal author of the work, tells Saplakoglu that most neurons have long dendrites, branches that are electrically signals. The new neuron, however, is a little different. "It's very bushy," he says. "[The dendrites are] very compact with many branching points, it looks a bit like a rosehip."
This type of neuron exists in humans, but not in rodents, which are often used as model species in neuroscience. Therefore, the existence of rosehip neuron may explain why so many treatments seem to work for brain disease in mouse models, but fail when applied to humans. "To fully understand mental disorders, we need to gain access to these specific types of neurons that exist only in humans," explains neuroscientist Joshua Gordon, director of the National Institute of Mental Health, Jon Hamilton in [1
"Our brains are not just enlarged mouse brains," says Bakken in the publication. "People have commented on this for many years, but this study comes from different angles."
"Many of our organs can be reasonably modeled in an animal model," co-author Gábor Tamás, a neuroscientist at the University of Szeged, says. "But what sets us apart from the rest of the animal kingdom is the capacity and output of our brain, which makes us human, so it turns out that humankind is very difficult to model in an animal system."
So What exactly does the rosehip neuron do? That is not very clear. The cells make up about 10 percent of the neocortex, the last part of our brain that connects to sight and hearing. Rosehip seems to be an inhibitory neuron that regulates the flow of information to certain parts of the brain. Saplakoglu reports that the rose hips are apparently associated with pyramidal cells, an "excitatory" neuron that accounts for about two thirds of neurons in the neocortex.
"It has these really discrete connections with [pyramidal] neurons," says Bakken. "It has the potential to manipulate the circuit in a targeted manner, but how that affects behavior must come in later work," says Bakken to Andrea Morris of Forbes . The teams hope to be able to study brain samples from people with neuropsychiatric disorders to see if they have changed rosehip neurons.
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