![]() ![]() The researchers then measured electrical activity in each of those compartments. “We found that there are some sophisticated wiring rules here, with different inputs going to different dendrites.” “Until now, there hasn't been much mapping of what inputs are going to those dendrites,” Harnett says. In a study of mice, the researchers first showed that three different types of input come into pyramidal neurons of the RSC: from the visual cortex into basal dendrites, from the motor cortex into apical oblique dendrites, and from the lateral nuclei of the thalamus, a visual processing area, into tuft dendrites. The RSC integrates information from many parts of the brain to guide navigation, and pyramidal neurons play a key role in that function. Harnett and his colleagues chose a part of the brain called the retrosplenial cortex (RSC) for their studies because it is a good model for association cortex - the type of brain cortex used for complex functions such as planning, communication, and social cognition. Basal dendrites extend below the body of the neuron, apical oblique dendrites extend from a trunk that travels up from the body, and tuft dendrites are located at the top of the trunk. They focused on a population of neurons called pyramidal cells, the principal output neurons of the cortex, which have several different types of dendrites. In the new study, the MIT researchers wanted to determine whether different types of inputs are targeted specifically to different types of dendrites, and if so, how that would affect the computations performed by those neurons. ![]() This phenomenon, known as supralinearity, is believed to help neurons distinguish between inputs that arrive close together or farther apart in time or space, Harnett says. When a dendrite receives many incoming signals through AMPA receptors at the same time, the threshold to activate nearby NMDA receptors is reached, creating an extra burst of current. ![]() These are voltage-sensitive neurotransmitter receptors that are dependent on the activity of other receptors called AMPA receptors. Previous research has shown that dendrites can amplify incoming signals using specialized proteins called NMDA receptors. Neuroscientists have hypothesized that these dendrites can act as compartments that perform their own computations on incoming information before sending the results to the body of the neuron, which integrates all these signals to generate an output. Mathieu Lafourcade, a former MIT postdoc, is the lead author of the paper, which appears today in Neuron.Īny given neuron can have dozens of dendrites, which receive synaptic input from other neurons. “Our hypothesis is that these neurons have the ability to pick out specific features and landmarks in the visual environment, and combine them with information about running speed, where I’m going, and when I’m going to start, to move toward a goal position,” says Mark Harnett, an associate professor of brain and cognitive sciences, a member of MIT’s McGovern Institute for Brain Research, and the senior author of the study. In the neurons that the researchers examined in this study, it appears that this dendritic processing helps cells to take in visual information and combine it with motor feedback, in a circuit that is involved in navigation and planning movement. These differences may help neurons to integrate a variety of inputs and generate an appropriate response, the researchers say. ![]() The researchers found that within a single neuron, different types of dendrites receive input from distinct parts of the brain, and process it in different ways. Researchers at MIT have now demonstrated how dendrites - branch-like extensions that protrude from neurons - help to perform those computations. Nature, 462, 920–924.Within the human brain, neurons perform complex calculations on information they receive. Stably maintained dendritic spines are associated with lifelong memories. Acta Neurobiologiae Experimentalis, 68, 264–288. Molecular basis of dendritic arborization. Urbanska, M., Blazejczyk, M., & Jaworski, J. Dendritic excitability and synaptic plasticity. The American Journal of Anatomy, 4, 130–161. His relation to institutions of learning. Nature Reviews Neuroscience, 14, 536–550. Molecular mechanisms of dendrite stability. Changes in morphology of dendritic spines on honeybee calycal interneurons associated with cumulative nursing and foraging experiences. ![]()
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