How we feel at home

Moheb Costandi writes: Home is more than a place on a map. It evokes a particular set of feelings, and a sense of safety and belonging. Location, memories, and emotions are intertwined within those walls. Over the past few decades, this sentiment has gained solid scientific grounding. And earlier this year, researchers identified some of the cells that help encode our multifaceted homes in the human brain.

In the early 1970s, neuroscientist John O’Keefe of University College London and his colleagues began to uncover the brain mechanisms responsible for navigating space. They monitored the electrical activity of neurons within a part of the brain called the hippocampus. As the animals moved around an enclosure with electrodes implanted in their hippocampus, specific neurons fired in response to particular locations. These neurons, which came to be known as place cells, each had a unique “place field” where it fired: For example, neuron A might be active when the rat was in the far right corner, near the edge of the enclosure, while neuron B fired when the rat was in the opposite corner.

Since then, further experiments have shown that the hippocampus contains at least two other types of brain cells involved in navigation. Grid cells fire periodically as an animal traverses a space, and head direction cells fire when the animal faces a certain direction. Together, place cells, grid cells, and head direction cells form the brain’s GPS, mapping the space around an animal and its location within it.

Neuroscientists assumed that these three types of cells in the hippocampus are how we humans, too, navigate our surroundings. But solid evidence of these cell types came only recently, when a research team implanted electrodes into the brains of epilepsy patients being evaluated before surgery. They measured the activity of neurons in the hippocampus while the patients navigated a computer-generated environment, and found that some of the cells fired at regular intervals, as grid cells in rodents did. The authors of the study, published last August, conclude that the mechanisms of spatial navigation in mice and humans are likely the same. [Continue reading…]

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