Anorexia Accelerates the Development of the Rat Hippocampus

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This image stack was used in the study to analyze spine density. Image courtesy of Tara Chowdhury, Ph.D. first author of the study.

To find out how anorexia nervosa changes the brain, scientists at New York University are studying a rat model of the disease called activity-based anorexia (ABA). Previously, they discovered that ABA rats develop unusually robust dendritic branching of neurons in part of the hippocampus. Their new study takes those findings a step further, illuminating more differences between the brains of healthy versus ABA rats, and offering evidence that ABA rats may be developing too early, closing a critical period of development too soon.

But before making any conclusions about ABA brains, the researchers made some interesting discoveries about normal brain development. Using Neurolucida to analyze CA1 pyramidal cells in the stratum radiatum layer of the ventral hippocampus, they found that after puberty, around postnatal day 51, dendrites go through a growth spurt, more than doubling the number of branches seen seven days earlier. This growth spurt is followed by a decrease, or a pruning, which the researchers say is part of the normal maturation process.

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Neurolucida Helps Ohio State Scientists Study Melatonin’s Effects on Brain Plasticity in Mice

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An acrylic painting by Don Cooper and Leah Leverich shows the transition zone between densely packed pyramidal neurons in the CA1 region.

In spring, days grow long, and the white-footed mouse looks for a mate. For some mammals, day length prompts behaviors like breeding or camouflaging, and scientists say it’s not just the arc of the sun that kicks off these seasonal events; substances in the brain also play a part.

One important element is melatonin, a hormone that the mammalian brain secretes at night. According to a study conducted at Ohio State University, changes in the duration of melatonin secretion not only affect the behavior of white-footed mice, they also induce changes in their brains.

The group’s previous research showed that white-footed mice held in short winter-like days showed changes in the mechanism behind how memories are formed and stored in the brain, which they say is associated with impaired spatial learning and memory.

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UCLA Scientists Count Cells with Stereo Investigator in Study Identifying Compensating Regions in Brain Damage

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If one area isn’t working, another part can step in. Plasticity is one of the brain’s most beautiful attributes. Recent research has documented the organ’s ability to compensate in the face of damage, and now a new study identifies a key region for compensation when the damage occurs in the hippocampus.

The region is the medial prefrontal cortex (mPFC). It’s an integral part of the hippocampal-prefrontal-amygdala circuit involved with memory formation – specifically with contextual fear memories. In their study, published last month in Proceedings of the National Academy of Sciences, researchers at the University of California, Los Angeles identify a microcircuit in the mPFC that can encode memories when the dorsal hippocampus is damaged.

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