Mouse Brain Cells

Mouse Brain Cells Activated, Reactivated in Learning and Memory :

Memories are made of this, says the song. Now neuro-scientists have shown for the first time individual cells turns mouse brain during learning and subsequently reactivated during memory recall. The results are published December 13.

We store episodic memories about events in our lives in a part of the brain called the hippo-campus  said Brian Wiltgen, now an assistant professor at the Center for Neuroscience and Department of Psychology, University of California, Davis. (Most of the work was done while working Wiltgen University of Virginia. In animals, the hippocampus is important for navigation and storage of memories about the places.

"The exciting part is that now we are able to answer a fundamental question about memory," Wiltgen said. "It has been long assumed that the hippocampus is essential for memory because it leads to the reactivation of neurons (nerve cells) in the crust. The reason I can remember an event of his life is that the hippocampus is able to recreate the pattern of cortical activity that was there at the time. "

According to this model, patients with hippocampal damage lost due to memory can not recreate the activity in the cortex of the memory when done. Wiltgen mouse experiment makes it possible to test this model for the first time.

"Now we can do a good test of hippo-cam-pal function," Wiltgen said.

Current thinking is that learning activates a group of neurons that undergo changes, making new connections with each other to store memory. Memory retrieval reactive network.

Researchers working with human subjects, UC Davis and elsewhere, using imaging techniques such as functional magnetic resonance imaging to see which brain areas are activated and deactivated in learning and recovery. But f MRI can not select an object as small as a single cell.

Wiltgen and the University of Virginia graduate student Kaycie Tayler used a transgenic mouse carrying a gene for a modified green fluorescent protein. When nerve cells are activated in the mouse produce a long lasting green fluorescence persists for weeks and a short red fluorescence which disintegrates in a couple of hours.

However, the whole system can be suppressed by dosing mice with the antibiotic doxycycline and Wiltgen Tayler and could manipulate the point where they began to label activated cells.

The mice were placed in a new cage with a strange smell and given a few minutes to explore. They were then given a mild electric shock through the floor of the cage. When he returned to the cage for a couple of days later, the mice would remember the shock and stay frozen in one place.

When they examined the brains of mice, the researchers could see that the cells were initially activated to form memory and recall were reactivated after.

About 40 percent of the cells in the hippocampal formation were labeled during the initial memory reactivated, said Wiltgen. There was also recovery of cells in parts of the cerebral cortex associated with learning the place and in the amygdala, which is important for emotional memory.

There was no evidence of recovery when the mice were tested in a new environment did not remember, Wiltgen said.

The researchers also analyzed whether reviving memories changed as got older. For several weeks, the recovery in the cortex and hippocampus of the pieces remained stable, but it decreased in other brain regions such as the amygdala.

In future work, Wiltgen team plans to examine the role of the hippocampus and other brain regions in the memories of training and explore new ways to enable or block memories.

Other authors are Kazumasa Tanaka of the University of Virginia and Leon Reijmers at Tufts University School of Medicine. The work was supported by the McKnight Foundation, the National Science Foundation and the Nakajima Foundation.