A Near-Whole Brain Activity Map in Fish

ORIGINAL: MIT Review

Susan Young

March 18, 2013

Neuron-level whole-brain activity maps could one day help explain brain function and disfunction.

Image: Neurons glow red as they fire in this whole zebrafish larva brain. Credit: Misha Ahrens and Philipp Keller

Researchers have for the first time been able to image most of an entire vertebrate brain at the level of single cells, reports Nature.

A study from the Howard Hughes Medical Institute’s Janelia Farm Research Campus, published in Nature Methods, shows that modifications to existing microscopy techniques enable researchers to take snap shots of neuron-by-neuron activity in the whole brain of a living zebrafish larvae. The zebrafish larvae, whose bodies are transparent and brains are tiny, were genetically engineered to produce a protein in their neurons that glows in response to the chemical changes that occur when that neuron fires.

With conventional techniques, capturing the activity of even 2,000 neurons at once is difficult. With the modified fish and microscopy methods, the researchers were able to capture the activity of at least 80 percent of the baby fish’s 100,000 neurons over a time period of just 1.3 seconds. 

The result is an encouraging announcement for proponents of the Brain Activity Map project, a still-developing scientific collaboration to establish new technologies that can record the activity of all individual neurons in a brain circuit simultaneously (see “The Brain Activity Map”). According to Nature News, Rafael Yuste, a neurobiologist at Columbia University in New York and leader of the Brain Activity Map project, thinks the zebrafish results are “phenomenal.”

“It is a bright star now in the literature, suggesting that it is not crazy to map every neuron in the brain of an animal,” [says Yuste].

Fish Are Warmer, Faster, Stronger: Unexpected Benefits of Living in a Changing Climate, Biologists Find

ORIGINAL: Science Daily

Zebrafish embryos, taken 28 hours after fertilization (a little over a third of the way through embryonic development). (Credit: Ian Johnston)

ScienceDaily (Aug. 14, 2012) — New research by McMaster University biologist Graham Scott suggests that growing up at warmer temperatures helps some aquatic animals cope with climate change, raising questions about the limits of adaptation.

Working with Ian Johnston at the University of St Andrews in Scotland, Scott has found that raising zebrafish at warmer temperatures as embryos actually improves their ability to adjust to both higher and lower temperatures as adults.

Their research shows the fish are hardier after being raised in a warm-water nursery, and raises the question of how far the temperature can rise before the advantage becomes a liability, as inevitably it will, Scott says.

"What limits are there to their coping abilities? That's what we're really trying to understand," says Scott, a specialist in animals' adaptation to challenging environments. "If we want to appreciate how the natural world is affected by climate change, that's what we need to know."

The research appears in the Proceedings of the National Academy of Sciences.

Zebrafish are native to freshwater habitats of Southern Asia, and over their lives can experience a range of temperatures from almost 40°C to nearly freezing. The fish under study were raised across the range of temperatures they would normally experience in their natural breeding season (22°C to 32°C).

The biology of zebrafish -- especially their short gestation period -- makes them ideal research subjects.

Scott and Johnston found that when embryos raised in warm water experienced temperature variation as adults, they could swim faster, their muscle was better suited for aerobic exercise, and they expressed at higher levels many of the genes that contribute to exercise performance.

The improvements were true for the adult fish in warmer and colder water alike -- a finding that surprised the researchers.

"We thought that they might do better under warmer conditions because they grew up in warmer conditions. We didn't think they'd also do better under colder conditions, but they did."