Bat Memories

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Perhaps because bats fly at night, they easily provoke fears and conjure up eerie visions of witches and vampires. Yet in Chinese mythology bats are happy omens, portending good luck. And at the Weizmann Institute, bats promise to bring good fortune by helping reveal the secrets of human memory.

 

These chatty nocturnal mammals – who constantly communicate with one another through high-pitched shrieks and clicks – have long been used in the study of hearing. But in addition, bats have remarkable navigational and memory skills. Thus fruit bats, the most common bat species in Israel and the one studied at Weizmann, have no problem returning to the same cave, no matter how small, after covering distances of dozens of kilometers in the course of the night.

 

Dr. Nachum Ulanovsky, who recently joined the Weizmann Institute as a senior scientist in the Neurobiology Department, has pioneered the use of bats in the study of learning and memory. According to him, bats are an excellent research model in this area not only because of their impressive spatial memory but also due to their highly developed senses and unique behaviors. “Most studies of memory-related brain activity have been done with rats and mice,” he points out, “and it’s important to perform a ‘reality check’ to see whether those findings are relevant for other mammals. By comparing different animals we can find the features that all mammals have in common, and such features can help us understand our own memory.”

 

Ulanovsky is particularly interested in the brain area called the hippocampus, a bunch of cells on either side of the brain that is responsible for spatial navigation and episodic memory. As opposed to motor memory (remembering how to ride a bike) or factual memory (knowing the name of the queen of England), episodic memory deals with day-to-day events and enables us to remember what we did yesterday, for instance, or whom we met two days ago.

 

The central role of the hippocampus in episodic memory is mainly known from the classical case of a patient who in the 1950s had his hippocampus removed and lost the ability to remember new events as a result. However, it is still unknown which nerve cells or neuronal networks are involved in episodic memory, and that is precisely what Ulanovsky seeks to find out by using bats.

 

He intends to study the brain activity of bats as they fly or crawl. In the “flight room” in his lab, bats will be outfitted with advanced telemetry equipment that transmits information about the activity of individual neurons or neuronal networks as the bat performs certain tasks in flight. The relatively large Israeli fruit bat is perfect for such studies: At 150 grams it can fly while carrying about 9 grams of equipment. Telemetry systems are generally heavy, but this miniature device – a world first – has been developed in the past two years by an American company in collaboration with Ulanovsky. The nerve cell signals will be picked up by another kind of innovative equipment developed in the 1990s: tetrodes – micro-electrodes that have four wires instead of one – enabling a more precise recording of the activity of individual nerve cells. Ulanovsky started using these technologies during his postdoctoral studies at the University of Maryland, where he made a number of significant discoveries about the bat hippocampus.

 

An additional room in Ulanovsky’s lab will be devoted to the study of crawling bats, the goal being to find out how the brain processes and remembers sounds over time. Yet another experimental room will be devoted to behavioral studies. To avoid disrupting their natural behavior, the bats will all share one large, cave-like space with rough-hewn rocks in the ceiling.

 

Ulanovsky also conducts field studies in collaboration with the Hebrew University of Jerusalem. The bats’ bodies are outfitted with the smallest GPS system in the world – 10 grams including the battery – which was specially developed for this research.

 

These studies promise to shed new light not only on human memory but also on diseases involving the hippocampus, including epilepsy and such neurodegenerative diseases as Alzheimer’s. And while the bats continue to chat away in a language we don’t understand, other discoveries might emerge from the study of their outstanding capabilities.