Bad memories written with lasers

By Victoria Gill
Science reporter, BBC News

This work in flies will help understand how the human brain makes memories

Laser-controlled flies may be the latest addition to the neuroscientist's tool kit, thanks to a new technique.

Researchers have devised a way to write memories onto the brains of flies, revealing which brain cells are involved in making bad memories.

The researchers said that in flies just 12 brain cells were responsible for what is known as "associative learning".

They describe their findings in the journal Cell.

Associative memories are made when an animal learns to link a cue to a particular outcome. It might for example learn that a certain odour is a sign that a predator is nearby.

"So the appearance of that odour predicts that something bad is going to happen," explained Gero Miesenbock from the University of Oxford, UK, who led this study.

Previous research had already identified that the brain cells or neurons responsible for this type of learning are those that produce dopamine. This is a chemical which acts as a signal that can be transmitted from cell to cell in the brain.

Professor Miesenbock and his team "tapped into these gene regulatory mechanisms" of the neurons - programming them to respond to a laser.

A laser flash releases a chemical that activates the neurons

They modified the neurons by adding a sort of trigger, or receptor, to each one. This receptor was activated by a chemical called ATP.

"Since there's no ATP floating around in the fly's brain, the [modified] receptors remain closed and the flies behave just like normal flies that don't have the receptor," said Professor Miesenbock.

Now for the laser-activated trickery.

The scientists injected ATP into the flies' brains, in a form that was locked inside a light-sensitive chemical cage.

"[Then] we turned on the laser light and the light sensitive cage fell apart," Professor Miesenbock explained. "The ATP was released and acted only on the cells [with] the receptor."

Memory circuit

The laser flash was paired with an odour, which allowed the scientists to find out if their memory-writing experiment had been successful.

They gave the flies a simple choice between two odours - one of which the flies had been exposed to just before the laser flash.

"[The flies] moved along a narrow chamber and at the midpoint they were presented with an odour on the left and an odour on the right," said Professor Miesenbock.

He knew that the laser had successfully written a bad memory into the fly's brain when the insect avoided the odour that had been paired with the laser flash.

This is a real breakthrough in our understanding of how memories are formed David Shepherd, neuroscientist

The flies associated the smell with a bad experience, so the laser flash gave the fly a memory of a bad experience that it never actually had.

Simply by looking inside the flies' brains with a microscope, the researchers were able to narrow this memory formation process down to just 12 neurons.

"We labelled the cells .... that were made responsive to light and which ones were not, so by elimination we could narrow it down."

This finding, said Professor Miesenbock, has begun to unravel how animals and humans learn from mistakes and how "error signals" drive animals to adapt their behaviour.

"In the fly we have isolated and manipulated these error signals, so what we can now do is try to understand how these signals are calculated in the brain and how this works mechanistically.

"I have every expectation that the fundamental mechanisms that produce these error signals are the same in the brain of the fly as they are in the brain of the human.

David Shepherd, a neuroscientist from the University of Bangor in North Wales described the study as "a fantastic piece of work".

Professor Shepherd, who was not involved in this study, told BBC News: "We have known for years that flies are capable of sophisticated behaviours such as learning and memory. We have also been able to manipulate gene and cell function in flies.

"This work combines these elements to make a real breakthrough in our understanding of how memories are formed."

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Endangered species list released

KOCHI: The Ministry of Environment and Forests has issued a notification under the Biological Diversity Act (2002) and released a revised list of endangered species in Uttarakhand, Uttar Pradesh, Himachal Pradesh and Kerala.

The National Biodiversity Authority has issued alerts to protect 13 animal species and 26 plant species threatened with extinction in Kerala, the state with the most number of threatened species in the list.

Uttarakhand comes next, with 16 plant species and 15 animal species, while Himachal Pradesh has eight plant species and Uttar Pradesh has just one plant species threatened with extinction.

As per the conditions, no plant or animal species shall be collected live or dead by any person, except for scientific research, by herbariums and museums of scientific and academic institutions and for scientific investigation only. This can be done only with a State Biodiversity Board approval.

The notification, issued by MoEF joint secretary A K Goyal, has asked the State Biodiversity Board to conduct awareness programmes and provide educational material on notified species to Forest Department personnel, biodiversity management committees, ecotourism programmes, forest dwellers and tribals.

The 13 threatened species in Kerala include Fruit bats, the Malabar Large- Spotted Civet, Blue Whales, Sea Cows, Tigers, the Indian Vulture, Leatherback Sea Turtles, Hawkbill Sea Turtles, Hawkbill Sea Turtles, Murthi’s Frog, the Toad-skinned Frog, Green Saw Fishes and the Philautus Chalaziodes.

The 26 plant species named include Syzygium Palghatense, Syzygium Periyarensis (Wild Jamuns), Vanda Thwaitesii (Nyarapazham) and Janakia aryapathra (Aryalpathram).


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Family comes first, among plants too

SAIRA KURUP

Caring and sharing within the family are traits we associate with humans and animals. But a startling new study has found that for plants too, “blood is thicker than water”.

They cannot speak, move, see or hear, but plants apparently recognize family and respect their space, says the study. It was conducted by scientist Harsh Bais and his colleagues at the University of Delaware. “At least 3,000 plants were researched and it took us three years,” Bais tells Eureka via email. He says that Arabidopsis thaliana, a member of the mustard family and widely used as a model organism in plant biology, behaves nicely to ‘siblings’ – i.e. plants grown from seeds from the same ‘mother’. Interestingly, it is intensely competitive with strangers.

Fascinating and unbelievable though this may be, talk of plants and their ‘siblings’ is not new. In 2007, a team of Canadian researchers showed that plants can indeed identify ‘siblings’. But Bais and his team went a step further by discovering how a plant recognizes its ‘brother’ or ‘sister’, namely by root secretions. When the plant sensed unfamiliar root secretions, it began competing by growing more roots in order to absorb more of the soil’s mineral nutrients and water. But with ‘siblings’, they threw out fewer roots. When Bais treated a plant to a chemical that blocked the secretions, it seemed to lose its discriminatory sense. Clearly, there is something in these secretions that tells a plant whether it is related to others around it.

Strangers planted next to each other are often shorter, it noted, because so much of their energy is concentrated on root growth. “It’s possible that when kin are grown together, they may balance their nutrient uptake,” says Bais.

Harsh Bais with a PhD student at the University of Delaware

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