LIGHT: Scientists can use light to switch on a neuron
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In the film Amèlie, the main character is a young eccentric woman who attempts to change the lives of those around her for the better. One day Amèlie finds an old rusty tin box of childhood mementos in her apartment, hidden by a boy decades earlier. After tracking down Bretodeau, the owner, she lures him to a phone booth where he discovers the box. Upon opening the box and seeing a few marbles, a sudden flash of vivid images come flooding into his mind. Next thing you know, Bretodeau is transported to a time when he was in the schoolyard scrambling to stuff his pockets with hundreds of marbles while a teacher is yelling at him to hurry up.
We have all experienced this: a seemingly insignificant trigger, a scent, a song, or an old photograph transports us to another time and place. Now a group of neuroscientists have investigated the fascinating question: Can a few neurons trigger a full memory?
In a new study, published in Nature, a group of researchers from MIT showed for the first time that it is possible to activate a memory on demand, by stimulating only a few neurons with light, using a technique known as optogenetics. Optogenetics is a powerful technology that enables researchers to control genetically modified neurons with a brief pulse of light.
To artificially turn on a memory, researchers first set out to identify the neurons that are activated when a mouse is making a new memory. To accomplish this, they focused on a part of the brain called the hippocampus, known for its role in learning and memory, especially for discriminating places. Then they inserted a gene that codes for a light-sensitive protein into hippocampal neurons, enabling them to use light to control the neurons.
With the light-sensitive proteins in place, the researchers gave the mouse a new memory. They put the animal in an environment where it received a mild foot shock, eliciting the normal fear behavior in mice: freezing in place. The mouse learned to associate a particular environment with the shock.
Next, the researchers attempted to answer the big question: Could they artificially activate the fear memory? They directed light on the hippocampus, activating a portion of the neurons involved in the memory, and the animals showed a clear freezing response. Stimulating the neurons appears to have triggered the entire memory.
The researchers performed several key tests to confirm that it was really the original memory recalled. They tested mice with the same light-sensitive protein but without the shock; they tested mice without the light-sensitive protein; and they tested mice in a different environment not associated with fear. None of these tests yielded the freezing response, reinforcing the conclusion that the pulse of light indeed activated the old fear memory.
In 2010, optogenetics was named the scientific Method of the Year by the journal Nature Methods. The technology was introduced in 2004 by a research group at Stanford University led by Karl Deisseroth, a collaborator on this research. The critical advantage that optogenetics provides over traditional neuroscience techniques, like electrical stimulation or chemical agents, is speed and precision. Electrical stimulation and chemicals can only be used to alter neural activity in nonspecific ways and without precise timing. Light stimulation enables control over a small subset of neurons on a millisecond time scale.
Over the last several years, optogenetics has provided powerful insights into the neural underpinnings of brain disorders like depression, Parkinson’s disease, anxiety, and schizophrenia. Now, in the context of memory research, this study shows that it is possible to artificially stimulate a few neurons to activate an old memory, controlling an animals’ behavior without any sensory input. This is significant because it provides a new approach to understand how complex memories are formed in the first place.
Lest ye worry about implanted memories and mind control, this technology is still a long way from reaching any human brains. Nevertheless, the first small steps towards the clinical application of optogenetics have already begun. A group at Brown University, for example, is working on a wireless optical electrode that can deliver light to neurons in the human brain. Who knows, someday, instead of new technology enabling us to erase memories á la Eternal Sunshine of the Spotless Mind, we may actually undergo memory enhancement therapy with a brief session under the lights.
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Add CommentThis experiment proves that mouse memories of electroshock treatment can be controlled by a single neuron. This might be great news for psychotic mice, but human beings' more complex memories of painful associations and relationships throughout their life may encoded through many much more complex interactions among many neurons. People's memories may be much more difficult to control than this experiment seems to indicate...
Reply | Report Abuse | Link to thisHow about a light guide collimator & receptive action, that has already been used for a bad purpose - guess where?
Reply | Report Abuse | Link to thisHopefully this technology will be confined to the cause of good, not otherwise...
Reply | Report Abuse | Link to thisAfter Lieutenant Willis, shining the light pen flashing intermittently in the officer's vacant eyes, said "Officer Smith, you will forget everything after you exited the C-17 Globemaster with your team into Afghanistan, and to the point that I snap my fingers and say the word 'resume', do you understand?" In a deadpan voice he replied "Yes, Ma'am."
Adjusting her meticulously coiffed hair, then snapping her fingers she said "Resume. Officer Smith, you are being debriefed at an undisclosed Army base. Welcome back. Do you remember anything after your team was dispatched to Afghanistan?"
Looking rather shaken, Officer Smith says slowly, "No. That's the problem. I don't remember anything. What happened after we made the jump? ..."
Actually, this is not the first example of optogenetic control of neurons to activate memories; Claridge-Chang et al (Cell 2009) from the Miesenboeck lab were able to write and activate an aversive olfactory memory in Drosophila.
Reply | Report Abuse | Link to thisActually, this is not the first example of optogenetic control of neurons to activate memories; Claridge-Chang et al (Cell 2009) from the Miesenboeck lab were able to write and activate an aversive olfactory memory in Drosophila.
Reply | Report Abuse | Link to this"Then they inserted a gene that codes for a light-sensitive protein into hippocampal neurons, enabling them to use light to control the neurons."
Reply | Report Abuse | Link to this-----I'm a little confused with the relationship between light-sensitive protein and hippocampal neurons.
In the mouse test, no words about the light directing on the light-sensitive protein,but just "the light-sensitive proteins in place" and "a mild foot shock".
Who could help me to understand it? Thanks!
Here is a case study using another pathway to irradiate the mid-brain - through the nasal cavity, using a technique called "Intranasal Light Therapy" - see http://www.mediclights.com.
Reply | Report Abuse | Link to thisWe wanted to see if it would affect the HUMAN subject's epileptic condition but the immediate outcome is the reactivation of old repressed memory! Much like the outcome in the related animal study published in Nature, in which negative memories are involved.
Between the nasal cavity and the hippocampus is a relatively short distance of soft tissue. This may be a more elegant pathway than have so far been deployed in optogenetic experiments, which has largely been transcranial. With the intranasal pathway, there may not be a need for the higher energy as well as longer wavelength (infra-red) involving the use of lasers. The Intranasal Light Therapy device used is only of 8 mW in energy driving a visible red LED with the wavelength of 633 nM. Completely safe and easy to deploy by all accounts.
Our own evidence (albeit largely anecdotal) have provided an astonishingly large percentage of successful outcomes with regard to successful brain-related disorders such as sleep disorders and post-stroke conditions. Chinese studies (notwithstanding some generic reservations of North American scientists with regard to the country's credibility)have supported our observations.
Would any research group be interested to investigate the optogenetic outcomes further with a ready, simple-to-use light irradiation device? I can be contacted at contact@mediclights.com.
Didn't Wilder Penfield in the 1930s assume that he had retrieved memories from a discrete location in the brain using electrical stimulation? And didn't he later change his mind to believe that the memories involved a large number of neurons throughout the brain and that he was only catching the signal that passed through the spot he activated? Why, except for the instrumentation, would these latest results be different? Was Penfield's reevaluation wrong?
Reply | Report Abuse | Link to thisIt should be clear that situational recall is coupled to current sensory input. Otherwise our memories would be random and not relate meaningfully to ongoing circumstance. We could not function appropriately or benefit from past learning experience. This experiment confirms what is rather obvious.
Reply | Report Abuse | Link to thisThere is also extensive evidence to indicate a link between memory and protein synthesis as in synaptic elaborations, but this does not mean that memories are stored in protein. It means that recall is linked to protein synthesis controlled by protein enzymes that are not themselves chemically altered in reactions they regulate. Their active sites are not co-valent. See the link on how gene expression works at http://www.cosmic-mindreach.com/Gene_Expression.html.
Recall also works vice versa when memories keep recycling in thought due to strong associated emotional energy patterns that keep refluxing patterns of thought into conscious reflection via the primitive hippocampus. The extensive work by P. D. MacLean on the Limbic System is well documented. The whole brain is involved but there is a built in schizo-physiology as MacLean called it. There are no direct biological controls of the neo-cortex (higher conscious functions) over the ancient Limbic cortex which is intimately connected to the autonomic nervous system. Our reasoning left-brain language hemisphere, our mute right brain intuitive hemisphere and our emotional Limbic brain can function independently and they are confined to live in the same house together, with frequent disagreements.
We seek a satisfactory balance between our three brains through how we intuitively perceive and behaviourally relate to a transcending context of some kind. For animals the behavioural context is their physical territory. For humans our social-spiritual-psychological environment takes precedence. For a much simplified illustration see the link: http://www.cosmic-mindreach.com/Three-Brains.html.
Interesting stuff. I curious about whether or not there's any relationship between light and <a href="http://lumositymindgames.com">Memory</a>
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