Navigation Links
Making sense of sensory connections

PASADENA, Calif.A key feature of human and animal brains is that they are adaptive; they are able to change their structure and function based on input from the environment and on the potential associations, or consequences, of that input. For example, if a person puts his hand in a fire and gets burned, he learns to avoid flames; the simple sight of a flame has acquired a predictive value, which in this case, is repulsive. To learn more about such neural adaptability, researchers at the California Institute of Technology (Caltech) have explored the brains of insects and identified a mechanism by which the connections in their brain change to form new and specific memories of smells.

"Although these results were obtained from experiments with insects, the components of the mechanism exist also in vertebrate, including mammalian, brains which means that what we describe may be of wide applicability," says Stijn Cassenaer, a Broad Senior Research Fellow in brain circuitry at Caltech and lead author of a paperpublished in the journal Nature on January 25that outlined the findings. The study focused on insects because their nervous systems are smaller, and thus likely to reveal their secrets sooner than those of their vertebrate counterparts.

To home in on sensory memories, the researchers concentrated on olfaction, or the sense of smell. When a person encounters a favorite food or the perfume of a loved one, she will typically experience a recall, usually positive, based on the memories evoked by those smells. Such a recallto a smell, sound, taste, or any other sensory stimulusis evidence of "associative" learning, says Gilles Laurent, a former professor of biology at Caltech and senior author of the study, as learning often means assigning a value, such as beneficial or not, to inputs that were until then neutral. The original, neutral stimulus acquires significance as a result of being paired, or associated, with a reinforcing reward or punishmentin this case, the pleasant emotion recalled by a smell.

"When we learn that a particular sensory stimulus predicts a reward, there is general agreement that this knowledge is stored by changing the connections between particular neurons," explains Cassenaer. The problem, however, is that the biological signals that represent value (positive or negative) are broadcast nonspecifically throughout the brain. How then, are they assigned specifically to particular connections, so that a certain sensory input, until then neutral, acquires its new, predictive value? "In this study, we carried out experiments to investigate how the brain identifies exactly which connections, out of an enormously large number of possibilities, should be changed to store the memory of a specific association."

To get a closer look at these connections, Cassenaer and Laurentwho is now director at the Max Planck Institute for Brain Research in Germanymeasured neural activity in an area of the locust brain where olfactory memories are thought to be stored. They found that what allows the brain to identify which synapses should be modified, and thus where the nonspecific reward signal should act, is a very transient synchronization between pairs of connected neurons.

"When pairs of connected neurons fire in quick succession, the strength of their connection can be altered. This phenomenon, called spike-timing dependent plasticity, has been known for many years. What is new, however, is recognizing that it also makes these connections sensitive to an internal signal released in response to a reward," says Cassenaer. "If no reward is encountered, the cells' sensitivity fades. However, if the sensory stimulus is followed by a reward within a certain time window, then these connections are the only ones altered by the internal reward signal. All other connections remain unaffected."

Laurent says that the molecular underpinnings of this phenomenon, as well as the process by which the stored memories are later read out, are an area of much-needed exploration.

"We are currently developing the necessary tools to examine this with sufficient specificity, which will allow us to evaluate animals' behavior as they learn," says Cassenaer.


Contact: Deborah Williams-Hedges
California Institute of Technology

Related biology news :

1. The making of Dig It! the Secrets of Soil exhibit
2. Making metabolism more inefficient can reduce obesity
3. Making flies sick reveals new role for growth factors in immunity
4. Scientists present moving theory behind bacterial decision-making
5. Making the ultimate family sacrifice
6. Tips for making a green holiday from the worlds largest scientific society
7. How chromosomes meet in the dark -- Switch that turns on X chromosome matchmaking
8. Process can cut the cost of making cellulosic biofuels
9. U of Minnesota research finds most road salt is making it into the states lakes and rivers
10. MacArthur Foundation awards planning grant to improve decision-making in energy policy
11. It takes a genome: How a clash between our genes and modern life is making us sick
Post Your Comments:
Related Image:
Making sense of sensory connections
(Date:11/17/2015)... 17, 2015 Paris ... --> Paris , qui s,est ... DERMALOG, le leader de l,innovation biométrique, a inventé le ... et empreintes sur la même surface de balayage. Jusqu,ici, ... l,autre pour les empreintes digitales. Désormais, un seul scanner ...
(Date:11/12/2015)... 2015  Arxspan has entered into an agreement ... for use of its ArxLab cloud-based suite of ... partnership will support the institute,s efforts to electronically ... information internally and with external collaborators. The ArxLab ... the Institute,s electronic laboratory notebook, compound and assay ...
(Date:11/9/2015)... , Nov. 09, 2015 ... the addition of the "Global Law ... their offering. --> ) ... "Global Law Enforcement Biometrics Market 2015-2019" ... Research and Markets ( ) has ...
Breaking Biology News(10 mins):
(Date:12/1/2015)... -- Today the Allen Institute announced the opening of ... South Lake Union neighborhood, the city,s biotechnology hub. Located ... Avenue North, the 270,000 square foot life sciences building ... and the Allen Institute for Cell Science. ... Allen Institute. "We started by building a map of ...
(Date:12/1/2015)... 2015 Frost & Sullivan is proud ... addresses ways companies can innovate and transform themselves ... --> ... --> --> ... as the disrupting factors altering the industry, such ...
(Date:12/1/2015)... , Dec. 01, 2015 ... addition of the "2016 Europe Cell ... Innovative Technologies, Competitive Strategies, Opportunities for Suppliers--France, ... their offering. --> ) ... "2016 Europe Cell Surface Markers: Country Volume ...
(Date:12/1/2015)... ... December 01, 2015 , ... RURO, Inc., a leading ... laboratory animal colony management software solution, ezColony®, is now available as a subscription-based, ... , Many organizations are moving to cloud-hosting for LIMS ...
Breaking Biology Technology: