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First glimpse of brain circuit that helps experience to shape perception
Date:
March 4, 2014
Source:
Cold Spring Harbor Laboratory
Summary:
How
do our memories shape the way sensory information is collected? For the
first time, scientists have demonstrated a way to observe how our
experiences shape sensory information in awake animals. The team was
able to measure the activity of a group of inhibitory neurons that links
the odor-sensing area of the brain with brain areas responsible for
thought and cognition. This connection provides feedback so that
memories and experiences can alter the way smells are interpreted.
CSHL
researchers have engineered a system to observe how experiences shape
the way sensory input is collected. For the first time, they were able
to measure the activity of inhibitory neurons that link the sense of
smell with memory and cognition in awake animals, offering insight into
how our expectations influence the way we perceive the world around us.
Credit: © masha_batt / Fotolia
Odors
have a way of connecting us with moments buried deep in our past. Maybe
it is a whiff of your grandmother's perfume that transports you back
decades. With that single breath, you are suddenly in her living room,
listening as the adults banter about politics. The experiences that we
accumulate throughout life build expectations that are associated with
different scents. These expectations are known to influence how the
brain uses and stores sensory information. But researchers have long
wondered how the process works in reverse: how do our memories shape the
way sensory information is collected?
In work published today in Nature Neuroscience,
scientists from Cold Spring Harbor Laboratory (CSHL) demonstrate for
the first time a way to observe this process in awake animals. The team,
led by Assistant Professor Stephen Shea, was able to measure the
activity of a group of inhibitory neurons that links the odor-sensing
area of the brain with brain areas responsible for thought and
cognition. This connection provides feedback so that memories and
experiences can alter the way smells are interpreted.
The inhibitory neurons that forge the link are known as granule cells. They are found in the core of the olfactory bulb, the area of the mouse brain responsible for receiving odor information from the nose. Granule cells in the olfactory bulb receive inputs from areas deep within the brain involved in memory formation and cognition. Despite their importance, it has been almost impossible to collect information about how granule cells function. They are extremely small and, in the past, scientists have only been able to measure their activity in anesthetized animals. But the animal must be awake and conscious in order to for experiences to alter sensory interpretation. Shea worked with lead authors on the study: Brittany Cazakoff, graduate student in CSHL's Watson School of Biological Sciences, and Billy Lau, PhD, a postdoctoral fellow. They engineered a system to observe granule cells for the first time in awake animals.
Granule cells relay the information they receive from neurons involved in memory and cognition back to the olfactory bulb. There, the granule cells inhibit the neurons that receive sensory inputs. In this way, "the granule cells provide a way for the brain to 'talk' to the sensory information as it comes in," explains Shea. "You can think of these cells as conduits which allow experiences to shape incoming data."
Why might an animal want to inhibit or block out specific parts of a stimulus, like an odor? Every scent is made up of hundreds of different chemicals, and "granule cells might help animals to emphasize the important components of complex mixtures," says Shea. For example, an animal might have learned through experience to associate a particular scent, such as a predator's urine, with danger. But each encounter with the smell is likely to be different. Maybe it is mixed with the smell of pine on one occasion and seawater on another. Granule cells provide the brain with an opportunity to filter away the less important odors and to focus sensory neurons only on the salient part of the stimulus.
Now that it is possible to measure the activity of granule cells in awake animals, Shea and his team are eager to look at how sensory information changes when the expectations and memories associated with an odor change. "The interplay between a stimulus and our expectations is truly the merger of ourselves with the world. It exciting to see just how the brain mediates that interaction," says Shea.
NARESH KUMAR 2 SEM
The inhibitory neurons that forge the link are known as granule cells. They are found in the core of the olfactory bulb, the area of the mouse brain responsible for receiving odor information from the nose. Granule cells in the olfactory bulb receive inputs from areas deep within the brain involved in memory formation and cognition. Despite their importance, it has been almost impossible to collect information about how granule cells function. They are extremely small and, in the past, scientists have only been able to measure their activity in anesthetized animals. But the animal must be awake and conscious in order to for experiences to alter sensory interpretation. Shea worked with lead authors on the study: Brittany Cazakoff, graduate student in CSHL's Watson School of Biological Sciences, and Billy Lau, PhD, a postdoctoral fellow. They engineered a system to observe granule cells for the first time in awake animals.
Granule cells relay the information they receive from neurons involved in memory and cognition back to the olfactory bulb. There, the granule cells inhibit the neurons that receive sensory inputs. In this way, "the granule cells provide a way for the brain to 'talk' to the sensory information as it comes in," explains Shea. "You can think of these cells as conduits which allow experiences to shape incoming data."
Why might an animal want to inhibit or block out specific parts of a stimulus, like an odor? Every scent is made up of hundreds of different chemicals, and "granule cells might help animals to emphasize the important components of complex mixtures," says Shea. For example, an animal might have learned through experience to associate a particular scent, such as a predator's urine, with danger. But each encounter with the smell is likely to be different. Maybe it is mixed with the smell of pine on one occasion and seawater on another. Granule cells provide the brain with an opportunity to filter away the less important odors and to focus sensory neurons only on the salient part of the stimulus.
Now that it is possible to measure the activity of granule cells in awake animals, Shea and his team are eager to look at how sensory information changes when the expectations and memories associated with an odor change. "The interplay between a stimulus and our expectations is truly the merger of ourselves with the world. It exciting to see just how the brain mediates that interaction," says Shea.
NARESH KUMAR 2 SEM
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