|
 |
||
      |
|
|
|
 Research & Giving News Article  on Human Anxiety Disorders New insights into the neural basis of anxiety In a recent issue of the journal Nature Neuroscience, Dr. Gross and colleagues reported that a specific receptor for the neurotransmitter serotonin and a neural circuit involving a brain region called the hippocampus play crucial roles in mediating fear responses in ambiguous situations. When a mouse learns that a certain cue, for example an audible tone, is always followed by an electrical shock, it comes to associate the two and freezes with fear whenever it hears the tone--even if the shock is not delivered. But in real life, the situation is not always so clear; a stimulus will only sometimes be followed by a threat, while other times nothing might happen. The scientists demonstrated that normal mice show less fear toward such ambiguous cues than to clearly threatening stimuli. Dr. Gross’s team has discovered that this response to ambiguous stimuli requires a specific receptor molecule for serotonin, a neurotransmitter that helps many nerve cells in the brain to communicate. Mice that lack the serotonin receptor dubbed “1A” have problems processing ambiguous stimuli and react to them with full-fledged fear responses. The cause of this overreaction is wrongly connected cells in their brains. Serotonin signaling is very important for brain development and if the 1A receptor is missing, defects arise in the wiring of the brain that affect the behavior of mice later on in life. “In humans,” Dr. Gross says, “serotonin signaling has been implicated in disorders including depression and anxiety, and like our mouse ‘patients,’ people suffering from these conditions also overreact to ambiguous situations. We have identified the brain regions responsible for such complex fear behavior and the processing of ambiguous cues.” Using a new technique to switch off neural activity in specific brain cells in living mice, Dr. Gross and his colleagues discovered that a specific part of the hippocampus is required for correct processing of ambiguous stimuli. “Shutting down a specific circuit in the hippocampus abolished fear reactions only to ambiguous cues,” says Theodoros Tsetsenis, a member of the research team. “The pathway must be involved in processing and assessing the value of stimuli. It seems to bias mice to interpret situations as threatening.” The hippocampus is known to play an important role in both learning and memory, but the results of Dr. Gross’s experiments reveal its more general role in evaluating information and assessing contingencies. Neural circuits that govern fundamental behaviors like fear are often similar across different species, their “conservation” by evolution attributable in part to their utility, from the point of view of an organism’s survival or well-being. It is not surprising, then, that human studies have suggested a role for the hippocampus in the human anxiety response that might be similar to that just discovered in mice. The new insights gained into serotonin signaling via the 1A receptor and the role of the hippocampus in fear behavior in mice may therefore help shed light on the neural basis of human anxiety disorders and open up new avenues for therapies. This article was adapted with permission of the European Molecular Biology Laboratory. |
Media Contact
Upcoming NARSAD Events
Latest News from NARSAD
Spotlight
|
|
For the Media