Download CP Herry Nature December 8, 2011 - Host Laboratories / Research

Paris, 8th December 2011
Press information
The cortex plays an essential part in emotional learning
Cooperation between a team of French researchers from Inserm’s “Neurocentre
Magendie, Bordeaux” Research Unit 862 directed by Cyril Herry and a team of Swiss
researchers from the Friedrich Miescher Institute of Biomedical Research directed by
Andreas Lüthi at that institute has shown, for the first time, that the cortex, which is
the largest zone of the brain and which is generally associated with high cognitive
functions, is also a key zone for emotional learning. The study, initiated by the Swiss
researchers and published in Nature, constitutes ground-breaking work in exploring
emotions in the brain.
Anxiety disorders constitute a complex family of pathologies affecting about 10% of adults.
Patients suffering from such disorders fear certain situations or objects to exaggerated
extents totally out of proportion to the real danger they present. The amygdala, a deep-brain
structure, plays a key part in processing fear and anxiety. Its functioning can be disrupted by
anxiety disorders.
Although researchers are well acquainted with the neurons of the amygdala and with the part
those neurons play in expressing fear, their knowledge of the involvement of other regions of
the brain remains limited. And yet, there can be no fear without sensory stimulation: before
we become afraid, we hear, we see, we smell, we taste, or we feel something that triggers
the fear. This sensory signal is, in particular, processed in the cortex, the largest region of
the brain.
For the first time, these French and Swiss scientists have succeeded in visualising the path
of a sensory stimulus in the brain during fear learning, and in identifying the underlying
neuronal circuits.
What happens in the brain?
During the experiments conducted by the researchers, mice learnt to associate a sound with
an unpleasant stimulus so that the sound itself became unpleasant for the animal.
The researchers used two-photon calcium imaging to visualise the activity of the neurons in
the brain during this learning process. This imaging technique involves injecting a chemical
indicator that is then absorbed by the neurons. When the neurons are stimulated, the
calcium ions penetrate into the cells, where they increase the brightness of the indicator,
which can then be detected under a scanning microscope.
Under normal conditions, the neurons of the auditory cortex are highly inhibited. During fear
learning, a “disinhibitory” microcircuit in the cortex is activated: thus, for a short time window
during the learning process, the release of acetylcholine in the cortex makes it possible to
activate this microcircuit and to disinhibit the excitatory projection cells of the cortex. Thus,
when the animal perceives a sound during fear learning, that sound is processed much more
intensely than under normal conditions, thereby facilitating formation of memory. All of these
stages have been visualised by means of the techniques developed by the researchers.
In order to confirm their discoveries, the researchers used another highly innovative recent
technique (optogenetics) to disrupt the disinhibition selectively during the learning process.
When they tested the memories of their mice (i.e. the association between the sound and the
unpleasant stimulus), the next day they observed a severe deterioration in memory, directly
showing that the phenomenon of cortical disinhibition is essential to the process of learning
fear.
The discovery of this cortical disinhibitory microcircuit opens up interesting clinical prospects,
and researchers can now imagine, in very specific situations, how to prevent a traumatism
from establishing itself and from becoming pathological.
Pour en savoir plus:
Source
A disinhibitory microcircuit for associative fear learning in the auditory cortex
Johannes J. Letzkus1*, Steffen B. E.Wolff1,2*, Elisabeth M. M. Meyer1,2, Philip Tovote1,
Julien Courtin3, Cyril Herry3 & Andreas Lüthi1
1Friedrich Miescher Institute for Biomedical Research, Maulbeerstrasse 66, CH-4058 Basel,
Switzerland.
2University of Basel, CH-4003 Basel, Switzerland.
3INSERM U862, Neurocentre Magendie, 146 Rue Léo-Saignat, 33077 Bordeaux, France.
Nature, décembre 2011 http://dx.doi.org/10.1038/nature10674
Contact chercheur
Cyril Herry
Unité Inserm U862 « Neurocentre Magendie »
Tel: 05 57 57 37 26
Email: [email protected]