Different behaviourally relevant stimuli evoke different forms of adaptation in the olfactory system

Sensory neurons are continuously exposed to a large diversity of stimuli and adjust their response according to the recent stimulation history, in a process called adaptation. Recent studies have demonstrated that many sensory neurons not only depress (decrease their response to repetitive sensory stimulation) but some neurons exhibit facilitation: a small initial response followed by increase in response amplitude. Adaptation has been mainly studied with neutral stimuli and it is not known whether different behaviourally relevant stimuli evoke adaptation with similar or different properties. Here we used ethologically relevant stimuli to study adaptation in the zebrafish olfactory system. We found that repetitive presentation of food odour caused a variety of adaptations ranging from very strong depression to facilitation, but depression was the predominant dynamic. On the other hand, a different behaviourally-relevant stimulus, alarm substance, evoked much stronger facilitation and also decreased the amplitude of responses to food presentation. Other sensory modalities, aversive mechanosensory and attractive visual stimuli, also caused adaptation with different properties in the same brain area. Different forms of adaptation may therefore be used for processing sensory stimuli evoking different behavioural reactions. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=113 SRC="FIGDIR/small/612693v1_ufig1.gif" ALT="Figure 1"> View larger version (33K): org.highwire.dtl.DTLVardef@1cd5c18org.highwire.dtl.DTLVardef@1592ea1org.highwire.dtl.DTLVardef@4841corg.highwire.dtl.DTLVardef@7d88d9_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsFood odour evokes a diversity of adaptations ranging from extreme depression to facilitation Alarm substance evokes much stronger facilitation than food odour Alarm substance inhibits responses to food odour Mechanosensory stimulation evokes both depression and facilitation Visual stimuli evoke responses in the olfactory bulbs that strongly and quickly depress