Associative Conditioning Tunes Transient Dynamics of Early Olfactory Processing

FERNANDEZ P *; LOCATELLI F *; PERSON-RENNELL N; DELEO G; SMITH B; * AMBOS AUTORES CONTRIB POR IGUA

JOURNAL OF NEUROSCIENCE

Society for Neuroscience

Lugar: Washington DC EEUU; Año: 2009 vol. 29 p. 10191 - 10202

0270-6474

Odors evoke complex spatiotemporal responses in the insect antennal lobe (AL) and mammalian olfactory bulb. However, the behavioural relevance of spatiotemporal coding remains unclear. In the present work we combined behavioral analyses with calcium imaging of odor induced activity in the honeybee AL to evaluate the relevance of this temporal dimension in the olfactory code. We used a new way for evaluation of odor similarity of binary mixtures in behavioral studies, which involved testing whether a match of odor-sampling time is necessary between training and testing conditions for odor recognition during associative learning. Using graded changes in the similarity of the mixture ratios, we found high correlations between the behavioral generalization across those mixtures and a gradient of activation inALoutput. Furthermore, short odor stimuli of 500msor less affected how well odors were matched with a memory template, and this time corresponded to a shift from a sampling-time-dependent to a sampling-time-independent memory. Accordingly, 375 ms corresponded to the time required for spatiotemporal AL activity patterns to reach maximal separation according to imaging studies. Finally, we compared spatiotemporal representations of binary mixtures in trained and untrained animals. AL activity was modified by conditioning to improve separation of odor representations. These data suggest that one role of reinforcement is to “tune” the AL such that relevant odors become more discriminable.