Title: 1 a Model of Cholinergic Modulation in Olfactory Bulb and Piriform Cortex 2

15 In this work we investigate in a computational model how cholinergic inputs to the 16 olfactory bulb (OB) and piriform cortex (PC) modulate odor representations. We use 17 experimental data derived from different physiological studies of ACh modulation of the 18 bulbar and cortical circuitry and the interaction between these two areas. The results 19 presented here indicate that cholinergic modulation in the OB significantly increases 20 contrast and synchronization in mitral cell output. Each one of these effects is derived 21 from distinct neuronal interactions, with different groups of interneurons playing 22 different roles. Both bulbar modulation effects contribute to more stable learned 23 representations in PC, with pyramidal networks trained using cholinergic modulated 24 inputs from the bulb exhibiting more robust learning than those trained with unmodulated 25 bulbar inputs. This increased robustness is evidenced as better recovery of memories 26 from corrupted patterns and lower concentration inputs as well as increased memory 27 capacity. 28