Neurons in the barrel cortex turn into processing whisker and odor signals: a cellular mechanism for the storage and retrieval of associative signals

Dangui Wang,Jin-Hui Wang,Wei Lu,Changfeng Chen,Na Chen,Bo Wen,Zhuofan Lei,Yahui Liu,Zilong Gao,Jun Zhao,Jing Feng

doi:10.3389/fncel.2015.00320

Abstract

Associative learning and memory are essential to logical thinking and cognition. How the neurons are recruited as associative memory cells to encode multiple input signals for their associated storage and distinguishable retrieval remains unclear. We studied this issue in the barrel cortex by in vivo two-photon calcium imaging, electrophysiology, and neural tracing in our mouse model that the simultaneous whisker and olfaction stimulations led to odorant-induced whisker motion. After this cross-modal reflex arose, the barrel and piriform cortices connected. More than 40% of barrel cortical neurons became to encode odor signal alongside whisker signal. Some of these neurons expressed distinct activity patterns in response to acquired odor signal and innate whisker signal, and others encoded similar pattern in response to these signals. In the meantime, certain barrel cortical astrocytes encoded odorant and whisker signals. After associative learning, the neurons and astrocytes in the sensory cortices are able to store the newly learnt signal (cross-modal memory) besides the innate signal (native-modal memory). Such associative memory cells distinguish the differences of these signals by programming different codes and signify the historical associations of these signals by similar codes in information retrievals.

Highlights

Associative learning and memory are the bases of the cognitions (Byrne et al, 2007; Mayes et al, 2007; Suzuki, 2008; Lansner, 2009; Sanhueza and Lisman, 2013)
Pairing Stimulations to Whiskers and Olfaction Leads to Odorant-induced Whisker Motion Mice were divided into three groups to receive the simultaneous pairing of unconditioned Whisker stimuli (WS) and conditioned odorant stimulus (OS; paired-stimulus group, paired stimulus group (PSG)), the unpairing of WS and Odor stimuli (OS) or no stimulations
We study the recruitment of the cortical neurons and astrocytes for the storage and retrieval of the associated signals in a new mouse model of conditioned reflex

Summary

Introduction

Associative learning and memory are the bases of the cognitions (Byrne et al, 2007; Mayes et al, 2007; Suzuki, 2008; Lansner, 2009; Sanhueza and Lisman, 2013). Associative learning is a process in that experience and knowledge are acquired by the associations of two sensory signals or a sensory signal with a behavioral operation. The memories of these signals indicatively arise if they can be retrieved by cues. In term of the cellular mechanisms for associative memory, activity-dependent plasticity at the synapses and neurons, e.g., long-term. Experience-dependent learning led to structural plasticity in spines and excitatory synapses (Trachtenberg et al, 2002; Sadaka et al, 2003; Holtmaat and Svoboda, 2009; Mégevand et al, 2009; Harlow et al, 2010; Wilbrecht et al, 2010; Ashby and Isaac, 2011; Cheetham et al, 2012; Margolis et al, 2012). How the neurons are recruited to be associative memory cells that compute the associated signals for their storage remains to be addressed, especially in vivo, as memory processes are better to be examined in vivo (Hasegawa et al, 1998; Cadoret and Petrides, 2007; Won and Silva, 2008)

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