A recent study published in eLife demonstrates that the anterior piriform cortex (APC), which is an olfactory sensory cortex, is important for the active information maintenance in working memory. This work was performed by researchers in Dr. LI Chengyu’s Lab at the Center for Excellence in Brain Science and Intelligence Technology, Institute of Neuroscience, State Key Laboratory of Neuroscience, Chinese Academy of Sciences.

　　Working memory is a critical brain function for maintaining and manipulating information over delay periods of seconds. It is debated whether delay-period neural activity in sensory regions is important for the active maintenance of information during the delay period.

　　In this study, the researchers tackle this question by examining the anterior piriform cortex (APC), an olfactory sensory cortex, in head-fixed mice performing several olfactory working memory tasks. Active information maintenance is necessary in these tasks, especially in a dual-task paradigm in which mice are required to perform another distracting task while actively maintaining information during the delay period. Optogenetic suppression of neuronal activity in APC during the delay period impaired performance in all the tasks. Furthermore, electrophysiological recordings revealed that APC neuronal populations encoded odor information in the delay period even with an intervening distracting task.

　　Thus, delay activity in APC is important for active information maintenance in olfactory working memory.

　　This work was published online in eLife on July 17^th, entitled "Active information maintenance in working memory by a sensory cortex". Xiaoxing Zhang and Wenjun Yan contribute equally to this work. Dr. Chengyu Li is the corresponding author. The work was supported by the National Science Foundation for Distinguished Young Scholars of China (31525010, to CTL), the Shanghai Municipal Science and Technology Major Project (Grant No. 2018SHZDZX05), the Strategic Priority Research Program of the Chinese Academy of Sciences (Grant No. XDB32010100), the General Program of the Chinese National Science Foundation (31471049), the Instrument Developing Project of the Chinese Academy of Sciences (Grant No. YZ201540), the Key Research Program of Frontier Sciences of the Chinese Academy Sciences (QYZDB-SSW-SMC009), the Key Project of the Shanghai Science and Technology Commission (No.15JC1400102, 16JC1400101), the China–Netherlands CAS-NWO Programme: The Future of Brain and Cognition (153D31KYSB20160106), the Spanish Ministry of Science, Innovation and Universities and the European Regional Development Fund (BFU2015-65318-R, to AC), and the CERCA Programme/Generalitat de Catalunya (to AC).

　　Figure legend: (a) Diagram of the experimental setup. (b) Design of the DNMS task. (c) Correct rates in the DNMS task following delay-period optogenetic suppression in APC. Each point in the figure represents the averaged result from one mouse. ***, p<0.001, mixed-between-within-ANOVA, genotype laser interaction; error bars show the 95% confidence intervals of the means from bootstrapping of 1000 repeats. Numbers in brackets show the effect size measured by Cohen’s d for control (in black) and ChR2 (in blue) groups.(d) Behavioral diagram for the dual-task design. (e) False alarm rate after suppressing the APC activity during the later-phase delay period after distractors in the dual-task. P values were obtained from mixed-between-within-ANOVA, genotype laser interaction; error bars show the 95% confidence intervals of the means from bootstrapping of 1000 repeats. Numbers in brackets represent the effect size as measured by Cohen’s d for control (in black) and ChR2 (in blue) groups. *, p = 0.014. (f) Spike raster (top) and peristimulus time histogram (PSTH, bottom) of an example neuron recorded during the DNMS task. Shadow for PSTH shows the 95% confidence intervals. Top inset: spike waveforms from tetrode recording. The data in this and the following panel contained only correct trials. (g) Distribution of single unit sample-odor selectivity for the DNMS task. See research article for details.