Growing evidence shows that top-down projections from excitatory neurons in piriform cortex selectively synapse onto local inhibitory granule cells in the main olfactory bulb, effectively gating their own inputs by controlling inhibition. An open question in olfaction is the role this feedback plays in shaping the dynamics of local circuits, and the resultant computational benefits it provides. Using rate models of neuronal firing in a network consisting of excitatory mitral and tufted cells, inhibitory granule cells and top-down piriform cortical neurons, we found that changes in the weight of feedback to inhibitory neurons generated diverse network dynamics and complex transitions between these dynamics. Changes in the weight of top-down feedback supported a number of computations, including both pattern separation and oscillatory synchrony. Additionally, the network could generate gamma oscillations though a mechanism we termed Top-down control of Inhibitory Neuron Gamma (TING). Collectively, these functions arose from a codimension-2 bifurcation in the dynamical system. Our results highlight a key role for this top-down feedback, gating inhibition to facilitate often diametrically different computations.

中文翻译：

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主嗅球中抑制性颗粒细胞的自上而下控制重塑神经动力学，从而产生计算的多样性


越来越多的证据表明，梨状皮质中兴奋性神经元的自上而下的投射选择性地突触到主嗅球中的局部抑制性颗粒细胞，通过控制抑制来有效地控制它们自己的输入。嗅觉中的一个悬而未决的问题是这种反馈在塑造局部电路的动态方面所发挥的作用，以及它所提供的计算效益。使用由兴奋性二尖瓣和簇状细胞、抑制性颗粒细胞和自上而下的梨状皮层神经元组成的网络中的神经元放电速率模型，我们发现抑制性神经元反馈权重的变化产生了不同的网络动态以及这些动态之间的复杂转换。自上而下反馈权重的变化支持许多计算，包括模式分离和振荡同步。此外，该网络可以通过一种我们称为“抑制神经元伽玛自上而下控制”（TING）的机制产生伽玛振荡。总的来说，这些函数源自动力系统中的余维 2 分叉。我们的结果强调了这种自上而下的反馈、门控抑制的关键作用，以促进通常截然不同的计算。