提出可自适应先验的生成模型,解释视觉皮层如何动态调整感知策略。
TAVAE: A VAE with Adaptable Priors Explains Contextual Modulation in the Visual Cortex
- 构建基于变分自编码器的TAVAE模型,实现任务相关先验的快速学习与重用
- 模型预测的后验不确定性与小鼠视觉皮层响应中的双峰特征高度一致
- 揭示任务驱动的上下文先验可早期部署于视觉初级皮层,支持灵活感知
大脑通过学习到的规律解释视觉信息,这一过程可形式化为在先验约束下的概率推断。视觉皮层建立此类先验,部分由自上而下的连接传递高层统计信息至低层皮层。尽管已有证据表明适应性可使先验反映自然图像结构,但尚不清楚在特定任务学习中能否实现类似灵活性。为此,我们构建了一个针对简单辨别任务优化的V1生成模型,并结合小鼠执行类似任务的大规模神经记录进行分析。依据近期研究假设,将V1神经活动视为生成模型中的潜在后验,从而探究任务相关的先验特性。为获得灵活的测试平台,我们扩展了变分自编码器(VAE)框架,使任务可通过复用先前学习的表征高效获取。由任务-摊销变分自编码器(TAVAE)学习到的任务特异性先验,用于分析当刺激违反训练统计时产生的偏差。模型后验中出现的不匹配信号反映了不确定性,其特征与真实小鼠记录中观察到的双峰响应模式相符。该任务优化的生成模型成功解释了V1群体活动的关键特性,包括每日内响应的更新。结果证实,视觉系统可按需学习并部署灵活的任务特异性上下文先验,且可作用于视觉皮层的入口层级。
原文摘要 · Abstract (English)
The brain interprets visual information through learned regularities, a computation formalized as probabilistic inference under a prior. The visual cortex establishes priors for this inference, some delivered through established top-down connections that inform low-level cortices about statistics represented at higher levels in the cortical hierarchy. While evidence shows that adaptation leads to priors reflecting the structure of natural images, it remains unclear whether similar priors can be flexibly acquired when learning a specific task. To investigate this, we built a generative model of V1 optimized for a simple discrimination task and analyzed it together with large-scale recordings from mice performing an analogous task. In line with recent approaches, we assumed that neuronal activity in V1 corresponds to latent posteriors in the generative model, enabling investigation of task-related priors in neuronal responses. To obtain a flexible test bed, we extended the VAE formalism so that a task can be acquired efficiently by reusing previously learned representations. Task-specific priors learned by this Task-Amortized VAE were used to investigate biases in mice and model when presenting stimuli that violated trained task statistics. Mismatch between learned task statistics and incoming sensory evidence produced signatures of uncertainty in stimulus category in the TAVAE posterior, reflecting properties of bimodal response profiles in V1 recordings. The task-optimized generative model accounted for key characteristics of V1 population activity, including within-day updates to population responses. Our results confirm that flexible task-specific contextual priors can be learned on demand by the visual system and deployed as early as the entry level of visual cortex.
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