Adaptation and multivoxel codes in high-level visual cortex

描述(申请人提供)：认知神经科学的一个核心问题是理解不同大脑区域所产生的代表性差异。在功能磁共振成像(FMRI)研究中，通常使用两种技术来研究这一问题：多体素模式分析(MVPA)和功能磁共振自适应(FMRIa)。MVPA检查不同刺激引起的体素反应模式，以确定哪些项目引发可区分的模式，而FMRIa在重复代表性相似的项目将引发减少反应的假设下，检查随着时间的推移重复项目的影响。虽然MVPA和fMRIa已经成为认知神经科学的核心工具包的一部分，但关于这两项技术背后的神经机制，人们知之甚少。因此，很难将通过MVPA获得的结果与通过FMRIa获得的结果联系起来。事实上，我们实验室以前的工作已经表明，FMRIa和MVPA可以获得明显不一致的结果，即使这些技术应用于相同的数据集。目前项目的主要目标是测试关于MVPA和FMRIa可能背后的不同神经机制的几个假说。具体地说，我们将测试fMRIa是否索引神经元或亚神经元调谐(Exp。1)、刺激相似性或知觉预期(实验2)，并对MVPA(Exp.3)。这一初步项目的重点将放在观看真实世界视觉场景时的海马体旁区域(PPA)和观看物体时的枕侧复合体(LOC)的功能磁共振信号上。虽然目前的实验没有直接检查康复或疾病，但如果成功，它们将为此类调查提供重要的分析工具。例如，试图使用MVPA和fMRIa来理解弱视或盲人视力恢复后的可塑性和皮质重组，只有在充分理解对潜在神经机制的解释的情况下才能取得成果。

DESCRIPTION (provided by applicant): A core concern of cognitive neuroscience is understanding the representational distinctions made by different brain regions. Two techniques are commonly used in functional magnetic resonance imaging (fMRI) studies to investigate this issue: multivoxel pattern analysis (MVPA) and fMRI adaptation (fMRIa). Whereas MVPA examines the voxelwise response patterns elicited by different stimuli to determine which items elicit patterns that are distinguishable, fMRIa examines the effect of repeating items over time under the hypothesis that repetition of representationally-similar items will elicit a reduced response. Although MVPA and fMRIa have become part of the central toolkit of cognitive neuroscience, little is known for certain about the neuronal mechanisms that underlie these two techniques. Consequently, it has been difficult to relate results obtained through MVPA to results obtained through fMRIa. Indeed, previous work from our lab has shown that apparently inconsistent results can be obtained from fMRIa and MVPA, even when these techniques are applied to the same dataset. The main goal of the current project is to test several hypotheses about the different neuronal mechanisms that might underlie MVPA and fMRIa. Specifically, we will test whether fMRIa indexes neuronal or subneuronal tuning (Exp. 1), stimulus similarity or perceptual expectations (Exp. 2), and we will test the spatial scale of functional organization indexed by MVPA (Exp. 3). The focus of this preliminary project will be on fMRI signals in the parahippocampal place area (PPA) during viewing of real-world visual scenes and in the lateral occipital complex (LOC) during the viewing of objects. Although the current experiments do not directly examine recovery or disease, they will, if successful, provide important analytical tools for such investigations. For example, attempts to use MVPA and fMRIa to understand plasticity and cortical reorganization in amblyopia, or after recovery of sight in the blind, can only bear fruit if the interpretation of the findings in terms of underlying neural mechanisms is fully understood.