Adaptation and multivoxel codes in high-level visual cortex

描述（由申请人提供）：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表征差异。功能磁共振成像（fMRI）研究中常用两种技术来研究这个问题：多体素模式分析（MVPA）和功能磁共振成像适应（fMRI）。MVPA研究的是由不同刺激引起的体向反应模式，以确定哪些项目引发的模式是可区分的，而fmri研究的是在重复代表性相似的项目会导致反应减少的假设下，随着时间的推移重复项目的影响。尽管MVPA和fmri已经成为认知神经科学的核心工具，但人们对这两种技术背后的神经元机制知之甚少。因此，很难将通过MVPA获得的结果与通过fmri获得的结果联系起来。事实上，我们实验室之前的工作已经表明，即使将这些技术应用于相同的数据集，也可以从fMRIa和MVPA中获得明显不一致的结果。当前项目的主要目标是测试关于MVPA和fmri背后可能存在的不同神经元机制的几个假设。具体来说，我们将测试fmri是否索引神经元或亚神经元调谐（Exp. 1），刺激相似性或感知期望（Exp. 2），我们将测试MVPA索引的功能组织的空间尺度（Exp. 3）。这个初步项目的重点将是在观看真实世界的视觉场景时海马旁区（PPA）和观看物体时枕侧复合体（LOC）的fMRI信号。虽然目前的实验不能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fmri来了解弱视或盲人视力恢复后的可塑性和皮层重组，只有在充分理解潜在神经机制方面的发现才能取得成果。

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.