Department of Psychology, Counselling and Therapy, School of Psychology and Public Health, La Trobe University, Victoria, Australia.
Department of Psychology, Counselling and Therapy, School of Psychology and Public Health, La Trobe University, Victoria, Australia.
Cortex. 2022 Sep;154:135-148. doi: 10.1016/j.cortex.2022.04.020. Epub 2022 Jun 7.
Research findings on which brain areas demonstrate fMRI adaptation to the form, orientation, and size of visual stimuli has been mixed. Studies demonstrate effects in various subdivisions of the lateral occipital complex (LOC), including retinotopically tuned areas LO-1 and LO-2, and dorsal stream areas in the intraparietal sulcus (IPS). Therefore, we aimed to examine fMRI adaptation in four subdivisions of the LOC (LO-proper, posterior fusiform sulcus, LO-1, and LO-2) and three discrete regions in the IPS (caudal IPS, IPS-proper, and anterior IPS) to clarify the role that these structures play in form, orientation, and size processing. Participants performed three tasks which involved judging whether two serially presented novel objects shared the same form, orientation, or size. On each version of the task, one feature varied from trial-to-trial (e.g., form) while the other two features (e.g., orientation and size) were held constant. In this way, we were able to examine the unique fMRI signal changes in response to changes in form, orientation, and size in isolation. Form adaptation - a decrease in fMRI signal following repeated presentation of the same stimulus - was present in LO-proper and pFS, highlighting the role of LOC in form processing. Size repetition enhancement - an increase in fMRI signal following repeated presentations of the same stimulus - was observed in pFs. We propose that the latter result demonstrates the effects that top-down factors can have on visual areas, specifically when there is stimulus uncertainty. There was no evidence of orientation processing in any of the regions examined. Neither form adaptation nor size repetition enhancement was present in the three IPS regions-of-interest. Last, retinotopically defined LO1 and LO2 could not be reliably identified in participants and therefore we were unable to examine adaptation in these areas as we originally intended to do.
关于哪些大脑区域表现出对视觉刺激的形状、方向和大小的功能磁共振成像（fMRI）适应的研究结果一直存在分歧。研究表明，在外侧枕叶复合体（LOC）的各个细分领域中存在影响，包括具有视网膜调谐的区域 LO-1 和 LO-2，以及顶内沟（IPS）中的背侧流区域。因此，我们旨在检查 LOC 的四个细分领域（LO-适当、后梭状回、LO-1 和 LO-2）和 IPS 的三个离散区域（尾 IPS、IPS-适当和前 IPS）中的 fMRI 适应，以阐明这些结构在形状、方向和大小处理中所扮演的角色。参与者执行了三项任务，这些任务涉及判断两个连续呈现的新物体是否具有相同的形状、方向或大小。在每个任务版本中，一个特征会在试验之间变化（例如，形状），而其他两个特征（例如，方向和大小）保持不变。通过这种方式，我们能够单独检查响应形状、方向和大小变化的独特 fMRI 信号变化。形态适应 - 重复呈现相同刺激后 fMRI 信号减少 - 出现在 LO-适当和 pFS 中，突出了 LOC 在形态处理中的作用。大小重复增强 - 重复呈现相同刺激后 fMRI 信号增加 - 在 pFs 中观察到。我们提出，后者的结果表明，在存在刺激不确定性的情况下，自上而下的因素可以对视觉区域产生影响。在检查的任何区域都没有观察到方向处理的证据。在三个 IPS 感兴趣区域中都没有形态适应或大小重复增强的证据。最后，无法在参与者中可靠地识别出具有视网膜定义的 LO1 和 LO2，因此我们无法按照最初的意图检查这些区域的适应。
