The "parahippocampal place area" responds preferentially to high spatial frequencies in humans and monkeys.
The "parahippocampal place area" responds preferentially to high spatial frequencies in humans and monkeys.
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DOI：
10.1371/journal.pbio.1000608
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发表时间：
2011-04
期刊：
影响因子：
9.8
通讯作者：
Tootell RB
中科院分区：
文献类型：
--
作者：
Rajimehr R;Devaney KJ;Bilenko NY;Young JC;Tootell RB
一个被认为是编码高级“位置”信息的视觉大脑区域对低级“边缘”信息做出反应。在非人类物种中证明了相应的大脑区域。定义大脑处理视觉对象和场景的确切机制仍然是一个尚未解决的挑战。这个过程的有价值的线索已经出现在下颞叶皮层的神经元（“模块”）簇显然选择性地响应特定类别的视觉刺激，如地点/场景的演示。然而，高阶的“类别选择”反应也可以反映特定的低层次的空间因素。在这里，我们在人类和猕猴的多个功能性MRI实验中测试了这个想法，通过系统地操纵几何形状和自然图像的空间内容。这些测试表明，视觉空间不连续性（表现为对高空间频率的反应增加）选择性地激活人类视觉皮质的一个众所周知的位置选择区域（“海马旁位置区”）。在猕猴中，我们展示了一个同源的皮质区，并表明它也选择性地响应更高的空间频率。海马旁位置区可以使用这些信息来检测空间感知和导航期间的物体边界和场景细节。许多报告表明，不同类别的视觉刺激是在视觉皮层中相应的特定“模块”中处理的。例如，面部图像在一个皮质模块（“梭状面区”）中处理，而场景图像在相邻模块（“海马旁区”或PPA）中处理。PPA如何为如此高级、复杂的视觉场景进行编码？在这项研究中，我们表明，至少有一部分的PPA响应是由于一个较低的水平变量，反映为较高的空间频率。这些在场景的边缘和细节中很突出，但在面部和其他刺激中不太突出。当我们改变人脸和地点的标准图像，使它们只包含低、中或高空间频率时，我们发现PPA对包含高空间频率的图像有强烈的反应。重要的是，使用与人类研究相同的刺激，我们还证明了猕猴颞叶皮层中的人类PPA的同源物（“mPPA”）。与人类一样，mPPA选择性地对更高的空间频率做出反应。这种示范PPA在猕猴铺平了道路，进行进一步的电生理和解剖学研究，可能有助于阐明的神经机制，在人类视觉皮层的位置选择性。
A visual brain area that is thought to encode higher-level "place" information responds instead to lower-level "edge" information. A corresponding brain area is demonstrated in non-human species. Defining the exact mechanisms by which the brain processes visual objects and scenes remains an unresolved challenge. Valuable clues to this process have emerged from the demonstration that clusters of neurons (“modules”) in inferior temporal cortex apparently respond selectively to specific categories of visual stimuli, such as places/scenes. However, the higher-order “category-selective” response could also reflect specific lower-level spatial factors. Here we tested this idea in multiple functional MRI experiments, in humans and macaque monkeys, by systematically manipulating the spatial content of geometrical shapes and natural images. These tests revealed that visual spatial discontinuities (as reflected by an increased response to high spatial frequencies) selectively activate a well-known place-selective region of visual cortex (the “parahippocampal place area”) in humans. In macaques, we demonstrate a homologous cortical area, and show that it also responds selectively to higher spatial frequencies. The parahippocampal place area may use such information for detecting object borders and scene details during spatial perception and navigation. Many reports suggest that different categories of visual stimuli are processed in correspondingly specific “modules” in the visual cortex. For instance, images of faces are processed in one cortical module (the “fusiform face area”), while images of scenes are processed in an adjacent module (the “parahippocampal place area,” or PPA). How does the PPA encode for such high-level, complex visual scenes? In this study, we show that at least part of the PPA response is due to a lower-level variable, reflected as higher spatial frequencies. These are prominent in the edges and details of scenes, but less prominent in faces and other stimuli. When we altered standard images of faces and places so that they only contained low, medium, or high spatial frequencies, we found that the PPA responded strongly to images containing high spatial frequencies. Importantly, using the same stimuli as for the human studies, we also demonstrated a homolog of human PPA in macaque temporal cortex (“mPPA”). As in humans, mPPA responds selectively to higher spatial frequencies. This demonstration of PPA in macaques paves the way for carrying out further electrophysiological and anatomical studies that may help elucidate the neural mechanisms for place selectivity in the human visual cortex.
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