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大的GPS格 (文)

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A new study on bats reveals an unexpected representation of three-dimensional space in the brain

一蝙蝠的新研究揭露，一於大中三空，意想不到的示方式。

In a new study published in Nature today, Weizmann Institute of Science researchers, in collaboration with colleagues from the Hebrew University of Jerusalem, unveiled for the first time how three-dimensional space is represented in the mammalian cortex by the brain’s “GPS” system.

在表於2021年8月12日《自然》期刊的一新研究中，以色列魏茨曼科研究所的研究人，耶路撒冷希伯大的同僚合作，首度揭露，三空於哺乳物的皮中，如何被大的“全球定位系”(GPS：Global Positioning System)系所呈。

The team of researchers, led by Prof. Nachum Ulanovsky of Weizmann’s Neurobiology Department, were surprised to find that this representation is very different from the way in which two-dimensional space is represented, turning several long-standing hypotheses on their heads.

由魏茨曼神生物系，Nachum Ulanovsky教授的研究人，地，示方式截然不同於，二空被呈的方式。覆了，若干他海中，期存在的假。

Mammals, including humans, know their position in space, owing to several types of specialized neurons in the hippocampus and its next-door neighbor the entorhinal cortex – regions located deep inside the brain. Head-direction cells, the internal compasses of the brain, indicate to the animal the direction in which its head is turned.

由於海及其隔壁居的嗅皮(位於大深的域)中，有若干特化型的神元。包括人等，哺乳物知其在空中的位置。部方向胞(大的部指南)物指示，其部的方向。

Place cells, thought to construct a mental map of the environment, are activated when an animal crosses a specific location. Grid cells, by contrast, respond not to one, but to multiple such locations, and they are thought to provide the brain with a GPS system of sorts.

物穿一特定位置，被建境之心理地的位置胞，被激活。相之下，格胞(嗅皮的一神元，物在域行，它定期放，而透存及整合有位置、距方向的信息，了解其在空中的位置)不是一位置作出反，而是多此位置作出反，因此被，大提供了一，於多型的GPS系。

1. 埃及果蝠：於哺乳物皮中，三空的示方式，似於一盒珠(?)。 (援用自原文)

The study of grid cells and the brain’s GPS was awarded the Nobel Prize in 2014. However, these and other studies focused solely on how two dimensions are represented and said very little about the representation of three-dimensional space. To bridge this gap, Ulanovsky and colleagues set out to elucidate how grid cells act in three dimensions in freely behaving bats.

有格胞及大之GPS的研究，得了2014年。不，此些及其他研究著重於，二如何被呈，很少涉及三空的示方式。了填此空白，Ulanovsky同僚著手明，於自由行之蝙蝠中，格胞如何在三中起作用。

In the past, when grid cells were studied in rodents running on two-dimensional surfaces, they were found to be activated in multiple circular areas, known as firing fields, which are arranged in a symmetrical hexagonal pattern–resembling millimeter graph paper – that tiles the surface.

於去，研究在二表面上奔跑之物中的格胞，此些胞被，在多以六形案(似於毫米方格)排列平此表面，被通激的形域，被激活。

This unparalleled symmetry and periodicity suggest that these cells may be involved in geometric spatial computations that form the core of the cerebral GPS. The entorhinal cortex, where grid cells are located, is the brain area that is first affected in Alzheimer’s disease, and it is possible that spatial disorientation, one of the early manifestations of Alzheimer’s, is due to the grid cells’ dysfunction – and the loss of the hexagonal “millimeter paper” of grid cells.

比的性及周期性暗示，此些胞可能涉及，形成大之GPS的核心何空算。格胞所在的嗅皮，是阿海默氏症中，最先遭影的大域。因此，空定向障(阿海默氏症的早期徵候之一)可能是，由於格胞的功能障。也就是，失了上述格胞的六形“毫米”。

Mathematically, the optimal way to pack circles in two dimensions is in a hexagonal pattern, like a honeycomb: This is possibly the reason why the circular firing fields of grid cells are represented in the brain in a hexagonal lattice when animals walk over two-dimensional surfaces. Therefore, the researchers expected the activity pattern in three dimensions to be similarly symmetrical and hexagonal.

上，在二中使多在一起的最佳方法，是以六形案，就像蜂一：可能是，物在二表面上行走，何格胞的形激射，在大中以六形格子被呈的原因。因此，些研究人期，於三中的活模式，是相似的及六形。

“We and many other researchers hypothesized that we’d see hexagonally stacked balls, like oranges in a grocery store neatly stacked in a pyramid, or any other extremely ordered three-dimensional arrangement,” Ulanovsky says.

Ulanovsky宣：「他及多其他研究人假，他看到六形堆的球，如同店中的橙子，被整堆成一金字塔，或任何其他度有序的三排列。」

To test this hypothesis, the researchers, led by doctoral student Gily Ginosar, together with Staff Scientist Dr. Liora Las, recorded the activity of grid cells in bats that had small mobile devices mounted on their heads, as the bats were flying around a room the size of a large living room. Feeding stations at different heights ensured that each bat covered most of the room’s volume in every run.

了此假，些由博士生Gily Ginosar下的研究人，同正科家Liora Las博士了，在上被安置小型移式置之蝙蝠，在一大客大小的房到行，格胞的活。不同高度的食位置保了，每蝙蝠在每次行中，涵房的大部分空。

Once the data started coming in, the researchers saw that grid cells did not behave as expected when responding to three-dimensional coordinates. “The well-ordered global grid that is the hallmark of their two-dimensional activity was altogether gone,” explains Ulanovsky.

一始入，此些研究人，三坐作出反，格胞不如期般作出表。Ulanovsky解：「是其二活特徵的有序球形格，完全消失。」

2. 局部秩序及全面秩序。先前的研究，在二空的示中，展了局部及全面秩序，且三行了相同的。不，新研究，三空有全面的格子，至少保持局部秩序。 (援用自原文)

Instead, the three-dimensional firing fields of the grid cells, shaped in this case as spheres rather than circles, were packed like a box full of marbles. They were not completely disordered, but were certainly less organized than the three-dimensional equivalent of a hexagonal lattice – as the new arrangement allowed the “marbles” some extra degrees of freedom.

相反，格胞的三激，在此情下，形成如同球，而不是圈，在一起如同一珠的盒子。它非完全秩序，不肯定不如六形格子的三同等物排列有序。因，此新排列容“珠”一些外的自由度。

Whereas any noticeable global order was lacking, the spheres did commit to a local order wheein the distance between one sphere and its nearest neighbors remained constant.

管缺乏任何明的全面秩序，此些球形遵循一局部秩序。在那情下，一球形其最近居之的距保持不。

To offer a mechanistic explanation of this phenomenon of local rather than global order, the experimental team – Ginosar, Las and Ulanovsky – collaborated with theoreticians Dr. Johnatan Aljadeff, a former postdoctoral fellow at Weizmann and now a professor at the University of California in San Diego, and Prof. Haim Sompolinsky and Prof. Yoram Burak from the Hebrew University of Jerusalem.

了提供一有局部，而非全面秩序象的有力解。Ginosar、Las及Ulanovsky，魏茨曼科研究所前博士後特研究、目前是美加州大地哥分校教授Johnatan Aljadeff博士及自耶路撒冷希伯大的Haim SompolinskyYoram Burak教授等，理家行了合作。

Together they constructed a model that uses principles, borrowed from statistical physics, that describe the interaction between particles. The model revealed that the spherical firing fields of grid cells seem to interact in almost the same way as particles do – they are “attracted” to one another when at a distance and are “repelled” once they get too close.

他一起建了一，借用自物理，描述粒子交互作用的多原理模型。模型揭露，格胞之球形激，似乎以乎如同粒子行般的相同方式交互作用。在，它彼此“吸引”，一旦靠得太近就“排斥”。

In particular, the balance of forces acting on particles could explain the local order that kept the spheres at constant local distances from one another, while avoiding any global lattice. Compared to other models that were used in the past to predict the three-dimensional organization of grid cells’ firing fields, the new model was the most loyal to the experimental data.

特是，作用於粒子上的力平衡，可以解使此些球物彼此保持定之局部距的局部秩序，同避免任何全面的格子。相於去，被用格胞激之三的其他模型，新模型最忠於。

Taken together, the surprising experimental data and theoretical model offer a new way of looking at the neural basis of three-dimensional navigation and the role that grid cells play in this cognitive process.

合起，令人的及理模型，探究三航之神基，及格胞在此知程中的角色，提供了一新方法。

While previous models extrapolated a similar three-dimensional arrangement from the two-dimensional grid, the work of Ulanovsky and colleagues and their “box of marbles” model show that things are much more complex. Since no periodic lattice is formed in three-dimensional space, the classical theories for understanding the intriguing behavior of grid cells will need to be revised.