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  3. The brain is organized into different regions, each responsible for different functions, and in humans this organization is very

The brain is organized into different regions, each responsible for different functions, and in humans this organization is very

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问题     The brain is organized into different regions, each responsible for different functions, and in humans this organization is very marked. The largest parts of the brain are the cerebral hemispheres, which occupy most of the interior of the skull. They are layered structures, the most complex being the outer layer, known as the cerebral cortex, where the nerve cells are extremely densely packed to allow great interconnectivity. Its function is not fully understood, but we can get some indication of its purpose from studies of animals that have had it removed. A dog, for example, can still move in a coordinated manner, will eat and sleep, and even bark if it is disturbed. However, it also becomes blind and loses its sense of smell-more significantly, perhaps, it loses all interest in its environment, not responding to people or to its name, nor to other dogs, even of the opposite sex. It also loses all ability to learn. In effect, it loses the characteristics that we generally refer to as indicating intelligence-awareness, interest and interaction with an environment, and an ability to adapt and learn. Thus the cerebral cortex seems to be the seat of the higher order functions of the brain, and the core of intelligence.
    The cerebral cortex has been the subject of investigation by researchers for many years, and is slowly revealing its secrets. It demonstrates a localization of functions, in that different areas of the cortex fulfill different functions, such as motion control, hearing, and vision. The visual part of the cortex is especially interesting. In the visual cortex, electrical stimulation of the cells can produce the sensation of light, and detailed analysis has shown that specific layers of neurons are sensitive to particular orientations of input stimuli, so that one layer responds maximally to horizontal lines, while another responds to vertical ones. Although much of this structure is genetically pre-determined, the orientation-specific layout of the cells appears to be learnt at an early stage. Animals brought up in an environment of purely horizontal lines do not develop neuron structures that respond to vertical orientations, showing that these structures are developed due to environmental input and not purely from genetic pre-determination. This is called self-organization of the visual cortex since there is no external teacher to guide the development of these structures.
According to the passage, a dog can still move in a coordinated manner, will eat and sleep, and even bark when______is(are)removed.
选项 A、nerve cells
B、the skull
C、the hemispheres
D、the cerebral cortex
答案D
解析 文章第一段表明“Its function is not fully understood，but we can getsome indication ofits purpose from studies of animals that have had it removed．”这里its function指的就是thecerebral cortex’s function(大脑皮层的功能)．同时后面所举的例子就是本题题目所说的狗的情况，因此选D。
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