then gradually "transferred" to the cortex (大脑皮层) for long-term storage. However, a new study

conducted by the Riken-MIT Center for Neural Circuit Genetics challenges this theory, suggesting that memories are stored in the hippocampus and Cortex at the same time, but remain "silent" in the cortex for about two weeks before reaching a mature state.

　　Scientists have assumed that the engram (记忆印痕) cells in the cortex that store memory were produced slowly. "The cells actually develop rapidly," said Takashi Kitamura, a lead author of the study.

　　The past theory that short-term memories in the hippocampus transfer to long-term memories in the cortex was developed in the 1970s, when a patient named Henry Molaison experienced a damaged hippocampus, and he lost his ability to make new memories.

　　Until recently, scientists lacked a reliable way to test memory consolidation (实变) theory, Kitamura explained. "Most previous studies of memory were based on analyzing how damage to certain brain areas affects memory", he said. In 2016, when Tonegawa Laboratory, a research lab at MIT, developed a way to label engram cells, opening the door to new ways to test memory consolidation theory.

　　Researchers used some mice during the experiment. A day after the mice received an electric shock. Its memories of the fear-causing event were stored in engram cells in both the hippocampus and the cortex. The engram cells in the cortex, however, remained silent. These cells did slight behavior when artificially awakened by light. Furthermore, when the connection between the hippocampus and cortex was blocked, long-term memory was unable to mature.

　　Researchers discovered that memory engram cells naturally change their status from active to silent and from silent to active. "If we identify the principles behind how silent memory can be active, we may find a treatment for amnesia (失忆症)", Kitamura said.

4. In which aspect does the new study differ from previous studies according to the text?

　A. The research subject. B. The research method.

　C. Their reliability. D. Their application.

5. What can be inferred about engram cells in the text?

　A. They only exist in the hippocampus.

　B. They only exist in the cortex.

　C. They are carriers of memories.

　D. They keep stable in status.

6. What is the key to the treatment for amnesia?