The author describes two problems: 1) hindering deep understanding ('digital amnesia') and 2) the impact on identity. The text explicitly states that the impact on identity is 'even more serious' (さらに深刻なのは). It explains that memory, with its emotions, forms our self-identity (自己同一性を形成する根幹をなす) and that externalizing it makes our self-image 'diluted and fragmented' (希薄で断片的なものになりかねない). This directly corresponds to the correct answer. The other options are incorrect: The text does not discuss technical risks. It implies a change in how the brain works, but not necessarily irreversible decline. It states the opposite of the last option, suggesting that outsourcing memory *frees up* cognitive resources.