Have you ever had brain exhaustion? Do you have examples?

In my first year of high school in grade 9, I would fall asleep while studying math but did not have that problem after first year.

In my first year of university, while studying psychology, I would fall asleep while reading my textbook, but after two months, my brain was used to the high volume of information I was newly absorbing and I no longer got sleepy during study sessions.

Today I tried to watch Sesame Street in Hebrew, and within 4 minutes, I wanted to sleep cause my brain was exhausted from learning a new language and absorbing all this new grammar and vocabulary.

Have you ever had brain exhaustion? Do you have examples?
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