The Nasdaq rose on Thursday as investors poured into technology stocks such as Nvidia, Apple and Microsoft.
The S&P 500 closed slightly lower, while the Dow, with a more pronounced drop, posted its fourth straight lower close.
Terence Gabriel, socks buzz analyst at Thomson Reuters, says investors embracing big tech again signals concern about how strong the economy is going to be moving forward.
"Certainly the action in growth stocks, and defensive names vs. falling yields and what's going on with commodities and more economically sensitive sectors is suggesting the possibility that the market is suddenly beginning to question how strong the economy will be moving forward."
The strengthening dollar, another by-product of the Fed news this week, pushed U.S. oil prices down from the multi-year high hit earlier in the week.
The energy index, in turn, was the biggest laggard among the 11 main S&P sectors.
Late in the trading session - Cruise operator Carnival disclosed it had detected unauthorized access to its computer systems in March, after which it alerted regulators and hired a cybersecurity firm to investigate the breach.
Shares closed down nearly 3%.