Feb 15 (Reuters) - Nvidia's bet on smaller AI firms from healthcare companies Nano-X Imaging and Recursion to chipmaker Arm Holdings boosted their shares in premarket trading on Thursday.

Nvidia, the biggest winner of the AI boom, revealed its new stakes in the firms as of Dec. 31 in a 13-F filing with the U.S. SEC late on Wednesday.

Fellow chip designer Arm Holdings drew the biggest investment from Nvidia, worth $147.3 million. The British company has said its processors complement Nvidia's chips for AI work in data centers.

Arm shares gained 2.6% on Thursday after surging more than 60% in value since its strong quarterly forecast last week.

Shares of biotech company Recursion Pharmaceuticals , in which Nvidia invested nearly $76 million, gained 16.5%. About eight months ago, Nvidia said it would invest in Recursion to speed up training of the biotech firm's AI models for drug discovery.

The Silicon Valley megacap firm also invested nearly $3.7 million in voice AI platform SoundHound AI, sending its shares 72% higher.

It bought shares of Israel-based medical device company Nano-X Imaging, which uses AI software to analyze reports. Nano-X shares rose 42.5% higher.

Autonomous driving technology TuSimple Holdings, which delisted from Nasdaq last week, also drew $3 million in capital from the chipmaker.

Shares of other small-cap chipmakers rose in tandem, with C3.ai Inc adding 1.5% and BigBear.ai Holdings gaining 8.9%.

Nvidia overtook Alphabet and Amazon.com this week to become the third most valuable U.S. company. (Reporting by Medha Singh in Bengaluru; Editing by Krishna Chandra Eluri)