The feature is called the Ad Review Center. Users can approve or disapprove of ads before they go into the feeds.
To do so, login to your AdSense account. Then look for the Ad Review Center in the 'Competitive Ad Filter' section under the 'AdSense Setup' tab. Choose the Client-ID starting with ca-feed-pub.
You'll have to put your ads on hold for 24 hours before you can filter through them. During that time, no ads will be served to your feeds, but afterwards you can go through the ad approval process.
Optimising Digital Marketing Campaigns with Search, Social and Analytics
At SES London (9-11 Feb) you'll get an overview of the latest tools, tips, and tactics in Paid, Owned, Earned, Integrated Media and Business Intelligence to streamline your marketing campaigns in 2015. Register by 31 October to take advantage of Early Bird Rates.