At times I felt my brain was racing too fast.

But the words had been a tremendous shock and my brain was racing, trying to get into gear.

Her brain raced, as she tried to think what to do.

As her brain raced she tried to work out the time.

She was beginning to sweat even as her brain raced ahead.

His brain raced frantically back over the events of the day before.

His brain was racing as he slipped into a higher stand of trees.

His brain raced as he tried to guess why that was.

My brain was racing with the thought of her.

He tried to look sleepy, but his brain was racing.