Using a comma after "that"

I would like to know if you can use "that" with a comma after it. For example:

Findings show that, during the initial stages of love, there is increased blood flow to the brain.

Solution 1:

Here's an example of a sentence that contains a parenthetical phrase (one that is not essential to the framing sentence): "Skye's sentence, which has no parenthetical phrase, needs no commas." Remove it, and the essential meaning of the sentence is preserved: "Skye's sentence needs no commas."

If you remove "during the initial stages of love" from Skye's sentence, you remove the condition essential to the findings, which leaves you with this meaningless statement: "Findings show that there is increased blood flow to the brain." So "during the initial stages of love" is not a parenthetical phrase.

Solution 2:

You use paired commas to set off a parenthetical.

Findings show that there is increased blood flow to the brain.

If you want to insert "during the initial stages of love" as a parenthetical, you set it off with commas, hence:

Findings show that, during the initial stages of love, there is increased blood flow to the brain.

This has nothing to do with the fact that the parenthetical happens to be preceded by the word "that". For example:

Findings show, during the initial stages of love, there is increased blood flow to the brain.

Findings show, during the initial stages of love, that there is increased blood flow to the brain.

Notice the commas are still there, still setting off the parenthetical. These are a bit awkward, but still perfectly legal grammatically.