In the following passage some of the words have been deleted. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.
A recent study that (1) ______ people’s brains at different points in their work day (2) ______ high-demand tasks which require intense, constant concentration can lead to build-up of a (3) ______ toxic chemical called glutamate. Normally used to (4) ______ signals from nerve cells, in large quantities glutamate alters the (5) ______ of a brain region involved in planning and decision making, the lateral prefrontal cortex (lPFC).
Select the most appropriate option to fill in blank number 4.

In the following passage some of the words have been deleted. Read the passage carefully and select the correct answer for the given blank out of the four alternatives.
A recent study that (1) ______ people’s brains at different points in their work day (2) ______ high-demand tasks which require intense, constant concentration can lead to build-up of a (3) ______ toxic chemical called glutamate. Normally used to (4) ______ signals from nerve cells, in large quantities glutamate alters the (5) ______ of a brain region involved in planning and decision making, the lateral prefrontal cortex (lPFC).
Select the most appropriate option to fill in blank number 4.