During a clinical study focused on the effects of stress on cognitive function, researchers discovered that individuals subjected to chronic stress exhibited alterations in the structure and function of certain brain regions. Notably, pharmacological interventions were found to modulate these brain changes positively. One specific neurotransmitter that plays a critical role in managing stress responses is known to be significantly affected during these conditions.

Which neurotransmitter is primarily implicated in the stress response and associated cognitive alterations as indicated in the study?