Not sure if I understood you correctly?
Okay, maybe I should put it the other way around. Psychologists have always been interested in new ways of measuring psychological phenomena. Sure we have always had tried-and-true methods like self-report questionnaires and button press tasks. But these measures have a lot of limitations.
When neuroimaging techniques came about, they thought 'yea" this could be a new tool for measuring psychological processes. Since all thoughts, reactions, attitudes and other cognitive processes must occur as activation patterns in the brain, we should be able to find brain 'signatures' of different psychological processes if we look hard enough.
So psychologists eagerly set about the task of finding neural activity patterns that could be signatures of different types of psychological phenomena.
Enthusiasm was highest in the field of psychopathology. People thought great, if we can find neural signature of depression, or anxiety, or gambling or addiction or somatisation, we have a new way to study these dysfunctional thoughts and behaviours.
Importantly, these researchers did
functional neuroimaging. They didn't use neuroimaging to find pathology
IN the brain that could explain the psychopathology (amyloid plaques, tau proteins, white matter lesions, shrinkage or whatever), because they didn't think there was any. They considered these disorders to be psychological. They wanted to look at
function, to find indices of the disordered thinking/behaviour that led to the problem.
So whenever you see a study that examines
functional abnormalities (e.g. abnormal activation patterns) in the brains of a special group - and doesn't seem at all interested in attributing these to a physiological dysfunction or other disease process - then you're talking about a psychological account.