Phenomenologically speaking, there is an area of the brain that is active only in the presence of religious experience. It’s only within the past 50 years that the technology existed to discover that. It is certainly objective fact now.
Just as certain areas of the brain respond to the wind, which is the movement of air in the presence of heat or cold (which can only be measured with sophisticated atmospheric instruments), perhaps the religious experience is also objectively true, just awaiting the technology to detect it.
Religious experience can mean many different things. That is why St. Paul tells us to test the spirits. If there is not some objective way of doing that, then we have no way of telling whether or not a religious experience is from God or Satan. Having a religious experience means nothing if it is not based upon the truth.