In general I worry that this is not a helpful line of thinking to pursue. Finding these effects would show that the time I've invested in meditating has affected the functioning of my brain with respect to attention and perception. Would this really be a surprising result to you?

It wouldn't be very close to the cognitive changes you describe, but it would be some outside confirmation that something is going on. The interesting claims are at higher level brain functions, but we don't currently have many ways of examining those in ways that don't require human interpretation that is itself vulnerable to bias. A not necessarily helpful approach would be to proceed to assume that only the effects measurable in some objective way are worth paying any attention to here.