[steven]

I wanted some clarification on some pronunciation that I've been hearing for a while now. I've noticed that verbs like つかった、もらった、くばった get changed to つこった、もろった、and　くぼった sometimes. In other words, the あ sound gets changed to an お sound. I have to say though, that it's not always a pure お sound... sometimes it's like partway inbetween. It reminds me of like an American east coast accent to a degree (if that makes any sense). As far as I know I've never had trouble understanding the meanings of any of these, but I was wondering if this is a normal pronunciation thing or not. Is it an older way of pronouncing words maybe? Is it just another regional thing?