Well actually, the neutral is bonded to ground at the meter base, not the panel.
Randy, the neutral is a current carrying conductor, not a ground. The ground wire is the one and only ground although is is sometimes mistakenly called a ground.
The reason I asked if the light circuit and HT circuit shared the neutral is because that's a common practice. Even if you have a separate breaker for both, that don't mean anything unless they are both GFCI breakers and wired to code as the neutral wire goes directly to the breaker and not the panel bonding strip.
Many electricians and builders run 12/3 romex for reasons of saving labor and material. It has three conductors and one ground (Black, Red, White, ground). This saves time because you only have to pull one run of romex back to the panel. At the most logical J-box, the electrician ties in a separate 2/12 romex for another run of devices. At this J-box, the neutrals are tied together and ran back to the panel as "shared".
