This relates to systems and methods for determining one or more of a user's physiological signals. The one or more of the user's physiological signals can be determined by measuring pulsatile blood volume changes. Motion artifacts included in the signals can be canceled or reduced by measuring non-pulsatile blood volume changes and adjusting the signal to account for the non-pulsatile blood information. Non-pulsatile blood volume changes can be measured using at least one set of light emitter-light sensor. The light emitter can be located in close proximity (e.g., less than or equal to 1 mm away) to the light sensor, thereby limiting light emitted by the light emitter to blood volume without interacting with one or more blood vessels and/or arterioles. In some examples, the systems can further include an accelerometer configured to measure the user's acceleration, and the acceleration signal can be additionally be used for compensating for motion artifacts.