Rewards interact with explicit knowledge to enhance skilled motor performance.

From typing on a keyboard to playing the piano, many everyday skills require the ability to quickly and accurately perform sequential movements. It is well known that the availability of rewards leads to increases in motivational vigor whereby people enhance both the speed and force of their movements. However, in the context of motor skills, it is unclear whether rewards also lead to more effective motor planning and action selection. Here, we trained human participants to perform four separate sequences in a skilled motor sequencing task. Two of these sequences were trained explicitly and performed with precues that allow for the planning of movements, while the other two were trained implicitly. Immediately following the introduction of performance-contingent monetary incentives, participants improved their performance on all sequences consistent with enhancements in motivational vigor. However, there was a much larger performance boost for explicitly trained sequences. We replicated these results in a second, preregistered experiment with an independent sample. We conclude from these experiments that rewards enhance both the planning of movements as well as motivational vigor.NEW & NOTEWORTHY Offering people rewards and incentives typically improves their performance on skilled motor tasks. However, the mechanisms by which motivation impacts motor skills remains unclear. In two experiments, we show that motivation impacts motor sequencing skills in two separate ways. First, the prospect of reward speeds up the execution of all actions. Second, rewards provide an additional boost to motor planning when explicit skill knowledge can be used to prepare movements in advance.

Experimental demonstration of evanescent coupling and photon confinement in oxide-clad silicon microcavities.

For use in on-chip and integrated applications, photonic crystals must not only be embedded in silica but must also be able to easily integrate with other photonic devices. Here we provide an experimental demonstration of resonance in a SiO(2)-clad two-dimensional photonic crystal microcavity that is coupled to standard Si strip waveguides. We further show that well over 90% of the resonant field is confined within the cavity's silicon layer, which is necessary if the microcavity is to be used as a high-efficiency electro-optic modulator.

Ultra-low power modulators using MOS depletion in a high-Q SiO2-clad silicon 2-D photonic crystal resonator.

In modulators that rely on changing refractive index, switching energy is primarily dependent upon the volume of the active optical mode. Photonic crystal microcavities can exhibit extremely small mode volumes on the order of a single cubic wavelength with Q values above 10(6). In order to be useful for integration, however, they must be embedded in oxide, which in practice reduces Q well below 10(3), significantly increasing switching energy. In this work we show that it is possible to create a fully oxide-clad microcavity with theoretical Q on the order of 10(5). We further show that by using MOS charge depletion this microcavity can be the basis for a modulator with a switching energy as low as 1 fJ/bit.