Spinalized rats given shock whenever 1 hind leg is extended learn to maintain that leg in a flexed position, a simple form of instrumental learning. Rats given shock independent of leg position do not exhibit an increase in flexion duration. Experiment 1 showed that 6 min of intermittent legshock can produce this deficit. Intermittent tailshock undermines learning (Experiments 2-3), and this effect lasts at least 2 days (Experiment 4). Exposure to continuous shock did not induce a deficit (Experiment 5) but did induce antinociception (Experiment 6). Intermittent shock did not induce antinociception (Experiment 6). Experiment 7 addressed an alternative interpretation of the results, and Experiment 8 showed that presenting a continuous tailshock while intermittent legshock is applied can prevent the deficit.

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the printing process. Previously, patterning of liquid metals by direct writing [ 9 ] and fi lling predefi ned microchannels has been demonstrated. [ 10-12 ] Furthermore, the use of liquid metal as conductors, [ 13,14 ] capacitors, [ 15 ] and antennas [ 16-24 ] has been shown. The illustrated circuit and sensor applications include embedded elastomer conductors, [ 13 ] hyperelastic pressure sensors, [ 10 ] stretchable radiation sensors, [ 17 ] passive wireless sensors, [ 11 ] deformable and tunable fl uidic antennas, [ 25 ] and tac-tile interfaces. [ 26 ] Given these advances, 3D printing can now be exploited to develop 3D electronic systems embedded within printed objects that facilitate personalized sensing and actuation function-alities. To illustrate this capability, we particularly demonstrate 3D printing of two fully integrated objects that deliver various sensing, actuation, and signal processing operations. These objects embed liquid metal-based passive/active components and commercially available silicon integrated circuits (ICs) to achieve the envisioned functionalities. The fi rst object demonstrates the capability of 3D printing approach to embed multi-layer electronic circuit boards within 3D structures. The second object demonstrates the application of 3D printing process to deliver wearable platforms that are specifi cally tailored to an individual's body and needs. Specifi cally, a form-fi tting glove is developed with embedded programmable heater, temperature sensor, and the associated control electronics for thermothera-peutic treatment. The process enables assembly of electronic components into complex 3D architectures and provides a new platform for creating personalized smart objects. As exemplifi ed in Figure 1 a, conductive channels are printed within an object (e.g., a glove) in various confi gurations to realize 3D liquid-state sensors, actuators, and circuit components (resistors, capacitors, and antennas). These components can be tunably printed within both stretchable and rigid sub-strates and can provide standalone functionalities. The channels are also used as interconnects to integrate readily available silicon IC chips and realize fully embedded systems inside the printed object. Integration of silicon IC chips enables advanced circuit functionalities that would not have been achieved otherwise by 3D printed liquid-state components alone. Figure 1 be illustrates the corresponding fabrication scheme. First, as shown in Figure 1 b, a base substrate, containing microchan-nels and slots for the integrated components, is fabricated by a 3D printer (MakerGear and Leapfrog). Second, the microchan-nels are injected with liquid metal to form the liquid-based circuit components, devices, and interconnects (Figure 1 c). Third, IC chips and other solid state electronic components including discrete resistors and capacitors are embedded within the Aligned with the vision of "Internet of Things," it is expected that the number of interconnected devices, equipped with sensing and actuation funct...

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