Responses to a target can be sped up or slowed down by a congruent or incongruent prime, respectively. Even though presentations are rapid, the prime and the target are thought to activate motor responses in strict sequence, with prime activation preceding target activation. In feature fusion, the opposite seems to be the case. For example, a vernier offset to the left is immediately followed by a vernier offset to the right at the same location. The two verniers are not perceived as two elements in sequence but as a single, aligned vernier. Here, we ask the question as to how features are integrated: before or after motor activation? We presented two vernier primes with opposite offset directions preceding a single vernier target. No priming effect occurred when the vernier primes were presented at the same location, indicating that verniers integrate before motor activation. There was also no priming effect when the primes were presented simultaneously at different locations, indicating that there is an integration stage different from the perceptual fusion stage. When the second prime is delayed, it determines priming, even for very long delays. To explain these long integration times, we argue that there is a buffer preceding motor activation.
Complex suture prostheses that deliver sensory and position feedback require a more sophisticated integration with the human user. Here a micro-size active implantable system that provides many-degree-of-freedom neural feedback in both sensory stimulation and motor control is shown, as one potential human-use solution in DARPA's HAPTIX program. Various electrical and mechanical challenge and solutions in meeting both sensory /motor performance as well as ISO 14708 FDA-acceptable human use in an aspirin-size active implementation are discussed.
One of the limitation of current prosthetics is the ability to provide sensory feedback to the human user. Due to this constraint, approximately 60–80 percent of amputees experience a phenomenon known as phantom limb pain, an ongoing painful sensations that to the individual, seems to be coming from the part of the limb that is no longer there. The lack of sensory feedback also limits the intuitive control of the user's hand movement, i.e. sense of grip or position. To address these limitations, we created am implantable system that could provide peripheral nerve stimulation, recording and motor control. The architecture of our Sensory-Stimulation Lead (SSL) system consist of multiple satellites connected to Draper's custom designed nerve electrodes. In this phase of the design, the implanted system is connected to a controller via percutaneous connections. The active electronics of the satellite is enclosed in a hermetic package approximately 14mm in diameter and less than 5mm thick. A custom ceramic feedthrough substrate provides the electrical connections of the internal electronics board to both the nerve electrodes and percutaneous leads. In this paper, we will describe the various packaging components of the system and the design, fabrication, and assembly considerations that drove our technology choices.
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