9.2.1 Devices with neural input
This class of neuroprosthetic devices consists of those that base their operation, either directly or indirectly, on measurements of neural activity (see Figure 9.1). The measurements are then interpreted to create control signals appropriate for the device. Those signals are then used to control the action of the device, be it movement, the release of materials, or some other action. In most cases, some sort of feedback exists. This feedback is critical for the body or device to regulate its action. In some instances the feedback may be entirely confined to the device; in other cases, the body's natural senses (such as vision) and nervous system may provide the feedback.
9.2.2 Devices with neural output
In this class of devices the stimulus for action does not arise from measurement (direct or indirect) of neural activity but from some other action (for example, pushing a button). This input signal is generally processed and manipulated to create a signal that is designed for transmission to a nerve (see Figure 9.2). Because this signal is to be transmitted back into a nerve, the design must take into account knowledge of other associated neural connections. Devices, such as pacemakers, which respond to the needs of the body but not to direct measurement of neural signals, fall into this category as they generate signals that interact with the nervous system. A group of devices that is placed in this class (rather than the second class) are those that are used to implement functional neuromuscular stimulation. These devices measure a nervous signal or some other input signal and transmit this signal, via electrodes, to a muscle. In this way external devices can control aspects of the body over which the subject has lost control.
Feedback to Body
Power Neuroprosthetic ^ Device
Action, movement, work, etc.
Figure 9.2 Interactions with a neuroprosthetic device that creates a signal that is transmitted to a nerve to achieve a desired function.
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