Biomedical Engineering Reference
In-Depth Information
Figure 4
. Schematic of sensory system. Both whisker and photoreceptor arrays sample the
frontal 120( of space. The spiking whisker units project topographically to both Hebb layers.
The photoreceptors drive the transient and sustained spiking layers that are connected to the
Hebb layers via modifiable, initially random connections. Each Hebb layer is excited by pro-
prioceptive spikes signaling left or right eye/head turns.
selectivity. In those sensory systems that have topographic arrangements (i.e.,
visual, somatosensory, auditory), neurons are found that respond selectively to
one direction of motion, whether it be in space or in some other dimension like
sound frequency. Such selectivity is important for higher neural processing of all
kinds, for example, our ability to use vision to guide ourselves through our envi-
ronment, or to recognize speech sounds.
6.
SIMULATED NETWORK
The simulated vehicle is equipped with two kinds of exteroceptors—
whiskers and photoreceptors—and proprioceptors that signal the vehicle's own
motion. Figure 4 shows the arrangement of sensors and the network of spiking
neurons whose activity can be used to guide movements of the vehicle as it
roams around an environment with obstacles.
The six whiskers and the 10-20 photoreceptors are fixed to the vehicle and
arrayed to sense the frontal 120( in the horizontal plane. Each whisker, when it
