Using the cockroach spine to mimic the human auditory system
Two electrodes are set into a spine of a cockroach leg which is stimulated by a probe that is attached to a vibrating speaker.
Sound is a sine wave comprised of time-dependent blends of tones with varying frequencies and amplitudes. To identify and interpret these signals, the ear uses an adaptive analyzer: the cochlea. The pre-cochlear region, which includes the mechanical link between the oval window and the tympanic membrane in the human ear, may be modeled by connecting the cockroach spine to a speaker. These sound waves can be encoded by the complex set up of the auditory system in the brain.
When a cockroach spine is deflected (mechanical stimulation), an action potential is transmitted like the human auditory system. For instance, we can simulate the action of the tympanic membrane and ossicles on the oval window to explore how this system encodes mechanical information. We mimic the mammalian auditory system by stimulating the spine using wax on a wooden stick attached to a speaker that produces arbitrary sinusoidal waves and tuning the speaker to different amplitudes to vary
the range of stimuli.
Measuring the spine’s extracellular voltage using electrodes provides useful neural signal information. At several spots along its length, the cochlea analyzes the incoming sound signal to divide the signal into its frequency components. Neuronal responses may convey different frequency, timing, and amplitude information about environmental stimulus.