Question on the trigeminal Nerve

[BMac]

It has been established that the Tympanic Membrane (Eardrum) receives all of its sensory from the trigeminal nerve according to studies and that it is supplemented only inconstantly and incompletely by the other cranial nerves X & IX.

 

With advances in Hearing Earpieces in the mobile phone industry, namely headphones. Would it be plausible that we could in effect attach an electrical device to the Eardrum itself to stimulate the eardrum with impulses causing it to react with minute vibrations thus creating audio?

 

Or if the Eardrum was to be electrically stimulated it will in effect stimulate the whole trigeminal nerve causing pain in the Ears, Eyes and Forehead muscles?

 

Is it possible that if you were to stimulate the Trigeminal Nerve with electricity would it as a side effect also cause muscle contractions in the Ears, Eyeballs and Forehead? I know it is a sensory only nerve for the sensation of pain and temperature but if we are to send a signal to the 3 branches would it activate motor control in those areas causing muscle contractions and stimulation of the tear ducts etc ?

 

Also since the eardrum itself is made up of two layers, the inner and outer layer and since the outer layer shares the ear canal and thus the vagus nerve, would electrical stimulation of the Eardrum cause the Arnold Reflex to occur in the voice box/throat causing contractions in the voice box muscles?

 

Thanks

Barry

[CharonY]

That does not sound right. Why would the eardrum receive sensory information from nerves? It is part of a sensory organ and thus the flow of information would be the other way round. Specifically it is not even actually a sensory system in the strictest sense, either. Its role is to enhance and transfer signals to the ossicles, which then end up in the chochlea where the actual sensing (by sensory hairs) happens.

 

As a rule of thumb: sensory signals originate at sensory neurons into the brain by afferent fibers. Efferent fibers send signals from the central nervous system to acting motor neurons. As the ear drum is a passive structure (essentially a membrane) that is not controlled by muscles, it does not make sense to have efferent signals going in there.

 

I should add that while not directly connected, the tensor tympani, which can move the malleus can adjust the eardrum.

Edited November 27, 2015 by CharonY

[BMac]

I got the information from: http://www.ncbi.nlm.nih.gov/pubmed/4005528

 

Tympanic membrane sensation.

Saunders RL, Weider D.

Abstract

Sensation from the tympanic membrane is generally believed to be mediated via at least four cranial nerves, some authors describing discrete territories for each of these nerves. The lack of critical evidence for independent sensory areas prompted a clinical study of tympanic membrane sensation in 32 patients having known cranial nerve deficits. Tympanic membrane sensation was tested in four quadrants using a 300 mg bristle under a Zeiss operating microscope. The findings were highly suggestive of a predominantly nociceptive system. Any change relative to the opposite tympanum was usually anaesthesia. No complete trigeminal deficit retained perception in all tympanic quadrants. Facial, glossopharyngeal and vagal deficits alone never affected tympanic sensation. These findings support the trigeminal nerve as the principal sensory nerve to the tympanic membrane, supplemented only inconstantly and incompletely by the other cranial nerves.

[CharonY]

I see how the last sentence could sound confusing in isolation. What they looked at was sensation of the membrane due to touch. This may include. tactile sensation and (in this case) nociception, and is totally independent of hearing (which happens in parts of the cochlea). It is the sensation you get when you got something stuck close to your eardrum, for example.

What they mean is that the trigeminal nerve serves as the sensory pathway for these types of sensations to the brain (in the sensory branch). This is clearly established by context.

 

Again, a) sensory branches lead to the brain and b) the hearing process does not happen at the eardrum.

Edited November 27, 2015 by CharonY

[BMac]

I also got this information from this website: http://www.scienceforums.net/topic/92381-question-on-the-trigeminal-nerve/

 

The external ear is supplied by the auriculotemporal (fifth cranial) nerve (and probably by contributions from cranial nerves VII, IX, and X) and the great auricular nerve. The posterior auricular and superficial temporal arteries of the external carotid artery provide the blood supply.

 

The tympanic membrane is highly sensitive (cranial nerves V and X laterally and IX medially).

 

The middle ear is supplied by the auriculotemporal (fifth cranial) and tympanic (ninth cranial) nerves and by the auricular branch of the vagus

I understand how the ear works. What i am asking is that can the eardrum be stimulated with an electrical signal in the audio spectrum to create audio the same way as vibrations in the air do to the eardrum.

 

in 1937–By passing an alternating electrical current in the audible frequency range from an electrode to the skin, Steven, Jones, Lurie and Flottorp found they could have people hear sounds.

 

What i mean is the Cochlear hearing aid works on the cochlear with electrical stimulation because the hairs etc. in deaf people are damaged badly so the acoustic nerve is stimulated with a spiral wire. With a person who has no hearing problems can you stimulate the eardrum or ear canal even, since it covers the outer side of the eardrum, with an electric current in the audible frequency range to achieve audio signals that you can hear like the Cochlear hearing works?.

 

And since Cranial Nerve 5 is the sensation nerve along with the vagus nerve in the ear canal, if you were to stimulate this area would it also stimulate the voice box (Like the Arnold Reflex) and eyes due to the trigeminal supplying sensory functions to the eyeballs, eyelids, eyebrows etc.

 

I know the trigeminal is for sensory only like touch, pain and temperature. I am asking that if you where to electrically stimulate that nerve would that stimulation use the trigeminal nerve to create muscle contractions on the target are's muscle groups. like the eyelids, eyebrows and voice box muscles etc?

[CharonY]

I am not sure what you mean. Do you mean that whether stimulating the eardrum could stimulate the cochlear hairs? Well, yes if it creates a pressure on the window it would be perceived as sound. Though the sensation may be quite different to what you apply as it is modulated during transfer. It does seem different to your initial question, though (unless I miss something here).

 

Stimulating a nerve can have various effects and I am not enough of an expert to assess what specifically would happen if you stimulate a whole nerve bundle. From what I read it would highly depend on the stimulus and range from modulating signals to full fledged cramps and seizures. If you could specifically target the sensory neurons as outlined in the paper, your sensation would be nociception. I.e. it would probably feel like you had something touching your eardrums (but you would not hear anything from that).

Edited November 28, 2015 by CharonY

[Xalatan]

If you vibrate the tympanic membrane through electrodes you may be able to generate audio. As long as the ossicles move and transmit the pressure impulses to the oval window it may achieve the goal. However, the adverse effects of mechanically vibrating the membrane may cause pain via the gsa as you described via trigeminal nerve. It may scar the tympanum membrane in the long term.