Tinnitus Memory Is in the Hippocampus

[Nick47]

The hippocampus and parahippocampal gyrus have been implicated as part of a tinnitus network by a number of studies. These structures are usually considered in the context of a "limbic system," a concept typically invoked to explain the emotional response to tinnitus. Despite this common framing, it is not apparent from current literature that this is necessarily the main functional role of these structures in persistent tinnitus. Here, we highlight a different role that encompasses their most commonly implicated functional position within the brain—that is, as a memory system. We consider tinnitus as an auditory object that is held in memory, which may be made persistent by associated activity from the hippocampus and parahippocampal gyrus. Evidence from animal and human studies implicating these structures in tinnitus is reviewed and used as an anchor for this hypothesis. We highlight the potential for the hippocampus/parahippocampal gyrus to facilitate maintenance of the memory of the tinnitus percept via communication with auditory cortex, rather than (or in addition to) mediating emotional responses to this percept.

→ What is the role of the hippocampus and parahippocampal gyrus in the persistence of tinnitus?

 

[momus]

Once tinnitus occurs, usually due to damage to the inner ear, signals from the inner ear to the brain create the tinnitus that we hear. These are at the synaptic connection level within the brain. I know of no science that relates tinnitus to memory. It's obviously in real time, since real time events like too much noise in our environment will trigger an increase in tinnitus.

 

[CricketEars]

I know of no science that relates tinnitus to memory. It's obviously in real time, since real time events like too much noise in our environment will trigger an increase in tinnitus.

So why is it that when the auditory nerve is cut, the ringing doesn't stop?

 

[BB23]

So why is it that when the auditory nerve is cut, the ringing doesn't stop?

Maybe because cutting the auditory nerve doesn't restore the lost potassium channels and the broken filtering mechanisms controlled by dopamine, serotonin and GABA, maybe because it doesn't reduce the hyperactivity of the neurons, or because it doesn't restore the lost GABAergic interneurons, or help with TMJ/posture related issues, or fix vitamin deficiencies like B12. Take your pick.

Pulling from memory is a thing when it comes to tinnitus though, based on the works of many researchers, so this aspect of our ailment (gift?) that keeps on giving shouldn't be ignored at all...

 

[HighleyTall]

So why is it that when the auditory nerve is cut, the ringing doesn't stop?

This is actually not correct. Not every tinnitus is the same.

Dr. Pulec performed 151 cases of cochlear nerve section between 1963 and 1993. Complete relief of tinnitus occurred in 101 patients, worthwhile improvement was obtained in 43 patients and 7 patients obtained no improvement. The case report in his paper is very interesting. Dr. Pulec was not a charlatan. But, he was probably very good at selecting candidates.

 

[Joeseph Stope]

(Smile) Are we in the realm of poetry here?

There is a competing theory out there which maintains that tinnitus is due to some filtering ability in the works that has got itself broken somehow.

Neither theory rhymes... But that's not to say that stating them won't bring us a step or two forward.

 

[Jammer]

This is actually not correct. Not every tinnitus is the same.

Dr. Pulec performed 151 cases of cochlear nerve section between 1963 and 1993. Complete relief of tinnitus occurred in 101 patients, worthwhile improvement was obtained in 43 patients and 7 patients obtained no improvement. The case report in his paper is very interesting. Dr. Pulec was not a charlatan. But, he was probably very good at selecting candidates.

That would suck for the patients who obtained no improvement.

 

[Tryn2BHopeful]

That would suck for the patients who obtained no improvement.

Maybe they had already lost most of their hearing?

 

[Jammer]

Maybe they had already lost most of their hearing?

Maybe they were already deaf and didn't mind?

 

[HighleyTall]

Maybe read the paper.

The case report:

A 34-year-old white man developed severe disturbing bilateral tinnitus, more marked on the right side, on October 8, 1975. Employed as an airtraffic controller in the Los Angeles area, he was, as part of his work, placed in an altitude test chamber which simulated the air pressure at 41,000 feet. During the test, something went wrong and he was suddenly pressurized to sea level and developed severe bilateral ear pain, fullness and hearing loss.

...

Tinnitus could be masked on the left ear with 4,000 Hz at 90 dB HL. The right ear could be masked but he could not tolerate the noise.

...

He wanted to commit suicide.

...

On 7/31/80, a right cochlear nerve section was performed by the middle cranial fossa approach. The facial nerve was retracted posteriorly and a 5 mm segment cochlear nerve was excised. The inferior vestibular and superior vestibular nerves were preserved. Electron microscopic examination of the excised segment of the right cochlear nerve revealed degenerative change consisting of a mild swelling and vacuolization of myelin sheaths.

...

Twelve days following surgery, he reported that he had no tinnitus on the left side since surgery and that tinnitus on the right side was 50%as loud as it had been before surgery. He had very slight, mild instability. On September 9, 1980, he reported that he had no vertigo and was riding his bicycle. He was at full activity. On October 31, 1980, he reported that he felt fine and planned to apply for a job. Tinnitus was gone on the left side. The right ear had a constant mild bearable high-pitched sound which he could hear in a quiet room. He reported that noise such as talking heard in the left ear would immediately cause the right tinnitus to become louder and that the tinnitus would stop immediately when he stopped hearing sounds in his left ear. He preferred to wear a wax earplug in his left ear. Hearing in the left ear was normal for pure tones and speech and his electronystagmogram showed some reduction of vestibular function on the right side.

There probably are different types of subjective tinnitus. Acoustic trauma causing specific damage in the cochlea (maybe macro-mechanical?), resulting in inflamed nerves and 'brain' tinnitus like phantom pain because of loss of signal (from cochlea). This would explain why cutting the cochlear nerve could still result in tinnitus. Like when a leg is amputated, not all patients experience phantom pain in that leg.

 

[Tryn2BHopeful]

Maybe they were already deaf and didn't mind?

I am just trying to be optimistic. I believe to have the surgery done, one would have to be pretty desperate, already knowing they would lose their hearing entirely as a result.

 

[Note]

Electron microscopic examination of the excised segment of the right cochlear nerve revealed degenerative change consisting of a mild swelling and vacuolization of myelin sheaths.

That's interesting. Are there supplements that help to repair the myelin sheaths?

 

[HighleyTall]

That's interesting. Are there supplements that help to repair the myelin sheaths?

B12, but this is probably not going to stop the problem because the cause is still there.

 

[dd314]

Just the term "tinnitus memory" is an assumptive premise. Are they saying it happens once and then gets stuck, or what? It's all just speculation on their part.

 

[IYIiKe]

That's interesting. Are there supplements that help to repair the myelin sheaths?

Whatever helps with MS. Snap, I just realized myelin sheaths and multiple scleroris have the same shorthand.

 

[MindOverMatter]

That's interesting. Are there supplements that help to repair the myelin sheaths?

Possibly Lion's Mane. I've used it for nerve pain myself (neuralgia).

 

[Pinhead]

That's interesting. Are there supplements that help to repair the myelin sheaths?

If there were immediate cures, multiple sclerosis would be mostly a thing of the past.

 

[UKBloke]

Maybe read the paper.

The case report:

There probably are different types of subjective tinnitus. Acoustic trauma causing specific damage in the cochlea (maybe macro-mechanical?), resulting in inflamed nerves and 'brain' tinnitus like phantom pain because of loss of signal (from cochlea). This would explain why cutting the cochlear nerve could still result in tinnitus. Like when a leg is amputated, not all patients experience phantom pain in that leg.

Interesting stuff. I was just researching articles on exactly that treatment situation - sectioning the cochlear nerve with a result that may or may not resolve tinnitus. It also happened during the trial that Dr. Pulec carried out.

Dr. Pulec's results looked stunning, but when we hear stories like the above, one wonders, as you do, whether or not he was just very good at selecting candidates.

I think this idea of whether or not tinnitus remains in the periphery is particularly relevant to the upcoming podcast with Professor McNaugton. I had a brief chat with him some months ago, and translating his work on pain into tinnitus seems to suggest an aversion to the idea that tinnitus somehow "migrates" into the CNS.

That said, clearly, Dr. Pulec's trials and the story of the ATC from LA suggest that sometimes tinnitus does migrate, but then again, sometimes it doesn't. What a conundrum.

 

[Nick47]

I think this idea of whether or not tinnitus remains in the periphery is particularly relevant to the upcoming podcast with Professor McNaugton. I had a brief chat with him some months ago, and translating his work on pain into tinnitus seems to suggest an aversion to the idea that tinnitus somehow "migrates" into the CNS.

I remember your astonishment at the fourfold decrease in tinnitus cited in the paper on electrical stimulation of the cochlear. Then we have the success of cochlear implants and, in some cases, nerve resection. We could throw in Professor McNaughton's work, albeit only preclinical evidence, to support the auditory nerves as a key target in a large percentage of tinnitus patients.

When I spoke to Professor McNaughton last year, he said the findings of the Shore Lab did not contradict his theory but backed it up, fitting in nicely. He means the polarization of auditory nerve cells affects cells in the first part of the brain stem.

Given technology at its advanced stage, I find it hard to accept that these middle ear implants are not already in use. The market for companies like MED-EL and Cochlear worldwide is huge, and they require less surgery than a cochlear implant.

 

[UKBloke]

He means the polarization of auditory nerve cells affects cells in the first part of the brain stem.

Ah, OK, that makes sense. The cochlear implant is also having the same effect I believe, although I've wondered how far upstream those voltages travel and whether or not they're making some difference there.

 

[Nick47]

The cochlear implant is also having the same effect I believe, although I've wondered how far upstream those voltages travel and whether or not they're making some difference there.

I don't know, pal. I do know they've put cochlear implant users in a soundproofed booth with the implant on and tinnitus is sometimes suppressed. So it's not a case of masking or sound therapy. Surely it can only be electrical 'therapy.'

 

[momus]

Have you all listened to the simulated sounds one would get from a cochlear implant? They are so alien and unlike what we hear with our ears that I would only think it's a last resort sort of thing accompanied by low expectations. The best estimate I could find of the number of people worldwide who had cochlear implants from the time they were first tried in 1961 up to 2019 is 736,900. That's not a lot of people over nearly half a century.

 

[Nick47]

Have you all listened to the simulated sounds one would get from a cochlear implant?

People have had their auditory nerve cut. They are then deaf, with a 50/50 chance of losing their tinnitus.

I guess you have moderate, fairly stable, non-sound reactive tinnitus?

 

[UKBloke]

Have you all listened to the simulated sounds one would get from a cochlear implant? They are so alien and unlike what we hear with our ears that I would only think it's a last resort sort of thing accompanied by low expectations.

In the context of the recent discussion here, I think cochlear implants are more about users' anecdotal evidence that they suppress tinnitus when switched on rather than promoting them as a tinnitus treatment per se.

My personal interest in the role cochlear implants might play in tinnitus suppression is more a speculation on what effect the voltage/current is having upstream of the cochlear rather than how a unit may or may not enhance the patient's hearing.

@Nick47, I re-read the referenced Hippocampus paper again. It seems more of an academic overview of existing evidence rather than something that offers new ground. It's also so heavily referenced that I found it a bit too complex to digest. With that said, I thought the following statement was intriguing:

"hippocampus is critical for establishing relationships between visual objects in a scene"

I wonder if it's aspects of this mechanism that feed into Clas Linnman's auditory mirror therapy?