Ipods: as dangerous as jet engines?

My work provides a better understanding of how tinnitus may

be triggered and as such could lead to the development of

better targeted drugs.

However, it is important to raise awareness that prolonged

exposure to sound levels within the range of an I-Pod causes

subtle changes in the brain which could cumulate into tinnitus.

1. Kaltenbach JA, Zacharek MA, Zhang J, Frederick S. 2004. Activity in the dorsal cochlear nucleus of

hamsters previously tested for tinnitus following intense tone exposure. Neuroscience letters 355:121-5

2. Zhang, J.S., and Kaltenbach, J.A. (1998). Increases in spontaneous activity in the dorsal cochlear

nucleus of the rat following exposure to high-intensity sound. Neurosci Lett 250, 197-200.

Aim of the study

Normal Hearing

Conclusion

I-PODS: AS DANGEROUS AS JET ENGINES?THOMAS TAGOE

Department of Cell Physiology and Pharmacology, Universty of Leicester

Prolonged exposure to sound intensities over 85 decibels (dB

SPL) can cause partial hearing loss and can eventually lead to

‘imaginary’ auditory perceptions known as tinnitus (1).

I-Pods and jet engines both exceed

85dB SPL and as such can be

equally damaging to the ears.

Therefore, the aim of this study is to

investigate if loud sound intensities

(110dB SPL) cause early changes

within the brain which could

eventually lead to tinnitus.

Sound is processed as electrical signals which pass

through many junctions or synapses within the brain.

The dorsal cochlear nucleus becomes overactive during the

tinnitus condition and it is also the first place in the brain to

process sound signals (2). Therefore, I tested how electrical

activity at synapses in the dorsal cochlear nucleus change

shortly after a prolonged exposure to loud sound.

The synapses serve as an

important point for controlling

the transfer of signals.

•After high frequency electrical

stimulations the size of the post

synaptic response increases.

•Using a drug to block type 2

receptors (NMDA receptors)

does not prevent this increase

I have shown that prolonged exposure to loud sound

affects how the brain processes sound signals.

This effect happens a few days after exposure and as such

could be an important step eventually leading to tinnitus.

Implications

References

Experimental approach

Auditory

Cortex

Dorsal

Cochlear

Nucleus

Prolonged exposure to loud

sound alters how the synapses

process the transfer of signals

•After high frequency electrical

stimulations, the size of the post

synaptic response decreases .

•Using a drug to block type 2

receptors (NMDA receptors)

prevents this decrease

10 20 30 400

0

1

1.2

1.6

No

rmali

sed

resp

on

se s

ize

Time (mins)

0.6

10 20 30 400Time (mins)

Electrical

signal

Transmitters

Receptors

Type 1 Type 2

Partial hearing loss

90-120 dB 110-140 dB

Electrical

signal

1.4

0.8

Normal hearing

Normal hearing

+ drug

Partial hearing loss

Partial hearing loss

+ drug

Synapse

Pre- Pre-

Post- Post-

Occupational

hazard

Recreational

pastime

or

Tinnitus

-to-

Signal transfer

alters

0

0.6

1.0

1.2

No

rmali

sed

resp

on

se s

ize

0.4

0.8

1.4

?