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Monday, January 14, 2008

Auditory "Brain stem Implant Electrode"- Frequency Tuning?

How important it is to fine tune the frequency specificity in the ventral cochlear nucleus and central inferior collicular neurons, the following research work published in the Oct 2007 issue of "Journal of Neurophysiology" used multichannel microelectrodes to map the frequency specfic patterns of activity in VCN and Inferior colliculus neurons.

Mohit N. Shivdasani1,2,3, Stefan J. Mauger1,2,3, Graeme D. Rathbone1,3 and Antonio G. Paolini1,2

Submitted 7 June 2007; accepted in final form 6 October 2007

Multichannel techniques were used to assess the frequency specificity of activation in the central nucleus of the inferior colliculus (CIC) produced by electrical stimulation of localized regions within the ventral cochlear nucleus (VCN). Data were recorded in response to pure tones from 141 and 193 multiunit clusters in the rat VCN and the CIC, respectively. Of 141 VCN sites, 126 were individually stimulated while recording responses in the CIC.....................

Sunday, January 13, 2008

Hearing Loss, what is Trigeminal Nerve doing instead of VIII Nerve?

Dorsal cochlear nucleus responses to somatosensory stimulation are enhanced after noise-induced hearing loss
S. E. Shore1,2,3
1Department of Otolaryngology, Kresge Hearing Research Institute
2Department of Molecular and Integrative Physiology and
3Department of Biomedical Engineering, University of Michigan Medical School, Ann Arbor, MI 48109, USA,
S. Koehler1,3
1Department of Otolaryngology, Kresge Hearing Research Institute
3Department of Biomedical Engineering, University of Michigan Medical School, Ann Arbor, MI 48109, USA,
M. Oldakowski1
1Department of Otolaryngology, Kresge Hearing Research Institute,
L. F. Hughes4
4Southern Illinois University School of Medicine, Department of Surgery/Otolaryngology, Springfield, IL, USA and
S. Syed1
1Department of Otolaryngology, Kresge Hearing Research Institute

The above article published in the latest issue of "European Journal of Neuroscience, discusses issues on hearing loss and possible involvement of trigeminal nerve?

Hearing loss due to VIII nerve damage or loss of synaptic connectivity of VIII nerve in the cochlear nucleus is a common degenerative changes observed in models of noise damage, similar degeneration of terminals also reported in cases of hearing loss in humans. However, the above article discusses the possiblity of the involement of "Trigeminal Nerve" as a compensatory response to the loss of VIII nerve connections following noise induced hearing loss in animal models. How much of this compensatory response is due to hearing loss or changes in VIII nerve connectivity is not clear, however, it is interesting to note how the neighbouring cranial nerve respond.

The authors observe the following changes in responses to trigeminal stimulation: The guinea pigs with noise-induced hearing loss had significantly lower thresholds, shorter latencies and durations, and increased amplitudes of response to trigeminal stimulation than normal animals. Noise-damaged animals also showed a greater proportion of inhibitory and a smaller proportion of excitatory responses compared with normal. Authors also argue that there is increased inhibitory responses and increased activity of somatosensory response, prompting them to conclude a role of somatosensory inputs in noise induced hearing loss? is yet to be clarified by extensive studies!.

Here is a Science Daily which is jumbing into conclusions of the following kind?.
'Ringing In The Ears' May Be Caused By Overactive Nerves, Acupuncture May Help, Study Suggests
ScienceDaily (Jan. 10, 2008) — Do your ears ring after a loud concert? Nerves that sense touch in your face and neck may be behind the racket in your brain, University of Michigan researchers say.
Note: the above image is from Science Daily.