Auditory system & Nexstim

The lecture dealt with the auditory system. Hearing is made possible by the outer ear, middle ear and inner ear. The pinna of the outer ear guides the sound waves into the auditory canal. At the end of the auditory canal is located tympanic membrane that the sound waves make vibrate. The vibrations are relayed to the ossicles which are three small bones that amplify the sound and relay it to the cochlea in the inner ear. The cochlea is a fluid filled cavity. Waves in the cochlear fluid stimulate the hair cells located inside the cochlea. The hair cells in the cochlear are organized tonotopically according to different frequencies. This activation is then relayed to the brain stem, from where it moves through the thalamus into the auditory cortex. The auditory cortex is also organized tonotopically.

On this week we had an excursion to the Nexstim. Nexstim is a Finland-born company that produces valuable technologies for transcranial magnetic stimulation (TMS). Their software provide pre surgical information of the functional areas of the cortex. For example, when removing tumor from the motor cortex it is essential to know what parts of the brain should be left untouched to provide better post surgical life for the patient.

During our visit in Nexstim we were introduced to the technologies they use by a short demo operation. After the demo we were told about the Nexstim’s vision and values and position in the TMS industry. We also had a tour in the facilities. In the demo motor cortex was stimulated with the TMS to locate the areas which are related to the movement of the right hands fingers. After stimulating the cortex with magnetic pulses the responses of the right hands muscles were recorded with EMG.

Posted by Timo Tommila

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