Expyriments, Ears and Elekta

Diving straight back to where we left off. The reaction times to aural and visual stimulus were tested using the Expyriment python program. From the figure shown last time, it was evident that the reaction times decreased in both cases as the repetition number increased. Also in general reaction times for aural stimuli tend to be quicker than for visual stimulus (although my own results seemed different). Now we can get to the why. The two stimuli are perceived and processed differently in our brains, resulting in different reaction times. Firstly the more we practice something, the more neural connections are formed in the brain and the time to process and react is decreased as a result of training. On the other hand, the information about seeing visual stimulus (the green box) travels longer in the visual pathway in comparison to the information of the auditory stimulus (the beep sound), which travels through the auditory pathway. According to research carried out by Kemp, the auditory stimulus takes only 8–10 ms to reach the brain, but on the other hand, a visual stimulus takes 20-40 ms.

This week’s lecture was about the human auditory system. It was interesting to visualize and affirm the point made earlier about how fast it takes for stimulus to reach the brain from the ears. The auditory cortex is removed only by two synapses from the cochlear hair cells whereas the visual cortex is all the way at the other end of the head from the eyes. Another interesting aspect was learning how the visual and auditory system are connected (audiovisual integration). Our vision can affect very much of what we hear. This was illustrated in the lecture with a YouTube video, where a person in two cases made the same sound but moved the mouth in different ways in each case. It caused many in the lecture hall to hear two different sounds, simply because the eyes were dominating what sound was expected to be heard.

Finally, we had our first excursion to Elekta! There we were introduced to the company, their history and what they do. The presentations went into quite a lot of detail on how their devices work and the current problems they are trying to solve. The coolest part was connecting how much of the theory presented to us related to other courses some from our group are taking (for example Principles of Biomedical Imaging or Signal Processing in BME). It was also in a sense a form of motivation as to why what we are learning in this course is so valuable, as it is constantly applied in other fields.

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