The Question I want to understand how a sound wave changes in the form of its signal into the brain. I don't know the terminologies. I don't know what this subject is called. If you know the right terms or know where I should look, please fill me in. My question is: What is the form of the signal that pertains to the sensation of sound? My Understanding Here I show you the way I view the question so you know what level of understanding I have. Since I have never been tested on this knowledge, you can assume that anything I say below could be wrong: First I know that sound wave is a transmitted in the form of changing pressure over time. It can be measured and plotted on a graph with force as the y-axis and time as the x-axis. A pure tone will appear as a sinewave on such a graph. Second I know that the ear is an organ that tranduces this pressure through a curved tube inside the ear. The lower the frequency of the incoming tone, the further it travels. There are receptors along the tube to detect vibration. These detectors transduce vibration into action potentials. Action potentials can be plotted on a 2D graph. The y-axis is voltage. The x-axis is time. The intensity of vibration translates into the frequency of occurance ot the spikes. A burst of spikes is loud. Along the tube, each detector is only responsible for detecting a certain frequency. Therefore, to send the signal corresponding to a song into the brain, it takes a bundle of nerves. If you order and label each nerve and plot the signal, it is a stack of 2D plots fi(x). x-axis is time. y-axis is the voltage. The index i is the identification number of a nerve. In some sense the ear is a spectrum analyzer. Third. . . What happens after that? I assume that the nerve bundle gets separated and nerve cells interact with each other as they are activated to form relays. Certain features of sounds are formed and detected in these relays. (What is the list of features that the pathway detects?) However, from here on the signals are still transmitted in the form of spikes. Meaning is formed and encoded in the connectivity of the nerve cells. For example, if nerve cell 1 is can excite nerve cell 2, then 1 means something to 2. Inhibition can also occur. Memory is a phenomenon cause by this connectivity. So, where is the song that I remember? It is in the connection in the brain. You remember it not because it is store somewhere in a certain format, but that the que you have in thinking about it reactivates the connections that you activated when you first heard that song. So to answer the question, "what is the form of the signal that pertains to the sensation of sound?" The answer is that, "by the time it gets to the level of sensation, sound is no long represented by a signal, but by the connectivity among the cells. It is not a signal. It is a map." Is this right?