Music and the Brain: Processing and Response (A General Overview)For anyone who avidly listens to or performs music, it is understood that many melodies have amazing effects on our emotions and our perception. To study the effects of music on the brain, it seems most logical to start by mapping the auditory and neural pathways of sound. In the case of humans, the mechanism responsible for receiving and transmitting sound to the brain is the ears. In short, the outer ear (or pinna) “captures” and amplifies sound by channeling it into the ear canal. Interestingly, the outer ear only serves to amplify high-frequency sound components (1). The resonance provided by the outer ear also serves to amplify a higher frequency range corresponding to the upper octave of the piano keyboard. The air pressure wave travels through the ear canal, eventually reaching and vibrating the tympanic membrane (i.e. eardrum). At this particular stage, the pressure wave energy of sound is translated into mechanical energy via the middle ear. Here, three small bones, the ossicles, vibrate in succession to produce a unique pattern of movement that embodies the frequencies contained in every sound we are capable of hearing. The middle ear is also an important element in music that we actually keep out of our "head." The muscles that grip the ossicles can contract to block up to two-thirds of sound from entering the inner ear. (1, 2) Mechanical movements of the ossicles directly vibrate a small membrane that connects to the fluid-filled inner ear. From this point, the vibration of the connective membrane (oval window) transforms the mechanical movement into a pressure wave in the fluid. This pressure wave therefore penetrates and transmits vibrations into the fluid-filled structure called the cochlea. The cochlea contains two membranes and between these two membranes are specialized neurons or receptors called hair cells. Once the vibrations enter the cochlea, they cause the lower membrane (basilar membrane) to move relative to the upper membrane (i.e. the tectorial membrane in which the hair cells are embedded). This movement bends hair cells to cause receptor potentials in these cells, which in turn cause transmitter release on auditory nerve neurons. In this case, the hair cell receptors are very sensitive to pressure. The greater the force of the vibrations on the membrane, the more the hair cells bend and therefore the greater the receptor potential generated by these hair cells...