Plasticity in Response to Music Perception

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In the previous section, I discussed changes that may occur in auditory cortex as a result of long-term exposure to auditory feedback during music production. Generalized changes within the brain may also result simply from exposure to music perception. The duration of exposure varies significantly across studies. In an influential study, Greg Recanzone, Christoph Schreiner, and Michael Merzenich trained monkeys to make pitch discriminations within particular frequency ranges over several weeks. After training, a frequency map of the primary auditory region was derived from multi-unit recordings. The cortical representation of the trained frequency band and its area correlated positively with performance.

Hans Menning, Larry Roberts, and Pantev carried out a related experiment in humans using MEG.

Volunteers were trained to make increasingly fine pitch discriminations referenced to 1000-Hz pure tones over a period of 3 weeks. The M100 in response to the frequencies trained increased in amplitude during training. After 3 weeks without training, it decreased. Increased amplitude of the M100 could indicate that more neurons are firing, and it is consistent with the increased area of cortical representation seen in the analogous monkey experiments.

Pantev and colleagues asked volunteers to listen to music from which a narrow band of frequencies centered at 1 kHz had been removed by a "notch" filter. Magnetic fields evoked by a bandpassed noise corresponding to the notch filter and a similar control stimulus centered at 0.5 kHz were recorded before and after 3hr of listening on 3 consecutive days. The amplitude of the response to the 1-kHz centered stimulus decreased after listening to the notched music,

Figure 13 Short-term reduction of neural response to a specific frequency range after listening to ''notched'' music. (a) Spectrum of the notch filter centered at 1 kHz that was applied to self-selected music. Spectrum of the two stimuli, band-passed noise bursts centered at 1 and 0.5 kHz, used to measure the evoked magnetic response. (b) Auditory evoked fields from one representative subject in response to the two bandpassed noise bursts immediately before and after 3 hr of attentive listening to notched music on 3 consecutive days. Note that response magnitude is diminished afterwards only for the test stimulus (1 kHz), corresponding to the removed frequencies. This effect was not present 24 hr later (i.e., at the beginning of the next session), suggesting that auditory cortical neurons reverted to their initial frequency tuning (reproduced with permission from Pantev et al., 2001a, modified from Pantev et al., 1999).

Figure 13 Short-term reduction of neural response to a specific frequency range after listening to ''notched'' music. (a) Spectrum of the notch filter centered at 1 kHz that was applied to self-selected music. Spectrum of the two stimuli, band-passed noise bursts centered at 1 and 0.5 kHz, used to measure the evoked magnetic response. (b) Auditory evoked fields from one representative subject in response to the two bandpassed noise bursts immediately before and after 3 hr of attentive listening to notched music on 3 consecutive days. Note that response magnitude is diminished afterwards only for the test stimulus (1 kHz), corresponding to the removed frequencies. This effect was not present 24 hr later (i.e., at the beginning of the next session), suggesting that auditory cortical neurons reverted to their initial frequency tuning (reproduced with permission from Pantev et al., 2001a, modified from Pantev et al., 1999).

but the response to the control stimulus was unaffected (Fig. 13). The 1-kHz response rebounded by the beginning of the next session. These findings point to the existence of more rapid and transient changes that may take place in response to changes in one's acoustic environment.

Finally, I consider claims regarding more generalized effects of music perception on the brain. In particular, much attention has been drawn recently to the so-called "Mozart" effect, or modest gains in cognitive test performance following 10 min of listening to a Mozart sonata (primarily in tests requiring visual-spatial manipulation). First, the effect is not specific to Mozart, and it has been reported by Glenn Schellenberg in response to Schubert, or even listening to a passage from a story. For a given individual it appears to be maximal for the preferred stimulus. Its persistence across time has not been demonstrated.

The Mozart effect appeals to the popular imagination in that it appears to promise a passive route to cognitive enhancement (much as the passive exercise machines of the 1950s did for physical improvement). Though considerable controversy still exists, perhaps the moral is that effort and time are required before long-lasting changes can be induced in the brain. Regardless, human beings will continue to make and listen to music, primarily for noncognitive reasons and without any goals for self-improvement.

As this article makes clear, music, even when only perceived, engages and activates the human brain at many levels: auditory, cognitive, emotional, and, when working memory or imagery are involved, motoric. Across a lifetime of exposure, musical experience, both active and passive, has the potential to leave lasting traces in our brains, not only through the formation of memories for specific musical sounds and gestures (a musical "lexicon") but also in more general ways.

Like language, music is an accumulated product of humankind that is continually being passed on and added to. Questions regarding how (and why) the human brain produces and responds to music will continue to occupy researchers and philosophers for many years to come and touch upon many of the brain's most complex and integrative abilities.

See Also the Following Articles

AUDITORY CORTEX • AUDITORY PERCEPTION • CREATIVITY • HEARING • LANGUAGE AND LEXICAL PROCESSING • NEUROPLASTICITY, DEVELOPMENTAL • SEMANTIC MEMORY

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