New Study - Music Affects Empirical Brain Networks
Specific music increases coherence between the global dynamics in empirical brain networks and the input signal. A group of researchers headed by Jakub Sawicki, Lenz Hartmann, Rolf Bader, and Eckehard Scholl from several German research institutions studied the effect of music on a network of FitzHugh-Nagumo oscillators with empirical structural connectivity assessed in healthy human individuals. They demonstrated that the amount of coherence is highly dependent on the frequency band. The findings were compared to experimental data, which described global neural synchronization between various brain areas in the gamma-band range and its rise right before transitions between other portions of the musical form. The findings revealed a divide in harmonic form-related brain synchronization between high brain frequencies associated with neocortical activity and low brain frequencies associated with the interaction between cortical and subcortical areas in the spectrum of dance movements. The experts spoke of the broad modalities of music's impact on the human brain. This work was published in the journal "Frontiers" during the first week of this month.
The cochlea, a portion of the human ear directly related to the auditory brain, is where sound is converted into neuronal spikes. The basilar membrane allows the brain to detect various frequencies grouped into so-called crucial bands. A cochlea model was used to convert a particular music song into an input signal that represented brain spikes elicited by the music song. After that, the input signal was fed into a synthetic network of neural oscillators with empirical structural connectivity. Dynamical scenarios were investigated in dependence on the introduced frequency band parameter by converting the dimensionless time units of the oscillator model to real-time units. We also devised a coherence metric to assess the overlap between the input signal and the network dynamics. It has been discovered that this coherence measure is heavily dependent on the frequency band parameter and reaches its maximum in the associated gamma band. In this case, there may be coherence, depending on the frequency range.
In an empirical structural brain network, a single FitzHugh-Nagumo (FHN) oscillator represented every area of interest. Averaged diffusion-weighted magnetic resonance imaging data from 20 healthy human participants was used to generate a weighted adjacency matrix of dimension 90 x 90 with node indices. The structural connectivity matrices are more of a realistic input for modeling than precise information on the presence and strength of each link in the human brain. While specific estimations of the power and direction of structural connections may be made from measures of brain activity, the relationship between these might change drastically depending on (experimentally unknown) characteristics of the local dynamics and coupling function. In humans, the auditory cortex in the temporal lobe region processes auditory information. It is positioned bilaterally and is a component of the auditory system, conducting fundamental and higher-level roles in hearing.
The nodes in the right hemisphere have equal mean phase velocity, indicating frequency synced, but the left hemisphere is desynchronized and has quicker dynamics on average. This might imply that the system can display partial synchronization independent of the input I(t). Such behavior is comparable to the dynamics of unihemispheric sleep, in which no external information is supplied to the dynamical system. One hemisphere is fully synced in such cases, while the other is slightly desynchronized. It is located approximately on the top sides of the temporal lobes.
Music has also been shown to cause a degree of synchronization in the human brain. This research found that listening to music significantly impacts brain dynamics, namely a periodic alternation between synchronization and desynchronization closely connected to the music heard. The researchers conducted an in-depth experimental study of the effect of actual music on neural activity in standard frequency bands in the brain. Using thThe gamma-band was crucial for musical form perception using the Pearson correlation coefficientiscovered a strong maximum for this frequency range, just as they did in the computer simulation. Furthermore, the findings point to a distinction in musical form-related brain synchronization between high brain frequencies associated with neocortical activity and low brain frequencies in the range of dance motions related to the interaction between cortical and subcortical areas. In addition, the alternation of synchronization and desynchronization shows how flexible the system is. This may be seen as a critical step between a completely synchronized and a desynchronized state, and it can help us understand how the system works.
Music sent to the brain promotes strong coherence and correlation between musical input and brain dynamics, particularly in the gamma band. This knowledge can help us understand how music affects the human brain in many different ways.