Even simple auditory rhythms can change how the brain organizes itself, as shown in a recent study published in Advanced Science. Researchers created a new tool called FREQ-NESS, which investigates how brain networks function across different frequencies. The findings indicate that listening to rhythmic tones activates the auditory cortex and can reorganize the brain’s broader network, shifting dominant rhythms and improving the interaction between slower and faster brain activities.
Cognitive neuroscience focuses on understanding the brain’s dynamic system as it processes ongoing environmental information. One challenge researchers have faced is capturing how various brain networks, with their unique frequency characteristics, operate simultaneously, particularly when reacting to external stimuli like music or speech. Previously, research tended to concentrate on specific regions or broad frequency bands, leading to somewhat fragmented insights. A further complication is that many brain processes overlap, making it difficult to isolate networks using traditional methods.
To tackle this issue, the researchers devised a technique that could capture frequency-specific brain networks with detailed spatial and temporal resolution. This approach sought to avoid the limitations of earlier methods relying on pre-defined anatomical regions or general frequency categories. Thus, FREQ-NESS was born, which stands for FREQuency-resolved Network Estimation via Source Separation.
“We aimed for a clear way to observe how various brain networks function at specific frequencies simultaneously, and how this organization changes when the brain engages with sound and rhythm,” explained study author Mattia Rosso, a postdoctoral researcher at the Center for Music in the Brain at Aarhus University.
They recruited 29 participants, mostly non-musicians, to record brain activity using magnetoencephalography (MEG). Participants completed two five-minute sessions: the first involved resting while watching a silent movie, and the second consisted of passively listening to rhythmic tones at a steady rate of 2.4 Hz—around two beats per second.
The MEG data helped estimate the activity of over 3,500 brain voxels, allowing the researchers to analyze specific frequency activity separate from background signals. This led to the identification of networks most active at different frequencies. They looked at 86 frequencies, ranging from 0.2 Hz up to nearly 100 Hz, to characterize each frequency’s network structure and examine how lower frequency activity influenced higher frequency networks—a process called cross-frequency coupling.
During the resting state, the brain’s activity showed a typical 1/f pattern, dominated by low frequencies. Familiar networks emerged, like the default mode network (DMN) and a parieto-occipital alpha network, along with a motor-related beta network. These observations align with previous studies showing that particular brain areas tend to work better in certain frequency bands.
Listening to the rhythmic tones brought about three significant changes in the brain’s network landscape. First, new networks emerged that were closely tuned to the stimulation frequency of 2.4 Hz, found within the auditory cortex and extending to regions like the hippocampus and insula, known for their roles in various auditory processing stages.
Second, existing networks adjusted their frequency preferences and spatial configurations. For example, the primary alpha activity shifted from 10.9 Hz to 12.1 Hz, and its focus moved from parieto-occipital areas to sensorimotor ones. This hints that the alpha network, often associated with attention and inhibition, reorganized in response to the rhythmic input—possibly in preparation for movement or sensory prediction.
Finally, some networks, like the motor-related beta network, showed little change. It remained prominent through both experimental conditions, indicating not all networks respond equally to external stimuli.
Additionally, the researchers discovered that listening to rhythmic tones improved the interplay between slower and faster rhythms. Specifically, the phase of the auditory network at 2.4 Hz influenced the amplitude of gamma-band activity—quick oscillations above 60 Hz—in brain areas such as the insula and frontal operculum. This coupling was more pronounced during listening than resting, suggesting that the brain heightens coordination across different rhythms to process rhythmic stimuli.
Interestingly, the gamma-band networks weren’t located in the auditory cortex but in broader associative regions, hinting that the brain’s response to rhythm extends beyond sound processing to include sensory input integration and attention.
“While our simulations suggested the primary auditory network would mainly respond to the auditory stimulus, we were surprised by the global reorganization of the entire network landscape,” Rosso commented. “Not only did the alpha network speed up, but it also shifted focus—indicating preparation for action.”
The researchers validated their method through various replication tests and randomization checks. They found that scrambling the voxel arrangement broke down meaningful networks, reinforcing that the detected patterns genuinely reflect brain dynamics.
“Even with simple listening tasks, the brain reconfigures itself to sync its internal dynamics with the external world for effective information processing,” Rosso concluded.
FREQ-NESS, as a tool for mapping frequency-specific brain networks, does have some limitations. The study included a modest sample size and minimalistic task design, pointing to potential improvements with more ecologically valid stimuli and broader applications.
“The brain’s complexity goes beyond just frequency organization,” Rosso noted. “FREQ-NESS is crafted to separate and analyze interactions based on frequency specifics. We’re well aware it doesn’t provide all the answers.”
Looking ahead, the researchers aim to expand the method’s applicability and have already developed a broadband variant hoping to explore further how the brain’s network structures change in various conditions.
The FREQ-NESS toolbox and methodology are openly available for others to use, with the researchers eager to collaborate on further insights into brain rhythms and their influence on perception and action.
