Music and Cognitive Benefits: Exploring the Neural Mechanisms
Music has been recognized as a valuable stimulus in various healing and rehabilitation practices. Earlier research indicated that brief exposure to music could enhance the spatio-temporal performance of brain regions, a phenomenon known as the Mozart effect. However, subsequent studies suggested that this effect is not exclusive to Mozart's compositions or spatio-temporal reasoning.
Further investigations proposed that any stimulus inducing a moderate level of arousal and a pleasant mood in the subject could lead to significant enhancements in cognitive performance. This led to the arousal-mood hypothesis, which posits that enhanced cognitive performances are a result of the stimulus's effect on the subject's mood, rather than direct activation of neurons by music to enhance cognitive performances.
While some earlier studies supported the idea that music directly influences brain networks to enhance spatial abilities, others showed that music activates brain regions responsible for attention and cognitive tasks. A recent finding even suggests that music activates regions linked to memory, cognition, and IQ. However, previous studies have struggled to convincingly establish detailed and systematically parameterized direct mechanisms between music and cognitive enhancement.
Recent works reveal a new aspect of interconnections between music and brain signals. Music and signals such as EEG and fMRI share a striking similarity between them, of being scale free in nature. Indeed, sonification of brain signals into music has given a deeper insight into neuro-activities of the brain from musical perspective.
To understand these mechanisms, it's important to consider neuropsychological constructs like intelligence and sustained attention.
Intelligence and Music
Numerous groups have researched on Intelligence Quotient (IQ) to account for the observed variation in cognitive performances between individuals. Two complementary theories have been well received in this regard- the Neural efficiency hypothesis of Intelligence (NEH), and the Parieto-Frontal Integration Theory of intelligence (P-FIT).
NEH postulates that individuals with higher IQ perform a cognitive task with fewer brain resources compared to their counterparts. P-FIT theory proposes that the frontal and parietal parts of the brain are centres primarily responsible for intelligence, along with the cingulate cortex, temporal lobe, occipital lobe and association cortices between frontal and parietal lobes.
Accordingly, a number of EEG variables have been shown to strongly correlate with the IQ of the individual. EEG power and coherence are positively and negatively correlated with IQ respectively. Enhanced power is observed in high IQ participants in the frontal cortex, in particular in the prefrontal cortex (area linked to cognitive functioning) and in the occipital cortex.
Connectivity measures such as phase delay for short inter-electrode distance especially in the frontal lobe, have been found to reduce in high IQ individuals suggesting speedy processing at the frontal cortex. Phase slope index for long inter-electrode distance has been found to reduce in participants with high IQ especially between frontal and parietal lobe implying reduced information flow between them; optimization of the widespread activity of the brain resources for efficient functioning. This led to small world characteristics in high IQ subjects with increased hub order at the frontal and parietal lobes.
Recent fMRI studies have also led to a resurgence in the importance of brain areas related to temporal, occipital, and insular cortex in cognitive processing.
 model of intelligence)
Parieto-Frontal Integration Theory (P-FIT) model of intelligence
Sustained Attention and Music
Sustained attention is vital for any task performance. It serves prominently three purposes - (a) excitation of task-relevant processes, (b) monitoring and evaluating of ongoing cognitive processes, and (c) inhibition of task-irrelevant processes. The important regions responsible for sustained attention is fronto-parietal system.
Some preliminary studies have indicated that music listening broadens the range of attention and a notable contribution to intelligence’ variance is explained by attention control capacities. Thus, this suggests a possible link among music, attention, and intelligence.
Brain Oscillations and Music
Multiple types of oscillatory signals - theta, delta, alpha, beta, and gamma signals, modulate brain functions at all sensory and cognitive levels. Hence, selection of the most suitable oscillation band fundamental to cognitive processes is vital. Alpha band oscillations are known to play an active role in cognitive process. Furthermore, the most significant correlations between music and the psychometric measures of IQ have been consistently found in the alpha band.
Hence, in the present work, we focused our analyses on the alpha band spectrum.
Cultural Context of Music
Another important aspect in establishing a quantitative framework of mechanisms in music induced cognitive changes is the type of music that is used in the experimental study. Earlier studies used mostly Western music, especially Mozart, leaving scope to question whether other music forms from different cultural backgrounds would also show similar neural mechanisms. We used a famous eastern instrumental composition of Raga Darbari, played on flute by a professional Indian musician, as the stimulus in the present study. The stimulus maintains the cultural salience of the music for the participants.
Investigating Brain Network Changes with EEG
In summary, with Raga Darbari as the external musical stimulus, we investigate the changes in EEG patterns of brain networks during the resting state with the intent to explore the neural mechanisms responsible for enhanced cognitive abilities. Primarily, we tested (a) changes in alpha power at the prefrontal and occipital cortex, and (b) variations in the information flow between long-distance connections in alpha band, especially between frontal and parietal cortex. Based on findings from these experiments, we propose a novel comprehensive model to explain the role of music in stimulating the dedicated regions of brain that lead to observed cognitive effects.
Results of EEG Analysis
The study involved analyzing phase coherence, phase delay, and phase slope index (PSI) to understand how music affects brain network dynamics. Here's a summary of the key findings:
Phase Coherence Analysis
Phase coherence reflects the synchrony of neural activity between different brain regions. The analysis revealed:
- A significant reduction in phase coherence post-music, indicating increased brain efficiency.
- Maximum effect observed at 100 seconds after music exposure.
- Connections between parietal and occipital regions with frontal, central, and temporal regions showed reduced coherence.
- Long-distance connections were more affected than short-distance ones.
- The left hemisphere showed more connections with reduced coherence compared to the right hemisphere.
Phase coherence analysis
Phase Delay Analysis
Phase delay is inversely related to information flow and directly proportional to brain efficiency. The analysis showed:
- Cumulative phase delay continuously increased until 100 seconds, confirming this as the most efficient period.
- A total of 104 connections showed a significant increment in phase delay.
- Connections between parietal and occipital brain regions with frontal, central, and temporal brain regions as well as interlinking parietal with occipital brain region
- Long-distance connections were more affected than short-distance ones.
- The left hemisphere had more connections with enhanced phase delay compared to the right hemisphere.
Phase delay analysis
Phase Slope Index (PSI) Analysis
PSI is an index of brain efficiency. The analysis revealed:
- Significant reduction in PSI for all time periods, most prominent at 100 seconds.
- Connections interlinking frontal region with central, parietal, and temporal regions showed reduced PSI value.
Phase Slope Index analysis
Summary of Results
The following table summarizes the key findings from the EEG analysis:
| Analysis | Key Findings | Implication |
|---|---|---|
| Phase Coherence | Significant reduction post-music | Increased brain efficiency |
| Phase Delay | Continuous increase until 100 seconds | Maximum brain efficiency at 100 seconds |
| Phase Slope Index (PSI) | Significant reduction post-music | Increased brain efficiency |