What Are Brain Waves?

Neural oscillations, also known as brain waves, are rhythmic patterns of neural activity that occur at various levels of the central nervous system. But how do they work? And what are they for? Here, we explore neural oscillations and their significance.

What are the different brain wave bands?

Neural oscillations can be generated by individual neurons or groups of neurons interacting with one other. They occur at various frequencies, and each is associated with specific cognitive functions or states of consciousness. For instance:

• Delta waves (0.5-4 Hz) are slow waves predominant during deep sleep. It is argued that they facilitate restorative processes and memory consolidation.
• Theta waves (4-8 Hz) are prominent during REM sleep and deep relaxation. They are implicated in creative thinking and meditation.

• Alpha waves (8-12 Hz) are observed during relaxed wakefulness with eyes closed. They tend to indicate a state of calm alertness and are, again, associated with enhanced creativity and mindfulness.
• Beta waves (12-30 Hz) are often present during active thinking, problem-solving, and focused attention. They reflect heightened cognitive engagement and are typical during wakeful consciousness.
• Gamma waves (>30 Hz) are the highest frequency brain waves. They tend to be studied in relation to perception, learning, and memory encoding. They represent synchronized firing of neuronal assemblies and are thought to facilitate neural integration and information processing.

Where do neural oscillations come from?

Neural oscillations occur at different levels of brain function. They can be observed as alterations in the electrical charge across the cell membrane of single neurons (known as changes in membrane potential).

They also emerge at the meso-scale as coordinated patterns of activity across many neurons. In fact, these synchronized groups of neurons are often responsible for the kind of electrical activity described by electroencephalography (EEG).

Finally, at the macro-scale, different brain regions can interact with each other and generate large-scale oscillations.

Various mechanisms contribute to the generation of neural oscillations across these different scales. These include the intrinsic properties of neurons and network properties arising from synaptic interactions. Additionally, neuromodulators regulate oscillatory activity over longer time scales.

In fact, external stimuli can also modulate neural oscillations. For instance, environmental factors like sound and light can influence the amplitude and frequency of brainwaves.

As an example of this, consider steady state visually evoked potentials (SSVEPs), which describe how brain oscillations are entrained by a flickering light. That is, if you look at a flickering light long enough, neurons in the visual cortex will fire at the same frequency as the flickering light. This is detectable by EEG.

We explored SSVEPs in BCIs and SSVEPs as a way to increase signal-to-noise ratio in previous blog posts.

In fact, in recent work, Hainke and colleagues managed to induce gamma-range neural oscillations during sleep by creating a sleep mask that flickers light gently during the night. This provides a promising technique to promote gamma oscillations in patients with Alzheimer’s.

How can I measure brain waves?

To identify brain waves, researchers have to select a method that is appropriate to the scale they are investigating. For instance, at the lowest level, researchers may conduct so-called single-unit recordings, where they measure individual neurons using techniques like patch-clamping.

Patch clamping was developed by Erwin Neher and Bert Sakmann some 50 years ago. It allows researchers to study the electrical current across individual living cells or cell membranes. This is, of course, particularly useful for brain research.

Patch clamping employs either a voltage clamp or current clamp to control membrane voltage or current, respectively. A micropipette filled with electrolyte solution and connected to an amplifier is used to form an electrical circuit with an isolated cell membrane. Researchers can then measure the ionic currents and channels in real time.

Of course, patch clamping, and other single-unit recordings using microelectrodes are invasive procedures. However, this is not the only way to research brain waves.

Anyone who has used EEG will have come into contact with synchronized firing patterns. This is because neural oscillations are so prevalent that if you place an electrode on a participant’s head, you are bound to identify at least one (although more commonly multiple) bands of oscillations.

Importantly, small, mobile EEG amplifiers, like Mentalab Explore Pro, are capable of detecting these frequency bands and associating them particular brain function. They allow participants to engage in ecologically valid experiments without obstructive wires that are tethered to a stationary amplifier.

What are brain waves for?

Scientists have studied neural oscillations since the early 20th century. Significant advancements in brain imaging technologies greatly contributed to their study.

Researchers believe neural oscillations have diverse functions in cognition. For instance, they appear to be implicated in cortical information transfer. That is, by synchronizing their firing rates, neurons that are far apart from one another, but are responsive to the same stimulus, generate a so-called “relational code” that allows them to jointly process information.

Neural oscillations are also thought to be implicated in feature binding. The feature binding problem describes how we attribute features to objects. For instance, Zhang and colleagues used EEG to argue that alpha oscillations have a causal role in feature binding.

In any case, a unified understanding is still evolving. What we can say is that abnormal oscillations are associated with neurological disorders like epilepsy and Parkinson’s disease.

Therefore, understanding the mechanisms and roles of brain waves is crucial for advancing our knowledge of brain function and developing potential therapeutic interventions.

Conclusion

In summary, neural oscillations are the rhythmic patterns of electrical activity in the brain that coordinate communication between different brain regions. By studying brainwaves, we may gain insights into the mechanisms underlying consciousness and cognitive functions.