Top-Down vs. Bottom-up Processing
An ongoing debate involves top-down versus bottom-up perceptual processing. Researchers have wondered whether information from the one’s environment are perceived first in the lower part of the brain, consisting of more unconscious processes like detecting danger, compared to the top of the brain, consisting of more conscious processes like rational thought. Picture you are walking through the woods and come across a pack of hungry wolves. Top-down processing would involve you seeing the wolves, consciously thinking about how dangerous they are, and then experiencing physiological reactions, like increased heartrate. Bottom-up processing would involve you coming across the wolves, but before you can even think about what you are seeing, your brain has begun to sound the alarms resulting in physiological reactions. Then, you notice your reaction to the situation and consciously interpret the bodily reactions. Most therapies dealing with cognition take a top-down approach to healing. Therapies dealing with affect and mood regulation tend to take a bottom-up approach to healing.
The nervous system is an important focal point for neurofeedback, as problems with the nervous system contribute to many mental health symptoms like anxiety or fatigue. For the sake of the blog, we will be focusing on the sympathetic and parasympathetic systems in the autonomic nervous system. The sympathetic division involves physiological reactions to intense and potentially dangerous situations. When someone’s sympathetic division is more active, they may exhibit symptoms related to anxiety and panic. The parasympathetic division is activated when a person feels safe and can rest. When someone cannot get out of this state, the person may suffer from symptoms of depression like chronic fatigue. The interplay between these two divisions is crucial and play an important role in things like intrapersonal and interpersonal functioning; especially for people with a history of traumatic experiences.
MacLean (1990) offered a somewhat oversimplified, yet effective, way to explain how perceptual processes occur in different parts of the brain. Picture the brain in three parts.
The reptilian brain involves processes that relate to survival and unconscious reactions like regulation of breathing. It is the oldest part of the brain in terms of evolution, and involves many instinctual reactions, including fight, flight, or freeze. Fight, flight, or freeze involves a physiological reaction to a threat where the person automatically and mostly unconsciously fights the threat, runs from the threat, or is stuck physically and mentally in a freeze-state.
The limbic brain is referred to as the “feeling brain” as it involves emotional experiences. It also relates to social functioning. This part of the brain can be seen in many mammals throughout the animal kingdom.
The neocortex involves the rational part of the brain where conscious thinking occurs. It is often referred to as the “human” brain.
Using MacLean’s (1990) theory allows one to better understand top-down and bottom-up processing. Top-down processing starts with the neocortex (a positive thought), causing a reaction in the limbic system (pleasant feeling), which will cause the reptilian brain to calm the body (release of muscle tension). Bottom-up is the opposite in that the person may feel a release of muscle tension because of an environmental trigger (pleasant smell) caused a reaction in the reptilian brain. This reaction then contributes to a reaction from the limbic system (pleasant feeling), which is interpreted by the neocortex as a pleasant feeling contributing to pleasant thoughts.
MacLean’s model, while oversimplified, helps to demonstrate the unique process of perception and how therapy can use these processes to treat clients. Many studies like the one by Solomon and Heide (2005) demonstrate the two-way street that is perceptual processing. Rather than argue whether the brain uses top-down or bottom-up, Solomon and Heide stressed the importance of being aware of how both processes play-out for a person; especially when working with someone who has traumatic experiences. Someone with trauma tends to have more bottom-up processing as their brain is more inclined to perceive a situation as dangerous. When this happens, the neocortex (rational brain) no longer receives resources and deactivates. Think of someone who was in a fit of rage and was impossible to talk to until they calmed down. That person’s neocortex was not functioning in that moment, so feelings and danger responses took over. Neurofeedback can be useful for helping to minimize these trauma responses (Gapen et. al, 2016) so a person’s neocortex can stay active, which helps the person feel more in control.
Feature Integration Theory
Another important theory to understand with perceptual processing involves feature integration theory (Treisman & Gelade, 1980). The theory supports the idea that bottom-up processing is more prevalent in the brain when people are perceiving visual stimuli. Treisman and Gelade (1980) found that the lower parts of the brain gathered information about a stimulus before the neocortex. This means people unconsciously took in information from their environment before consciously recognizing what they were perceiving. A good example of this involves subliminal advertising where the brain is recognizing cues from an ad and encoding the brand without the person consciously noticing. Feature integration theory helped to push researchers towards an understanding of bottom-up processing, and how this process may be much more common than once thought.
Polyvagal Theory-“Trusting your gut”
Have you ever been told to trust your gut? Many people get a tingling sensation in their stomachs when something bad is about to happen causing them to leave, which has saved many people from dangerous situations. When people experience a dangerous situation, they usually have an intense reaction from their nervous system. This reaction is something the brain never wants to forget, so when people comes across situations resembling the traumatic situation, the body has a reaction, often through bottom-up processing (Solomon &Heide, 2005).
Porges (2011) posed the polyvagal theory to demonstrate the process of gut instincts. There is a nerve in our bodies called the vagus nerve, which has two branches: ventral and dorsal. The dorsal branch is active when someone is facing an intense situation. The ventral branch helps to deactivate the dorsal branch and get control of the nervous system. Porges (2011) mentions how the ventral branch contributes to social engagement and discusses how one’s interpersonal functioning can worsen when someone’s dorsal branch is overactive. For example, someone with a history of trauma may have an overactive dorsal branch and get gut reactions signaling danger in safe situations. Polyvagal theory helps neurofeedback clinicians understand the role of the nervous system in many mental health diagnoses; especially posttraumatic stress disorder.
How is this Relevant to Neurofeedback?
The theories and research discussed is important information for neurofeedback clinicians and clients. Neurofeedback clinicians utilize interventions like deep breathing to help people regulate their nervous system and EEG waves. It is important for clinicians to know how to identify symptoms and whether they are due to more top-down or bottom-up processes. For example, a clinician needs to know if someone is depressed because they have negative thoughts, because their parasympathetic system is overactive, or both. The clinician can then identify protocols to use. Protocols focusing on the back and lower part of the brain can help address issues with bottom-up processing, while protocols focusing on the upper and frontal areas of the brain address top-down processing. The information provided also helps clients gain awareness of their physiological processes and how they contribute to symptoms.
A neurofeedback clinician needs outcome measures to know when the work has helped. Being able to identify and assess the accuracy of perception and gut reactions of a client is a useful way to gauge the effects of a protocol. Four outcomes have been personally helpful when assessing outcomes, and each is related to the nervous system and perceptual processing. Neurofeedback for a client who has gut reactions alerting them to danger when the situation is safe would be different than neurofeedback for a person who is unable to detect a dangerous situation. The clinician and client can then measure changes in gut reactions and their accuracy to identify the effects of neurofeedback.
Overall, a neurofeedback clinician needs to understand the perceptual processes of the brain (top-down and bottom-up) and the functioning of different aspects of the nervous system to create an effective treatment focusing on developing a healthy balance between bottom-up and top-down processing, and a healthy balance between different branches of the nervous system.
Gapen, M., van der Kolk, B. A., Hamlin, E., Hirshberg, L., Suvak, M., & Spinazzola, J. (2016). A pilot study of neurofeedback for chronic PTSD. Applied psychophysiology and biofeedback, 41(3), 251-261.
Hamlin, E. (2018). Neurofeedback in a Clinical Practice. Lecture Hadley, MA.
MacLean, P. D. (1990). The triune brain in evolution: Role in paleocerebral functions. New York: Plenum Press.
Porges, S. W. (2011). The Polyvagal Theory: Neurophysiological foundations of emotions, attachment, communication, and self-regulation. New York: W.W. Norton.
Solomon, E. P., & Heide, K. M. (2005). The biology of trauma: Implications for treatment. Journal of interpersonal violence, 20(1), 51-60.
Treisman, A. M., & Gelade, G. (1980). A feature-integration theory of attention. Cognitive Psychology, 12(1), 97–136.