This is the third in our series of looking at brain circuits to better understand our behavior and emotions, based on research priorities set out by the NIMH. Last week, we investigated positive and negative emotions. This week, under the broad heading of cognition, we look at an intriguing distinction between attention and perception.
Rather than look for a definition, it is much easier to conceptualize attention as a process. According to the NIMH, in a 2011 workshop report, a vast number of inputs over a multitude of brain systems compete for attention. The brain has a way of screening the competition so that it enhances or suppresses information that travels along the neural circuits. Influences at work involve motivational inputs (such as hunger and sexual drives), sensory inputs, reward systems, emotion systems, and arousal.
Top-down processes tend to involve cortical-to-cortical circuits (as in working on a project) while bottom-up involves sensory projections into the cortex (such as that fly buzzing overhead as you are trying to work on a project).
A quick skim of this extract from the workshop report should provide an appreciation of the complexity of the topic:
In the psychological literature, attention is categorized according to multiple schemata, such as spatial vs. object; featural vs. temporal; divided vs. selective; alternating vs. sustained; single channel vs. multichannel; unimodal vs. crossmodal; exogenous vs. endogenous; overt vs. covert; internal vs. external.
See? It’s really complex. How complex? The research has only just barely scratched the surface.
Perception involves the brain’s ability to make sense of the external world. Perception overlaps with attention (and other constructs of the brain) but if I understand the NIMH correctly, perception tends to involve how the brain interprets the sensory and other inputs that have come to its attention. Since not all inputs deliver complete information or flow at the same speed, initial perceptions can be enormously distorted. Further complicating matters is that perceptions are typically influenced by past experience and what is coming in through the emotional circuitry.
Ultimately, our cognition is affected. The NIMH makes it clear that the brain does not produce objective bitmap representations of our environment. Let’s see if we can sort through this:
Situation One: You are walking down the street, talking into your phone. So focused are you on the conversation that you fail to notice a person coming in the other direction.
Situation Two: This time you spot the person coming toward you. You automatically tense up.
Situation Three: A second or two later, you recognize the person as a good friend.
Situation Four: Your buddy next to you sees your friend as a threat.
Wrapping It Up
If we take the NIMH at face value, mental illness has to do the breakdown in neural circuits (which includes how we respond to our environment). Obviously, attentional deficits may involve attentional deficit disorder. But it’s far more complex than that. A number of years back, I was at a psychiatric conference where a researcher talked about how some individuals with schizophrenia have trouble screening out background noise. This involves a process called "gating" in the neural circuits. Thus, an air-conditioner that everyone else can tune out may prevent the affected individual from concentrating. Thinking becomes an enormous effort.
Stressful situations also play havoc with attention-perception-cognition. Our limbic circuits may overload. We may perceive a threat, even in non-threatening situations. We lose the capacity to think things through. We lose it.
Maybe you can see where I’m going with this: Depression, mania, anxiety, and psychosis don’t just come out of the blue. Our faulty perceptions may throw our emotions off. Our faulty emotions may throw our perceptions off. It’s a vicious cycle, but if one is tied in to the other, maybe then we have an opportunity to control one through the other.
In other words, maybe if we get a better read on our perceptions our moods will present less of a problem. The NIMH in its workshop report refers to perceptual learning. This is a natural process where we learn to become more discriminating and less sensitive to various stimuli in our environment.
There are no easy answers here. Bipolar may be an illness categorized by our moods cycling in an out of depression and mania, but many many external forces affect that cycle, such as sleep and stress. Perception is yet one more confounding variable we need to keep in mind.