Bodily Defenses Image Map

What Does the Brain Do?

 The Brain Makes Us Aware

What would it be like if you "saw" all the radio signals in the world? There is short-wave radio, AM, FM. There is communication among pilots and airports, military communications, satellite uplinks and downlinks. If we could see all that, we would go crazy. Fortunately, our brains are wired to see only what we have to see for effective operation in this world. We don't need to see radio signals, but we do need to see objects that we would otherwise walk into.

Similar things could be said about sound. The point is that we are aware of only part of what is "out there" in the world.

This diagram is intended to make the point that our sensory systems detect only a fraction of the information in the world. And of the part that is detected, even smaller amounts reach our consciousness and still smaller amounts get remembered. 

We humans have detector cells for:

  • Light waves (eyes)
  • Sound waves (ears)
  • Chemicals that we smell (sensors in the nose)
  • Chemicals that we taste (tongue sensors)
  • Physical forces (touch, pressure, cold, heat) (skin sensors)
  • Muscle tone and limb position (sensors in muscles)

Two things to remember about these sensations:

1.  They tend to be mapped in our brains. That is mapped in terms of location outside of our body or location inside our body, depending on where the sensation is coming from.

View of the brain from the ventral (bottom) side. Blue lines show paths taken by nerve fibers leaving each eye. Note that half of the fibers cross over to the other side.  

The lateral geniculate body is a relay station in the brainstem. Some processing of visual information occurs at this level, but conscious evaluation of what you see occurs in the visual cortex.


Mapping can be very specific. For example, neurons in the visual cortex (see above) respond to a line on a TV screen, but the degree of response depends on the orientation of the line (vertical, horizontal, angular) and the line's location in the field of view. Click here to perform an on-line simulation that illustrates this.

2. We can be consciously aware of many of these stimuli. That is, we not only know this information, we are aware that we are aware of it.

Brain Makes Us Conscious

Where Does Consciousness Come From? 

It comes from the interaction between:

  • the cerebral cortex (outer part of the brain)
  • a cluster of cells in the core of the brainstem

Lower animals do not have nearly as many cells in their cortex as we do. Therefore, they cannot operate at the same high level of consciousness as we do. In both lower and higher animals, the brainstem core is crucial. Damage in this area can cause permanent coma. But the cortex is also crucial. Without it, we cannot see, hear, or think consciously, even if there is nothing wrong with the brainstem arousal system.

What Triggers Consciousness?


Strong or meaningful stimuli wake us up (like a dog barking will wake up a sleeping cat). By whatever route stimuli arrive, some of the input goes to the brainstem reticular formation while the rest goes to the cortex. It is as if this allows the brainstem to say "wake up brain, information is coming in you need to attend to!

Attention Determines the Registration of Stimuli

You are aware of what you attend to and not aware of what is not attended. See this video of a basketball game.

Paying attention affects how well a stimulus is registered (scientists call this encoding)

Neurons in visual cortex are tuned to respond to stimuli at specific angles of orientation. Recording number of a neuron's impulses (spikes) from a stimulus at various angles produces what is called a "tuning curve." This tuning curve shows that the strength of encoding for a visual stimulus is greatly influenced by paying attention.

Moral of the story: if you want to learn and remember, pay attention!


Stimuli That Trigger Emotions Grab Your Attention

Rather than consciously focus our attention, our attention usually just drifts until something grabs it. Stimuli that are strong, especially meaningful, or have emotional associations are most affective at grabbing our attention. When we let that happen, our environment controls our behavior rather than our conscious mind and will. Exerting will is called "executive function" and this function has to be learned. Very young children have little executive function ability.


Eye movement tracking when two visual scenes are presented, one which has emotional associations (red bordered box) and one which does not (black bordered box). Without conscious intervention, eyes automatically move (colored part of track) from the center visual fixation point (red spot) to the emotional stimulus and spend most of the time scanning that stimulus. Switching left-right positions of the stimuli does not changes this basic response.

Ability to focus and concentrate is learned. If we are continually distracted and shifting attention from one thing to another, we are training out brains to be scatterbrained. But if we through force of will practice concentrating, we create a HABIT of attentiveness.

Training Attentiveness

1. Recognize just how important attentiveness is, since your reality is constructed from what you attend to.
2. Live in the now. The expert on this philosophy, Eckhart Tolle, says, “The clock’s hands move, but it is always now.” Grab the present intensely. You cannot know the future and you cannot re-do the past.
3. Think in terms of targets for attentiveness and take mental aim at them. Targets should be interesting or have a clear value. If these attributes are not apparent, you must consciously enable them.  Choose challenging targets of attention, ones that push you to the edge of your competence.
4. Make tough choices about what to attend to. Attending orders but limits your experience. Attend to those things that best serve your own best interests.
5. Develop an eye for detail. See the forest, but also see the trees (and the leaves, bark, insects, birds, squirrels, and everything else there). Notice the small pleasures of life. It teaches you how to focus and makes you happier.
6. Shut out distractions. Stay on target. In memory tournaments, contestants wear ear plugs,  wear glasses with side blinders. Some contestants face a blank wall.
7. Set goals and keep track of them and how you are getting them achieved.
8. Change the pace of your attention. Stay on task, but don’t let it become a drill. Enliven dull work by thinking of it in novel ways. Make targets of attention more engaging by creating competition or making them into some sort of game.
9. Don’t multitask. This is the arch enemy of attentiveness and profoundly interferes with the ability to learn and especially to remember. Multitasking creates a superficial way of thinking that also imperils the ability to think deeply in mentally demanding situations. It trains you to be distractible.
10. Be more self-aware, what you are doing, why, and how.
11. Develop a passion for what you experience, as that will rivet your attention. Use your emotions to focus attention. Both negative and positive emotions work. The kiss of death for learning is to be bored and detached from what you are trying to learn. Become emotionally invested in what you are trying to learn and remember. Emotions are well known to influence memory, and one of the main reasons is that emotions influence how you pay attention to events or information in the first place.
12. Practice attentiveness. Practice concentrating on routine tasks. Psychologist Ellen Langer suggests staring at your finger. Attentiveness is cultivated from the more you notice: the dirt, distribution of hair, pattern of skin folds, shape of the knuckles, and features of the nail (shape, color of quick, ridges, etc.). Do similar exercises with any object you encounter. Learn how to meditate. See how long you can sustain focus on your breathing and keep out all intruding thoughts and the silent chatter you usually hear in the mind's ear. Notice all things associated with the breathing, but nothing else. Hear the sound of the moving air with each breath. Breathe slowly: six counts in, eight counts out. Notice the rhythm and the gradual slowing. Feel your clothes shifting position and the tension flowing out of your muscles, first in the jaw, then back and legs. Not only does meditation teach your brain how to concentrate, it also lowers anxiety and contributes to peace of mind.



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