I think a good place to start is by touching your own hand. Really. Now realize that you didn't experience the sensation until the touch activated receptors in the skin, and those receptors sent information to the spinal cord, and the spinal cord sent the information to the brain.
The touch receptors are called somatosensory receptors, and they come in different types. Some are sensitive to gentle touch, others to strong touch, still others to pain -- including the pain you feel when you touch a hot stove. (The book discusses the different types of somatosensory receptors, but that's not key here.)
What's interesting to think about here is that you don't feel the touch sensation at the moment that something makes contact with your skin. Instead, the 'feeling' arises from brain activity. And so the brain needs to find out about the touch to your skin.
How does the touch information which begins at the somatosensory receptors in your skin get all the way to the brain? Neurons carry the information. And so understanding what neurons are, and how they carry 'information', becomes key to understanding any inner experience, including the experience of touch. We'll think about neurons a little later.
But before we get to neurons, let's briefly go through the key regions of the brain that you would encounter if you were to travel from the base of the brain (the brainstem), through the brain areas below the cortex (subcortical regions), in order to finally reach the outer layers of the brain, the cerebral cortex, where sensations of touch, hearing, and vision occur.
The brainstem includes the medulla, pons, and midbrain - in that order as you climb above the spinal cord and ascend into the brain.
To get a sense of the position of these brainstem structures, take a look here:
On the bottom right, you'll also notice a large cabbage-shaped structure attached to the back of the pons called the cerebellum.
Which brainstem structure is directly on top of the spinal cord?
What brain area is just above the medulla?
What brain area lies just behind the pons?
Try to answer questions 1-3 without looking at a brain image. If you haven't done this yet refresh the page and answer them again.
If you think of the brainstem as the basement of the brain and the cerebral cortex as the penthouse (we'll get to the cortex), there are a number of important brain structures between the two. For now, we'll consider just five of the most important ones: the hypothalamus, thalamus, hippocampus, amygdala, and basal ganglia.
Now take a look in Google to find images that include these brain regions. It's possible that you'll have to look at multiple images, for some brain illustrations will only show a subset of them. The idea is not to become a neuroanatomist today -- but to get a feel for where they lie with respect to one another.
Because these five areas are below the cortex, they are called "subcortical areas". when we talk of subcortical areas, we don't usually include the brainstem, even thoughit is below the cortex. When you feel comfortable with the descriptions of these subcortical areas, try the questions below. They're straightforward.
Damage to this area can abolish the motivation to eat and drink.
As you recall what you ate for dinner last night, you are activating your _____.
This collection of brain structures is needed in order for actions that you repeat many times to become automatized habits.
the basal ganglia
Bob received a gunshot wound to the , an area of the brain housing several brain regions, including the medulla, pons, and midbrain. The injury didn't affect all of these regions. Fortunately, there was no damage to the that sits just above the spinal cord. However, he did suffer damage to the where his dopamine cell bodies (the origin of the dopamine neurons) are located. It's likely he'll survive, but it's possible he'll have particular problems with . If the damage were to his hippocampus, it's likely he'd have had problems with .
brainstem, medulla, midbrain, motivation, memory
The cerebral cortex is comprised of lobes that are critical for vision (occipital lobe), audition (temporal lobe), touch or 'somatosensation' (parietal lobe), actions (frontal lobe) and cognition (various lobes, but perhaps the frontal lobe especially). In this drawing,Cerebral Cortex
you'll notice that in addition to the four lobes, there are pointers to grooves 1) between the left and right hemispheres of the brain (longitudinal fissure), 2) behind the frontal lobe (central sulcus), and 3) above the temporal lobe (lateral sulcus). As you might have guessed from the drawing, the word we use for a groove within the cortical surface is sulcus (sulci, pl.) or fissure. The terms sulcus and fissure are sometimes used interchangeably. For instance the lateral sulcus is sometimes called the Sylvian fissure.
I wouldn't worry about remembering the names of these sulci/fissures at this point. But you should remember that the term sulci (or fissure) refers to grooves in the cortex. You'll notice that the illustration shows many sulci in the cortical surface, with only a few labeled. Also, notice that between sulci, the cortex bulges outward. Each of the bulges between sulci is called a gyrus (gyri, pl.). Take a moment to Google some images for 'sulcus' and 'gyrus' and point to some of the sulci and gyri so you become accustomed to their appearance.
Finally, notice that a few paragraphs above, I said that the central sulcus is behind the frontal lobe. Neuroscientists rarely use the terms 'in front of' or 'behind', but instead say anterior (toward the nose) or posterior (toward the back of the head). So, as you can see in the Cortex illustration, the frontal lobe is anterior to the parietal lobe. The central sulcus and the parietal lobe are posterior to the frontal lobe. Sometimes, instead of anterior vs posterior, you'll see rostral vs caudal. Finally, instead of saying above vs below, we say dorsal vs ventral. So, if you look at the illustration of the cortex, you'll see that the lateral sulcus is dorsal to the temporal lobe, and the temporal lobe is ventral to the lateral sulcus
You are looking at a tree and the visual experience is due to activity in the lobe. The scene reminds you of a childhood memory which comes to mind thanks to activity of your . You walk to the tree and raise your arm toward a branch. The movement of your arm requires that you activate neurons in your lobe which generates actions. Suddenly you hear a sound. Your immediate detection of the sound -- before you've had a chance to process the details of what the sound is -- involves activation of neurons in an area of the midbrain called the superior . A brief moment later you recognize the sound to be the song of a bird. The auditory perception required activation of neurons in your lobe.
hippocampus, colliculus, occipital, temporal, frontal