What does dopamine do?

Dopamine is a neurotransmitter,* and pretty doggone fun as neurotransmitters go. It works with serotonin and norepinephrine to regulate various components of your well-being: mood, attention, motivation, desire, pleasure, and as you might imagine from the rest, sexuality. Dopamine itself helps to generate the feeling of pleasure associated with rewarding experiences — food, sex, and drugs can set it to flowing. Consequently, it can kick-start motivation, desire, and other reactions that naturally follow a pleasurable experience.

Dopamine helps you to think, too. In the frontal lobe, it plays a part in memory and problem-solving. Also, you know the good feeling you can get from learning something new? That’s dopamine at work, encouraging you to continue, and thereby helping to thicken the myelin sheath that makes brain signals zip along faster.

Sweet stuff, huh? But get too much of it and you can go schizophrenic or even psychotic. Too little of it, on the other hand, and your basal ganglia can malfunction, leading to Parkinson’s disease. No fun. So if you were thinking of eating a chocolate truffle while snorting coke off the thigh of a Cuban virgin, you might want to reconsider.

* Its chemical formula is C₆H₃(OH)₂-CH₂-CH₂-NH₂. You wanted to know that.

What do the basal ganglia do?

First off: As I’ve mentioned before, clusters of neural co-laborers in the brain are called nuclei. However, certain nuclei are referred to en masse as the basal ganglia. That’s just the way it is. We may as well learn to live with the situation.

Anyway. The basal ganglia are functionally related nuclei, comprising the putamen, globus pallidus, substantia nigra, nucleus accumbens, and the caudate and subthalamic nuclei. They’re involved in the inhibition of movement (so that we don’t flail around all the time), and consequently in motivation and appetitive behavior: when you’re hungry, you don’t want your movement inhibited — you need to get to that bag of pork rinds before your jobless brother-in-law notices them.

Irregularities in the basal ganglia most often manifest themselves as disorders in movement, notably:

• Parkinson’s Disease, characterized by tremors and trouble with initiating movement, and
• Huntington’s Disease, characterized by uncontrollable spastic movements called chorea.

Both of these sound roundly irritating, not to mention life-threatening. My heart goes out to the people who have to wake up to them every day.

What does the hypothalamus do?

The hypothalamus lies quietly under the thalamus,* but it doesn’t mind its own business: Together with the pituitary gland, it links the nervous system to the endocrine system. In that capacity it’s quite the busybody, playing a role in fear and anger, hunger and thirst, blood pressure and pulse rate, fatigue, body temperature, and circadian rhythms. It gets involved in sex, too, processing pheromones as olfactory stimuli. Cheeky thing.

* By the way, the word hypothalamus comes from Greek roots meaning “under the thalamus”. Go figure.

What are neurotransmitters?

Neurotransmitters are chemicals used to transmit signals between neurons. (Makes sense, doesn’t it?) They’re emitted from the axon of the sender, cross the synapse to the receiver, and attach to a receptor site on a dendrite there. If the receiver is properly excited by the intrusion, it sends its own neurotransmitters to its neighbors; and so on. In this way, long concatenations of impulses are sent coursing through you, and you yelp when you stab your finger with the needle. Again.

Some gripping examples of neurotransmitters are dopamine, serotonin, and norepinephrine. You really should look them up.

What does the nucleus accumbens do?

The nucleus accumbens — Latin for leaning nucleus — is a cluster of neurons* that acts as a liaison between the limbic system and the central gray nuclei. It’s a paired structure, like the hippocampus, and is involved in the brain’s reward system, releasing dopamine and other neurotransmitters that produce a feeling of pleasure. For this reason, it also plays a large part in addictive behavior, appetitive eating, and behavioral motivation in general. It has a role in fear responses and the placebo effect as well. Feel free to blame it for the bad things you do.

* In brain physiology, a nucleus is a cluster of neurons that perform functions together. Outside of the brain, such a cluster is called a ganglion. Inside of the brain, it’s too dark to read.

What does the hippocampus do?

The hippocampus (Greek for seahorse, someone’s idea of its shape) is a paired structure, with mirror-image parts on both sides of the brain. Part of the limbic system, it lurks beneath the surface of the temporal lobe. It’s involved in:

• The perception and navigation of space
• Behavioral inhibition
• Memory of experienced events

Its role in memory is important but not clearly defined. Deterioration of the hippocampus can result in age-related memory loss, and damage to it can result in amnesia, both retrograde and anterograde. There’s an interesting Wikipedia entry on an example of what happens when the hippocampus is removed. It reminds me of the movie 50 First Dates.

You’ll note that I omitted any references to hippopotamuses in college. I think my restraint is to be congratulated.

What does the amygdala do?

Or rather, the amygdalae — there are two of them. They’re part of the limbic system (about which more later), and each consists of several nuclei. The nuclei are roughly almond-shaped; the Greek word for almond is “amygdale” (αμυγδαλη); you see the connection. Together they are involved in many brain functions, including:

• Fear conditioning
• Appetitive conditioning
• Processing and memory of emotions
• Memory consolidation
• Neurotransmitter activation
• Sympathetic nervous system activation
• Facial muscle movement

Irregularities in the amygdalae have been linked to borderline personality and bipolar disorders, schizophrenia, and autism. Damage to them can cause a general wacky fearlessness. So keep yours safe.

What is the hindbrain?

The hindbrain comprises the cerebellum, pons, and medulla oblongata. It is the rearmost of the three primary divisions of the brain; namely, the:

• Hindbrain (rhombencephalon),
• Midbrain (mesencephalon), and
• Forebrain (prosencephalon)

As the picture below shows, the hindbrain itself has two parts, the metencephalon and the myelencephalon. I may talk about them later. To labor the point just now would be unseemly.

What does the midbrain do?

The midbrain is the top portion of the brain stem, adjoining the diencephalon above and the pons below. It comprises the inferior and superior colliculi (together called the tectum), and the tegmentum, crus cerebri, and substantia nigra (together the cerebral peduncle). It’s involved in vision, hearing, body movement in general, and eye movement in particular.

Some language notes: The Latin word tectum can mean roof or ceiling. Tegmentum is a corruption of tegumentum, which means a covering. The midbrain is also called the mesencephalon, from Greek roots meaning — get this — “midbrain”.

What does the medulla oblongata do?

The medulla oblongata is the lower portion of the brain stem, adjoining the pons above and the spinal cord below. It aids in communication between the spinal cord and the brain, and between the brain hemispheres. It also plays a role in several autonomic functions, such as respiration and circulation, swallowing and vomiting, urination and defecation, and reflex responses.

A personal observation: “Medulla oblongata” is fun to say, and would be a good name for a band.

What does the pons do?

The pons is in the middle of the brain stem, between the midbrain and the medulla oblongata. Its primary function is to relay information between the cerebellum and the cerebrum, thereby acting as a kind of bridge — the meaning of the Latin word pons. It plays a part in relaying other brain messages, too; and it helps to regulate various autonomic functions, including respiration, circulation, and heartbeat.

Great. Now I have “Sur Le Pont D’Avignon” going through my head. L’on y danse …

What is the brain stem?

The brain stem is the narrow part of the brain adjoining the spinal cord. It comprises the medulla oblongata, the pons, and the midbrain. There will be a test on this later.

My desktop

I really like my new Windows desktop, mainly because I really like Degas. But I’m also pleased with the sleek and unobtrusive look of the widget bars. They were dead easy to set up, thanks to a neat little tool called Rainmeter.

What does the cerebellum do?

The cerebellum (Latin for “little brain”) helps to control sensory perception, coordination, and motor control. It sends information to the motor cortex, which causes muscles to move, and to the spinocerebellar tract, which regulates proprioception.

Note: I plan to mention what a few different parts of the brain are used for. The notes, however brief, will no doubt seem more final than I mean them to be. A recent book points out that, contrary to recent dogma, the brain is highly plastic – that is, neurons can be recruited to serve purposes different from their typical ones.

It’s a terrific book. Read it. I command thee.