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Parts of the brain
As presented in class, new technologies like PET scans and fMRI’s are allowing more and more functional areas of the brain to be mapped and described. Here are a “top ten surface regions of the brain” and a “top eleven internal parts of the brain” to consider.
Surface features of the brain
The first seven features of the surface are all part of the cerebrum of the brain. The word “cortex” means “outer layer”, so the cerebral cortex is the outer layer of the cerebrum
1. Prefrontal Cortex
Mary was an intelligent, driven college student focusing on long-term goals of medical school and starting a family with her fiancé. Unexpectedly she started drinking, experimenting with drugs, seeing other men and skipping class. An MRI later revealed a tumor in her prefrontal cortex.
What is the prefrontal cortex responsible for?
There’s a sub-area of the prefrontal cortex called the orbitofrontal cortex, just behind the eyes (“orbitae” is Latin for eye socket!). A patient named Elliot had a small tumor removed in that area. Afterwards he was just fine, except for the fact that he would now spend hours choosing which radio station to listen to, which pen to use, where to park in a parking lot, etc.
What is this particular area of the prefrontal cortex responsible for?
2. Motor Cortex
Juan had a stroke which left him unable to unable to move the left side of his body. An MRI revealed significant damage to the right motor cortex.
What specifically is the motor cortex responsible for?
3. Sensory Cortex or “Somatosensory” Cortex
Gladys experienced numbness in certain parts of her body, particularly on her left side. An MRI revealed that there was damage to part of her right sensory cortex.
What specifically is the sensory cortex responsible for?
4. Broca’s Area
Anne had a stroke that damaged cells in Broca’s area, which is only on the left side of the brain. Anne can understand what is said to her, but when she tries to speak she finds it nearly impossible to say words and put them together to form sentences. She can not come up with the names of everyday objects when asked to identify them.
What specifically is Broca’s area responsible for?
5. Wernicke’s Area
Michael had a stroke that damaged cells in Wernicke’s area, which is only on the left side of the brain. Michael can speak with ease...but the problem is that he often chooses the wrong words for things and his speech comes out as a string of garbled words. When asked to give directions to his house he began by saying, “Every river turn street in the horse red boat.”
What specifically is Wernicke’s area responsible for?
6. ______Cortex
Several patients with damage in this area reported being able to not make sense of what people were saying to them. They can, however, still read and can still understand written language. Other patients report no hearing at all.
What would you call this area? What is it responsible for?
7. Occipital Lobe or ______Cortex
A patient named Julia had damage on the left side of her brain in this area. She first thought nothing was wrong with her and then noticed little things like not being able to find the mouse for her computer and not being able to find a knife or spoon when she sat down to eat in a restaurant. Other people with damage in this area might “see stars” or experiences sparkles or flashes of light.
What is the occipital lobe responsible for? What else, then, could you call this area?
8. Cerebellum
Amir had lost the ability to ride his bike. He also reported unsteadiness when walking, difficulty in tying his shoes, and even trouble clapping on beat to music. An MRI later revealed damage to his cerebellum.
What is the cerebellum responsible for?
9. Brainstem
The brainstem has several regions including the medulla oblongata, the pons and the midbrain. During a fraternity initiation ceremony several college students were each asked to drink an entire case of beer in less than one hour. Their brainstems became saturated with alcohol and they died; the alcohol had disrupted nerve signals in the brainstem.
What functions do you think the brainstem is responsible for?
10. Spinal cord
Patients whose spinal cords are severly damaged are paralyzed below the site of the spinal cord injury. What, then, is the specific function of the spinal cord?
Internal features of the brain
The first four internal items are often called the “Limbic System”
A. Hippocampus
Bob first started noticing that he was forgetting little things like where he parked his car and who he had spoken to earlier in the day. Later his forgetting became more pronounced and severe. Bob was diagnosed with Alzheimer’s disease, which often damages the hippocampus.
What does the hippocampus do?
B. Amygdala
After her stroke, Shelley’s family noticed that she was no longer startled by loud sudden noises. She was unlikely to flinch when watching horror movies. She was also unable to notice expressions of fright in other people’s faces. A brain scan detected damage to her amygdala. Some studies of serial killers suggest that their amygdalas have a very low level of function.
What does the amygdala do?
C. Thalamus
The thalamus is the relay station for touch, sight and sound information coming into the brain. The thalamus receives signals from sensory organs (eyes, ears, etc.) and relays them to the proper portion of the cerebral cortex.
There is a rare condition called synesthesia in which the “wires” transmitting sensory information through the brain get “crossed” What do you think a symptom of synesthesia might be?
D. Hypothalamus
The hypothalamus regulates basics like hunger, thirst, body temperature, and sleeping, and it oversees the pituitary gland (see below).
What do you think happens if there is damage to the hypothalamus?
E. Corpus callosum
Marco was diagnosed with severe epilepsy (too much electrical activity in the brain, resulting in seizures, unwanted muscle contractions). He underwent a surgical procedure that involved severing his corpus callosum. Shortly after the operation, if Marco was handed, say, a pencil in his RIGHT hand and asked what it was he could say it was a pencil. But if the pencil was put it in hisLEFT hand, he could not say what it was.He knew what the object was for, but he just couldn’t come up with its name.
A few weeks after surgery, Marco regained the ability to name objects no matter which hand they were placed in.
What do you think is the function of the corpus callosum?
What does Marco’s eventual recovery from his post-surgical problem tell you about the brain?
F. Pituitary Gland
Depending on who gets them, tumors here can cause irregularities in menstrual cycle in women, impotence in men, inability to grow in children, excessive growth in adults, and inability to manage water retention.
What kinds of chemicals are produced in the pituitary gland? Hint: Think back to last year.
G. Insula
The insula is a layer of brain cells located underneath the cortex, and it appears to have numerous functions. In one famous case, a patient with insula damage was unafraid to eat food that had fallen on the floor or drink soup into which a fly had landed. Others with insula damage show no concern for changing dirty diapers.
In addition, recent research at the University of Iowa has shown that cigarette smokers who suffer stroke damage to the insula have their addiction to cigarettes practically eliminated. A famous case involved an addicted smoker who developed insula damage and then “forgot to smoke”.
What, then, may the insula be involved with?
H. Basal Ganglia
People with Parkinson’s Disease display involuntary shaking and tremors. It’s been discovered that a group of cells called the basal ganglia are damaged in Parkinson’s patients.
What are the basal ganglia responsible for?
J. Olfactory Bulb(s)
Phoebe was an expert rider but she was kicked in the face one day by a horse. A subsequent MRI showed that her olfactory bulbs had been badly damaged. Phoebe could no longer smell and she also noticed that her ability to taste foods was diminished as well.
What does this tell you about the olfactory bulb?
K. Pineal Gland
Saiko went through long periods of insomnia and odd sleep patterns. After seeing a doctor, a blood test revealed a significant deficiency of the hormone melatonin, the important hormone produced by the pineal gland.
When should the pineal gland be producing and releasing melatonin? When should it be less active?
L. Midbrain
The midbrain is technically part of the brainstem that contains several structures that produce the important chemical dopamine. Two especially important sub-areas you may read about are the Ventral Tegmental Area (VTA) and the Nucleus Accumbens (NA or NAcc). Dopamine is produced by these structures whenever we do things like eat, win a contest, get the correct answer, try to mate, etc. Dopamine is then transported throughout areas of the brain.
How does dopamine, then, make us feel? Why is dopamine sometimes referred to as a “natural drug”? What might be a symptom of lower-than-normal dopamine levels?