I have a new post up on BrainBlogger about Alien Limb Syndrome. Here’s the link.
Video site for watching surgeries
I’m quite fascinated by human anatomy, especially neuroanatomy. The human body is amazing; it’s something of a miracle that it develops and works as well and as often as it does. The brain is very complex with up to 100 million neurons (that’s also an estimate of the number of stars in our galaxy) and 100 trillion synapses (connections between neurons)! 100 trillion is an estimate of how many individual cells the entire human body has. We have as many synapses as cells in the entire body. The brain is complex and beautiful. It has symmetry but individuality.
I discovered a website that allows you to watch some surgeries live (or to view archives of past surgeries). OR-Live.com is informational and free. For those interested in neurosurgeries – everything from scoliosis surgery to tumor resection to deep brain stimulation – here is the direct link. Most of the videos are available in Flash format for web-viewing. Many are also available to download as a video podcast. Warning – please don’t watch the videos if you get queasy easily; if you feel queasy while watching one, take a break and do something else for a while.
I hope my readers enjoy this site as much as I have in the past and will continue to in the future.
Banjo Pickin’ Brain Surgery
Mo at Neurophilosophy posted a great video of Deep Brain Stimulation (DBS) surgery being performed on a man with essential tremor, while he plays the banjo. As with most brain surgeries, the patient was awake, alert, and talking. The doctors had him play the banjo so they could fine tune (pun intended) the electrode placement in order to have the best response.
An Introduction to and Overview of the Brain
The human brain is a wondrous thing. It is the single most complex organ on the planet. It sits atop the spinal cord. Gazing upon the brain, one sees four main distinct areas – two roughly symmetrical hemispheres, a cerebellum stuck up underneath the posterior part of the brain, and a brainstem sticking out and down from the middle of the brain. Each cerebral hemisphere is divided into four visible lobes: frontal, temporal, parietal, and occipital. The frontal lobes jut out at nearly a 90 degree angle from the spinal cord and are the largest part of the human brain. The temporal lobes stick out the sides of the brain, like thumbs pointing forward at the side of a fist. The parietal lobes are harder to distinguish. They are just posterior to the frontal lobes and dorsal to (above) the temporal lobes. The occipital lobes are at the very back of the brain, like a caboose on a train.
The outside of the brain is covered with a series of bumps and grooves. The bumps are called gyri (sing. gyrus) whereas the grooves are called sulci (sing. sulcus). This outside part of the brain is filled with tiny cell bodies of neurons, the main functional cell of the brain. Some people estimate that there are 100 billion neurons in the central nervous system (brain + spinal cord). This outer layer of the brain is called the cortex (which means “bark”). The cortex is only about 5mm thick, or about the thickness of a stack of 50 sheets of copy paper, yet it is responsible for much of the processing of information in the brain.
At room temperature the brain is the consistency of warm cream cheese. If removed from the skull and placed on a table, it would flatten and widen out a bit, like jello that is warming up. The brain is encased in a series of protective sheaths called meninges. The outermost encasing is called the dura mater (L. “tough mother”), which is thick and tough and is attached to the skull. The next layer in is softer. It is called the arachnoid layer; it adheres to the brain. Just underneath this layer is where cerebrospinal fluid (CSF) flows. This fluid is produced in holes in the middle of the brain called ventricles. CSF helps cushion the brain as well as remove waste products from the brain. Underneath this is a very thin and fine layer called the pia mater (L. “soft mother”), which adheres directly to the cortex and is difficult or impossible to remove without damaging the cortex. These three layers of meninges serve to protect the brain.
The brain can be roughly split into three functional areas, each one more “advanced” than the previous. The brainstem (and midbrain), which includes such structures as the medulla, pons, and thalamus, activates and regulates the general arousal of the cortex. Damage to the brainstem often results in coma or death. The next rough functional area is the posterior portion of the brain (parietal and occipital lobes and portions of the temporal lobes). This area is heavily involved in sensory processing – touch, vision, hearing. It sends information to other parts of the brain largely through the midbrain structures. The last functional area includes the frontal lobes. This area can regulate all other parts of the brain but is essential for goal-setting, behavior inhibition, motor movements, and language. The frontal lobes are the most advanced area of the brain and arguably the most important for human functioning – for what makes us human. In summary the three areas roughly are responsible for:
- Overall arousal and regulation
- Sensory input
- Output, control, and planning
Underneath the cortex is a large area of the brain that looks white. This area is comprised of the axons of the neurons of the cortex and subcortical structures. These axons are the pathways between neurons – like superhighways connecting cities. The axons look white because the majority are covered with a fatty tissue called myelin. Myelin helps axons work more efficiently and transmit more quickly. The white matter of the brain is as important for normal brain functioning as the gray (neurons) matter is.
The brain is energy-hungry. It cannot store energy so it needs a constant supply of nutrients from blood. However, blood can be toxic* to neurons so the brain has to protect itself from the blood and other toxic materials through what is called the blood-brain barrier. This barrier keeps blood cells out of the brain but allows molecules of nutrients (e.g., glucose) to pass into or feed the cells. The entire surface of the brain is covered with blood vessels, with many smaller vessels penetrating deep into the brain to feed the subcortical structures. Deoxygenated blood must be removed from the brain. Veins take the blood out of the brain and drain into venous sinuses, which are part of the dura matter.
The brain works as a whole to help us sense, perceive, interact with, and understand our world around us. It is beautiful in its form and function.
*”Today, we accept the view that the BBB limits the entry of plasma components, red blood cells, and leukocytes into the brain. If they cross the BBB due to an ischemic injury, intracerebral hemorrhage, trauma, neurodegenerative process, inflammation, or vascular disorder, this typically generates neurotoxic products that can compromise synaptic and neuronal functions (Zlokovic, 2005, Hawkins and Davis, 2005 and Abbott et al., 2006).” From Zlokovic, B. V. (2008). The blood-brain barrier in health and chronic neurodegenerative disorders. Neuron, 57(2), 178-201.
Image: Bi Sang by Seung Ji Baek
Learning and Recall – Hippocampal Firing
Today in Science a team of scientists (Hagar Gelbard-Sagiv, Roy Mukamel, Michal Harel, Rafael Malach, and Itzhak Fried) at the Weizmann Institute of Science in Israel, UCLA, and Tel Aviv University published their research where they directly recorded via implanted electrodes the firing of hippocampus neurons during learning and free recall. This represents the first time in humans this has been done. Here’s the abstract from Science:
The emergence of memory, a trace of things past, into human consciousness is one of the greatest mysteries of the human mind. Whereas the neuronal basis of recognition memory can be probed experimentally in human and nonhuman primates, the study of free recall requires that the mind declare the occurrence of a recalled memory (an event intrinsic to the organism and invisible to an observer). Here, we report the activity of single neurons in the human hippocampus and surrounding areas when subjects first view television episodes consisting of audiovisual sequences and again later when they freely recall these episodes. A subset of these neurons exhibited selective firing, which often persisted throughout and following specific episodes for as long as 12 seconds. Verbal reports of memories of these specific episodes at the time of free recall were preceded by selective reactivation of the same hippocampal and entorhinal cortex neurons. We suggest that this reactivation is an internally generated neuronal correlate of the subjective experience of spontaneous emergence of human recollection. (Published Online September 4, 2008; Science DOI: 10.1126/science.1164685)
The New York Times also has an article about the research.
Frontal Lobes and Memory
I’ve been developing an interest in the role that the frontal lobes play in memory. We traditionally think of memory as heavily based in the medial temporal lobes. At least, the medial temporal lobes are larely responsible for the creation of new memories. Without the hippocampus and the surrounding area people have anterograde amnesia, which is the inability to form new memories. The classic and most well known example of this is the patient H.M. Researchers recognize the role that other areas of the brain have in memory but most memory research has focused on the medial temporal lobes – at least until recently (with recently being the last 20 years or so). New ideas take a while to develop and gain acceptance so some of these ideas about the role of other brain areas in memory creation are still developing.
For example, we now know that when information needs to be organized, such as in something like the Rey-Osterrieth Complex Figure (read here for a short description of the test) or with a list learning task with words from specific semantic categories, the frontal lobes are involved.
If the frontal lobes are heavily involved in the organization of information it follows that memory tests that require more organization of material should be affected by dysfunctioning of the frontal lobes. Some researchers are now trying to place certain functions with greater specificity within the frontal lobes. This isn’t really phrenology because the methods of phrenology were entirely suspect. Phrenologists extrapolated personality and cognitive characteristics of people based of measurements of their skulls. Many researchers who are interested in localizing brain functions do so by testing people with specific brain
lesions (injuries). If enough patients have damage to X part of the brain and subsequently have Y deficits, then we can assume that X is necessary for Y to occur (but is not necessarily sufficient for Y to occur). Phrenologists never looked at the brain or the head in this manner. Paul Broca was one of the first, with his patient Tan, to systematically look at the relationship between brain injury and behavior.
For a long time many people believed (and many still do) that certain areas of the frontal lobes, specifically the most anterior areas of the frontal lobes, are essentially superfluous. They base this idea on cases where
people have had damage to this area of the brain but apparently suffered no ill effects. Research has consistently not supported that view. We don’t have any non-necessary brain. What we do have are tests and measures that are not sufficiently sensitive nor specific. The brain is also very complex and most functions rely on networks of brain structures. We are also learning that the white matter in the brain is very involved in behavior and cognition (this is my own area of research). The more we learn, the more we realize our ignorance about the brain. There are layers upon layers to be unwrapped and understood about the brain.
Image by Debbi in California.
First Successful Brain Transplant
Recently, French scientists at the University of Southern North Dakota – Baltimore performed the first successful human brain transplant. Said the chief neurosurgeon, Dr. Cranial Head, MD, “This is a breakthrough of unprecedented magnitude. I’m ecstatic all our research and hard work finally paid off. We couldn’t be more pleased with how things turned out.”
The patient, who only agreed to be called Jose Ivanovich O’Malley, III for anonymity reasons, suffered a massive anterior communicating arterial stroke that left him severely incapacitated. He was a veterinarian at a local clinic before his stroke. His family heard about the research Dr. Head’s team was doing with rats and contacted him about the possibility of being his first human subject. Dr. Head agreed immediately, “I saw this as the perfect opportunity to advance our research out of animals and into humans. We’ve had great success – recently – with brain transplants in rats so it was only logical to start human trials.”
“This new brain transplant surgery is quite remarkable,” said Dr. Head. “My colleague, Dr. Sarah Wu, and I first came up with the idea 40 years ago while we were competing in a triathlon. It came out of the blue, really, neither of us are quite sure why we thought of it but here we are.”
What’s remarkable about the surgery is that it is done all under local anesthetic and the patient is kept talking throughout the procedure, except for the time when the brains are switched (during this time the patient is placed on life support). In this case, the transplanted brain came from a local high school physics teacher Stephen Cabeza who suffered an unexpected heart attack. He was not only young but also in good health. The Cabeza family wishes remain anonymous. The transplanted brain is removed from the original body and cooled to halt neuronal death. The end of the severed spinal column is treated with a new nanoglue that automatically splices individual axons to the new spinal cord when the transplant brain is placed on top.
“It’s incredible,” said Dr. Head, “surprisingly we don’t have much work to do because with this new nanoglue the process of reconnecting nerve fibers is automatic. It only takes 4 minutes. We just inspect the brain and spinal cord to make sure everything is lined up correctly. The nanoglue is also applied to areas like the optic nerves, that need to be spliced into the new brain.”
After the surgery, Jose made a speedy recovery. Within 24 hours he was moving his limbs and within a week he was walking and talking. His wife said, “It’s a miracle. We thought Jose was gone forever but Dr. Head saved him. He doesn’t know who any of us are, of course, and calls himself Stephen but we are all willing to work with the new Jose and learn to love him and hope he will learn to love us.” The medical team, however, remains baffled why Jose insists his name is Stephen. When asked if he planned on returning to work at his veterinary clinic, Jose stated that he couldn’t wait to return to teaching physics: “I’ve always had a love of physics. There’s something about gravity research that really attracts me.” Jose doesn’t remember any of his past self or his work as a veterinarian.
Disclaimer: this post was written in 2008 as an April Fool’s Day joke years before the idea of a head/body transplant was popularized by news media. It was written years before the “Fake News” trendy label. This post is completely made up and was written to be humorous. Surgeons cannot at the present time perform brain transplants, regardless of what is published online. The surgeon who claims he can perform a head transplant will not be successful. The idea of a brain/head/body replacement is interesting both as a potential medical advancement and as a point of ethical discussion. Is it theoretically possible? Yes. Will it happen anytime soon? No. Should it happen? That’s a discussion for another time.
Leukoaraiosis and Lacunes – A Very Brief Overview
As people age, it is common for their brain white matter to change. These changes often appear as bright white spots on T2-weighted MR scans. These areas or spots of hyperintensity (i.e., white matter hyperintensities {WMH}) are also called leukoaraiosis (LA). Researchers are still investigating the exact nature and pathology of these abnormalities but our understanding of them is increasing. They most often seem to start around the lateral ventricles and spread from there, although it is possible to have punctate WMH throughout the brain white matter (i.e., WMH that are not connected to other regions). WMH on brain MRIs represent rarefaction of the white matter, including swelling, demyelination, and damage, although the exact nature and combination of the white matter changes is not known. These WMH can interfere with normal cognitive functioning, including processing speed, attention, inhibition, as well as global executive functioning (although these claims are still being investigated).
Other damage to white matter includes lacunes, which are little holes in the brain, much like the holes in Swiss cheese. They are caused by mini infarcts, or strokes, or other processes. Most of the time they are due to “silent strokes”, or strokes that are small enough that the person does not have any noticeable stroke symptoms. These lacunes can have similar impact on cognition as WMH. Both WMH and lacunes are related to vascular risk factors, such as hyper- or hypo-tension, diabetes, etc.
Moral Development and the Brain
Moral reasoning is the ability a person has to reason in and through social, ethical, and emotional situations. One component of moral reasoning is moral behavior, which is the intentional and voluntary acting in a prosocial manner (Walker, 2004). Moral behavior and reasoning are the foundation for “many human social and cultural institutions such as family structures, legal and political government systems that affect the lives of virtually every person” (Eslinger, Flaherty-Craig, & Benton, 2004, p. 100). Often situations in life are morally ambiguous and involve a choice between two actions that both have consequences that may or may not be in opposition to each other. Some researchers, such as Lawrence Kohlberg, believe that people will reason through these situations at varying levels or stages, with some in a very concrete and egotistic manner and others in an abstract and universal manner.
Lawrence Kohlberg was the first researcher to come up with a major testable theory of moral development. He formulated six stages of development, with most adults reaching stage four, a few five, and very few stage six. The first two stages are at the pre-conventional level (typically self-centered and concrete reasoning), stages three and four are at the conventional level (recognition of social norms and laws), and the last two stages at the post-conventional level (recognition of universal rights and responsibilities). While Kohlberg’s theory of moral development is a stage model, the progression through the stages is not necessarily viewed as invariant. This means that people reach them at different rates and do not always reason at a particular stage with any given dilemma. There is significant variability within and between people in moral reasoning abilities. Most research focuses on between-person variability.
Continue reading “Moral Development and the Brain”
Hypothalamic Hamartomas
I saw an interesting case today. It was a child with a hypothalamic hamartoma, a tumor (likely present from birth or shortly thereafter) right on the midline of the brain by the hypothalamus and the third ventricle. These tumors are quite rare and result in some interesting behaviors. A common result of these hamartomas is what is called precocious puberty – very early puberty onset; this early puberty often occurs before age 2. This can occur because the hypothalamus is one of the major brain areas that creates hormones and modulates the endocrine system.
Another common result of these hamartomas is gelastic seizures. Gelastic seizures are laughing seizures. The seizure manifests with the child (or adult) having sudden laughing fits for no apparent reason. They can occur many times a day. Some people also have dacrystic seizures, or crying seizures. Developmental delays are also common in this type of brain disorder as is hyperactive behavior.
Hypothalamic hamartomas are sometimes treatable by resection. This surgery has the possibility of eliminating the seizures and stopping most or all of the hormonal abnormalities.