Clive Wearing is a 70 year old British man who contracted herpes simplex encephalitis in 1985. The virus destroyed his hippocampi bilaterally (as well as surrounding areas). He has complete anterograde amnesia and can only remember up to about 20 seconds. He retained the ability to play the piano and conduct a choir (which he did previously to his illness); this is because this procedural memory involves different areas of the brain, including the basal ganglia and the cerebellum. I’ll revisit this case over the coming days. Meanwhile, here is a clip from a BBC production that presents part of Clive’s story.
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
Site Going Through Revisions
I’m working on finding a new look for my site. It will be going through revisions over the next few days as I get everything situated. Please forgive any bumps in the process.
The Death of Psychotherapy
I’m going to preface my post by stating that the following post was written to help me think through the relationship between neuroscience and therapy. As such, it is a philosophical journey through some of my thoughts and is not even necessarily what I really believe because I’m still working on discovering what I believe. Thought processes like this are one way I try to keep some of my beliefs about psychology and neuroscience balanced. If I start leaning too strongly one way, I’ll start looking for things that disconfirm those beliefs and see what I discover. It’s a bit of playing the Devil’s Advocate with myself and a bit of philosophizing. Some of my friends and I used to do things like this in junior high and high school – having philosophical discussions where we discussed things and even tried to argue for things that we didn’t necessarily believe (e.g., classic topics such as supposing that this world and universe really aren’t real but are just reflections of reality. Again, that’s not something I believe but we would speculate). What does this all have to do with psychology and neuroscience?
The brain is what drew me to psychology initially. However, I vowed I would never go into clinical psychology because I didn’t think I would like therapy or dealing with people’s problems. Over time I discovered neuropsychology. Most neuropsychologists are clinical psychologists so in order or me to be a neuropsychologist, I had to be trained as a clinical psychologist. There are many things I enjoy about clinical psychology but therapy is not one of those things. Granted, most neuropsychologists do not actually do therapy, but we have to be trained in it. I enjoy talking with people in sessions but I haven’t been that impressed with therapy as a whole so far. Maybe that’s just because I haven’t exactly found the particular type of therapeutic method that really “clicks” with me. Cognitive-behavioral therapy is fine but so much of actual therapy in practice is just plain common sense. However, not everyone has a lot of common sense so they need some training in it. Part of me recognizes the validity of therapy but another part of me struggles with it. Now on to my main article.
The more I study the brain and the more exposure I have to therapy (giving, not receiving), the more biased towards the brain I become. What I mean is that we continue to discover more about the brain and as we discover more, the more behavior we can explain based on biology or neurophysiology and the less important I think therapy is. I’ve written about this topic in the past but wanted to briefly revisit it. This is somewhat of a second chapter to that post. Before I continue I wanted to expose one of my biases; I believe humans have free will. Even though some of my beliefs about the brain could be seen as mechanistic and deterministic, I do not believe that a strongly-biological foundation for behavior rules out free will. You can still assume biological foundations without assuming determinism. If, for example, you have a monistic set of assumptions that incorporates both mind – “nonmaterial” – and body – “material” – in one. [I have quotes around nonmaterial and material because mind is not necessarily nonmaterial and body is not necessarily material, well at least philosophically speaking]. Monism is a similar idea to a unified field theory (e.g., Grand Unified Theory) or the Theory of Everything for which some theoretical physicists are searching. That’s not what I’m going to write about and if it didn’t make sense, then don’t worry about it (I discussed this topic in a couple different posts: here {I linked to that post previously} and here). To summarize, I view behavior through a strong biological bias but I do not assume determinism.
As I said earlier, the more I learn about the brain and behavior (through research and observation), the more I lean towards neuroscience and away from “traditional psychology.” However, I still appreciate the psychosocial aspects of behavior; the nature versus nurture dispute will never be resolved because both are important. The environment is important – all external stimuli are important – but the problem with downplaying biology is that it is the medium of behavior. What I mean is, everything we think, sense, perceive, or do is translated and transmitted through the firing of neurons. This means that all abnormal behavior, which is what psychologists often are interested in, originates in a neuron or related cell. Whether or not the cause of that behavior was internal or external is irrelevant. All events and stimuli are translated into patterns of neuronal firings.
This is why I think that understanding the biology of the brain is the best way to understand a person’s behavior. However, because we have an imperfect understanding of the biology of the brain, we have an imperfect understand of the biological foundations of behavior. This means that until we have a perfect understanding, we cannot ignore the psychosocial aspects of behavior; even with a perfect understand we couldn’t either because even if we understand the “translation” process we may not understand the origin of what needs to be translated. This is where traditional talk therapy can be most beneficial. However, I still believe less and less that talk therapy is the best solution for dealing with many psychological issues. Over time as we discover more and more about the brain, therapy will become even less important.
That is a fairly radical position to take as a student of clinical psychology – it’s more in line with psychiatry, or rather, I believe it’s more in line with neuroscience. I’m not saying that therapy is useless, I’m just saying that as we gain a more perfect understanding of the brain and how various chemicals interact in the brain, we will have less need for people to help others by “talking” through their problems. The better we understand the physiology of the brain, the more natural our pharmaceuticals will be. In other words, it will be easier to mimic and create normal brain functioning. Of course, many will ask, “What is normal?” That’s a good question.
Some may argue that with depression, for example, many people will have negative image and self-evaluations, which can lead to depression. That is true but it’s the classic chicken and egg question. Which came first? Did the negative thoughts cause the depression or did the person experiencing negative thoughts have a biological predisposition to those thoughts and depression? In other words, it is possible that biology originally led to the negative thoughts and not vice versa. This is all speculation but I think there is increasing evidence for this view.
The big problem with my point though is that at some point, it does become a deterministic system in that it’s possible that we could medicate away people’s free will. This is an unacceptable outcome. There would be a lot of power with this knowledge and many opportunities for abuse. That’s an ethical discussion for a later time.
To summarize, I think that as we (speaking in the collective) gain a more perfect understanding of the brain (and even individual differences in the brain) we will be better able to eradicate and prevent many or most psychological disorders. We could potentially stop schizophrenia through genetic engineering or other modifications. Again, I’m not addressing whether or not we should but I believe we will have the ability to at some point. This is why, at the moment I lean more towards neuroscience than I do psychotherapy. Of course, tomorrow I could [I won’t] write a post that completely contradicts this one. As I said, this is a process. I think it’s important to argue both sides of the issue.
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.
Neuroscience: Psychotherapy’s Executioner?
I wrote another post called Neuroscience: Psychotherapy’s Executioner? for BrainBlogger.com. You can read it here.
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.
Encephalon #42
I know I’m a few days late but Of Two Minds hosted the latest Encephalon. It’s a well-written collection of hot neuroscience geek writing. Although, I don’t understand how somehow the contributors all managed to miss the Douglas Adams connection with this Encephalon. The Paris Hilton thing was quite funny but this could have been THE ULTIMATE Encephalon, providing the answers to life, the universe, and everything. I, unfortunately, have not participated in an Encephalon yet but I’ll get around to it one of these days.
UK Scientists Create Hybrid Embryos
Hybrid embryos were created in the UK. Scientists used bovine eggs that had the DNA removed and injected human DNA (from skin) into the eggs. The eggs grew for as long as 3 days. The researchers plan on working towards a 14 day lifespan, at which time the embryos would be destroyed. No, they aren’t trying to create a Minotaur or something of that sort; they are seeking for new ways to create stem cells. The researchers see this hybridization as one of the most promising ways. While the researchers on the team state that their research is completely ethical, a broader debate is occurring in the UK. If the research is completely ethical then there wouldn’t really be a debate. What’s ethical to one person is not necessarily ethical to another. Parliament will debate the issue in about a month. The Catholic Church, of course, has condemned the research.
It seems though that there are better ways to get stem cells that aren’t as controversial. I’ll admit that I am ignorant about this type of research but scientists already successfully can get stem cells from other sources, such as skin. There are very few people who believe that it is unethical to derive stem cells from such sources. I’m not saying whether or not I think that they should be doing this research I just think that those of us who are researchers think very carefully about the ethical and moral implications of our research. We can’t just seek consensus among fellow researchers either; we need to be willing to listen to people outside of science.
Read more about the issue here.