My wife recently had a baby so I’ll resume posts in a few more days as we adjust to two children.
MRI Quenching
I learned something new this week. Modern MRI scanners produce high-strength magnetic fields (typically 1.5T up to about 20T – scanners for use with humans max out at about 7T right now {those are very rare though, 1.5T and 3T are more common). To produce these fields the scanners need to have strong electric currents. In order to handle large currents, scanners use superconductors cooled with liquid helium. In cases of serious malfunction or emergency the MRI scanner can be quenched, which releases all of the liquid helium. The helium turns into a gaseous state rapidly and expands to fill the room. The quench will make a loud sound like a jet engine or a pop. If the room is small enough, all of the air can be pushed out as the helium expands and increases the pressure. Most MRI rooms have fail-safe systems that release the helium outside, which prevents the occupants from suffocating.
Image from here.
The Threat of Obesity
The APA online linked to an article from the UK about the threat of obesity. With all of the recent news about climate change, some people are pointing out a threat that is as bad or worse than climate change: obesity. As a clinician I haven’t dealt with obesity issues (i.e., helping people with weight problems learn how to control their eating better) yet but it causes a lot of problems for people.
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Birth Order and IQ
I “clipped” this off of CNN for a couple reasons. One is to comment on the fact that I first saw this research months ago – CNN is pretty slow sometimes – okay, slow most of the time – at reporting new research. Second, even though there was a statistically significant difference between IQ scores of 1st, 2nd, and 3rd born children, there is only a difference of 3 points between 1st and 3rd. That doesn’t really mean anything in real life. Also, this is significant in part as a result of the huge same size – 200,000+. Additionally, the subjects all were male. There are other limitations pointed out in the CNN article.
We shouldn’t be so set on statistical significance (I worry about it in my research, of course). There is internal and experimental validity and then there is ecological validity. Intelligence research means very little without good ecological validity.
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Cool Image of Ventricles in the Brain
For my research, I’ve been spending time processing brain MRIs and measuring the volume of the brain and lateral ventricles. Here is an image of one of the brains (visualization by FSLView 3.0, with ventricles measured by ITK-Snap). The image is slightly messy because the brain did not extract perfectly (separating brain from non-brain). Also, portions of the ventricles are missing (especially the occipital and temporal horns) due to imperfect MRI resolution and processing. The ventricles are viewed through a cut-away of the 3D-rendered brain.
Note: You MAY NOT use this image without express written consent from me.
Psycholinguistics and Language
Although I am not a psycholinguist I thought I would introduce basic principles of language.
There are four main components of language: phonology, semantics, syntax, and pragmatics.
- Phonology is the sounds of language.
- Semantics is the meaning of language.
- Syntax is the structure of language.
- Pragmatics is the use of language.
1. Phonology: language is made up of phonemes and morphemes. Phonemes are the smallest units of sound in a language (e.g., in English /p/ is a phoneme) and morphemes are the smallest units of meaninful sounds. Morphemes may be smaller than words (e.g., -ing) or may even be words (e.g., call); the word calling is thus composed of two morphemes.
2. Semantics refers to the meanings of words. In general, semantics helps us understand the difference between hymn and him. In psychology, semantics can be important as a way for understanding people’s language functioning. A person with Alzheimer’s Disease may have difficulty coming up with words that start with a particular letter (G, for example) but would do relatively better on a task where they need to name tools. Tools or animals or sports can all be considered semantic categories and are relatively structured in our memories. People who have better memories tend to have better memory strategies than people with poorer memories have. These strategies often include semantic categorization, where things that need to be remembered are grouped into categories.
3. Syntax is the structure of language – the grammar. In English adjectives are typically placed before the objects (nouns) they are modifying – the red ball; in Spanish the adjectives go after the modified nouns – la bola roja. Syntax can have a significant impact on the meanings of sentences: “The boy hit the ball” versus “The ball hit the boy.” Both sentences have identical phonemes, morphemes, and semantics but differ in overall meaning as a result of different syntax.
4. Pragmatics refers to the use or application of language. It is typically viewed as a social aspect of language. Pragmatics is about applying language so that others understand what you are trying to convey. For example, someone who is good at pragmatics may be able to say one thing and convey a completely different message, if needed.
Each aspect of language can develop well or poorly in humans. Brain damage or degeneration can also selectively impair one of the aspects of language. For example, a person might have intact semantics, language production (phonemes and morphemes), and syntax but impaired pragmatics (this is referred to as a word salad or Wernicke’s aphasia – where a person strings words together that may even be grammatically correct but aren’t meaningful overall).
Image by wlau1.
Brain Heatsink to Reduce Seizures
Some Japanese researchers applied for a patent on an implanted brain radiator to reduce heat in areas of focal seizures. This device works in the same way as heatsinks in computers and radiators in cars. The researchers found that seizure activity increases the temperature of the affected brain area so they want to decrease seizures by decreasing the temperature. I have to admit, this is one of the strangest brain disorder treatments I’ve seen in quite a while.
Diffusion Tensor Imaging and High Angular Resolution Diffusion Imaging
I attended an interesting lecture this week. The professor who spoke talked about Diffusion Tensor Imaging (DTI) as well as about a newer technology they are trying to help develop – High Angular Resolution Diffusion Imaging (HARDI). DTI is based on tensor mathematics and physics. The tensor in DTI is basically a 3×3 matrix (x, y, and z planes) of numbers that represent the diffusion per voxel in the brain. A voxel is a volumetric pixel – a 3D portion of the brain in MR imaging. The highest resolution we can typically get with clinical MR scanners is a cubic mm voxel. So with DTI we have a tensor, a matrix, that describes the diffusion of water molecules within each voxel in the brain. Diffusion in a jar of water or in the ventricles of the brain tends to be fast and spherical. It is less spherical in the gray matter and even less so in the white matter. In fact, the diffusion of water is highly directional in white matter (the myelinated axons of neurons). This means that the water molecules tend to diffuse somewhat parallel to the length of the axon. The movements of these water molecules are picked up by the MR scanner (which is technically “focusing” on the hydrogen atoms in water).
The diffusion per voxel can be quantified by measures of fractional anisotropy (how directional is the movement), Mean Diffusivity (total diffusion within the voxel), and by the eigenvalues of the matrix (basically how far the molecules moved in the direction of the eigenvector).
Back to HARDI. HARDI improves upon DTI by allowing for more directions of the white matter fibers to be separated out than is possible with DTI. There are some areas of the brain where there are a lot of crossing fibers and these areas show up as dark spots on DTI (which looks like a hole in the brain). With HARDI, you can see that the fibers are just more complex than is possible to calculate with DTI.
Both of these methods are useful for measuring the overall integrity (and potentially connectivity) of the white matter in the brain.
Dealing with TBIs from the Iraq War
I read a good article on CNN that details some of the problems that veterans and health professionals face when dealing with TBIs acquired during military action. The article provides a good perspective of the “human side” of TBI.
I’ve posted about this topic before but felt that we should revisit it because so many veterans are affected by TBIs (as well as mental health issues). I don’t know the exact number of veterans affected by TBIs but studies have shown that >30% of soldiers and Marines have some sort of psychological issue related to their service in Iraq and/or Afghanistan. The military and the government are realizing how salient this problem is and will be.
“Congress included $900 million in the DoD’s supplemental budget fir fuscal years 2007 and 2008 to fund more mental health services, as well as more research on the effects of traumatic brain injuries (TBI) and treatments for TBI and post-traumatic stress disorder (PTSD)” (Monitor on Psychology, Sep. 2007, pp. 38-39).
Continuing the Introduction to Human Development
I’m now back in the country after my long and very eventful trip. The brain imaging conference was fabulous. Anyway, I just wanted to add a few more of my development lecture slides in PDF format. They are fairly brief and again, just outlines of the material but I tried to fill in a little more info.
I’ll post some more neuroscience material soon – I just have to get caught up on a week’s worth of missed school and related work.
Biological Influences on Development