Cautions for fMRI Researchers – evidence that dead Salmon produce some brain activity may start correction and re-checking fMRI studies. Hopefully, all advances in this area will produce greater evidence that can be relied upon for how neural activity can be studied in more depth.

fMRI studies on dead Atlantic Salmon and the research poster on the study.

As summarised by Neuroskeptic, “…but not everyone uses multiple comparisons correction. This is where the fish comes in – Bennett et al show that if you don’t use it, you can find “neural activation” even in the tiny brain of dead fish. Of course, with the appropriate correction, you don’t. There’s nothing original about this, except the colourful nature of the example – but many fMRI publications still report “uncorrected” results”

• Slashdot
• http://neuroskeptic.blogspot.com
• http://languagelog.ldc.upenn.edu

Hey everyone, saw the video? Good.  This is a very simple blog as far as complex blogs go.  First a little about myself, I am a pre-med student at the College of New Jersey (TCNJ) I am entering my third year.  I am a psychology major, concentrating in biopsychology.  I am obviously planning to go to medical school, and my top choices are ivy league schools.  I do intend on studying to become a neurosurgeon or a neurologist.  Now that you know a little about me, we can begin.

This neural activity blog aims to do one thing, and one thing only.  Help me organize my thoughts on different readings, classes, courses, lectures, and wherever else I may hear information regarding the body’s most vital organ – the brain.  In order to explain the mind fully, I will have to delve into both the psychological and biophysiological aspects of the brain.  Which means to say somedays my posts will be more geared towards emotions and why we do the things we do, and other days the posts will be more geared by what happens biologically.  While I understand that some of it may be a lot to grasp – it will be college level, and some med school level terminology, I will do my best to explain it all, and feel free to leave questions in the comments, I will answer them to the best of my knowledge.

The video above describes neurons  (don’t mind the questions towards the end of the video, she seems to dumb it down way too much for everyone else).  It is important, extremely important, to understand what a neuron is before you can understand anything about the biology of the brain (and how it works in conjunction with thoughts and feelings).  While you may be saying to yourself you may know what the cortex is, or the lobes, so why would I need to understand a neuron to understand those. The reason is, while it’s true that you don’t need to understand a neuron to understand the anatomy of the brain, it is essential to understanding it’s function.  The neuron, in it’s very simplest form is made of nervous tissue that is so microscopic it’s barely visible to the naked eye (it’s smaller than a strand of hair) and it is composed of almost transparent material.  Most pictures you see of a neuron are pictures where the neurons have been died so they show up.

The neuron very simply is a messenger.  It is composed of an axon and a soma.  The axon is basically the body, and the soma is the end of the neuron from whence messages are recieved and sent via dendrites (later I will go into more depth about the structure of the neuron and each of their specific functions).  The messages are simple electrochemical signals – which simply means that there is something in the chemical makeup of the atoms passing through that lends itself to positive and negative charges.  The play between these two charges makes up the message and the encoded details that follow (I will also describe these signals in more depth soon).  As said in the video, the are billions upon billions of neurons in your brain, and they compose a random and complex network that is very hard to replicate but easier to understand (albeit still hard to fully understand)!  This network is responsible for each association you have with one thought or image, why you see images so vividly for no reason, or why you’re able to see, smell, hear, taste, and touch the world around you.

This was written after an article in CNet.com www.news.com/8301-10784_3-9932054-7.html?tag=nefd.top

Neuroscientists at the University of California, Berkeley, have measured the electrical activity of nerve cells and correlated it to changes in blood flow in response to transcranial magnetic stimulation (TMS), a noninvasive method to stimulate neurons in the brain.

Illustration of the visual cortex during transcranial magnetic stimulation (TMS). In this non-invasive brain stimulation technique, pulses of current (arrows) are passed through a figure-eight shaped coil placed above the scalp. The induced electric field elicits long-lasting alterations in neural activity which can be measured with blood flow-based imaging methods. (Credit: Elena Allen/UC Berkeley)

Their findings could substantially improve the effectiveness of brain stimulation as a therapeutic and research tool.

With technological advances over the past decade, TMS has emerged as a promising new tool in neuroscience to treat various clinical disorders, including depression, and to help researchers better understand how the brain functions and is organized.

TMS works by generating magnetic pulses via a wire coil placed on top of the scalp. The pulses pass harmlessly through the skull and induce short, weak electrical currents that alter neural activity. Yet the relative scarcity of data describing the basic effects of TMS, and the uncertainty in how the method achieves its effects, prompted the researchers to conduct their own study.

“There are potentially limitless applications in both the treatment of clinical disorders as well as in fundamental research in neuroscience,” said Elena Allen, a graduate student at UC Berkeley’s Helen Wills Neuroscience Institute (HWNI) and co-lead author of the study. “For example, TMS could be used to help determine what parts of the brain are used in object recognition or speech comprehension. However, to develop effective applications of TMS, it is first necessary to determine basic information about how the technique works.”

Other techniques for studying neural activity in humans, such as functional magnetic resonance imaging (fMRI) or electroencephalogram (EEG), only measure ongoing activity. TMS, on the other hand, offers the opportunity to non-invasively and reversibly manipulate neural activity in a specific brain area.

In a set of experiments, the researchers used TMS to generate weak, electrical currents in the brain with quick 2- to 4-second bursts of magnetic pulses to the visual cortex of cats. Direct measurements of the electrical discharge of nerve cells in the region in response to the pulses revealed that TMS predictably caused an initial flurry of neural activity, significantly increasing cell firing rates. This increased activity lasted 30 to 60 seconds, followed by a relatively lengthy 5 to 10 minutes of decreased activity.

What the researchers were able to determine for the first time was that the neural response to TMS correlated directly to changes in blood flow to the region. Using oxygen sensors and optical imaging, the researchers found that an initial increase in blood flow was followed by a longer period of decreased activity after the magnetic pulses were applied.

“This long-lasting suppression of activity was surprising,” said Brian Pasley, a graduate student at HWNI and co-lead author of the study. “We’re still trying to understand the physiological mechanisms underlying this effect, but it has implications for how TMS could be used in clinical applications.”

The critical confirmation of the connection between blood flow and neural activity means that researchers can use TMS to alter neural activity, and then use fMRI, which tracks blood flow changes, to assess how the nerve cells respond over time.

“One of the most exciting applications of TMS is the ability to non-invasively modify neural activity in specific ways,” said Pasley. “The brain is malleable, so brain stimulation may be used to alter and promote specific functions, like learning and memory, or suppress abnormal activity that underlies neurological disorders. If we can figure out the right ways to stimulate the brain, TMS will likely be useful in attempts to improve neural function.”

The researchers noted that one of the difficulties in using TMS for specific applications is the fact that its effects vary in different brain regions and individuals.

“Using TMS is inherently challenging because its neural effects can be so variable,” said Ralph Freeman, UC Berkeley professor of vision science and optometry and principal investigator of the study. “Fortunately, we can determine empirically what the end result is by making measurements with fMRI. This should be valuable to clinicians who must evaluate the effectiveness of a stimulation treatment. In turn, fMRI may serve as a guide to determine adjustments in treatment parameters.”

Science. 2007 Sep 28;317(5846):1918-21. <!– var Menu17901333 = [ ["UseLocalConfig", "jsmenu3Config", "", ""], ["LinkOut", "window.top.location='http://www.ncbi.nlm.nih.gov/sites/entrez?Cmd=ShowLinkOut&Db=pubmed&TermToSearch=17901333&ordinalpos=1&itool=EntrezSystem2.PEntrez.Pubmed.Pubmed_ResultsPanel.Pubmed_RVAbstractPlus' ", "", ""] ] –

Transcranial magnetic stimulation elicits coupled neural and hemodynamic consequences.

Allen EA, Pasley BN, Duong T, Freeman RD.

Helen Wills Neuroscience Institute, Group in Vision Science, School of Optometry, University of California, Berkeley, CA 94720, USA.

Transcranial magnetic stimulation (TMS) is an increasingly common technique used to selectively modify neural processing. However, application of TMS is limited by uncertainty concerning its physiological effects. We applied TMS to the cat visual cortex and evaluated the neural and hemodynamic consequences. Short TMS pulse trains elicited initial activation (approximately 1 minute) and prolonged suppression (5 to 10 minutes) of neural responses. Furthermore, TMS disrupted the temporal structure of activity by altering phase relationships between neural signals. Despite the complexity of this response, neural changes were faithfully reflected in hemodynamic signals; quantitative coupling was present over a range of stimulation parameters. These results demonstrate long-lasting neural responses to TMS and support the use of hemodynamic-based neuroimaging to effectively monitor these changes over time.