Tag Archives: Brain

An fMRI study of transcranial alternating current stimulation (tACS)

9 Aug

I have been following the research on transcranial electrical stimulation of the brain and I have blogged about both positive and negative findings. Here’s an interesting paper, just published in Personality and Individual Differences, that shows correlations between transcranial alternating current stimulation and functional changes in the brain:

The past decades have witnessed a huge interest in uncovering the neural bases of intelligence (e.g., Stelmack, & Houlihan, 1995; Stelmack, Knott, & Beauchamp, 2003). This study investigated the influence of transcranial alternating current stimulation (tACS) on fluid intelligence performance and corresponding brain activation. Previous findings showed that left parietal theta tACS leads to a transient increase in fluid reasoning performance. In an attempt to extend and replicate these findings, we combined theta tACS with fMRI. In a double-blind sham-controlled experiment, N = 20 participants worked on two intelligence tasks (matrices and paper folding) after theta tACS was applied to the left parietal cortex. Stimulation-induced brain activation changes were recorded during task processing using fMRI. Results showed that theta tACS significantly increased fluid intelligence performance when working on difficult items in the matrices test; no effect was observed for the visuo-spatial paper folding test. Whole-brain analyses showed that left parietal brain stimulation was accompanied by lower activation in task-irrelevant brain areas. Complemental ROI analyses revealed a tendency towards lower activation in the left inferior parietal cortex. These findings corroborate the functional role of left parietal theta activity in fluid reasoning and are in line with the neural efficiency hypothesis.

Note that this study looks at alternating current stimulation, while most are focused on direct current stimulation.

The Higher Efficiency of the Bilingual Brain

2 Jun

A paper in The Journal of Neurolinguistics: “Interference Control at the Response Level: Functional Networks Reveal Higher Efficiency in the Bilingual Brain.” Here is the abstract:

The bilingual advantage in interference control tasks has been studied with the Simon task, among others. The mixed evidence from the existing studies has led to contradictions in the literature regarding the bilingual advantage. Moreover, fMRI evidence on the neural basis of interference control mechanisms with the Simon task is limited. Previous work by our team showed that equivalent performance on the Simon task was associated with different activation maps in elderly bilinguals and monolinguals. This study aims to provide a more in-depth perspective on the neural bases of performance on the Simon task in elderly bilinguals and monolinguals, by adopting a network perspective for the functional connectivity analysis. A node-by-node analysis led to the identification of the specific topology that characterized the bilingual and monolingual functional networks and the degree of connectivity between each node across groups. Results showed greater connectivity in bilinguals in the inferior temporal sulcus, which plays a role in visuospatial processing. On the other hand, in monolinguals, brain areas involved in visual, motor, executive functions and interference control were more connected to resolve the same task. In other words, in comparison to the monolingual brain, the bilingual brain resolves visuospatial interference economically, by allocating fewer and more clustered regions. These results demonstrate a larger global efficiency in task performance in bilinguals as compared to monolinguals. Also, the provided evidence filters out the task-specific so-called bilingual advantage discussed in the literature and posits that bilinguals are strategically more efficient in a given performance than monolinguals, thus enhancing our understanding of successful aging.

You can read about the Simon Task here.


The Effects of Toxins on the Developing Brain

27 Mar

(Hat tip to Monitor on Psychology)

Atypical neural oscillation as a cause of dyslexia?

15 Feb

Neural oscillation refers to the rhythmic activity of large numbers of the brains neurons. It is these oscillations that produce the brain waves that are measured on a EEG. Here’s a recent paper suggesting that dyslexia may be caused by abnormal neural oscillation in parts of the brain related to auditory and visual processing. Here is the abstract:

It has been proposed that atypical neural oscillations in both the auditory and the visual modalities could explain why some individuals fail to learn to read and suffer from developmental dyslexia. However, the role of specific oscillatory mechanisms in reading acquisition is still under debate. In this article, we take a cross-linguistic approach and argue that both the phonological and orthographic specifics of a language (e.g., linguistic rhythm, orthographic depth) shape the oscillatory activity thought to contribute to reading development. The proposed theoretical framework should allow future research to test cross-linguistic hypotheses that will shed light on the heterogeneity of auditory and visual disorders and their underlying brain dysfunction(s) in developmental dyslexia, and inform clinical practice by helping us to diagnose dyslexia across languages.


“The Amazing Spider Brain”

3 Feb

Another interesting story about invertebrate brains, in this case the spider:

“Spiders are very smart, that’s why we’re studying them,” says Ronald Hoy, a professor of neurobiology and behavior at Cornell University. “They use visual cues to steer by, and the kind of mazes that they can solve is considered to be pretty impressive for an invertebrate.”

Bizarre advice on web site affiliated with education secretary nominee

23 Jan

It was brought to my attention that education secretary nominee Betsy DeVos is an investor in a company that promises “brain enhancement. ” While visiting the site I found this amazing claim:

The cavemen had it right all along! Because bone broth is full of collagen (and 30% of our bodies’ protein consists of this), it acts as a “gut healer.” According to research by clinical nutritionist Dr. Josh Axe, gut health and brain health are highly connected to each other. And, gut-healing is said to help lower anxiety and other mood-related disorders.

I am almost speechless. Where to begin? I guess we could start by asking who the heck is Josh Axe? He is

a certified doctor of natural medicine, doctor of chiropractic and clinical nutritionist with a passion to help people get healthy by using food as medicine.

I have no special prejudice against chiropractors, but the DeVos affiliated website claims that he has conducted research. If he has, why aren’t links provided?

It is true that there is collagen in the brain, but it doesn’t follow from that that consuming collagen helps brain performance. Moreover there is evidence that bone broth may have high levels of the neurotoxin lead.

The butter brain hypothesis

10 Oct

I always enjoyed reading the late Seth Robert’s blog. He never hesitated to question orthodoxies and always had some interesting new idea. However, some of the things he advocated were troubling. One example, of this was the butter brain hypothesis, the idea that consumption of butter might improve cognitive performance.

The idea is not implausible. The brain, after all, contains many lipids and the idea that consuming certain lipids might improve its performance does not sound unreasonable. The problem is butter is high in saturated fats and has been linked to heart disease.

I know, I know, many recent news reports tell us that “butter is safe” or that “butter is back.” These kind of person-bites-dog stories are popular in the media, but the science around saturated fats and cardiovascular disease is well established.

Here is an article from the New York Times reflecting on evolution and the dietary needs of the brain.

And here is a recent paper on the dangers of saturated fats. The abstract reads:

In recent years, many nutrition news headlines exclaimed that saturated fat was not linked to heart disease, leaving the public confused about whether to limit intake, as has been the dietary recommendation for several decades. However, a more nuanced look at the evidence indicates that high saturated fat diets are in fact not benign with respect to heart disease risk. Dietary recommendations should emphasize replacing saturated fats typical in red and processed meats, and certain tropical oils and dairy forms, with healthier polyunsaturated and monounsaturated fat-rich foods, such as nuts, olive oil, and fatty fish, as well as healthy sources of carbohydrates, such as fiber-rich whole-grain foods, rather than refined-grain and sugar-laden foods.


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