Tag Archives: Brain

The case of Tatiana And Krista Hogan

17 Nov

Tatiana And Krista Hogan are co-joined twins who share brain tissue. According to Wikipedia they are joined at the thalamus, brain structure that projects sensory information onto the cerebral cortex. According to a post on the CBC website:

Neurological studies have stunned the doctors. Tatiana can see out of both of Krista’s eyes, while Krista can only see out of one of Tatiana’s. They also share the senses of touch and taste and the connection even extends to motor control. Tatiana controls 3 arms and a leg, while Krista controls 3 legs and an arm.
Amazingly, the girls say they also know one another’s thoughts without needing to speak. “We talk in our heads” is how they describe it.

The CBC has produced a documentary about the twins, unfortunately not yet available in the U.S.

“Tympanic Membrane Temperature and Hemispheric Cognitive Style”

4 Oct

I am a co-author on this paper, just published in The Journal of Genetic Psychology:

The authors tested the hypothesis that there is a correlation between hemispheric cognitive style and ear temperature. A sample of 100 participants completed a measure of hemispheric cognitive style, the Hemispheric Consensus Prediction Profile. Ear temperatures were taken in 2 sessions, 2 times for each ear at each session. Average left ear temperature was subtracted from average right ear temperature as an index of dominant temperature. Only 56 of the participants showed a stable dominant ear temperature. For these 56 participants, there was a statistically significant positive correlation between scores on the Hemispheric Consensus Prediction Profile and tympanic member temperature (Spearman’s ρ =.29, 95% CI [.04,.51]). Individuals with a left hemispheric cognitive style tended to have a warmer left tympanic membrane temperature while those with a right hemispheric cognitive style tended to have a warmer right tympanic membrane temperature. Tympanic membrane temperatures are easily obtained using inexpensive and noninvasive technology. The relationship suggested by these findings may open new opportunities for the study of cerebral asymmetry.

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.”

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