How the brain works

Having a male twin improves mental rotation performance in females

October, 2010

A twin study suggests prenatal testosterone may be a factor in the innate male superiority in mental rotation*.

Because male superiority in mental rotation appears to be evident at a very young age, it has been suggested that testosterone may be a factor. To assess whether females exposed to higher levels of prenatal testosterone perform better on mental rotation tasks than females with lower levels of testosterone, researchers compared mental rotation task scores between twins from same-sex and opposite-sex pairs.

It was found that females with a male co-twin scored higher than did females with a female co-twin (there was no difference in scores between males from opposite-sex and same-sex pairs). Of course, this doesn’t prove that that the differences are produced in the womb; it may be that girls with a male twin engage in more male-typical activities. However, the association remained after allowing for computer game playing experience.

The study involved 804 twins, average age 22, of whom 351 females were from same-sex pairs and 120 from opposite-sex pairs. There was no significant difference between females from identical same-sex pairs compared to fraternal same-sex pairs.

* Please do note that ‘innate male superiority’ does NOT mean that all men are inevitably better than all women at this very specific task! My words simply reflect the evidence that the tendency of males to be better at mental rotation is found in infants as young as 3 months.

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More on the importance of calpain

January, 2010

A new study suggests that all the great benefits of BDNF for learning and memory are in fact due to calpain.

Last month I reported on a finding that estrogen acts through calpain, a protein crucial to learning and memory, that acts as a neurotransmitter in the brain. Now a new study has found that BDNF activates calpain, and when it does, the spine structure changes in ways similar to those that occur during learning. When activation was blocked with calpain inhibitors, the addition of BDNF had no effect. All this implies that all the great benefits of BDNF for learning and memory are in fact due to calpain.

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Brain implant reveals the neural patterns of attention

February, 2010

A paralyzed patient implanted with a brain-computer interface device has allowed scientists to determine the relationship between brain waves and attention.

A paralyzed patient implanted with a brain-computer interface device has allowed scientists to determine the relationship between brain waves and attention. Recordings found a characteristic pattern of activity as the subject paid close attention to the task. High-frequency beta oscillations increased in strength as the subject waited for the relevant instruction, with peaks of activity occurring just before each instructional cue. After receiving the relevant instruction and before the subject moved the cursor, the beta oscillation intensity fell dramatically to lower levels through the remaining, irrelevant instructions. On the other hand, the slower delta oscillation adjusted its frequency to mirror the timing of each instructional cue. The authors suggest that this "internal metronome" function may help fine-tune beta oscillations, so that maximum attention is paid at the appropriate time.

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Face coding varies by gender, sexual orientation, & handedness

July, 2010

Why are women better at recognizing faces? Apparently it has to do with using both sides of your brain, and homosexual men tend to do it too.

Why do women tend to be better than men at recognizing faces? Two recent studies give a clue, and also explain inconsistencies in previous research, some of which has found that face recognition mainly happens in the right hemisphere part of the face fusiform area, and some that face recognition occurs bilaterally. One study found that, while men tended to process face recognition in the right hemisphere only, women tended to process the information in both hemispheres. Another study found that both women and gay men tended to use both sides of the brain to process faces (making them faster at retrieving faces), while heterosexual men tended to use only the right. It also found that homosexual males have better face recognition memory than heterosexual males and homosexual women, and that women have better face processing than men. Additionally, left-handed heterosexual participants had better face recognition abilities than left-handed homosexuals, and also tended to be better than right-handed heterosexuals. In other words, bilaterality (using both sides of your brain) seems to make you faster and more accurate at recognizing people, and bilaterality is less likely in right-handers and heterosexual males (and perhaps homosexual women). Previous research has shown that homosexual individuals are 39% more likely to be left-handed.

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Proverbio AM, Riva F, Martin E, Zani A (2010) Face Coding Is Bilateral in the Female Brain. PLoS ONE 5(6): e11242. doi:10.1371/journal.pone.0011242

[1611] Brewster, P. W. H., Mullin C. R., Dobrin R. A., & Steeves J. K. E.
(2010).  Sex differences in face processing are mediated by handedness and sexual orientation.
Laterality: Asymmetries of Body, Brain and Cognition.

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Neural evidence for sudden insight

July, 2010

A rat study supports the idea that rule learning occurs in sudden switches in the activity pattern of neurons, that may be experienced as moments of sudden insight.

A rat study has revealed that as the rats slowly learned a new rule, groups of neurons in the medial frontal cortex switched quite abruptly to a new pattern corresponding directly to the shift in behavior, rather than showing signs of gradual transition. Such sudden neural and behavioral transitions may correspond to so- called "a-ha" moments, and support the idea that rule learning is an evidence-based decision process, perhaps accompanied by moments of sudden insight.

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