Sunday 25 February 2024

Male vs female brain, whale songs & human cooperation | Last Week in Science (25th Feb 2024)


Is the male and female brain really different?



Medically speaking, we know that some neuropsychiatric and neurological diseases affect women more than men. Hormones are/may be one of the reasons for this difference. But is the brain of a male individual different from a female's? 

Researchers at Stanford University used artificial intelligence to find it out. They trained the AI to identify MRI scans of females and males by showing it brain scans of both the sexes. When tested with 1500 brain scans taken from individuals across USA and EU, the AI could correctly identify the sex of the individual. This increased the confidence in the training as it could work on diverse populations. So, what do we do by identifying males and females just by looking at a brain scan?

The scientists digged into how the AI was identifying the sex of the individual. This process makes it an explainable artificial intelligence instead of a black box of mystery. What they observed was that the identification was happening by studying the organization of three different brain regions, default mode network - which helps in understanding of self, striatum - which plays a role in reward, and limbic network - which is involved in learning amongst its other functions. 

What makes their study useful according to the authors is - 1. The differences in the male and female brain organization that they have undercovered can help in research for neuropsychiatric and neurological diseases. 2. Their AI model will help in identifying the brain circuits responsible for any type of behaviour - like say for a learning disability.

Reference: Stanford Medicine study identifies distinct brain organization patterns in women and men


What makes you cooperate?

Helping your family or friend makes sense, although it may not to everyone, but helping someone whom you would never meet again or someone from whom you have nothing to gain, how do we explain that? The origin of these one time altruistic interactions are difficult to explain. What we know about human cooperation is that when two individuals will be meeting repeatedly then they would want to ensure they remain on good terms so they cooperate, again does not apply to all individuals and all interactions. But then this hypothesis cannot explain the one time interactions. Another hypothesis is 'group competition'. A group which has more cooperative individuals would be at an advantage than a group with selfish or non-cooperative (the terms can be used interchangeably in this context) individuals. But both the hypotheses are not sufficient to explain why 'cooperation' or to say 'altruism' as a trait evolved and remained in today's population (and society). 

Researchers in University of Zurich created a model to understand this 'cooperative' human behavior. They then conducted a test on two different groups in Papua New Guinea. They paired individuals - once with a member of their own group (in-group) and then with a member of the other group (out-group). They asked the first member to give a certain amount of that individual's money to their partner following which they would give the double of that amount to their partner. They saw that in case of in-group partners the first member gave a higher sum and the second member gave back a much higher sum of money. While in the case of out-group pairings - the first member gave a smaller sum and the receiving individual gave a much lesser sum to the first one.

Now, when the researchers tested this result in their model then they found that such type of behaviour can explain the cooperation they saw in Papua New Guinea by a combination of both repeated interactions and group competition.

Reference: Why reciprocity is common in humans but rare in other animals


Eerie whale songs



Sailors would often tell stories of haunting sounds that could be heard in the ocean. It was only when the recordings of these songs became available to marine biologists that we understood that these sounds were whale songs. The mystery of how the songs were produced by the whales remained unexplainable for long because of the difficulty of studying these large marine mammals. But the researchers in Denmark might have found a piece of this puzzle that can help understand how whales are producing these sounds. The most interesting of the facts is that some of these whales can produce two different sounds at the same time. So, let us see what these scientists found.

Larynx the sound box has vocal cords or vocal folds present that is responsible for producing sound in mammals. As air passes through the larynx vocal cords - present on either side of the tube shaped larynx - vibrate to produce sound. The scientists studied the whale larynx dissected out from the dead bodies of whales. They passed air from the whales larynx to understand how sound is being produced. Now, the larynx in the whale has two different compartments unlike the larynx in land animals. A layer of fat - fat cushion, lines one side of the larynx creating a second compartment between fat cushion & vocal folds. Now, this creates two different surfaces - because of the presence of two vocal folds - lining next to the fat cushion that can vibrate as sound gets squeezed between the fat cushion and the vocal folds. Vibration of these two different surfaces can explain the production of two sounds at the same time. It also appears that the major sound production is via fat cushion- vocal fold instead of the air passing through the vocal folds.

This explanation still needs to be tested further in models where larynx is in an environment that still has the surrounding tissues intact. Another question that needs to be answered is how the sound is being produced underwater. And lastly, it would be interesting to see how some distinct and unusual whale sounds like - 'gunshot' and 'star wars' light-saber' like sounds are produced by whales.


Reference: An innovative way for whales to sing

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