Brain #2: Airport Network Metaphor

 In Seven and a Half Lessons About the Brain, Lisa Barrett describes the structure of the brain. The brain is a network of neurons, around 128 billion of them in case of humans. The neurons continuously fire and communicate with other neurons they are connected to. And here’s something not everyone realizes:

“Your brain network is always on.”

Put differently, that means neurons are not triggered into action only when something happens inside or outside the body. Rather, they are talking with each other continuously. But the strength of the signal will change based on triggering events and also, yes, frequency of usage of those pathways.

 

A metaphor that Barrett uses to describe the brain is the airport network. Just as every combination of airports don’t have direct flights between them, similarly all neurons don’t communicate with all other neurons. Instead, both have “hubs” – a small number of points that connect to a huge number of other points. The rest (majority) connect to just a handful of other points. Also, both the brain and airport networks are flexible and scalable – neither is rigid or fixed:

  1. Tuning: Frequently used connections get stronger over time.
  2. Pruning: Lesser used connections grow weaker and eventually die off.

 

The airport network metaphor is relevant in another way. When a major hub like Heathrow has problems, the cascading effects can be felt world over, even in routes that don’t pass through London. Similarly, when a hub of the brain has problems, it can lead to problems in multiple functions.

“Hubs are points of vulnerability because they are points of efficiency.”

 

In times of crisis, planes can be diverted via other routes. On this matter too, neurons are like planes – they do not have exactly one “single, psychological function”. They can change the role they play when injuries occur to other parts of the brain. This is why terms like “visual cortex” or “language network” should not be taken as written in stone...

 

And just as different plane routes can get you from A to B, multiple neuron pathways can be involved in the same actions – the phenomenon is called “degeneracy”.

 

In engineering, degeneracy is a feature. A backup. But in case of the brain, degeneracy can create unintended effects. For example, the brain doesn’t store memories like “files on a computer”. Rather:

“It constructs them on demand with electricity and swirling chemicals.”

Barrett then makes a statement that would explain a lot:

“We call this process remembering but it’s really assembling.”

It gets even more interesting. The same memories can be “assembled” by a different combination of neurons at different times! Is that why our memories can be so unreliable at times?

Comments

Post a Comment

Popular posts from this blog

Need for an Informed Aadhar Debate

As Aadhar increases in scope, supporters consider it necessary, says L.Viswanath : “We have Aadhaar getting linked to ration cards, NREGA payments, PAN cards, bank accounts, mobile SIMs, mid-day meals in schools, school admissions, university admissions…the list is endless. In a country plagued by corruption and bureaucratic inefficiency, the hope is that Aadhaar will help eliminate fraudulent identities, thereby saving the direct and indirect losses to the nation.” Conversely, opponents don’t cite concrete use-cases of how it might be abused apart from throwing phrases (“Orwellian state”) that sound scary. Until its opponents provide such details, supporters will win the argument by simply asking why Aadhar should be restricted only to subsidy schemes, as Subhashis Banerjee points out : “Admittedly there are substantial leakages in these schemes, but surely the need for de-duplication and strict record keeping and audits are as much, if not more, in the domains of tax co...
Read more

Nazis and the Physics Connection

When the Nazi government seized power, they started removing Jews from more and more positions, including the civil services, and the science departments of Germany. Those physicists who saw the writing on the wall fled to either UK (like Schrodinger) or the US (like Einstein), writes Adam Becker in What is Real?   The great physicist, Enrico Fermi, wasn’t a Jew. But when Mussolini aligned with Hitler, Fermi came under suspicion since his wife was a Jew. To make matters problematic, Mussolini’s new laws had made it illegal to take “more than pocket change” out of Italy. Neils Bohr broke an unwritten rule of the Nobel and told Fermi that he (Fermi) was in the running for the Nobel that year. Perhaps Fermi, should he win, could consider escaping from Stockholm with the prize money to start a new life? Fermi agreed, but it was touch and go – his wife’s passport had been confiscated, which meant she couldn’t come to Stockholm. Fermi managed to pull a few strings to get her passport...
Read more

1991 - Liberalization

After the fall of Chandra Shekhar’s government, elections were called in 1991. During the campaign, Rajiv Gandhi got assassinated. That set off a sympathy wave – during the phases before Rajiv’s murder, the Congress won 50 of the 196 seats; post-that, it won 177 of 285 seats. The Congress now had enough seats (227) to try and form a coalition government. But who should head it? There was no obvious “heir” from the Family. With 100 of the 227 seats being from the south, PV Narasimha Rao (PV from here for short) had an edge, and he became the Prime Minister, writes Sanjaya Baru in 1991 .   The first order of business was, yes, that balance of payments crisis. PV’s first choice for Finance Minister was IG Patel, who had been Chandra Shekhar’s first choice too. Patel declined both PM’s offers to be the Finance Minister (FM). As PV continued his search, he found Manmohan Singh.   In his first address to the nation, in his deadpan manner, PV made a couple of statements that ...
Read more