Tag Archives: brain

The Evolutionary History of the Brain

The devel­op­ment of the human brain is intric­ately linked with almost every moment of our evol­u­tion from sea-dwell­ing anim­als to advanced, social prim­ates. That is the the over­whelm­ing theme from New Sci­ent­ist’s brief his­tory of the brain.

The enga­ging art­icle ends with a look at the con­tin­ued evol­u­tion of the human brain (“the visu­al cor­tex has grown lar­ger in people who migrated from Africa to north­ern lat­it­udes, per­haps to help make up for the dim­mer light”), and this on why our brains have stopped grow­ing:

So why did­n’t our brains get ever big­ger? It may be because we reached a point at which the advant­ages of big­ger brains star­ted to be out­weighed by the dangers of giv­ing birth to chil­dren with big heads. Or it might have been a case of dimin­ish­ing returns.

Our brains are pretty hungry, burn­ing 20 per cent of our food at a rate of about 15 watts, and any fur­ther improve­ments would be increas­ingly demand­ing. […]

One way to speed up our brain, for instance, would be to evolve neur­ons that can fire more times per second. But to sup­port a 10-fold increase in the “clock speed” of our neur­ons, our brain would need to burn energy at the same rate as Usain Bolt’s legs dur­ing a 100-metre sprint. The 10,000-calorie-a-day diet of Olympic swim­mer Michael Phelps would pale in com­par­is­on.

Not only did the growth in the size of our brains cease around 200,000 years ago, in the past 10,000 to 15,000 years the aver­age size of the human brain com­pared with our body has shrunk by 3 or 4 per cent. Some see this as no cause for con­cern. Size, after all, isn’t everything, and it’s per­fectly pos­sible that the brain has simply evolved to make bet­ter use of less grey and white mat­ter. That would seem to fit with some genet­ic stud­ies, which sug­gest that our brain’s wir­ing is more effi­cient now than it was in the past.

Oth­ers, how­ever, think this shrink­age is a sign of a slight decline in our gen­er­al men­tal abil­it­ies.

via @mocost

Our Amazing Senses

As neur­os­cient­ist Brad­ley Voytek points out, “we’re used to think­ing of our senses as being pretty shite”, and this is mostly thanks to the pleth­ora of anim­als that can see, hear, smell and taste far bet­ter than we can. “We can­’t see as well as eagles, we can­’t hear as well as bats, and we can­’t smell as well as dogs”, he con­cludes… and that seems to be the con­sensus on every nature doc­u­ment­ary I’ve ever watched.

How­ever our brain is a mag­ni­fi­cent con­struc­tion (and our senses are equally as won­drous), and so Voytek tries to reverse this idea by explain­ing just how sens­it­ive and amaz­ing our senses really are:

It turns out that humans can, in fact, detect as few as 2 photons enter­ing the ret­ina. Two. As in, one-plus-one. It is often said that, under ideal con­di­tions, a young, healthy per­son can see a candle flame from 30 miles away. That’s like being able to see a candle in Times Square from Stam­ford, Con­necti­c­ut. Or see­ing a candle in Can­dle­stick Park from Napa Val­ley.*

Sim­il­arly, it appears that the lim­its to our threshold of hear­ing may actu­ally be Browni­an motion. That means that we can almost hear the ran­dom move­ments of atoms.

We can also smell as few as 30 molecules of cer­tain sub­stances. […]

These facts sug­gest that we all have some level of what we’d nor­mally think of as “super human” sens­ory abil­it­ies already.

But what the hell? If I can sup­posedly see a candle from 30 miles away, why do I still crack my frakkin’ shin on the cof­fee table when it’s only slightly dark in my liv­ing room?

It may not sur­prise you to hear that the answer to that ques­tion is atten­tion.

* For the Europeans among you, that’s more than a fifth longer than the Chan­nel Tun­nel’s under­wa­ter sec­tion (or Hyde Park to Stansted Air­port for the Lon­don­ers).

Social Cognition and Staving Off Dementia

A lon­git­ud­in­al study of health and men­tal lucid­ity in the aged—focusing on the huge retire­ment com­munity of Laguna Woods Vil­lage south of Los Angeles—is start­ing to show some res­ults.

From study­ing mem­bers of the so-called ‘super memory club’ (people aged 90+ with near-per­fect cog­nit­ive abil­it­ies) it is being sug­ges­ted that not all men­tal activ­it­ies are equal when it comes to stav­ing off demen­tia, and social intereac­tions may be vastly more import­ant that pre­vi­ously thought.

The research­ers have also demon­strated that the per­cent­age of people with demen­tia after 90 does not plat­eau or taper off, as some experts had sus­pec­ted. It con­tin­ues to increase, so that for the one in 600 people who make it to 95, nearly 40 per­cent of the men and 60 per­cent of the women qual­i­fy for a dia­gnos­is of demen­tia.

So far, sci­ent­ists here have found little evid­ence that diet or exer­cise affects the risk of demen­tia in people over 90. But some research­ers argue that men­tal engage­ment — doing cross­word puzzles, read­ing books — may delay the arrival of symp­toms. And social con­nec­tions, includ­ing inter­ac­tion with friends, may be very import­ant, some sus­pect. In isol­a­tion, a healthy human mind can go blank and quickly become dis­or­i­ented.

via Mind Hacks

The Infant Brain, Redux

An inter­est­ing fol­low-up if you enjoyed read­ing about the devel­op­ment of the infant brain last week: Seed Magazine inter­views Alis­on Gopnik, ask­ing about her research and “why everything we think we know about babies is wrong”.

Seed: You describe chil­dren as being “use­less on pur­pose.” What do you mean by that?

AG: It’s related to one of the basic things that came out of our research: Why do chil­dren exist at all? It does­n’t make tre­mend­ous evol­u­tion­ary sense to have these creatures that can­’t even keep them­selves alive and require an enorm­ous invest­ment of time on the part of adults. That peri­od of depend­ence is longer for us than it is for any oth­er spe­cies, and his­tor­ic­ally that peri­od has become longer and longer.

The evol­u­tion­ary answer seems to be that there is a tradeoff between the abil­ity to learn and imagine — which is our great evol­u­tion­ary advant­age as a species — and our abil­ity to apply what we’ve learned and put it to use.

The art­icle also men­tions how Gopnik believes “Freud’s and Pia­get’s con­cep­tions of young chil­dren’s the­ory of mind are wrong”. A recent (cor­rel­at­ive) study has shown that she may be cor­rect.

Development of the Infant Brain

Look­ing primar­ily at the research of Alis­on Gopnik, Jonah Lehr­er looks at the devel­op­ment of the infant brain.

Gopnik argues that, in many respects, babies are more con­scious than adults. She com­pares the exper­i­ence of being a baby with that of watch­ing a riv­et­ing movie, or being a tour­ist in a for­eign city, where even the most mundane activ­it­ies seem new and excit­ing. “For a baby, every day is like going to Par­is for the first time,” Gopnik says. “Just go for a walk with a 2‑year-old. You’ll quickly real­ize that they’re see­ing things you don’t even notice.”

via Mind Hacks, which itself has a word of cau­tion about the claim that babies have more neur­ons than adults.