The Mental Life of Plants and Worms, Among Others (di Oliver Sacks)

Oliver Sacks

Charles Darwin’s last book, published in 1881, was a study of the humble earthworm. His main theme—expressed in the title, The Formation of Vegetable Mould through the Action of Worms—was the immense power of worms, in vast numbers and over millions of years, to till the soil and change the face of the earth. But his opening chapters are devoted more simply to the “habits” of worms.

Worms can distinguish between light and dark, and they generally stay underground, safe from predators, during daylight hours. They have no ears, but if they are deaf to aerial vibration, they are exceedingly sensitive to vibrations conducted through the earth, as might be generated by the footsteps of approaching animals. All of these sensations, Darwin noted, are transmitted to collections of nerve cells (he called them “the cerebral ganglia”) in the worm’s head.

“When a worm is suddenly illuminated,” Darwin wrote, it “dashes like a rabbit into its burrow.” He noted that he was “at first led to look at the action as a reflex one,” but then observed that this behavior could be modified—for instance, when a worm was otherwise engaged, it showed no withdrawal with sudden exposure to light.

For Darwin, the ability to modulate responses indicated “the presence of a mind of some kind.” He also wrote of the “mental qualities” of worms in relation to their plugging up their burrows, noting that “if worms are able to judge…having drawn an object close to the mouths of their burrows, how best to drag it in, they must acquire some notion of its general shape.” This moved him to argue that worms “deserve to be called intelligent, for they then act in nearly the same manner as a man under similar circumstances.”

As a boy, I played with the earthworms in our garden (and later used them in research projects), but my true love was for the seashore, and especially tidal pools, for we nearly always took our summer holidays at the seaside. This early, lyrical feeling for the beauty of simple sea creatures became more scientific under the influence of a biology teacher at school and our annual visits with him to the Marine Station at Millport in southwest Scotland, where we could investigate the immense range of invertebrate animals on the seashores of Cumbrae. I was so excited by these Millport visits that I thought I would like to become a marine biologist myself.

(continua qui)

Annunci

Intoppi sulla strada del tempo

Disegni di persone affette da neglect

Chi ha sfogliato i libri di Oliver Sacks – tra gli altri – sarà rimasto colpito dalle anomalie percettive che evidenziano le persone affette da neglecto anche negligenza spaziale unilaterale. Si tratta di soggetti che, dopo aver subito una particolare lesione all’emisfero cerebrale destro, improvvisamente trovano un’assurda difficoltà nel percepire e nell’esplorare lo spazio che si trova alla loro sinistra. Senza che neanche se ne rendano conto, il loro mondo improvvisamente si dimezza. Se devono disegnare un fiore, ne disegnano solo la parte destra (ma non ne sono consapevoli). Se devono mangiare un piatto di pasta, divorano gli spaghetti che si trovano sulla destra (ma non ne sono consapevoli). Se devono passarsi il rossetto sulle labbra, si dimenticano di farlo anche sulla parte sinistra. Ma quando si scrutano allo specchio a loro pare tutto ok. Non c’è niente che non vada. Metà dell’universo è sparita, ma questo non gli fa né caldo né freddo.

Partendo dalle caratteristiche certamente sorprendenti di questo disturbo, alcuni studiosi hanno proposto un esperimento a mio parere assai brillante che riguarda il nostro modo di concettualizzare il fluire degli eventi.

Se è vero – ed è vero – che noi occidentali ci rappresentiamo mentalmente il tempo come una serie di fatti che scorrono in maniera inesorabile da sinistra a destra, cosa succede quando è un soggetto affetto da neglect a dover svolgere questo tipo di operazione? Che differenza c’è, a livello percettivo e mnemonico, tra ciò che si trova sulla parte sinistra della sua linea del tempo (il passato) e ciò che si trova sulla parte destra (il futuro)? O tra lui e le persone sane che svolgono lo stesso compito? La risposta in questo interessante articolo (qui di seguito incollo l’incipit) tratto da New Scientist:

DRAW a line across a page, then write on it what you had for dinner yesterday and what you plan to eat tomorrow. If you are a native English speaker, or hail from pretty much any European country, you no doubt wrote last night’s meal to the left of tomorrow night’s. That’s because we construct mental timelines to represent and reason about time, and most people in the West think of the past as on the left, and the future as on the right.

Arnaud Saj at the University of Geneva, Switzerland, and his colleagues wondered whether the ability to conjure up a mental timeline is a necessary part of reasoning about events in time.

To investigate, they recruited seven Europeans with what’s called left hemispatial neglect. That means they have damage to parts of the right side of their brain, limiting their ability to detect, identify and interact with objects in the left-hand side of space. They may eat from only the right side of a plate, shave just the right side of their face, and ignore numbers on the left side of a clock.

The team also recruited seven volunteers who had damage to the right side of their brain but didn’t have hemispatial neglect, and seven people with undamaged brains.

All the volunteers took part in a variety of memory tests. First, they learned about a fictional man called David. They were shown pictures of what David liked to eat 10 years ago, and what he might like to eat in 10 years’ time. Participants were then shown drawings of 10 of David’s favourite foods, plus four food items they hadn’t seen before. Participants had to say whether it was a food that David liked in the past or might like in future. The tests were repeated with items in David’s apartment, and his favourite clothes.

(continua qui)

Hacking your brain

Sempre a proposito di cerebro et similia, la sempre ganzissima pagina FB I fucking love science mi segnala la seguente infografica. Leggendola vengono a mente molti racconti di Sacks e Ramachandran – penso per esempio alla più volte sottolineata relazione tra deprivazione sensoriale e allucinazioni, ma non solo. In special modo, si percepisce come il trucco della mirror box (un video esplicativo) ideato da quest’ultimo abbia influenzato parecchia gente, spingendola a sperimentare e sperimentare ancor di più, confrontandosi con idee che a prima vista paiono le più assurde ma che, se ben sfruttate, possono portare benefici pratici.

Hacking your brain
(A scanso di equivoci: no, io non ho provato a fare niente del genere)