An anti-cancer drug about to be tested in a clinical trial by a biomedical company in Ohio as a possible treatment for Alzheimer’s disease has failed to work with the same type of brain plaques that plague Alzheimer’s patients, according to results of a study by University of Florida researchers.
Suppose you hear someone say, “The man gave the ice cream the child.” Does that sentence seem plausible? Or do you assume it is missing a word? Such as: “The man gave the ice cream to the child.”
A new study by MIT researchers indicates that when we process language, we often make these kinds of mental edits. Moreover, it suggests that we seem to use specific strategies for making sense of confusing information — the “noise” interfering with the signal conveyed in language, as researchers think of it.
“Even at the sentence level of language, there is a potential loss of information over a noisy channel,” says Edward Gibson, a professor in MIT’s Department of Brain and Cognitive Sciences (BCS) and Department of Linguistics and Philosophy.
Gibson and two co-authors detail the strategies at work in a new paper, “Rational integration of noisy evidence and prior semantic expectations in sentence interpretation,” published today in the Proceedings of the National Academy of Sciences.
“As people are perceiving language in everyday life, they’re proofreading, or proof-hearing, what they’re getting,” says Leon Bergen, a PhD student in BCS and a co-author of the study. “What we’re getting is quantitative evidence about how exactly people are doing this proofreading. It’s a well-calibrated process.”
The paper is based on a series of experiments the researchers conducted, using the Amazon Mechanical Turk survey system, in which subjects were presented with a series of sentences — some evidently sensible, and others less so — and asked to judge what those sentences meant.
A key finding is that given a sentence with only one apparent problem, people are more likely to think something is amiss than when presented with a sentence where two edits may be needed. In the latter case, people seem to assume instead that the sentence is not more thoroughly flawed, but has an alternate meaning entirely.
“The more deletions and the more insertions you make, the less likely it will be you infer that they meant something else,” Gibson says. When readers have to make one such change to a sentence, as in the ice cream example above, they think the original version was correct about 50 percent of the time. But when people have to make two changes, they think the sentence is correct even more often, about 97 percent of the time.
Thus the sentence, “Onto the cat jumped a table,” which might seem to make no sense, can be made plausible with two changes — one deletion and one insertion — so that it reads, “The cat jumped onto a table.” And yet, almost all the time, people will not infer that those changes are needed, and assume the literal, surreal meaning is the one intended.
This finding interacts with another one from the study, that there is a systematic asymmetry between insertions and deletions on the part of listeners.
“People are much more likely to infer an alternative meaning based on a possible deletion than on a possible insertion,” Gibson says.
Suppose you hear or read a sentence that says, “The businessman benefitted the tax law.” Most people, it seems, will assume that sentence has a word missing from it — “from,” in this case — and fix the sentence so that it now reads, “The businessman benefitted from the tax law.” But people will less often think sentences containing an extra word, such as “The tax law benefitted from the businessman,” are incorrect, implausible as they may seem.
Another strategy people use, the researchers found, is that when presented with an increasing proportion of seemingly nonsensical sentences, they actually infer lower amounts of “noise” in the language. That means people adapt when processing language: If every sentence in a longer sequence seems silly, people are reluctant to think all the statements must be wrong, and hunt for a meaning in those sentences. By contrast, they perceive greater amounts of noise when only the occasional sentence seems obviously wrong, because the mistakes so clearly stand out.
“People seem to be taking into account statistical information about the input that they’re receiving to figure out what kinds of mistakes are most likely in different environments,” Bergen says.
Reverse-engineering the message
Other scholars say the work helps illuminate the strategies people may use when they interpret language.
“I’m excited about the paper,” says Roger Levy, a professor of linguistics at the University of California at San Diego who has done his own studies in the area of noise and language.
According to Levy, the paper posits “an elegant set of principles” explaining how humans edit the language they receive. “People are trying to reverse-engineer what the message is, to make sense of what they’ve heard or read,” Levy says.
“Our sentence-comprehension mechanism is always involved in error correction, and most of the time we don’t even notice it,” he adds. “Otherwise, we wouldn’t be able to operate effectively in the world. We’d get messed up every time anybody makes a mistake.”
The most magnetic massive star seen yet is dragging a giant cloak of trapped charged particles around it.
Image: An artist’s interpretation of a magnetar. Credit: ESA - Christophe Carreau
This newly discovered star, NGC 1624-2, could help shed light on what role the magnetism of stars plays in the evolution of stars and their galaxies.
NGC 1624-2, which lies about 20,000 light-years from Earth in the constellation Perseus, has about 35 times the sun’s mass. Its hefty mass gives it plenty of fuel, making it bright and hot and thus likely to burn out relatively quickly after a lifetime of about 5 million years, or one-tenth of 1 percent of the sun’s current age at midlife.
When animals are on the hunt for food they likely use many senses, and scientists have wondered how the different senses work together.
New research from the laboratory of CSHL neuroscientist and Assistant Professor Adam Kepecs shows that when rats actively use the senses of smell (sniffing)…
#10 Play brain games
Your cognitive abilities can be maintained or improved by exercising the brain. Playing chess, bridge, sudoku and other brain training games will help improve your memory and brain abilities.
These games rely on logic, word skills, math and more. These games are also…
Researchers have been able to identify the precise moment when a network of nerve cells (neurons) in the brain creates the signal to perform an action, before a person is even aware of deciding to take that action. Now they are building on this work to make initial attempts to interfere with consciously made decisions by decoding the pattern of brain activity in real time before an action is taken.
Professor Gabriel Kreiman will tell the British Neuroscience Association Festival of Neuroscience (BNA2013) today (Tuesday): “This could be useful to help elucidate the mechanistic basis by which neuronal circuits orchestrate ‘free’ will.”
Normally it is difficult to research the activity of neurons in the brain because it involves implanting electrodes – an invasive procedure that would not be ethical to do simply for scientific curiosity alone. However, Prof Kreiman, who is an associate professor at the Harvard Medical School, Boston, USA, together with neurosurgeon Itzhak Fried from University of California at Los Angeles (UCLA), had a rare opportunity to record the activity of over 1,000 neurons in two areas of the brain, the frontal and temporal lobes, when patients with epilepsy had had electrodes implanted to try to identify the source of their seizures.
“These patients have epilepsy that does not respond to drug treatment; Itzhak Fried implanted their brains with very thin electrodes (microwires) of about 40 micrometres in diameter in order to localise the focus of a seizure onset for a potential surgical procedure to alleviate the seizures. The microwires capture the extracellular electrical activity of neurons. Patients stay in the hospital for about a week. During this time, we have a unique opportunity to interrogate the activity of neurons and neural ensembles in the human brain at high spatial and temporal resolution,” explains Prof Kreiman.
The researchers asked the patients to move their index finger to click a computer mouse and to report when they made that decision. “Based on the activity of small groups of neurons, we could predict this decision several hundreds of milliseconds and, in some cases, seconds before the action. In a variant of the main experiment, the patients were allowed to choose whether to use their left hand or right hand and we showed that we could also predict this decision.”
The researchers found that an increasing number of neurons in two specific brain regions started to become active before the person was aware of their decision to move their finger. The two regions were the supplementary motor area, which is thought to be the area for preparing to perform motor actions, and the anterior cingulate cortex, which has a number of roles including the signalling processes associated with reward.
Prof Kreiman believes that these results provide initial steps to elucidate the mechanism for the emergence of conscious will in humans. “The activity of multiple neurons in extremely simple neural circuits precedes volition – in this case the decision to make a simple movement – until a threshold is crossed and the action is taken,” he will say.
Knowing when this threshold will be reached could enable researchers to see whether it is possible to interfere and maybe change the decision before any action is taken. “We are now making initial attempts to interfere with volition by decoding the neural responses in real time and asking whether there is a ‘point of no return’ in the hierarchical chain of command from unconscious decisions to volition to action,” says Prof Kreiman.
How these findings fit into the concept of “free will” is more complicated. “The concept of free will has been debated for millennia. Ultimately, current scientific understanding strongly suggests that ‘will’ has to be orchestrated by neurons in our brains (as opposed to magic or religious beliefs or other notions). We have provided initial steps to try to disentangle which neurons are involved, to show where and how ‘will’ or ‘volition’ could be implemented in the brain.
“Our work does not say that life is predetermined, that we can predict the future and that we can, for instance, determine what you are going to eat for lunch two weeks from now, or who you are going to marry.
“We are saying that volition (like other aspects of consciousness) is a brain phenomenon that is instantiated by physical hardware, i.e. neurons. We are making claims about volition for very simple tasks, such as moving an index finger or choosing which hand to use, over scales of hundreds of milliseconds to seconds. Nothing more. Nothing less.
“Ultimately, our actions depend on multiple variables, several of which are external (for instance, it rains, hence, I will take my umbrella) and cannot be decoded or predicted from neurons. However, our volitional decision of whether to take the red umbrella or the blue one today – ultimately perhaps the real core of free will – is dictated by neurons,” Prof Kreiman will conclude.
In Alzheimer’s Disease, Maintaining Connection and ‘Saving Face’
I’ve decided that all older men with gray beards must look alike, because each week I am mistaken for someone else. But, if I were to shave my beard - which I have worn for over 40 years - I believe that my friends and colleagues would fail to recognize me. I would be a different person to them because of this small, physical change.
If such a small change affects the way people see me, then the larger mental changes that Alzheimer’s patients experience must truly and deeply change the way their loved ones see them. Dr. Daniel Potts, a neurologist at the University of Alabama, has begun studying the concept of “saving face” and preserving the “person” in people with dementia.
Dr. Potts’ father, Lester Potts, became an acclaimed watercolor artist after his Alzheimer’s diagnosis. He had lost his verbal abilities but could express his feelings through his art. This bolstered his retention of self-worth and dignity. His paintbrush let him bypass the part of his brain that Alzheimer’s blocked, and communicate in a new way.
But before we find out more about art and Alzheimer’s patients, let’s go back to the “face” part of saving face for just a moment.