Wednesday, September 30, 2009

OUT OF DARKNESS, SIGHT

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Cases of restored vision after a lifetime of blindness, though exceedingly rare, provide a unique opportunity to address several fundamental questions regarding brain function. After being deprived of visual input, the brain needs to learn to make sense of the new flood of visual information. Very little is known about how this learning takes place, but a new study by MIT neuroscientists suggests that dynamic information — that is, input from moving objects — is critical.

In the United States, as in most developed nations, infants with curable blindness are treated within a few weeks of birth. However, in developing nations such as India, there are relatively more instances of children born with curable forms of blindness that are left untreated for want of medical or financial resources. Such children face greatly elevated odds of early mortality, illiteracy and unemployment. Doctors have been hesitant to treat older patients because the conventional dogma holds that the brain is incapable of learning to see after age 5 or 6.

MIT brain and cognitive sciences professor Pawan Sinha, through his humanitarian foundation, Project Prakash (Sanskrit for "light"), has treated and studied several such patients over the past five years. The Prakash effort serves the dual purpose of providing sight to blind children and, in the process, tackling several foundational issues in neuroscience.

The new findings from Sinha's team, reported in the November issue of the Journal of Psychological Science, provide clues about how the brain learns to put together the visual world. They not only support the idea of treating blindness in older children and adults, but also offer insight into modeling the human visual system, diagnosing visual disorders, creating rehabilitation procedures and developing computers that can see.

This work builds on a 2007 study in which Sinha and graduate student Yuri Ostrovsky showed that a woman who had had her sight restored at age 12 had nearly normal visual processing abilities. These findings were significant since they challenged the widely held notion of a "critical age" for acquiring vision.

However, because they came across the woman 20 years after her sight was restored, the researchers had no chance to study how her brain first learned to process visual input. The new work focuses on three adolescent and young adult patients in India, and follows them from the time of treatment to several months afterward. It suggests that "not only is recovery possible, but also provides insights into the mechanism by which such recovery comes about," says Sinha.

Testing the patients within weeks of sight restoration, Sinha and his colleagues found that subjects had very limited ability to distinguish an object from its background, identify overlapping objects, or even piece together the different parts of an object. Eventually, however, they improved in this "visual integration" task, discovering whole objects and segregating them from their backgrounds.

"Somehow our brain is able to solve the problem, and we want to know how it does it or how it learns to do it," says Ostrovsky, lead author of the new paper.

One of their subjects, known as S.K., suffered from a rare condition called secondary congenital aphakia (a lack of lenses in the eye) and was treated with corrective optics in 2004, at the age of 29. After treatment, S.K. participated in a series of tests asking him to identify simple shapes and objects.

S.K. could identify some shapes (triangles, squares, etc.) when they were side-by-side, but not when they overlapped. His brain was unable to distinguish the outlines of a whole shape; instead, he believed that each fragment of a shape was its own whole. For S.K. and other patients like him, "it seems like the world has been broken into many different pieces," says Sinha.

However, if a square or triangle was put into motion, S.K. (and the other two patients) could much more easily identify it. (With motion, their success rates improved from close to zero to around 75 percent.) Furthermore, motility of objects greatly influenced the patients' ability to recognize them in images.

During follow-up tests that continued for 18 months after treatment, the patients' performance with stationary objects gradually improved to almost normal.

These results suggest that movement patterns in the world provide some of the most salient clues about its constituent objects. The brain is programmed to use similarity of dynamics to infer which regions constitute objects, says Sinha. The significance of motion may go even further, the team believes. It may serve to "bootstrap" the learning of rules and heuristics by which the brain comes to be able to parse static images. The idea is simple but far-reaching. Starting from an initial capability of grouping via motion, the brain begins to notice that similar dynamics are correlated with similarity in other region attributes such as orientation and color. These attributes can then be used even in the absence of motion.

In addition to understanding how the human visual system works, the findings could help researchers build robots with visual systems capable of autonomously discovering objects in their environment.

"If we could understand how the brain learns to see, we can better understand how to train a computer to do it," says Ostrovsky.

(Photo: Pawan Sinha)

MIT

EVIDENCE POINTS TO CONSCIOUS 'METACOGNITION' IN SOME NONHUMAN ANIMALS

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J. David Smith, Ph.D., a comparative psychologist at the University at Buffalo who has conducted extensive studies in animal cognition, says there is growing evidence that animals share functional parallels with human conscious metacognition -- that is, they may share humans' ability to reflect upon, monitor or regulate their states of mind.

Smith makes this conclusion in an article published the September issue of the journal Trends in Cognitive Science (Volume 13, Issue 9). He reviews this new and rapidly developing area of comparative inquiry, describing its milestones and its prospects for continued progress.

He says "comparative psychologists have studied the question of whether or not non-human animals have knowledge of their own cognitive states by testing a dolphin, pigeons, rats, monkeys and apes using perception, memory and food-concealment paradigms.

"The field offers growing evidence that some animals have functional parallels to humans' consciousness and to humans' cognitive self-awareness," he says. Among these species are dolphins and macaque monkeys (an Old World monkey species).

Smith recounts the original animal-metacognition experiment with Natua the dolphin. "When uncertain, the dolphin clearly hesitated and wavered between his two possible responses," he says, "but when certain, he swam toward his chosen response so fast that his bow wave would soak the researchers' electronic switches.

"In sharp contrast," he says, "pigeons in several studies have so far not expressed any capacity for metacognition. In addition, several converging studies now show that capuchin monkeys barely express a capacity for metacognition.

"This last result," Smith says, "raises important questions about the emergence of reflective or extended mind in the primate order.

"This research area opens a new window on reflective mind in animals, illuminating its phylogenetic emergence and allowing researchers to trace the antecedents of human consciousness."

Smith, a professor in the UB Department of Psychology and Center for Cognitive Sciences, is recognized for his research and publications in the field of animal cognition.

He and his colleagues pioneered the study of metacognition in nonhuman animals, and they have contributed some of the principal results in this area, including many results that involve the participation of Old World and New World monkeys who have been trained to use joysticks to participate in computer tasks.

Their research is supported by the National Institute of Child Health and Development and the National Science Foundation.

Smith explains that metacognition is a sophisticated human capacity linked to hierarchical structure in the mind (because the metacognitive executive control processes oversee lower-level cognition), to self-awareness (because uncertainty and doubt feel so personal and subjective) and to declarative consciousness (because humans are conscious of their states of knowing and can declare them to others).

Therefore, Smith says, "it is a crucial goal of comparative psychology to establish firmly whether animals share humans' metacognitive capacity. If they do, it could bear on their consciousness and self-awareness, too."

In fact, he concludes, "Metacognition rivals language and tool use in its potential to establish important continuities or discontinuities between human and animal minds."

(Photo: U. Buffalo)

University at Buffalo

DEPRESSION INCREASES CANCER MORTALITY RATE

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A number of studies have shown that individuals’ mental attitudes can impact their physical health. To determine the effects of depression on cancer patients’ disease progression and survival, UBC Dept. of Psychology graduate student Jillian Satin and colleagues analyzed all studies to date that they could identify related to the topic.

The researchers found 26 studies with a total of 9,417 patients that examined the effects of depression on patients’ cancer progression and survival. Their analysis is published online today by the American Cancer Society journal Cancer.

“We found an increased risk of death in patients who report more depressive symptoms than others and also in patients who have been diagnosed with a depressive disorder compared to patients who have not,” said Satin. In the combined studies, the death rates were as much as 25 per cent higher in patients experiencing depressive symptoms and 39 per cent higher in patients diagnosed with major or minor depression.

The increased risks remained even after considering other clinical characteristics that might affect survival, indicating that depression may actually play a part in shortening survival. However, the authors say additional research must be conducted before any conclusions can be reached. The authors add that their analysis combined results across different tumor types, so future studies should look at the effects of depression on specific kinds of cancer.

The investigators note that the actual risk of death associated with depression in cancer patients is still small, so patients should not feel that they must maintain a positive attitude to beat their disease. Nevertheless, the study indicates that it is important for physicians to regularly screen cancer patients for depression and to provide appropriate treatments.

The researchers did not find a clear association between depression and cancer progression, although only three studies were available for analysis.

University of British Columbia

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