In an update to their groundbreaking earlier demonstration that high-IQ children initially show a thinner cortex, and later show an initially thicker one than their average-IQ peers, Shaw et al. have now documented those trajectories of cortical thickening which are invariant to socio-economic status and IQ, but vary between regions of the brain. These videos show the peak in gray matter in cortex between the ages of 5 and 15 years, as assessed from magnetic resonance imaging (MRI) of 375 subjects of varying ages.
And another video below the fold...
Dark red areas indicate those…
Play cognitive engineer: if you were designing an intelligent system, you'd probably use the same system to detect novelty as that used to detect familiarity. After all, one is simply the inverse of the other - so novelty can be thought of as a below-threshold value for some familiarity signal.
Upon reflection, however, you might notice some subtle problems with your design. First, novelty is informative only insofar as it is engages a change in the behavior of your system: novelty indicates an opportunity for learning which has not been exploited by the system. Critically, this includes…
To efficiently direct learning, it may be useful for the brain to attend to those items which are maximally novel - this novelty may obscure some predictive or rewarding value that has not yet been learned or exploited. This is widely acknowledged, usually in passing; but ambiguities in what counts as "novel" have profound and unacknowledged consequences for research on high-level cognition (generalization, rule-use, etc).
But let's start with what we do know about novelty processing in the brain.
As would be expected from a creature that has much to learn, infants show a very robust "…
What if training ourselves on one task yielded improvements in all other tasks we perform? This is the promise of the cognitive training movement, which is increasingly showing that such "far transfer" of training is indeed possible, while short of being "universal transfer." Interestingly, this phenomenon might be most likely to occur for some of the most abstract and challenging cognitive functions.
New evidence for this claim comes from an in-press article at Psychological Science, by Persson & Reuter-Lorenz. The authors used several tasks which have been shown to engage the left…
If you said 1/1000, you've given the answer provided more often by second graders than by undergraduates. And you're also right.
Evidence from functional neuroimaging and developmental psychology indicate that the human brain possesses an abstract system for magnitude comparison, perhaps relying on the intraparietal sulcus of the posterior parietal cortex. One "feature" of this system is that it follow's Weber's Law - larger quantities are less discriminable from one another than smaller quantities. Thus, in this part of the brain numerical representations are not linear but logarithmic.…
My friend Geoff once said that "all cognition is social." Smugly, I reminded myself that the conclusions of cognitive psychologists are drawn on evidence where social cues are kept constant. But even in the absence of confounding social cues, perhaps the underlying cognitive processes themselves are caused by social factors.
A great example of this comes from today's issue of Science, in which Topal et al describe how a well known "cognitive" phenomenon - perseveration - may be dramatically influenced by social cues.
Topel et al focus on a situation in which very young infants will…
Much has been written about the nonspatial functions of the parietal lobe, but these nonspatial functions are rarely evaluated as to whether they are also nonmotoric or reflect some covert form of spatial attention. Establishing whether the parietal lobe has truly nonmotoric and nonspatial functions is essential for understanding why parietal cortex appears to be involved in so many different tasks. Here I've attempted to evaluate whether the parietal lobe truly has nonspatial, and perhaps also nonmotoric functions by reviewing the relevant literature...
Magnitude processing - the size…
Much evidence supports the idea that parietal cortex is involved in the simple maintenance of information, such as in object permanence paradigms (also here) and other tasks. This evidence is part of the justification for the "parietofrontal integration theory", which suggests that parietal areas work in concert with prefrontal regions of the brain to accomplish the maintenance and manipulation of information. Orthodoxy holds the prefrontal cortex is more involved than parietal cortex in information manipulation (eg).
However, some have suggested that the spatial transformations…
Visual perception is constantly challenged by visual occlusion: objects in our environment constantly obscure one another, and seem to "disappear" when in fact they are nonetheless present.
Young infants begin to demonstrate a basic understanding of "object permanence" at some point during the first six months of life. On more complex tasks, understanding of object permanence is not observed until months later, as in Piaget's A-Not-B task. Even in these more demanding tasks, however, some understanding of object permanence can be revealed by the direction in which children gaze: kids will…
An absence of evidence is not itself evidence for the absence of a particular effect. This simple problem - generally known as the problem of null effects - yields many difficulties in cognitive science, making it relatively easier to parcellate cognitive and neural processes into ever-finer detail than to show when two processes are identical. Recently, this problem has emerged for the wonder child of cognitive science, functional magnetic resonance imaging (fMRI). The problem in this case is how to determine whether two tasks recruit at least one of the same areas of the brain in the…
Is it possible to form and execute motor intentions without being aware of when those intentions were formed? Precisely this pattern was observed by among (ha!) patients with parietal damage, as reported by Sirigu et al. They showed that patients with parietal damage are specifically impaired at estimating the time they formed the intention to commit a voluntary action, although they are unimpaired on other visual and temporal aspects to the task relative to healthy controls and to patients with cerebellar damage.
The authors argue that intentions formed in prefrontal cortex may be used…
Ideally, our real-world behavior is strongly determined by our context, for the simple reason that some behaviors are only appropriate in some situations (e.g., eating during an internal context of hunger, or using slang during an external context of casual interaction).
Context-inappropriate behavior is often seen as a failure of cognitive control (e.g., continuing to eat when no longer hungry, or using a common slang phrase in a formal setting).
This perspective is called "context processing," based on work pioneered by Todd Braver, Dianna Barch, Jon Cohen, and others. This framework is…
Parietal cortex is critical for the maintenance of object information over delays. This is true both in tests of working memory (e.g., 1, 2 and 3) as well as simple visual manipulations involving the occlusion of visible objects.
A great example is this study by Olson et al., who demonstrated that neurons in human intraparietal sulcus (IPS) and middle temporal (MT) cortex increased their activity in response to objects which disappeared due to occlusion (i.e., they were hidden behind another object) relative to those which simply disappeared without an occluder. This was particularly…
Andersen et al discuss both the attentional and intentional aspects to the function of the intraparietal sulcus. What's the distinction between attention and intention?
First, let's talk about attention. The modal view, based on the biased competition model of Desimone and Duncan, and the Miller & Cohen model presented yesterday, is probably that prefrontal regions actively bias particular spatial locations, as represented in parietal cortex, in accord with the current task or goal.
However, some evidence apparently conflicts with this modal view: Anderson et al. review two studies…
People often use the concept "hand-eye coordination" without appreciating its neural basis. Evidence collected by Andersen & colleagues over the past ten years indicates that different areas of parietal cortex are recruited to represent targets which require different effectors, all using a common eye-based coordinate system. Thus these areas are precisely those which contribute to "hand-eye coordination."
In a 1999 issue of Science, Batista, Buneao, Snyder & Andersen reported that 84% of neurons recorded from the "parietal reach region" of 3 macaques showed a peculiar pattern of…
In their already-classic 2001 article, Miller & Cohen use a "train track" metaphor to illustrate the function of prefrontal cortex. The idea is that myriad learned associations interconnect sensory representations with motor commands (metaphorically, these are the "train tracks"). The important associations will change depending on the animal's current task (these are the "switching stations" which allow crossover between the train tracks). Thus, the role of prefrontal cortex is to bias activity in the brain (the "train") to undergo the sensory-motor transformations which are task- and…
To enhance any system, one first needs to identify its capacity-limiting factor(s). Human cognition is a highly complex and multiply constrained system, consisting of both independent and interdependent capacity-limitations. These "bottlenecks" in cognition are reviewed below as a coherent framework for understanding the plethora of cognitive training paradigms which are currently associated with enhancements of working memory, executive function and fluid intelligence (1,2, 3, 4, 5, 6, 7, 8, 9,
10, c.f. 11, 12, 13).
By far, the most common complaint about limitations in cognition is…
Most readers of this blog are probably familiar with "unilateral neglect," one of several behavioral manifestations of brain damage to the parietal lobe. Perhaps fewer readers are aware of other findings from unilateral neglect patients which are often omitted from classic descriptions of this syndrome.
First, the obligatory illustration of unilateral neglect; here's what happens when you ask a patient with right parietal lobe damage to copy a simple drawing of a clock and a flower:
Patients with this "unilateral" or "hemispatial" neglect are able to describe only those parts of a mental…
How would an ideal behavioral method for cognitive enhancement actually affect the brain? Perhaps cognitive enhancement would be accompanied by more activity in the prefrontal cortex, indicating more successful engagement of control - or perhaps by less, indicating more efficient processing? Perhaps it would be accompanied by a transition from prefrontal activation to parietal activation, suggesting more automatic processing of task information. Perhaps it would make representations in prefrontal cortex more abstract and generalizable, or perhaps it would cause representations there to…
Training high-level cognition or "executive function" is not always successful. Interestingly, some of the least robust training effects come from one of psychology's most robust paradigms - the Stroop task.
The Stroop task is simple to describe, but difficult to complete. In its simplest form, subjects must name the ink color in which a word is written but ignore potentially conflicting information from the meaning of the word itself. This typically results in three types of trials: neutral trials (where word meaning is irrelevant to the ink color"LOT"), incongruent trials (where word…