cognitive neuroscience
developingintelligence | February 6, 2007Humans are notoriously finicky decision makers, and new research is beginning to elucidate the neural networks that are responsible. For example, we are exquisitely sensitive to framing effects regardless of whether two decisions have mathematically equivalent value - a previous post reviews how this framing effect may arise in the brain. Another famous example is delay of gratification: often we are willing to accept less of something now rather than wait for more of it later. Today's post summarizes a recent article that begins to explain why.
In their 2004 article, authors McClure,…
developingintelligence | February 5, 2007What cognitive processes make up consciousness? One way of answering this question is to identify conscious processes as those involved in controlled but not in automatic behaviors. For example, if you see a bright dot appear in your field of vision, your eyes will automatically orient to that location in space. In contrast, if I have told you to look away from any bright dots that appear in your field of view, you will be able to do this - but only because you possess consciousness in the form of "cognitive control." So, what computations support "cognitive control"?
Cognitive control is…
developingintelligence | February 2, 2007To the extent that the cognitive sciences actually consider the brain, the focus is clearly on neurons. Even the name of the field "neuroscience" suggests that neurons take the center stage. However, neurons are vastly outnumbered by glia, a different type of cell that is now known to be involved in sleep, memory, the fMRI signal, Alzheimer's and Parkinson's, although many neuroscientists are still resistant to the idea that glia are involved in information processing per se. In a recent review article, Watkins et al. focus on the role of these cells in the experience of chronic pain.…
developingintelligence | February 1, 2007Yesterday I reviewed evidence showing that set switching (e.g., your ability to suddenly switch behaviors) and rule representation (your ability to represent rules in a game, for example), may be distinct processes, at least insofar as they may show distinct developmental trajectories and rely on distinct neural substrates. Today's post will review a new study from Developmental Neuropsychology that also aims to show distinct developmental trajectories for set switching and rule maintenance, and how these claims hold up to a deeper analysis.
Huizinga & van der Molen administered four…
developingintelligence | January 30, 2007If a large object were to suddenly disappear from your field of view, you might expect that you would notice its disappearance. However, change detection research has demonstrated that we have a surprisingly poor ability to detect even large changes to a visual scene (see here and here for examples).
Skeptics might complain that this "change blindness" could simply result from absent-mindedness: maybe you happened not to notice the changing feature. A 2002 article by Becker and Pashler actually rules out this explanation - indicating that our internal visual representations may indeed be as…
developingintelligence | January 29, 2007If presented with a novel and a familiar object, infants strongly prefer to touch and look at novel objects. However, if these objects are then obscured - in the dark, or by an occluding screen - infants tend to reach more in the direction of the familiar objects. Some argue that the familiar objects are represented more strongly by neural networks, whereas the relatively weaker representations of novel objects are more likely to decay in the absence of sensory input, and thus less likely to motivate an infant's reach.
Similar mechanisms may exist in adults. A review of the literature…
developingintelligence | January 26, 2007Yesterday I reviewed several detailed architectural asymmetries between the right and left hemispheres, but presented little information on asymmetries in long-range connectivity. Recent advances in a form of magnetic resonance imaging called "diffusion tensor MRI" have made possible whole-brain imaging of white matter tracts, which are important for long-range connectivity in the brain. So, how has this technology refined the study of hemispheric structural asymmetry?
First, the basics: dtMRI analyzes the "fractional anisotropy" of water in tissue: in other words, it demonstrates the…
developingintelligence | January 25, 2007 In their 2003 Trends in Neurosciences article, Hutsler & Galuske refer to the well-known history of hemispheric asymmetry research as too focused on large-scale morphological differences, at the expense of microanatomical and connectivity differences. An understanding of these more detailed structural differences might translate into a more detailed understanding of hemispheric differences in computation and function.
Hutsler & Galuske identify three levels of structural analysis in cerebral cortex: the microcolumn, the macrocolumn, and the functional column. Microcolumns contain…
developingintelligence | January 24, 2007"Imagine that the U.S. is preparing for the outbreak of an unusual Asian disease, which is expected to kill 600 people. Two alternative programs to combat the disease have been proposed." The first program will save 200 people. The second program has a 33% probability of saving all 600 people, but a 67% chance that no one will be saved. Which program would you choose?
If you're like most people, you'll pick the first program. However, if these choices had been framed in terms of losses (i.e., 400 people will die in the first program, where the second program has a 33% chance that no one…
developingintelligence | January 23, 2007Although grammar is usually considered the "uniquely human" aspect of language, and the capacity to use primitive symbols is thought to be common among primates, high-level cognition is nonetheless strongly impacted by the use of symbols. For example, symbols can help in putative inhibition tasks; labeling a stimulus-response relationship can result in increased proactive interference when the correct response changes; and providing infants with unique object labels allows them to demonstrate knowledge they wouldn't otherwise demonstrate for several months.
One hypothesis about the role of…
developingintelligence | January 19, 2007Although even the youngest infants have some ability to remember the past, this ability increases in both its reliability and its "temporal extent" with age. Such differences could result from changes in any of memory's constituent processes, including encoding, consolidation, or retrieval. Although this week's posts have focused on the idea that source monitoring difficulties underlie the apparent loss of early memories (i.e., a difficulty in retrieval), Bauer's 2006 TICS review emphasizes emerging evidence that encoding and storage or consolidation are also to blame.
Bauer has argued that…
developingintelligence | January 18, 2007Yesterday I outlined a few reasons to think that we may not actually forget all of our earliest memories; instead, they may merely be mislabeled due to a failure of source monitoring. According to a 2002 article by Drummey and Newcombe, a similar problem may underlie childhood amnesia - the fragmentary nature of autobiographical memory prior to age 6.
Failures of source monitoring are more frequent in patients with brain damage to the frontal cortex (and may be especially reliant on the right frontal lobe). Just like these frontal patients, preschool-aged children have a prefrontal cortex…
developingintelligence | January 17, 2007Freud famously suggested that infantile amnesia is an active suppression of early traumatic memories. However, a review of the modern cognitive literature suggests that at least in some ways, infantile amnesia may actually be a myth.
Perhaps the most intuitive explanation of infantile amnesia is simply that the infant's brain is not sufficiently developed to support episodic memory. However, substantial evidence argues against this view. For example, the same factors that affect episodic memory in adults also affect infant memory, including age, retention interval, context change,…
developingintelligence | January 12, 2007The cognitive science of hemispheric asymmetry has long been marred by drastic over-simplification. The left/right distinction has been associated with dichotomies like rational vs. emotional, specific vs. holistic, and analytical vs. synthetic. Such differences are much more graded than dichotomous, to the extent that they exist in the first place. So, before reviewing well-established kinds of hemispheric differences, it might be useful to dispel some "lateralization mythology."
First, although the left hemisphere is generally dominant in linguistic tasks, the right hemisphere also has…
developingintelligence | January 11, 2007As enigmatic as prefrontal function seems to be, the anterior portions of prefrontal cortex (aPFC) are even more mysterious. This results partly from the fact that aPFC is particularly difficult to access and study electrophysiologically in nonhuman primates, as Ramnani and Owen note in their 2004 Nature Reviews Neuroscience article, and so detailed neuroanatomical investigations of aPFC have been conducted only recently. The authors report how this work has led to a breakthrough in the understanding of aPFC's computations.
Ramnani and Owen review Brodmann's early analysis of aPFC, also…
developingintelligence | January 10, 2007As described in yesterday's post, many theories have been proposed on the possible functional organization of prefrontal cortex (PFC). Although it's clear that this region plays a large role in human intelligence, it is unclear exactly "how" it does so. Nonetheless at least some general conclusions on prefrontal computation can be made.
A reasonably uncontroversial view is that prefrontal cortex maintains over time representations that integrate sensori-motor with current goal and context information, and that this active maintenance biases processing elsewhere in the cognitive system in…
developingintelligence | January 9, 2007Although much progress has been made since neurologist Richard Restack called the brain one of science's last frontiers, the functions of some brain areas remain mysterious. Foremost among these is prefrontal cortex (PFC), a region that is much reduced in size in most other primates, is among the last areas to develop in human children, and yet is active in almost every cognitive task.
In general, prefrontal cortex is associated with higher-order cognition, such as those processes involved in planning, strategizing, self-monitoring, self-regulation, and more generally, the coordination of…
developingintelligence | January 3, 2007The prefrontal cortex is a major recipient of subcortical dopaminergic projections. Accordingly, almost all of the behavioral tasks that are known to critically depend on the prefrontal cortex are sensitive to dopamine levels. A curious exception is the Self Ordered Pointing task (SOPT), in which subjects must select each of 9 designs by pointing at each one once; after each selection, the locations of the designs are randomized. Therefore, in order to succeed at this task subjects must remember the designs themselves and not the locations to which they pointed.
The dorsolateral…
developingintelligence | January 2, 2007It seem reasonable that evolution might select for adaptive behaviors by increasing the relative size of particular brain regions that support those behaviors; for example, bats might have an enlarged auditory cortex since they navigate with echolocation. To some extent this does happen, but such differences are often apparent only after controlling for a much larger source of variance: changes in brain size that correlate with changes in body size - and the implications of this fact are wide-reaching.
As Barbara Finlay and coauthors wrote in this 2001 Behavioral and Brain Sciences article,…
developingintelligence | December 29, 2006While subjects are generally faster to respond to a stimulus if it is presented at a previously "cued" location, they are paradoxically slower to respond if the spatial "cue" occurred more than 300 ms beforehand. This strange phenomenon is known as inhibition of return (IOR), and is thought to result from the reflexive "suppression" of previously-attended locations in space. IOR can be considered an adaptive characteristic of neural information processing, in that IOR ensures that the environment is being constantly searched for new information.
It turns out that IOR may have other…