cognitive neuroscience
developingintelligence | March 13, 2007Some theories suggest that color and shape information - processed in different parts of the brain - must be integrated by attention in order to give rise to a coherent visual experience (in other words, attention is thought to solve the "binding problem"). Although that explanation is probably not satisfying to many, no doubt mostly because attention itself is an ill-defined construct, at least it's a beginning in solving the binding problem. However, a recent article from Allen, Baddeley & Hitch argues that even this humble claim may be entirely wrong.
Allen et al. suggest that the…
developingintelligence | March 9, 2007"Simplicity is the ultimate sophistication." - Leonardo Da Vinci
"The aim of science is to seek the simplest explanation of complex facts. We are apt to fall into the error of thinking that the facts are simple because simplicity is the goal of our quest. The guiding motto in the life of every natural philosopher should be ``Seek simplicity and distrust it.'' - Alfred North Whitehead
No one ever said the brain was going to be simple - and this is precisely why there is a need to use simple tasks in cognitive neuroscience; even the "simplest" tasks may be subserved by bewildering complex…
developingintelligence | March 8, 2007The infamous "binding problem" concerns how a coherent subjective experience of the world can emerge from the widely-distributed processing of individual object characteristics (for example, object identity and object spatial locations appear to be processed by independent neural systems). It is clear that binding requires focused attention (at least, according to "Feature Integration Theory"), but the specific mechanism by which attention binds remains elusive. Partly because of this, Baddeley has even revised the standard model of working memory to include an "episodic buffer" for binding…
developingintelligence | March 7, 2007According to artificial neural network models that implement lateral inhibition, activation and inhibition are two sides of the same coin. These models often assume that patterns of activation compete with one another. In other words, in a given space of neural tissue (or "layer" in network terms), some particular pattern will become most active. This pattern will effectively suppress the emergence of other patterns through lateral inhibition; other patterns are less likely to emerge if the current dominant pattern is very strongly represented.
This assumption of "competition for…
developingintelligence | March 6, 2007Prospective memory involves remembering to remember - in other words, successfully executing a planned intention after having completed an unrelated task. If computational models of prospective memory (PM) are to be believed, then PM relies on many of the same mechanisms involved in a huge variety of other tasks. For example, the successful execution of a planned action should rely on the intention being strongly represented in the first place, as well as good retrieval of the intention from memory. In turn, these should both relate to the strength of active maintenance processes in…
developingintelligence | March 5, 2007To what extent is music like language? Previously, I've reviewed how music and language share semantic characteristics, at least insofar as similar scalp electrical activity follows incongruent musical passages as follows incongruent words. But is it also possible that music has grammar, just like language?
In the context of language, ungrammatical words are often accompanied by a sharp rise in scalp electrical activity, around 600 milliseconds after the grammatical violation. This is known as the P600, or sometimes as the syntactic positive shift (SPS). Because this scalp electrical…
developingintelligence | March 1, 2007Cognitive theories of "executive function" vary greatly in the number of distinct cognitive processes they propose to subserve the goal-directed coordination of behavior. Some theories suggest that strong active maintenance of information, and a way of "updating" the information that is maintained, is sufficient to explain performance on executive function (EF) tasks, which typically require careful control over behavior. Other theories propose that a process of "inhibition," distinct from updating and maintenance, must also exist. And then there are those theories that propose yet other…
developingintelligence | February 28, 2007Yesterday I was invited to give this 15-minute presentation (PPT, PDF) to LearningRX about recent perspectives on working memory limitations, and their potential for informing cognitive training and enhancement programs.
In case you're curious, here's a list of references:
Baddeley, A. D. (1986) Working Memory. Oxford University Press.
Broadbent, D.E. (1975), The magic number seven after fifteen years. In A. Kennedy and A. Wilkes (eds.), Studies in Long-Term Memory, New York: Wiley, 3-18.
Duncan J, Emslie H, Williams P, Johnson R, Freer C (1996) Intelligence and the frontal lobe: the…
developingintelligence | February 26, 2007Memory, defined as "any lasting effect of experience," is an overly broad term. Those with damage to the hippocampus lose their long-term memory but retain the ability to maintain conversations (at least for short periods of time). But new perspectives on the nature of short-term or "working" memory suggests that such a neat division between memory systems is overly simplistic.
In the current issue of Psychological Review, Unsworth & Engle argue that working memory is best understood as an "override" mechanism serving two functions: 1) the active maintenance of novel or important…
developingintelligence | February 21, 2007Findings in the laboratory do not always apply to the real-world - a myriad of factors can influence real-world phenomena, and scientists actively seek to eliminate many of them in their laboratories. But ecological validity can be particularly difficult to establish in cognitive science, where real-world levels of motivation, stress, and memory load can not always be practically (or ethically) simulated in the laboratory.
Ecological validity may be particularly important in tests of prospective memory - the ability to remember to perform a planned future action. One salient example: young…
developingintelligence | February 20, 2007In the middle of the work day, you realize you'll need to stop at a store on your way home from work. Your ability to actually do so, hours later, relies on what some psychologists call "prospective memory." Although prospective memory is clearly important for human intelligence, very little is known about how it works.
Clearly there are at least two kinds of prospective memory. In the example above, you may tell yourself "stop at the store" again and again until you pull into the store's parking lot - this is known as a vigilance or monitoring strategy. Or the store may simply catch your…
developingintelligence | February 19, 2007The distributions of reaction times are always positively skewed, which seems to reflect two independent processes: a normal gaussian distribution of reaction times, in addition to an exponentially-decaying distribution of a few very long trials. Measures of this reaction time (RT) variability show surprisingly strong correlations with fluid intelligence, and have been interpreted to reflect things as diverse as goal neglect, overly liberal updating of working memory, erratic bursts of dopamine release, or tonically elevated levels of noradrenaline. But these explanations are not mutually…
developingintelligence | February 16, 2007How do the symptoms of ADHD relate to the circuitry underlying executive function and working memory? An in-press article at Neuropsychopharmacology investigates the roles of dopamine and norepinephrine in ADHD, with evidence from both behavioral and simulated experiments. This post will make more sense if you've read my previous posts on norepinephrine and dopamine.
Frank, Santamaria, O'Reilly & Willcutt review evidence that ADHD can be characterized by low dopamine levels in the basal ganglia, resulting from abnormally high levels of dopamine transporters. Recent work suggests that…
developingintelligence | February 15, 2007Dopamine is probably the most studied neurotransmitter, and yet the neuroscience literature contains a huge variety of perspectives on its functional role. This post summarizes a systems-level perspective on the function of dopamine that has motivated several successful drug studies and informed the construction of artificial neural network models. The details of this perspective are maddeningly complex (at least for me), which is why I thought it would be useful to summarize it here, in the simplest terms possible.
There are at least two ways to talk about dopamine release. We can talk…
developingintelligence | February 14, 2007In a 2006 Psychopharmacology article, Niv et al. suggest that while transient dopamine release is frequently modeled computationally (as encoding reward-prediction error, for example, or as gating information into working memory) the role of more constant dopamine release is not. In the neuroscience literature, these two patterns of release are known as "phasic" and "tonic," respectively.
The authors argue that current models of dopamine release have three major shortcomings: first, they do not explicitly address the effect of dopamine manipulation on response latency or "vigor"; second,…
developingintelligence | February 13, 2007According to some perspectives, anterior cingulate cortex (ACC) may become activate in situations where the reward value of given representation or stimulus has decreased, resulting in more competition between representations. Activation of this region may help increase tonic norepinephrine, resulting in more exploratory behavior, and thus more variable responding.
A different perspective on ACC is advocated in this 2001 article by Braver, Barch, Gray, Molfese and Snyder. They also suggest that ACC is important for resolving conflict between multiple responses - and would therefore be…
developingintelligence | February 12, 2007Whereas yesteryear's artificial neural networks models were focused on achieving basic biological plausibility, today's cutting edge networks are modeling cognitive phenomena at the level of neurotransmitters. In a great example of this development, McClure, Gilzenrat & Cohen have an article in Advances in Neural Information Processing Systems where they propose a role for both dopamine and norepinephrine in switching behavior between modes of "exploration" and "exploitation."
First, a little background. In artificial intelligence circles, the "temporal difference" algorithm has been a…
developingintelligence | February 9, 2007Khalil Gibran said that "music is the language of the spirit," but today many would claim it can convey only a general impression or mood. However, recent research has shown that the meaning of musical passages can be surprisingly specific. In their 2004 article, Koelsch et al. demonstrate that even 10-second musical excerpts can build up concrete semantic expectations, the same as short sentences. (I just learned that Cognitive Daily covered this same study yesterday, so I'll try to put a slightly different spin on it in this post.)
Normally, when people hear a sentence followed by an…
developingintelligence | February 8, 2007Intuitively, an adaptive information processing system should deal with unique or unusual information in a special way. For example, an unusual encounter might indicate that an organism's environment is changing, and by implication that there's a new potential for danger. Or novel information can represent a favorable change in circumstances. Either way, a system that takes special notice of infrequent stimuli is likely superior to one that is oblivious to stimulus frequency.
Recent work in the cognitive neurosciences is beginning to shed light on how the brain implements novelty or "…
developingintelligence | February 7, 2007Although "executive function" may seem like an elusive topic for study, in cognitive neuroscience it is largely approached simply as the ability to control one's own behavior in accord with some goal, despite interference from previous experiences. Central to many accounts of executive function is the ability to "cancel" or "inhibit" actions that are not currently appropriate - this is the same capacity that is said by many to deteriorate with age, with alcohol, with the onset of ADHD, and to be under-developed in young children. Despite the utility of "inhibition" as an explanatory…