cognitive neuroscience
mixingmemory | April 17, 2008Last month, a paper was published in Nature, in which Kay et al(1) were able to guess which of their stimuli a person was seeing by looking at their fMRI scans. The model looked something like this (from Kay et al's Figure 1, p. 352):
The image the participant is seeing is on the left, the numbers in the middle represent receptive fields, and the predicted brain activity is on the right. Just compare the predicted brain activity for each image to actual brain activity, and whichever matches the best is the image the person was viewing when they produced that brain activity. Simple, right?…
developingintelligence | April 10, 2008Peter Hankins has written an excellent commentary criticizing the "positive comparisons" I make after contrasting brains with computers.
Peter says:
"... the concept of processing speed has no useful application in the brain rather than that it isn't fixed."
While this statement may intuitively appeal to some philosophers, temporal limitations in neural processing are both critical for neuronal function and well accepted in both neuroscience and psychometrics. At the biological level, the membrane capacitance of neurons is important for regulating the firing rate of neurons, which itself has…
mixingmemory | March 20, 2008You know, just the other day, on this very blog, I swore I would never read another (cognitive) imaging paper again, but between then and now, I've read 5 of 6, so apparently my oath didn't take. It's sort of like my constantly telling myself, as I ride the bus to campus in the morning, that I'm going to stop drinking coffee. As soon as I get off the bus, I walk 30 or so feet to the little coffee stand where they have my 16 oz. coffee waiting for me, 'cause they know as well as I do that I ain't quittin'. Cognitive neuroscience is like coffee.
Anyway, one of the imaging papers I've read since…
mixingmemory | March 16, 2008That's it! I'm never reading another imaging paper again, ever. OK, I might read one or two, and I might even post about them, but for now I'm telling myself, for my own sanity, that I'm never, ever, under any circumstances, going to read another imaging study. If you read my last post, or have been hanging around here for a while, you may have realized that I'm not a big fan of cognitive neuroscience. More often than not (I'd argue, always), you can learn the same thing and more by doing behavioral studies, and in most cases it'll cost you several hundred dollars less per participant. For…
developingintelligence | February 25, 2008How does the human brain construct intelligent behavior? Computational models have proposed several mechanisms to accomplish this: the most well known is "Hebbian learning," a process mathematically similar to both principal components analysis and Bayesian statistics. But other neural learning algorithms must exist - how else could the brain disentangle mere correlations from true causation?
Temporal precedence helps to some extent - and does seem to play a large role in Hebbian learning (e.g., spike-timing dependent plasticity). But the smell of rain does not actually cause rain -…
developingintelligence | February 14, 2008Well, it's not quite as erotic as it sounds, but they could break the ice on more than a few Valentine's dates. Hayward's new article in Brain Research Bulletin describes all known tactile illusions. Some can be tried easily at home, but can work better when your gaze is averted and if someone else is performing these illusions on you (to reduce proprioceptive feedback):
The Aristotle: an object touched with crossed fingers will sometimes be identified as two objects (try it on your nose)
Comb: With a comb and a pencil, lay your index finger along the ends of the comb's teeth; use the pencil…
developingintelligence | February 11, 2008Caffeine is the most widely used stimulant in the world, but few use it to maximal advantage. Get optimally wired with these tips.
1) Consume in small, frequent amounts.
Between 20-200mg per hour may be an optimal dose for cognitive function.
Caffeine crosses the blood-brain barrier quickly (owing to its lipid solubility) although it can take up to 45 minutes for full ingestion through the gastro-intestinal tract. Under normal conditions, this remains stable for around 1 hour before gradually clearing in the following 3-4 hours (depending on a variety of factors).
A landmark 2004 study…
developingintelligence | February 5, 2008We often assume that true understanding is conveyed through spoken speech rather than gesture, but new research shows that "talking with your hands" can not only reveal different information than spoken language, it can be both more correct and yield better learning.
Goldin-Meadow and colleagues have previously shown that spontaneous gesture during speech contains a form of implicit knowledge - knowledge that cannot be verbally reported, but nonetheless affects performance. Similar phenomena are known as knowledge-action dissociations; for example, in Piagetian conservation tasks, children…
developingintelligence | January 11, 2008One of the bottlenecks in human memory capacity is its "filtering efficiency" - irrelevant information in memory only detracts from an already-constrained memory span. New work by McNab & Klingberg images the neural structure directly responsible for such filtering, and shows it can predict behavioral measures of memory span. Impressively, the location of this "memory filter" is the globus pallidus, as predicted by a computational network model of cortex, but in contrast to that model, it shows functional correlations with parietal in addition to frontal areas. This work has immediate…
developingintelligence | January 10, 2008A new educational system called "Tools of the Mind" teaches not facts and figures, but rather focuses on cognitive skills in structured play. In the largest and most compelling study yet, exposure to this curriculum in the classroom drastically improves performance on a variety of psychometric and neuropsychological tests.
Vygotskian theory posits that children need to "learn to learn" - by mastering a set of mental tools which bootstrap their mental abilities, the same way that physical tools can extend physical abilities. The consequent "mental exercise" may strengthen the mind just like…
developingintelligence | January 7, 2008A continuing challenge in cognitive neuroscience is determining which neural structures are actually responsible for certain thoughts and behaviors. For example, fMRI and other neuroimaging techniques cannot tell us if a certain region of visual cortex is necessary for perceiving motion, or if it is merely coactivated whenever motion is perceived. Such distinctions are both particularly important and particularly difficult to achieve in domains thought to be uniquely human: we cannot simply lesion human brains and observe the consequences as we can with animals trained to perform lower-…
developingintelligence | December 31, 2007Originally posted on 12/16 2006:
The term "executive function" is frequently used but infrequently defined. In attempting to experimentally define executive functions in terms of their relationship to age, reasoning and perceptual speed, Timothy Salthouse reviewed the variety of verbal definitions given to construct of "executive function." Although these differ in terminology and emphasis, they are clearly addressing a similar concept:
"Executive functions cover a variety of skills that allow one to organize behavior in a purposeful, coordinated manner, and to reflect on or analyze the…
developingintelligence | December 13, 2007If you encounter a difficult situation, you may be extra careful afterwards, even in a different or unrelated situation. This intuitive statement has recently been confirmed in a laboratory task, and extended to show that such carry-over "conflict adaptation" effects may affect the speed with which you approach subsequent tasks very differently from how it affects the probability of making a mistake.
A task often used to look at conflict is the flanker task: when subjects must respond to an arrow symbol that is surrounded by other arrow symbols, responses will be faster when the surrounding…
Dispute Over the Canonical Cortical Circuit: Structure-Function Dissociations in the Cortical Column
developingintelligence | December 10, 2007Is there a basic "computational unit" of the neocortex? In contrast to subcortical regions, neocortical architecture seems fairly regular and matrix-like - leading to it's other name, "isocortex." While there are many contenders for the title of the "canonical circuit" or "cortical algorithm", few would dispute that cortical columns are a fundamental organizational principle of cortex.
Or wouldn't they? In their new Neuron article, Douglas & Martin's argue that the cortical column is a poor contender for identifying the cortex's "canonical circuit." They describe how the anatomical…
developingintelligence | December 4, 2007How does memory help to accomplish moment-to-moment goal-directed action? Classic accounts, such as Baddeley's working memory model, suggest that there are separate storage and processing ("executive") mechanisms, whereas newer accounts (proposed by a variety of researchers) propose that storage and processing are intertwined in the form of maintained goal or context representations.
According to these newer theories, individual differences in the strength of goal representations can more or less efficiently "bias" perception and behavior, particularly in cases where habit or environmental…
developingintelligence | December 3, 2007Your IQ can be reliably predicted by simple reaction time tasks - perhaps even more reliably than with much more complex cognitive tasks. This surprising psychometric fact has led to the belief in human "processing speed." In the same way that a computer with a faster microprocessor might carry out more computations, with potentially less demand on memory, the idea is that brains with better neuronal efficiency also manifest both higher IQ and proportionately faster reaction times even in simple tasks.
To me, this story always seemed "too good to be true" - or perhaps merely "too simple to…
developingintelligence | November 29, 2007The world wide web can be understood as a giant matrix of associations (links) between various nodes (web pages). At an abstract level, this is similar to human memory, consisting of a matrix of associations (learned relationships, or neuronal connections) between various nodes (memories, or the distributed representations constituting them). In the new issue of Psych. Science, Griffiths et al. ask whether Google's famously accurate and fast PageRank algorithm for internet search might behave similarly to the brain's algorithm - whatever that might be - for searching human memory.
About…
developingintelligence | November 29, 2007The ability to actively maintain more information in memory, known as "working memory," seems to benefit performance in a variety of tasks. One idea is that these tasks require controlled attention, allowing for better control over behavior.
But there's a serious problem with this explanation: maybe this doesn't reflect improved control so much as superior motivation. In other words, maybe subjects with higher working memory are the only ones who care, and everyone else is just goofing off!
Thankfully, there are some cases where additional working memory has no benefit - or can even be a…
developingintelligence | November 16, 2007Neuroesthetics seeks to identify the neural basis of aesthetic experience - how does the brain give rise to the perception of beauty? A new paper in Network indicates that artists consistently create works which contain the same statistical properties as natural scenes, even when the objects being depicted do not themselves contain such statistics when photographed.
Redies, Hanisch, Blickhan and Denzler review previous work demonstrating that the "spatial frequencies" of natural scenes (essentially, their spatial complexity) follow a 1/f power spectrum, where increased spatial complexity is…
developingintelligence | November 7, 2007Speech recognition remains a daunting challenge for computer programmers partly because the continuous speech stream is highly under-determined. For example take coarticulation, which refers to the fact that the auditory frequencies corresponding to a given letter are strongly influenced by the letters both preceding and following it - sometimes interpreted to mean that there is no invariant set of purely auditory characteristics defining any given letter. Thus it's difficult to recover the words that a person is saying, since each part of that word is influenced by the words surrounding it…