cognitive neuroscience
developingintelligence | November 5, 2007Aging is associated with some slow but measurable forms of cognitive decline, but there is debate over the type of cognitive changes taking place. A recent study by Rush, Barch & Braver uses a series of interesting tasks to clarify the nature of this cognitive decline. The results seem to show that changes in "context processing" - the ability to internally represent environmental cues to control thought and action - but not inhibition or processing speed underlie aging-related decrements in cognitive function. The work has implications for our understanding of and interventions for…
developingintelligence | November 2, 2007Trueswell & Kim's paper in the Journal of Memory and Language describes a phenomenon known as "fast priming," in which a reading task is momentarily interrupted by a brief presentation of a "prime" word, usually lasting around 30 to 40 ms. The reading task then continues, and although subjects are typically unaware of the presentation of this word (usually describing it merely as a "flicker") the processing of subsequent words are influenced by many characteristics of the prime word, including its meaning as well as its sonic and orthographic characteristics.
Al Fin has an excellent…
developingintelligence | November 1, 2007When one object passes in front of another we know that the occluded object has not vanished, and yet representations in our visual cortex have been assumed not to reflect this information. Instead, such "object permanence" information has been thought to require active maintenance, perhaps with help from prefrontal regions, thus explaining why young children (with underdeveloped prefrontal cortices) often fail to show behavior that is consistent with knowledge of object permanence.
A recent study by Hulme & Zeki elaborates this view by presenting 13 subjects in an fMRI scanner with…
developingintelligence | October 31, 2007Several high-profile studies have shown that bilingual children outperform their monolingual peers in terms of several cognitive abilities - including tests of verbal and nonverbal problem-solving, selective attention, flexibility (e.g., task-switching) and others. These studies have captured the public imagination and probably guided many moms to expose their kids to a second language.
But a new article in Developmental Science suggests that these impressive results may be somewhat overblown: bilingual children may be likely to come from wealthier families than monolingual children (EDIT:…
developingintelligence | October 30, 2007Synaesthesia involves the inappropriate binding of one perception to another - for example, color-grapheme synaesthetes might perceive the letter "h" to be noticeably red, and are actually slower to identify the letter "h" when it is green than when it is red or gray. This "inappropriate binding" of color to other percepts can be disrupted in synaesthetes through transcranial magnetic stimulation of the parietal lobe.
While interesting, this work does not say much about how binding is accomplished in normal subjects, where various colors and various shapes need to be regularly and…
developingintelligence | October 29, 2007One of the more surprising findings to emerge from the intelligence literature is that an individual's ability to think in highly complex and abstract forms is related to speed in tasks as simple as "press the lighted button." Simple reaction time tasks like this have amazing predictive power for performance on much more elaborate tasks, leading some theorists to propose that such reaction time (RT) measures grossly index the integrity or speed of processing in a way that benefits all tasks.
Interestingly, the average speed on simple RT tasks is often not as predictive as other aspects of…
developingintelligence | September 27, 2007Cognitive scientists are increasingly aware of how individual differences can confound experimental results. That is, differences in group means cannot always be interpreted clearly if, for example, only some subset of individuals in each group demonstrates the effect. Consequently, even the oldest paradigms in cognitive psychology are undergoing a revival with new mixed experimental/correlational methods.
Consider the Stroop effect, studied in detail since the 1930's, which is today understood as reflecting not merely the frequencies of color-word incongruity, but also a dynamic…
developingintelligence | September 25, 2007Say you are writing an email when the phone rings. After the phone call, you return to finish the email. Are you slower to continue writing this email than you would be if you'd been doing something else prior to the phone call? In general, yes - at least according to the finding known as lag-2 repetition cost.
This idea has been tested in an experimental framework by having people perform three tasks (A, B and C) on the same set of stimuli. The critical question is whether you're slower to complete Task A if the previous trial order was A-B than if it was C-B. In general, you are slower…
developingintelligence | September 21, 2007The word "noise" comes from the latin nausea, meaning disgust or annoyance. But in the phenomenon known as stochastic resonance, noise can actually be a good thing: it can serve as a signal amplifier in thresholded systems.
This phenomenon is not nearly as arcane as it sounds. The image above (borrowed from Stein, Gossen & Jones, 2005), clearly shows how two very weak signals can look very similar (top row), but with additional noise, the characteristics of these signals can be more easily dissociated (bottom row; now you can see one signal is generated by a sine, and one generated by…
developingintelligence | September 20, 2007Can information be directed to different networks in the brain depending on the "transmission frequency", like the channels on a TV? A 2006 Cerebral Cortex paper reveals that this may not be as absurd as it sounds.
A relatively new technique in cognitive neuroscience is the use of frequency tagging, where a stimulus (whether visual or auditory) is presented at a certain rapid frequency, perhaps onsetting and offsetting six times per second (6Hz). A second stimulus may be presented at 4.5Hz. The frequencies can then be detected in the brain using magnetic or electric methods (MEG or EEG),…
developingintelligence | September 19, 2007In the "motion standstill" illusion, a rapidly moving object is perceived as motionless, and yet not blurred. This means that color, depth, and shape are accurately processed while the motion system fails: in fact, subjects are no better at detecting the direction of motion than chance.
At slightly different frequencies than those which elicit standstill, subjects can even be below chance at guessing the direction of motion, indicating motion aliasing (also observed in the wagon wheel illusion).
One hypothesis about the mechanism driving this illusion is that the temporal frequency of…
developingintelligence | September 14, 2007The claim that language processing can be carried out by purely "general purpose" information processing mechanisms in the brain - rather than relying on language-specific module(s) - may seem contradicted by a slew of recent neuroimaging studies demonstrating what appears to be a visual "word form" area in the left fusiform gyrus of the temporal lobe. By all appearances, this region is highly specialized for word processing. But this evidence causes a predicament for more than just domain-generalists; those who advocate an evolved language module may also be challenged by these results,…
developingintelligence | September 10, 2007An article in last week's Nature describes a highly experimental - but also highly promising - new treatment for patients who have undergone massive traumatic brain injury.
These patients are typically left in a "minimally conscious" state, showing little to no responsiveness to verbal commands, and little capacity to interact socially.
Schiff and colleagues identified one such patient who, despite having been in this state for nearly 4 years, nonetheless showed largely intact large-scale cerebral networks for processing language (as identified through functional neuroimaging). The authors…
mixingmemory | September 10, 2007Reading an article in the LA Times today, I learned something exciting: political differences in thought happen in the brain. At least that's what a new study published in Nature Neuroscience(1) purports to show, though I hear that the next issue of the journal will contain critical responses from Descartes, Malenbranche, and Eccles.
Seriously though, the paper by Amodio et al. takes as its launching point the large body of evidence that political conservatives and liberals differ on personality dimensions related to openness to experience, tolerance of uncertainty, and cognitive complexity…
mixingmemory | July 2, 2007Apparently so. Recent research has shown that pleasant smells can increase pain tolerance, and a recent paper by Prescott and Wilkie(1) suggests that it is specifically sweet smells that do so. I'll just skip to the experiment, and spare you the background, because the experiment contains all you need to know.
They started with three types of smells: sweet and pleasant (caramel), unsweet and pleasant (after shave), and unpleasant (civet musk, which I hear smells awful). The inclusion of both sweet and unsweet pleasant smells allowed Prescott and Wilkie to distinguish between the analgesic…
developingintelligence | June 28, 2007In 1948, Alan Turing wrote: "An unwillingness to admit the possibility that mankind can have any rivals in intellectual power occurs as much amongst intellectual people as amongst others: they have more to lose." Accordingly, comprehensive comparisons between the intellectual powers of great apes and humans are rare - perhaps because we feel safe in assuming that the human intellect is superior to that of other primates. But recent work suggests this assumption may not be entirely sound, as described below.
For example, a recent New Scientist article (via NeuroEthics) contains a provocative…
developingintelligence | June 27, 2007Though widely separated in terms of both neuroanatomical location and evolutionary development, there are surprising parallels between parietal cortex and the hippocampus:
- Both structures are important for spatial cognition, although parietal cortex is thought to maintain a "self-centered" map of the environment (i.e., where locations are represented relative to the direction of gaze) whereas hippocampus may maintain a "world-centered" or allocentric map (i.e., where locations are represented with respect to landmarks or surrounding geometry).
- Both structures are thought to represent…
developingintelligence | June 26, 2007Can you move a single matchstick to form a valid mathematical statement equation?
No sticks can be discarded, an isolated slanted stick cannot be interpreted as I (one), and a V (five) symbol must always be composed of two slanted sticks. UPDATE: The only valid symbols are Roman numerals and "+", "-" and "=". (Thanks Benjamin!) OK, now try this one:
[solutions here]
If you had trouble with that last puzzle, fear not - it means your frontal lobe is probably intact! Healthy adults are frequently outperformed by patients with frontal brain damage on that test, according to a 2005 study by…
developingintelligence | June 25, 2007Functional magnetic resonance imaging (fMRI) has captured the popular imagination since its introduction in the early 1990s, at least partially because of the stunningly beautiful images it generates. Although it has mostly used to identify brain regions involved in specific cognitive operations, new pattern classification techniques have been applied to fMRI data in what some have called "mind reading technology." These techniques go beyond simply showing which brain areas are more active than others during a particular task to reveal functional relationships among multiple brain areas,…
mixingmemory | June 22, 2007All of you are probably familiar with color opponency, but just in case, I'll give you a quick refresher. I'll even start with the history. In the 19th century, there were two competing theories of color vision. The first was the Young-Helmholtz theory (sometimes called the trichromatic theory), which argued that there were three types of photoreceptors: one for red, one for green, and one for blue. The second was Ewald Hering's color opponency theory, which argued that there were three color pairs: black-white, red-green, and blue-yellow. Each color in the pair canceled out, or inhibited the…