Prefrontal Cortex
Older news items (pre-2010) brought over from the old website
September 2009
New insights into memory without conscious awareness
An imaging study in which participants were shown a previously studied scene along with three previously studied faces and asked to identify the face that had been paired with that scene earlier has found that hippocampal activity was closely tied to participants' tendency to view the associated face, even when they failed to identify it. Activity in the lateral prefrontal cortex, an area required for decision making, was sensitive to whether or not participants had responded correctly and communication between the prefrontal cortex and the hippocampus was increased during correct, but not incorrect, trials. The findings suggest that conscious memory may depend on interactions between the hippocampus and the prefrontal cortex.
Hannula, D.E. & Ranganath, C. 2009. The Eyes Have It: Hippocampal Activity Predicts Expression of Memory in Eye Movements. Neuron, 63 (5), 592-599.
http://www.eurekalert.org/pub_releases/2009-09/cp-ycb090309.php
August 2009
Alcoholics show abnormal brain activity when processing facial expressions
Excessive chronic drinking is known to be associated with deficits in comprehending emotional information, such as recognizing different facial expressions. Now an imaging study of abstinent long-term alcoholics has found that they show decreased and abnormal activity in the amygdala and hippocampus when looking at facial expressions. They also show increased activity in the lateral prefrontal cortex, perhaps in an attempt to compensate for the failure of the limbic areas. The finding is consistent with other studies showing alcoholics invoking additional and sometimes higher-order brain systems to accomplish a relatively simple task at normal levels. The study compared 15 abstinent long-term alcoholics and 15 healthy, nonalcoholic controls, matched on socioeconomic backgrounds, age, education, and IQ.
Marinkovic, K. et al. 2009. Alcoholism and Dampened Temporal Limbic Activation to Emotional Faces. Alcoholism: Clinical and Experimental Research, Published Online: Aug 10 2009
http://www.eurekalert.org/pub_releases/2009-08/ace-edc080509.php
http://www.eurekalert.org/pub_releases/2009-08/bumc-rfa081109.php
June 2009
Study finds autistics better at problem-solving
A study involving 15 autistics and 18 non-autistics, aged 14 to 36 and IQ-matched, has found that while both groups completed patterns in a complex problem-solving test (the widely-used Raven's Standard Progressive Matrices) with equal accuracy, the autistics responded significantly faster, and showed a different pattern of brain activity. Specifically, they showed increased activity in extrastriate areas, and decreased activity in the lateral prefrontal cortex and the medial posterior parietal cortex — suggesting visual processing mechanisms may play a more prominent role in reasoning in autistics. The differences between groups did not appear when participants performed a simpler pattern-matching task.
Soulières, I. et al. 2009. Enhanced visual processing contributes to matrix reasoning in autism. Human Brain Mapping, Published Online June 15.
http://www.eurekalert.org/pub_releases/2009-06/uom-sfa061609.php
May 2009
Brain's problem-solving function at work when we daydream
An imaging study has revealed that daydreaming is associated with an increase in activity in numerous brain regions, especially those regions associated with complex problem-solving. Until now it was thought that the brain's "default network" (which includes the medial prefrontal cortex, the posterior cingulate cortex and the temporoparietal junction) was the only part of the brain active when our minds wander. The new study has found that the "executive network" (including the lateral prefrontal cortex and the dorsal anterior cingulate cortex) is also active. Before this, it was thought that these networks weren’t active at the same time. It may be that mind wandering evokes a unique mental state that allows otherwise opposing networks to work in cooperation. It was also found that greater activation was associated with less awareness on the part of the subject that there mind was wandering.
Christoff, K. et al. 2009. Experience sampling during fMRI reveals default network and executive system contributions to mind wandering. Proceedings of the National Academy of Sciences, 106 (21), 8719-8724.
http://www.eurekalert.org/pub_releases/2009-05/uobc-bpf051109.php
February 2009
Brain activity linked to anticipation revealed
Brain scans of students listening to their favorite music CDs has revealed plenty of neural activity during the silence between songs — activity that is absent in those listening to music they had never heard in sequence before. Such anticipatory activity probably occurs whenever we expect any particular action to happen. In this case, the activity took the form of excitatory signals passing from the prefrontal cortex (where planning takes place) to the nearby premotor cortex (which is involved in preparing the body to act).
Leaver, A.M. et al. 2009. Brain Activation during Anticipation of Sound Sequences. Journal of Neuroscience, 29, 2477-2485.
http://www.eurekalert.org/pub_releases/2009-02/gumc-rcw022509.php
December 2008
Prefrontal cortex activity in poor children like that of stroke victim
An imaging study of 26 normal 9- and 10-year-olds differing only in socioeconomic status has revealed detectable differences in the response of their prefrontal cortex. While not invariant, those from lower socioeconomic levels were more likely to have low frontal lobe response. This is consistent with earlier studies, but is the first to demonstrate the effect when there is no issue of task complexity (the task was very simple; the measure was how fast the child responded to an unexpected novel picture — the response of many from low socioeconomic backgrounds was similar to the response of adults who have had a portion of their frontal lobe destroyed by a stroke). The effect is thought to be due to growing up in cognitively-impoverished and stressful environments, since these have been found to affect the prefrontal cortex in animal studies. Further research is looking into whether these brain differences can be eliminated by training.
Kishiyama, M.M. et al. 2008. Socioeconomic Disparities Affect Prefrontal Function in Children. Journal of Cognitive Neuroscience
http://www.eurekalert.org/pub_releases/2008-12/uoc--esb120208.php
September 2008
Patients who recover well from head injury 'work harder' to perform at same level as healthy people
People who make a full recovery from head injury often report "mental fatigue" and feeling "not quite the same" – even though they scored well on standard cognitive tests. Now brain imaging reveals that even with recovered head injury patients performing as well as matched controls on a series of working memory tests, their brains were working harder — specifically, showing more activity in regions of the prefrontal cortex and posterior cortices. All the patients had diffuse axonal injury, the most common consequence of head injuries resulting from motor vehicle accidents, falls, combat-related blast injuries, and other situations where the brain is rattled violently inside the skull causing widespread disconnection of brain cells.
Turner, G.R. & Levine, B. 2008. Augmented neural activity during executive control processing following diffuse axonal injury. Neurology, 71, 812-818.
http://www.eurekalert.org/pub_releases/2008-09/bcfg-pwr090308.php
April 2008
Intelligence and rhythmic accuracy go hand in hand
And in another perspective on the nature of intelligence, a new study has demonstrated a correlation between general intelligence and the ability to tap out a simple regular rhythm. The correlation between high intelligence and a good ability to keep time, was also linked to a high volume of white matter in the parts of the frontal lobes involved in problem solving, planning and managing time. The finding suggests that the long-established correlation of general intelligence with the mean and variability of reaction time in elementary cognitive tasks, as well as with performance on temporal judgment and discrimination tasks, is a bottom-up connection, stemming from connectivity in the prefrontal regions.
Ullén, F. et al. 2008. Intelligence and variability in a simple timing task share neural substrates in the prefrontal white matter. The Journal of Neuroscience, 28(16), 4238-4243.
http://www.eurekalert.org/pub_releases/2008-04/ki-iar041608.php
August 2007
Maturity brings richer memories
New research suggests adults can remember more contextual details than children, and that this is related to the development of the prefrontal cortex. While in a MRI scanner, 49 volunteers aged eight to 24 were shown pictures of 250 common scenes and told they would be tested on their memory of these scenes. In both children and adults, correct recognition of a scene was associated with higher activation in several areas of the prefrontal cortex and the medial temporal lobe when they were studying the pictures. However, the older the volunteers, the more frequently their correct answers were enriched with contextual detail. These more detailed memories correlated with more intense activation in a specific region of the PFC. A number of studies have suggested that the PFC develops later than other brain regions.
The report appeared in the August 5 advance online edition of Nature Neuroscience.
http://www.eurekalert.org/pub_releases/2007-08/miot-msm080107.php
June 2007
Brain's voluntary chain-of-command ruled by not 1 but 2 captains
Previous research has shown a large number of brain regions (39) that are consistently active when people prepare for a mental task. It’s been assumed that all these regions work together under the command of one single region. A new study, however, indicates that there are actually two independent networks operating. The cingulo-opercular network (including the dorsal anterior cingulate/medial superior frontal cortex, anterior insula/frontal operculum, and anterior prefrontal cortex) is linked to a "sustain" signal — it turns on at the beginning, hums away constantly during the task, then turns off at dorsolateral prefrontal cortex and intraparietal sulcus) is active at the start of mental tasks and during the correction of errors. The findings may help efforts to understand the effects of brain injury and develop new strategies to treat such injuries.
Dosenbach, N.U.F. et al. 2007. Distinct brain networks for adaptive and stable task control in humans. Proceedings of the National Academy of Sciences, 104 (26), 11073-11078.
http://news.wustl.edu/news/Pages/9639.aspx
March 2007
Prefrontal cortex loses neurons during adolescence
A rat study has found that adolescents lose neurons in the ventral prefrontal cortex in adolescence, with females losing about 13% more neurons than males. Human studies have found gradual reductions in the volume of gray matter in the prefrontal cortex from adolescence to adulthood, but this finding that neurons are actually dying is new, and indicates that the brain reorganizes in a very fundamental way in adolescence. The number of neurons in the dorsal prefrontal cortex didn’t change, although the number of glial cells increased there (while remaining stable in the ventral area). The finding could have implications for understanding disorders that often arise in late adolescence, such as schizophrenia and depression, and why addictions that start in adolescence are harder to overcome than those that begin in adulthood.
Markham, J.A., Morris, J.R. & Juraska, J.M. 2007. Neuron number decreases in the rat ventral, but not dorsal, medial prefrontal cortex between adolescence and adulthood. Neuroscience, 144 (3), 961-968.
http://www.sciencedaily.com/releases/2007/03/070314093257.htm
Disentangling attention
A new study provides more evidence that the ability to deliberately focus your attention is physically separate in the brain from the part that helps you filter out distraction. The study trained monkeys to take attention tests on a video screen in return for a treat of apple juice. When the monkeys voluntarily concentrated (‘top-down’ attention), the prefrontal cortex was active, but when something distracting grabbed their attention (‘bottom-up’ attention), the parietal cortex became active. The electrical activity in these two areas vibrated in synchrony as they signaled each other, but top-down attention involved synchrony that was stronger in the lower-frequencies and bottom-up attention involved higher frequencies. These findings may help us develop treatments for attention disorders.
Buschman, T.J. & Miller, E.K. 2007. Top-Down Versus Bottom-Up Control of Attention in the Prefrontal and Posterior Parietal Cortices. Science, 315 (5820), 1860-1862.
February 2007
Common gene version optimizes thinking but carries a risk
On the same subject, another study has found that the most common version of DARPP-32, a gene that shapes and controls a circuit between the striatum and prefrontal cortex, optimizes information filtering by the prefrontal cortex, thus improving working memory capacity and executive control (and thus, intelligence). However, the same version was also more prevalent among people who developed schizophrenia, suggesting that a beneficial gene variant may translate into a disadvantage if the prefrontal cortex is impaired. In other words, one of the things that make humans more intelligent as a species may also make us more vulnerable to schizophrenia.
Meyer-Lindenberg,A. et al. 2007. Genetic evidence implicating DARPP-32 in human frontostriatal structure, function, and cognition. Journal of Clinical Investigation, 117 (3), 672-682.
http://www.sciencedaily.com/releases/2007/02/070208230059.htm
http://www.eurekalert.org/pub_releases/2007-02/niom-cgv020707.php
January 2007
Neural bottleneck found that thwarts multi-tasking
An imaging study has revealed just why we can’t do two things at once. The bottleneck appears to occur at the lateral frontal and prefrontal cortex and the superior frontal cortex. Both areas are known to play a critical role in cognitive control. These brain regions responded to tasks irrespective of the senses involved, and could be seen to 'queue' neural activity — that is, a response to the second task was postponed until the response to the first was completed. Such queuing occurred when two tasks were presented within 300 milliseconds of each other, but not when the time gap was longer.
Dux, P.E. et al. 2006. Isolation of a Central Bottleneck of Information Processing with Time-Resolved fMRI. Neuron, 52, 1109-1120.
http://www.eurekalert.org/pub_releases/2007-01/vu-nbf011807.php
November 2006
Hormone replacement therapy may improve visual memory of postmenopausal women
A study of 10 postmenopausal women (aged 50-60) found that those taking combined estrogen-progestin hormone therapy for four weeks showed significantly increased activity in the prefrontal cortex when engaged in a visual matching task, compared with those on placebo.
Smith, Y.R. et al. 2006. Impact of Combined Estradiol and Norethindrone Therapy on Visuospatial Working Memory Assessed by Functional Magnetic Resonance Imaging. The Journal of Clinical Endocrinology & Metabolism, 91 (11), 4476-4481.
http://www.eurekalert.org/pub_releases/2006-11/uomh-hrt111606.php
July 2006
Brain Imaging Identifies Best Memorization Strategies
Why do some people remember things better than others? An imaging study has revealed that the brain regions activated when learning vary depending on the strategy adopted. The study involved 29 right-handed, healthy young adults, ages 18-31, all of whom had normal or corrected-to-normal vision and reported no significant neurological history. Participants were given interacting object pair images (such as a turkey seated atop a horse and a banana positioned in the back of a dump truck) and told to study them in anticipation of a memory test. Earlier studies had indicated that while individuals use a variety of strategies to help them memorize new information, the following four strategies were the main strategies:
1) A visual inspection strategy in which participants carefully studied the visual appearance of objects.
2) A verbal elaboration strategy in which individuals constructed sentences about the objects to remember them.
3) A mental imagery strategy in which participants formed interactive mental images of the objects.
4) A memory retrieval strategy in which they thought about the meaning of the objects and/or personal memories associated with the objects.
Both visual inspection and verbal elaboration resulted in improved recall. Imaging revealed that people who often used verbal elaboration had greater activity in a network of regions that included prefrontal regions associated with controlled verbal processing compared to people who used this strategy less frequently. People who often used a visual inspection strategy had greater activity in a network of regions that included an extrastriate region associated with object processing compared to people who used this strategy less frequently.
Kirchhoff, B.A. & Buckner, R.L. 2006. Functional-Anatomic Correlates of Individual Differences in Memory. Neuron, 51, 263-274.
http://www.sciencedaily.com/releases/2006/08/060809082610.htm
May 2006
Planning is goal-, not action-, oriented
Studies in which monkeys were asked to perform a complex task involving several discrete steps have revealed that the brain's "executive" center, in the lateral prefrontal cortex, plans behaviors not by specifying movements required for given actions, but rather the events that will result from those actions.
Mushiake, H. et al. 2006. Activity in the Lateral Prefrontal Cortex Reflects Multiple Steps of Future Events in Action Plans. Neuron, 50, 631–641.
http://www.eurekalert.org/pub_releases/2006-05/cp-tbe051106.php
January 2006
Morning grogginess worse for cognition than sleep deprivation
People who awaken after eight hours of sound sleep have more impaired thinking and memory skills than they do after being deprived of sleep for more than 24 hours. The impairment is worst in the first three minutes, and the most severe effects have generally dissipated by ten minutes, but measurable effects can last up to two hours. This is consistent with reports indicating that cortical areas like the prefrontal cortex take longer to come “online” after sleep than other parts of the brain. The findings have implications for medical, safety and transportation workers who are often called upon to perform critical tasks immediately after waking, as well as for anyone abruptly woken to face an emergency situation.
Wertz, A.T., Ronda, J.M., Czeisler, C.A. & Wright, K.P.Jr. 2006. Effects of Sleep Inertia on Cognition. Journal of the American Medical Association, 295,163-164.
http://www.eurekalert.org/pub_releases/2006-01/uoca-mgm121905.php
Fitness counteracts cognitive decline from hormone-replacement therapy
A study of 54 postmenopausal women (aged 58 to 80) suggests that being physically fit offsets cognitive declines attributed to long-term hormone-replacement therapy. It was found that gray matter in four regions (left and right prefrontal cortex, left parahippocampal gyrus and left subgenual cortex) was progressively reduced with longer hormone treatment, with the decline beginning after more than 10 years of treatment. Therapy shorter than 10 years was associated with increased tissue volume. Higher fitness scores were also associated with greater tissue volume. Those undergoing long-term hormone therapy had more modest declines in tissue loss if their fitness level was high. Higher fitness levels were also associated with greater prefrontal white matter regions and in the genu of the corpus callosum. The findings need to be replicated with a larger sample, but are in line with animal studies finding that estrogen and exercise have similar effects: both stimulate brain-derived neurotrophic factor.
Erickson, K.I., Colcombe, S.J., Elavsky, S., McAuley, E., Korol, D., Scalf, P.E. & Kramer, A.F. 2006. Interactive effects of fitness and hormone treatment on brain health in postmenopausal women. Neurobiology of Aging, In Press, Corrected Proof, Available online 6 January 2006
http://www.eurekalert.org/pub_releases/2006-01/uoia-fcc012406.php
September 2005
Memory of fear more complex than supposed
It seems that fear memory is more complex than has been thought. A new mouse study has shown that not only the hippocampus and amygdala are involved, but that the prefrontal cortex is also critical. The development of the fear association doesn’t occur immediately after a distressing event, but develops over time. The process, it now seems, depends directly on a protein called NR2B.
Zhao, M-G. et al. 2005. Roles of NMDA NR2B Subtype Receptor in Prefrontal Long-Term Potentiation and Contextual Fear Memory. Neuron, 47, 859-872.
http://www.eurekalert.org/pub_releases/2005-09/uot-sco091505.php
June 2005
How sleep improves memory
While previous research has been conflicting, it does now seem clear that sleep consolidates learning of motor skills in particular. A new imaging study involving 12 young adults taught a sequence of skilled finger movements has found a dramatic shift in activity pattern when doing the task in those who were allowed to sleep during the 12 hour period before testing. Increased activity was found in the right primary motor cortex, medial prefrontal lobe, hippocampus and left cerebellum — this is assumed to support faster and more accurate motor output. Decreased activity was found in the parietal cortices, the left insular cortex, temporal pole and fronto-polar region — these are assumed to reflect less anxiety and a reduced need for conscious spatial monitoring. It’s suggested that this is one reason why infants need so much sleep — motor skill learning is a high priority at this age. The findings may also have implications for stroke patients and others who have suffered brain injuries.
Walker, M.P., Stickgold, R., Alsop, D., Gaab, N. & Schlaug, G. 2005. Sleep-dependent motor memory plasticity in the human brain.Neuroscience, 133 (4) , 911-917.
http://www.eurekalert.org/pub_releases/2005-06/bidm-ssh062805.php
March 2005
Primitive brain learns faster than the "thinking" part of our brain
A study of monkeys has revealed that a primitive region of the brain known as the basal ganglia learns rules first, then “trains” the prefrontal cortex, which learns more slowly. The findings turn our thinking about how rules are learned on its head — it has been assumed that the smarter areas of our brain work things out; instead it seems that primitive brain structures might be driving even our most high-level learning.
Pasupathy, A. &Miller, E.K. 2005. Different time courses of learning-related activity in the prefrontal cortex and striatum. Nature, 433, 873-876.
http://news.mit.edu/2005/basalganglia
February 2005
How the brain creates false memories
An imaging study has shed new light on how false memories are formed. The study involved participants watching series of 50 photographic slides that told a story. A little later, the subjects were shown what they thought was the same sequence of slides but in fact containing a misleading item and differing in small ways from the original. Two days later, the subjects’ memories were tested. It was found that, during the original encoding (the 1st set of slides), activity in the hippocampus and perirhinal cortex was greater for true than for false memories, while during the misinformation phase (2nd set), the activity there was greater for false memories. In other regions, such as the prefrontal cortex, activity for false memories tended to be greater during the original event. Activity in the prefrontal cortex may be correlated to encoding the source, or context, of the memory. Thus, weak prefrontal cortex activity during the misinformation phase indicates that the details of the second experience were poorly placed in a learning context, and as a result more easily embedded in the context of the first event, creating false memories.
Okado, Y. & Stark, C.E.L. 2005. Neural activity during encoding predicts false memories created by misinformation. Learning & Memory, 12, 3-11.
http://www.eurekalert.org/pub_releases/2005-02/cshl-htb012805.php
October 2004
How false memories are formed
An imaging study has attempted to pinpoint how people form a memory for something that didn't actually happen. The study measured brain activity in people who looked at pictures of objects or imagined other objects they were asked to visualize. Three brain areas (precuneus, right inferior parietal cortex and anterior cingulate) showed greater responses in the study phase to words that would later be falsely remembered as having been presented with photos, compared to words that were not later misremembered as having been presented with photos. Brain activity produced in response to viewed pictures also predicted which pictures would be subsequently remembered. Two brain regions in particular -- the left hippocampus and the left prefrontal cortex -- were activated more strongly for pictures that were later remembered than for pictures that were forgotten. The new findings directly showed that different brain areas are critical for accurate memories for visual objects than for false remembering -- for forming a memory for an imagined object that is later remembered as a perceived object.
Gonsalves, B., Reber, P.J., Gitelman, D.R., Parrish, T.B., Mesulam, M-M. & Paller, K.A. 2004. Neural Evidence That Vivid Imagining Can Lead to False Remembering. Psychological Science, 15 (10), 655-660.
http://www.eurekalert.org/pub_releases/2004-10/nu-nrp101404.php
http://www.northwestern.edu/newscenter/stories/2004/10/kenneth.html
Development of working memory with age
An imaging study of 20 healthy 8- to 30-year-olds has shed new light on the development of working memory. The study found that pre-adolescent children relied most heavily on the prefrontal cortex and parietal regions of the brain during the working memory task; adolescents used those regions plus the anterior cingulate; and in adults, a third area of the brain, the medial temporal lobe, was brought in to support the functions of the other areas. Adults performed best. The results support the view that a person's ability to have voluntary control over behavior improves with age because with development, additional brain processes are used.
http://www.eurekalert.org/pub_releases/2004-10/uopm-dow102104.php
September 2004
New technique sheds light on autobiographical memory
A new technique for studying autobiographical memory has revealed new findings about autobiographical memory, and may prove useful in studying age-related cognitive impairment. Previous inconsistencies between controlled laboratory studies of memory (typically, subjects are asked to remember items they have previously seen in the laboratory, such as words presented on a computer screen) and studies of autobiographical memory have seemed to indicate that the brain may function differently in the two processes. However, such differences might instead reflect how the memories are measured. In an effort to provide greater control over the autobiographical memories, volunteer subjects were given cameras and instructed to take pictures of campus scenes. The subjects were also instructed to remember the taking of each picture as an individual event, noting the physical conditions and their psychological state, such as their mood and associations with the subject of the images. The subjects were then shown a selection of campus photos they had not taken. While their brains were scanned, they were then shown a mix of their own photos with those they had not taken, and asked to indicate whether each photo was new, seen earlier in the lab, or one they had taken themselves. The researchers found that recalling the autobiographical memories activated many of the same brain areas as laboratory memories (the medial temporal lobe and the prefrontal cortex); however, they also activated brain areas associated with "self-referential processing" (processing information about one's self), and regions associated with retrieval of visual and spatial information, as well as showing a higher level of activity in the recollection areas in the hippocampus.
The report appeared in the November issue of the Journal of Cognitive Neuroscience.
http://www.eurekalert.org/pub_releases/2004-09/du-blm092904.php
March 2004
Different brain regions for arousing and non-arousing words
An imaging study has found that words representing arousing events (e.g., “rape”, “slaughter”) activate cells in the amygdala, while nonarousing words (e.g., “sorrow”, “mourning”) activated cells in the prefrontal cortex. The hippocampus was active for both type of words. On average, people remembered more of the arousing words than the others, suggesting stress hormones, released as part of the response to emotionally arousing events, are responsible for enhancing memories of those events.
Kensinger, E.A. & Corkin, S. 2004. Two routes to emotional memory: Distinct neural processes for valence and arousal. PNAS, 101, 3310-3315. Published online before print February 23 2004, 10.1073/pnas.0306408101
http://www.eurekalert.org/pub_releases/2004-03/miot-mlu030104.php
January 2004
More evidence for active forgetting
In an imaging study involving 24 people aged 19 to 31, participants were given pairs of words and told to remember some of the matched pairs but forget others. Trying to shut out memory appeared more demanding than remembering, in that some areas of the brain were significantly more when trying to suppress memory. Both the prefrontal cortex and the hippocampus were active. Those whose prefrontal cortex and hippocampus were most active during this time were most successful at suppressing memory.
Anderson, M.C., Ochsner, K.N., Kuhl, B., Cooper, J., Robertson, E., Gabrieli, S.W., Glover, G.H. & Gabrieli, J.D.E. 2004. Neural Systems Underlying the Suppression of Unwanted Memories. Science, 303 (5655), 232-235.
http://www.eurekalert.org/pub_releases/2004-01/su-rrb010604.php
August 2002
How emotions interfere with staying focused
In a new imaging study, Duke University researchers have shown how emotional stimuli and "attentional functions" like driving move in parallel streams through the brain before being integrated in a specific part of the brain's prefrontal cortex (the anterior cingulate, which is located between the right and left halves). Emotional stimuli are thus more likely than simple distractions to interfere with a person's efforts to focus on a task such as driving. These findings may help us understand the neural dynamics underlying emotional distractibility on attentional tasks in affective disorders.
Yamasaki, H., LaBar, K.S. & McCarthy, G. Dissociable prefrontal brain systems for attention and emotion. Proc. Natl. Acad. Sci. USA, 99(17), 11447-51.
http://www.pnas.org/content/99/17/11447.abstract
December 2001
Age-related changes in brain dopamine may underpin the normal cognitive problems of aging
A new model suggests why and how many cognitive abilities decline with age, and offers hope for prevention. Research in the past few years has clarified and refined our ideas about the ways in which cognitive abilities decline with age, and one of these ways is in a reduced ability to recall the context of memories. Thus, for example, an older person is less likely to be able to remember where she has heard something. According to this new model, context processing is involved in many cognitive functions — including some once thought to be independent — and therefore a reduction in the ability to remember contextual information can have wide-reaching implications for many aspects of cognition. The model suggests that context processing occurs in the prefrontal cortex and requires a certain level of the brain chemical dopamine. It may be that in normal aging, dopamine levels become low or erratic. Changes in dopamine have also been implicated in Alzheimer’s, as well as other brain-based diseases.
Braver, T.S., Barch, D.M., Keys, B.A., Carter, C.S., Cohen, J.D., Kaye, J.A., Janowsky, J.S., Taylor, S.F., Yesavage, J.A., Mumenthaler, M.S., Jagust, W.J., & Reed, B.R. 2001. Context Processing in Older Adults: Evidence for a Theory Relating Cognitive Control to Neurobiology in Healthy Aging. Journal of Experimental Psychology –General, 130(4)
http://www.eurekalert.org/pub_releases/2001-12/apa-ocf121701.php
November 2001
Physical brain changes with advancing age
Many of the cognitive deficits associated with advancing age are related to functions of the prefrontal cortex such as working memory, decision-making, planning and judgement. Postmortem examination of 20 brains ranging in age from 25 to 83 years, confirm that prefrontal regions may be particularly sensitive to the effects of aging. It also appears that white matter decreases at a faster rate than grey matter with age.
Kigar, D.L., Walter, A.L., Stoner-Beresh, H.J. & Witelson, S.F. 2001. Age and volume of the human prefrontal cortex: a postmortem study. Paper presented to the annual Society for Neuroscience meeting in San Diego, US.
October 2001
Role of prefrontal cortical regions in goal-directed behaviour
Goal-directed behaviour depends on keeping relevant information in mind (working memory) and irrelevant information out of mind (behavioural inhibition or interference resolution). Prefrontal cortex is essential for both working memory and for interference resolution, but it is unknown whether these two mental abilities are mediated by common or distinct prefrontal regions. An imaging study found there was a high degree of overlap between the regions activated by load and interference, while no region was activated exclusively by interference. The findings suggest that, within the circuitry engaged by this task, some regions are more critically involved in the resolution of interference whereas others are more involved in the resolution of an increase in load.
Bunge, S.A., Ochsner, K.N., Desmond, J.E., Glover, G.H. & Gabrieli J.D.E. (2001). Prefrontal regions involved in keeping information in and out of mind. Brain, 124 (10), 2074-2086.
http://brain.oupjournals.org/cgi/content/abstract/124/10/2074
Left prefrontal cortex
January 2009
Switchboard in the brain helps us learn and remember at the same time
It’s very common that we are required to both process new information while simultaneously recalling old information, as in conversation we are paying attention to what the other person is saying while preparing our own reply. A new study confirms what has been theorised: that there is a bottleneck in our memory system preventing us from doing both simultaneously. Moreover, the study provides evidence that a specific region in the left prefrontal cortex can resolve the bottleneck, possibly by allowing rapid switching between learning and remembering. This is supported by earlier findings that patients with damage to this area have problems in rapidly adapting to new situations and tend to persevere in old rules. The same region is also affected in older adults.
Huijbers, W., Pennartz, C.M., Cabeza, R. & Daselaar, S.M. 2009. When learning and remembering compete: A functional MRI study. PLoS Biology, 7(1), e1000011. doi:10.1371/ journal.pbio.1000011
http://www.eurekalert.org/pub_releases/2009-01/plos-sit010909.php
January 2003
Learning a sequence with explicit knowledge of that sequence involves same
Imaging studies have found that sequence learning accompanied with awareness of the sequence activates entirely different brain regions than learning without awareness of the sequence. It has not been clear to what extent these two forms of learning (declarative vs procedural) are independent. A new imaging study devised a situation where subjects were simultaneously learning different sequences under implicit or explicit instructions, in order to establish whether, as many have thought, declarative learning prevents learning in procedural memory systems. It was found that procedural learning activated the left prefrontal cortex, left inferior parietal cortex, and right putamen. These same regions were also active during declarative learning. It appears that, in a well-controlled situation where procedural and declarative learning are occurring simultaneously, the same neural network for procedural learning is active whether that learning is or is not accompanied by declarative knowledge. Declarative learning, however, activates many additional brain regions.
Willingham, D.B., Salidis, J. & Gabrieli, J.D.E. 2003. Direct Comparison of Neural Systems Mediating Conscious and Unconscious Skill Learning. Journal of Neurophysiology, 88, 1451-1460.
November 2001
Differential effects of encoding strategy on brain activity patterns
Encoding and recognition of unfamiliar faces in young adults were examined using PET imaging to determine whether different encoding strategies would lead to differences in brain activity. It was found that encoding activated a primarily ventral system including bilateral temporal and fusiform regions and left prefrontal cortices, whereas recognition activated a primarily dorsal set of regions including right prefrontal and parietal areas. The type of encoding strategy produced different brain activity patterns. There was no effect of encoding strategy on brain activity during recognition. The left inferior prefrontal cortex was engaged during encoding regardless of strategy.
Bernstein, L.J., Beig, S., Siegenthaler, A.L. & Grady, C.L. 2002. The effect of encoding strategy on the neural correlates of memory for faces. Neuropsychologia, 40 (1), 86 - 98.
Medial prefrontal cortex
May 2009
Brain's problem-solving function at work when we daydream
An imaging study has revealed that daydreaming is associated with an increase in activity in numerous brain regions, especially those regions associated with complex problem-solving. Until now it was thought that the brain's "default network" (which includes the medial prefrontal cortex, the posterior cingulate cortex and the temporoparietal junction) was the only part of the brain active when our minds wander. The new study has found that the "executive network" (including the lateral prefrontal cortex and the dorsal anterior cingulate cortex) is also active. Before this, it was thought that these networks weren’t active at the same time. It may be that mind wandering evokes a unique mental state that allows otherwise opposing networks to work in cooperation. It was also found that greater activation was associated with less awareness on the part of the subject that there mind was wandering.
Christoff, K. et al. 2009. Experience sampling during fMRI reveals default network and executive system contributions to mind wandering. Proceedings of the National Academy of Sciences, 106 (21), 8719-8724.
http://www.eurekalert.org/pub_releases/2009-05/uobc-bpf051109.php
February 2009
Brain hub links music and autobiographical memory
We all know that songs from our youth can evoke strong autobiographical memories. Now a new study explains why. Brain scans of students listening to excerpts of 30 different popular tunes found that a student recognized on average about 17 of the 30 excerpts, and of these, about 13 were moderately or strongly associated with an autobiographical memory. The strength of that memory was reflected in the amount of activity in the upper (dorsal) part of the medial prefrontal cortex, a region critically involved in integrating sensory information with self-knowledge and the retrieval of autobiographical information. Moreover, mapping the tones of each excerpt showed that the brain was tracking these tonal progressions in the same region as it was experiencing the memories: in the dorsal part of the medial prefrontal cortex, and the regions immediately adjacent to it. Again, the stronger the autobiographical memory, the greater the tracking activity. The finding explains why memory for autobiographically important music lingers in Alzheimer’s sufferers — the area is one of the last to be affected.
Janata, P. 2009. The Neural Architecture of Music-Evoked Autobiographical Memories. Cerebral Cortex, Advance Access published on February 24.
http://www.eurekalert.org/pub_releases/2009-02/uoc--sfb021809.php
May 2008
Brain region involved in false memories identified
We’re all susceptible to false memories, but brain damage can produce false memories beyond the normal level. The pathological production of false memories is known as confabulation, and because the patients who suffer this have showed damage to various parts of the brain, the cause has been unclear until now. But a new study of 50 patients has found the common element: all those who confabulated shared damage to the inferior medial prefrontal cortex.
Turner, M.S. et al. 2008. Confabulation: Damage to a specific inferior medial prefrontal system. Cortex, 44 (6), 637-648.
http://www.eurekalert.org/pub_releases/2008-05/e-wym052808.php
March 2007
Social memory localized
An imaging study has identified the medial prefrontal cortex as being the key structure in remembering social information (involving people and their interactions) from a picture. Previous studies have implicated this region with thinking about one’s self and others. This finding reveals that the region is involved not only in processing social information, but also storing it. The finding may help us understand disorders which affect social and relational skills, such as schizophrenia and autism.
Harvey, P.O., Fossati, P. & Lepage, M. 2007. Modulation of memory formation by stimulus content: specific role of the medial prefrontal cortex in the successful encoding of social pictures. Journal of Cognitive Neuroscience, 19, 351-362.
http://www.eurekalert.org/pub_releases/2007-03/c-tfo033007.php
May 2005
How the brain handles sarcasm
A study involving people with prefrontal lobe damage, people with posterior-lobe damage and healthy controls, found that those with prefrontal damage were impaired in comprehending sarcasm, whereas the people in the other two groups had no such problem. Within the prefrontal group, people with damage in the right ventromedial area had the most trouble in comprehending sarcasm. The researchers suggest that the frontal lobes process the context, identifying the contradiction between the literal meaning and the social/emotional context, while the ventromedial prefrontal cortex integrates the literal meaning with the social/emotional knowledge of the situation and previous situations.
Shamay-Tsoory, S.G., Tomer, R. & Aharon-Peretz, J. 2005. The Neuroanatomical Basis of Understanding Sarcasm and Its Relationship to Social Cognition. Neuropsychology, 19 (3)
http://www.eurekalert.org/pub_releases/2005-05/apa-tao051705.php
October 2004
Can't place a name to the face you just saw?
We’re all familiar with that “I know I know it, I just can’t bring it to mind” feeling. Among researchers, this is known as FOK — “feeling of knowing”. It is a common phenomenon, that occurs more frequently as we age. A new imaging study involving a dozen people aged 22 to 32, has investigated the FOK state using pictures of 300 famous and not-so-famous faces. They found that the medial prefrontal cortex showed activity during the FOK state, but not when the subjects either knew or did not know a face. Possibly this reflects a state in which subjects were evaluating the correctness of retrieved information. Additionally, the anterior cingulate area became activated both in the FOK state and when subjects successfully retrieved a name but with some effort. The anterior cingulate area is associated with cognitive conflict processes which allow a person to detect errors in automatic behavior responses. The results suggest that, during a FOK state, the brain may be enlisting additional processes to aid in recalling accurate memories.
http://www.eurekalert.org/pub_releases/2004-10/uoa-cpa102604.php