Posterior parietal cortex
Older news items (pre-2010) brought over from the old website
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
April 2009
Individual differences in working memory capacity depend on two factors
A new computer model adds to our understanding of working memory, by showing that working memory can be increased by the action of the prefrontal cortex in reinforcing activity in the parietal cortex (where the information is temporarily stored). The idea is that the prefrontal cortex sends out a brief stimulus to the parietal cortex that generates a reverberating activation in a small subpopulation of neurons, while inhibitory interactions with neurons further away prevents activation of the entire network. This lateral inhibition is also responsible for limiting the mnemonic capacity of the parietal network (i.e. provides the limit on your working memory capacity). The model has received confirmatory evidence from an imaging study involving 25 volunteers. It was found that individual differences in performance on a short-term visual memory task were correlated with the degree to which the dorsolateral prefrontal cortex was activated and its interconnection with the parietal cortex. In other words, your working memory capacity is determined by both storage capacity (in the posterior parietal cortex) and prefrontal top-down control. The findings may help in the development of ways to improve working memory capacity, particularly when working memory is damaged.
Edin, F. et al. 2009. Mechanism for top-down control of working memory capacity. PNAS, 106 (16), 6802-6807.
http://www.eurekalert.org/pub_releases/2009-04/i-id-aot040109.php
August 2007
Gene predicts better outcome as cortex normalizes in teens with ADHD
Recent research found that thickening of brain areas that control attention in the right cortex (right orbitofrontal/inferior prefrontal and posterior parietal cortex ) was associated with better clinical outcomes in ADHD. A new study has found that these brain areas are thinnest in those who carry a particular variant of a gene. The version of the dopamine D4 receptor gene, called the 7-repeat variant, was found in nearly a quarter of youth with ADHD and about one-sixth of the healthy controls. Although this particular gene version increased risk for ADHD, it also made it more likely that the areas would thicken during adolescence, with consequent improvement in behaviour and performance.
Shaw, P. et al. 2007. Polymorphisms of the Dopamine D4 Receptor, Clinical Outcome, and Cortical Structure in Attention-Deficit/Hyperactivity Disorder. Archives of General Psychiatry, 64, 921-931.
http://www.eurekalert.org/pub_releases/2007-08/niom-gpb080107.php
April 2004
Why working memory capacity is so limited
There’s an old parlor game whereby someone brings into a room a tray covered with a number of different small objects, which they show to the people in the room for one minute, before whisking it away again. The participants are then required to write down as many objects as they can remember. For those who perform badly at this type of thing, some consolation from researchers: it’s not (entirely) your fault. We do actually have a very limited storage capacity for visual short-term memory.
Now visual short-term memory is of course vital for a number of functions, and reflecting this, there is an extensive network of brain structures supporting this type of memory. However, a new imaging study suggests that the limited storage capacity is due mainly to just one of these regions: the posterior parietal cortex. An interesting distinction can be made here between registering information and actually “holding it in mind”. Activity in the posterior parietal cortex strongly correlated with the number of objects the subjects were able to remember, but only if the participants were asked to remember. In contrast, regions of the visual cortex in the occipital lobe responded differently to the number of objects even when participants were not asked to remember what they had seen.
http://www.eurekalert.org/pub_releases/2004-04/vu-slo040704.php
http://tinyurl.com/2jzwe (Telegraph article)
February 2004
More complex brain may have pre-dated Homo genus
New research supports Raymond Dart’s suggestion (in 1925) that the human brain started evolving its unique characteristics much earlier than has previously been supposed. One of the differences between human and ape brains is the position of the primary visual striate cortex (PVC), an area of the brain devoted exclusively to vision. In the ape brain, this is situated further forward than it is in human brains, making the PVC larger. It has been claimed that the PVC only decreased in size once the brain had grown substantially in size – when big-brained Homo (the hominid group that includes humans) appeared around 2.4 million years ago. However, new examination of an endocast of the brain of an Australopithecus africanus (Australopithecines pre-dated Homo, and their brains were similar in size to those of chimpanzees) has found evidence of a decreased PVC. This suggests an increase in the region lying in front of the PVC - the posterior parietal cerebral cortex, which is associated in humans with a variety of complex behaviors such as the appreciation of objects and their qualities, facial recognition and social communication.
Holloway, R.L., Clarke, R.J. & Tobias, P.V. 2004. Posterior lunate sulcus in Australopithecus africanus: was Dart right? In Press, Corrected Proof, Available online 28 January 2004