Brain Regions

Advice vs. experience: Genes predict learning style

May, 2011

Three gene variants governing dopamine response in the prefrontal cortex and the striatum affect how likely we are to persist with inaccurate beliefs in the face of contradictory experience.

We learn from what we read and what people tell us, and we learn from our own experience. Although you would think that personal experience would easily trump other people’s advice, we in fact tend to favor abstract information against our own experience. This is seen in the way we commonly distort what we experience in ways that match what we already believe. But there is probably good reason for this tendency (reflected in confirmation bias), even if it sometimes goes wrong.

But of course individuals vary in the extent to which they persist with bad advice. A new study points to genes as a critical reason. Different brain regions are involved in the processing of these two information sources (advice vs experience): the prefrontal cortex and the striatum. Variants in the genes DARPP-32 and DRD2 affect the response to dopamine in the striatum. Variation in the gene COMT, on the other hand, affects dopamine response in the prefrontal cortex.

In the study, over 70 people performed a computerized learning task in which they had to pick the "correct" symbol, which they learned through trial and error. For some symbols, subjects were given advice, and sometimes that advice was wrong.

COMT gene variants were predictive of the degree to which participants persisted in responding in accordance with prior instructions even as evidence against their correctness grew. Variants in DARPP-32 and DRD2 predicted learning from positive and negative outcomes, and the degree to which such learning was overly inflated or neglected when outcomes were consistent or inconsistent with prior instructions.

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The importance of the cerebellum for intelligence and age-related cognitive decline

March, 2011
  • A new study of older adults indicates atrophy of the cerebellum is an important factor in cognitive decline for men, but not women.

Shrinking of the frontal lobe has been associated with age-related cognitive decline for some time. But other brain regions support the work of the frontal lobe. One in particular is the cerebellum. A study involving 228 participants in the Aberdeen Longitudinal Study of Cognitive Ageing (mean age 68.7) has revealed that there is a significant relationship between grey matter volume in the cerebellum and general intelligence in men, but not women.

Additionally, a number of other brain regions showed an association between gray matter and intelligence, in particular Brodmann Area 47, the anterior cingulate, and the superior temporal gyrus. Atrophy in the anterior cingulate has been implicated as an early marker of Alzheimer’s, as has the superior temporal gyrus.

The gender difference was not completely unexpected — previous research has indicated that the cerebellum shrinks proportionally more with age in men than women. More surprising was the fact that there was no significant association between white memory volume and general intelligence. This contrasts with the finding of a study involving older adults aged 79-80. It is speculated that this association may not develop until greater brain atrophy has occurred.

It is also interesting that the study found no significant relationship between frontal lobe volume and general intelligence — although the effect of cerebellar volume is assumed to occur via its role in supporting the frontal lobe.

The cerebellum is thought to play a vital role in three relevant areas: speed of information processing; variability of information processing; development of automaticity through practice.

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Better reading may mean poorer face recognition

January, 2011

Evidence that illiterates use a brain region involved in reading for face processing to a greater extent than readers do, suggests that reading may have hijacked the network used for object recognition.

An imaging study of 10 illiterates, 22 people who learned to read as adults and 31 who did so as children, has confirmed that the visual word form area (involved in linking sounds with written symbols) showed more activation in better readers, although everyone had similar levels of activation in that area when listening to spoken sentences. More importantly, it also revealed that this area was much less active among the better readers when they were looking at pictures of faces.

Other changes in activation patterns were also evident (for example, readers showed greater activation in the planum temporal in response to spoken speech), and most of the changes occurred even among those who acquired literacy in adulthood — showing that the brain re-structuring doesn’t depend on a particular time-window.

The finding of competition between face and word processing is consistent with the researcher’s theory that reading may have hijacked a neural network used to help us visually track animals, and raises the intriguing possibility that our face-perception abilities suffer in proportion to our reading skills.

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Brain hub helps us switch attention

December, 2010

The intraparietal sulcus appears to be a hub for connecting the different sensory-processing areas as well as higher-order processes, and may be key to attention problems.

If our brains are full of clusters of neurons resolutely only responding to specific features (as suggested in my earlier report), how do we bring it all together, and how do we switch from one point of interest to another? A new study using resting state data from 58 healthy adolescents and young adults has found that the intraparietal sulcus, situated at the intersection of visual, somatosensory, and auditory association cortices and known to be a key area for processing attention, contains a miniature map of all the things we can pay attention to (visual, auditory, motor stimuli etc).

Moreover, this map is copied in at least 13 other places in the brain, all of which are connected to the intraparietal sulcus. Each copy appears to do something different with the information. For instance, one map processes eye movements while another processes analytical information. This map of the world may be a fundamental building block for how information is represented in the brain.

There were also distinct clusters within the intraparietal sulcus that showed different levels of connectivity to auditory, visual, somatosensory, and default mode networks, suggesting they are specialized for different sensory modalities.

The findings add to our understanding of how we can shift our attention so precisely, and may eventually help us devise ways of treating disorders where attention processing is off, such as autism, attention deficit disorder, and schizophrenia.

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[1976] Anderson, J. S., Ferguson M. A., Lopez-Larson M., & Yurgelun-Todd D.
(2010).  Topographic maps of multisensory attention.
Proceedings of the National Academy of Sciences. 107(46), 20110 - 20114.

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Brain area organized by color and orientation

December, 2010

Object perception rests on groups of neurons that respond to specific attributes.

New imaging techniques used on macaque monkeys explains why we find it so easy to scan many items quickly when we’re focused on one attribute, and how we can be so blind to attributes and objects we’re not focused on.

The study reveals that a region of the visual cortex called V4, which is involved in visual object recognition, shows extensive compartmentalization. There are areas for specific colors; areas for specific orientations, such as horizontal or vertical. Other groups of neurons are thought to process more complex aspects of color and form, such as integrating different contours that are the same color, to achieve overall shape perception.

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[1998] Tanigawa, H., Lu H. D., & Roe A. W.
(2010).  Functional organization for color and orientation in macaque V4.
Nat Neurosci. 13(12), 1542 - 1548.

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Damage to amygdala can be compensated by another region

September, 2010

A memory function thought to require a specific brain region called the amygdala has now been found to be able to be performed by another region, if the amygdala is impaired.

A number of studies in recent years have revealed the amazing ability of the human brain to compensate for damage down to its part. In the latest of these, it’s been found that loss of the amygdala doesn’t have to mean that new memories will be void of emotion. Instead, it appears, a region called the bed nuclei can step in to take its place. The bed nuclei are slower to process information than the amygdala, and in normal circumstances are inhibited by the amygdala. The study looked specifically at fear conditioning, for which the amygdala has been considered crucial.

The finding offers the hope that therapies to promote compensatory shifts in function might help those who have suffered damage to parts of their brain.

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Brain system behind general intelligence identified

February, 2010

Data from brain-lesion patients supports the idea that general intelligence depends on the brain's ability to integrate several different kinds of processing, and resides in a distributed network.

Using a large data set of 241 brain-lesion patients, researchers have mapped the location of each patient's lesion and correlated that with each patient's IQ score to produce a map of the brain regions that influence intelligence. Consistent with other recent findings, and with the theory that general intelligence depends on the brain's ability to integrate several different kinds of processing, they found general intelligence was determined by a distributed network in the frontal and parietal cortex, critically including white matter association tracts and frontopolar cortex. They suggest that general intelligence draws on connections between regions that integrate verbal, visuospatial, working memory, and executive processes.

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[173] Gläscher, J., Rudrauf D., Colom R., Paul L. K., Tranel D., Damasio H., et al.
(2010).  Distributed neural system for general intelligence revealed by lesion mapping.
Proceedings of the National Academy of Sciences. 107(10), 4705 - 4709.

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