How memory works

Link between brain acid and cognition offers hope for an effective ‘smart’ pill

September, 2010

Experiments with mice have found that inhibiting the production of kynurenic acid in the brain has dramatic benefits for cognitive performance.

Commercial use is a long way off, but research with mice offers hope for a ‘smart drug’ that doesn’t have the sort of nasty side-effects that, for example, amphetamines have. The mice, genetically engineered to produce dramatically less (70%) kynurenic acid, had markedly better cognitive abilities. The acid, unusually, is produced not in neurons but in glia, and abnormally high levels are produced in the brains of people with disorders such as schizophrenia, Alzheimer's and Huntington's. More acid is also typically produced as we get older.

The acid is produced in our brains after we’ve eaten food containing the amino acid tryptophan, which helps us produce serotonin (turkey is a food well-known for its high tryptophan levels). But serotonin helps us feel good (low serotonin levels are linked to depression), so the trick is to block the production of kynurenic acid without reducing the levels of serotonin. The next step is therefore to find a chemical that blocks production of the acid in the glia, and can safely be used in humans. Although no human tests have yet been performed, several major pharmaceutical companies are believed to be following up on this research.

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Tools that assess bias in standardized tests are flawed

August, 2010

Study shows the tools used to assess whether mental ability tests are biased couldn’t find bias when it was deliberately inserted, casting the fairness of common tests into doubt.

Manipulation of nearly 16 million individual samples of scores and more than 8 trillion individual scores on commonly used tests, including civil service and other pre-employment exams and university entrance exams, has revealed that the tools used to check tests of "general mental ability" for bias overwhelmingly and repeatedly missed the bias inserted in the data. In other words, we’ve been testing potential test bias with a biased procedure.

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[1668] Aguinis, H., Culpepper S. A., & Pierce C. A.
(2010).  Revival of Test Bias Research in Preemployment Testing.
Journal of Applied Psychology. 95(4), 648 - 680.

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Connection between navigation, object location, & autobiographical memory

January, 2010
  • The existence of specialized neurons involved in spatial memory has now been found in humans, and appear to also help with object location and autobiographical memory.

Rodent studies have demonstrated the existence of specialized neurons involved in spatial memory. These ‘grid cells’ represent where an animal is located within its environment, firing in patterns that show up as geometrically regular, triangular grids when plotted on a map of a navigated surface. Now for the first time, evidence for these cells has been found in humans. Moreover, those with the clearest signs of grid cells performed best in a virtual reality spatial memory task, suggesting that the grid cells help us to remember the locations of objects. These cells, located particularly in the entorhinal cortex, are also critical for autobiographical memory, and are amongst the first to be affected by Alzheimer's disease, perhaps explaining why getting lost is one of the most common early symptoms.

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[378] Doeller, C. F., Barry C., & Burgess N.
(2010).  Evidence for grid cells in a human memory network.
Nature. 463(7281), 657 - 661.

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Face recognition ability inherited separately from IQ

January, 2010

Providing support for a modular concept of the brain, a twin study has found that face recognition is heritable, and that it is inherited separately from IQ.

No surprise to me (I’m hopeless at faces), but a twin study has found that face recognition is heritable, and that it is inherited separately from IQ. The findings provide support for a modular concept of the brain, suggesting that some cognitive abilities, like face recognition, are shaped by specialist genes rather than generalist genes. The study used 102 pairs of identical twins and 71 pairs of fraternal twins aged 7 to 19 from Beijing schools to calculate that 39% of the variance between individuals on a face recognition task is attributable to genetic effects. In an independent sample of 321 students, the researchers found that face recognition ability was not correlated with IQ.

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Zhu, Q. et al. 2010. Heritability of the specific cognitive ability of face perception. Current Biology, 20 (2), 137-142.

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Intelligent people have 'unnatural' preferences and values

February, 2010

Findings from a survey of adolescents provides support for a theory that more intelligent people are more likely to adopt evolutionarily novel preferences and values, and that these values include liberalism, atheism, and, in men, monogamy.

A new theory suggests that more intelligent people are more likely than less intelligent people to adopt evolutionarily novel preferences and values, and that these values include liberalism (caring about numerous genetically unrelated strangers they never meet or interact with), atheism, and, in men, monogamy. Data from the National Longitudinal Study of Adolescent Health (Add Health) provide support: Young adults who self-identify as "very liberal" have an average IQ of 106 while those who self-identify as "very conservative" have an average IQ of 95; young adults who self-identify as "not at all religious" have an average IQ of 103, while those who self-identify as "very religious" have an average IQ of 97. The study follows on from a previous study showing that more intelligent individuals were more nocturnal, waking up and staying up later than less intelligent individuals. Being nocturnal is evolutionarily novel for humans.

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[184] Kanazawa, S.
(2010).  Why Liberals and Atheists Are More Intelligent.
Social Psychology Quarterly. 73(1), 33 - 57.

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Nouns and verbs are learned in different parts of the brain

February, 2010

An imaging study reveals that different brain regions are involved in learning nouns and verbs.

An imaging study reveals that different brain regions are involved in learning nouns and verbs. Nouns activate the left fusiform gyrus, while learning verbs activates instead the left inferior frontal gyrus and part of the left posterior medial temporal gyrus. The latter two regions are associated with grammatical and semantic information, respectively, while the former is associated with visual and object processing. The finding is consistent with several findings that distinguish nouns and verbs: children learn nouns before verbs; adults process nouns faster; brain damage can differentially affect nouns and verbs.

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Task determines whether better for neurons to generalize or specialize

July, 2010

A monkey study reveals that, although some neurons are specialized to recognize specific concepts, most are more generalized and these are usually better at categorizing objects.

Previous research has found that individual neurons can become tuned to specific concepts or categories. We can have "cat" neurons, and "car" neurons, and even an “Angelina Jolie” neuron. A new monkey study, however, reveals that although some neurons were more attuned to car images and others to animal images, many neurons were active in both categories. More importantly, these "multitasking" neurons were in fact the best at making correct identifications when the monkey alternated between two category problems. The work could lead to a better understanding of disorders such as autism and schizophrenia in which individuals become overwhelmed by individual stimuli.

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Memory replay not as simple as thought

March, 2010
  • Several reports have come out in recent years on how recent events replay in the hippocampus, a process thought to be crucial for creating long-term memories. Now a rat study suggests that these replays are not merely echoes of past events, but may include possible events that never happened.

Several reports have come out in recent years on how recent events replay in the hippocampus, a process thought to be crucial for creating long-term memories. Now a rat study suggests that these replays are not merely echoes of past events, but a dynamic process aimed at improving decision-making. Rather than being solely replays of recent or frequent paths through the maze, the replays were often paths that the rats had rarely taken or, in some cases, had never taken, as if the rats were trying to build maps to help them make better navigation decisions.

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Sign language study shows multiple brain regions wired for language

April, 2010

Perhaps we should start thinking of language less as some specialized process and more as a particular approach to thought. A study involving native signers of American Sign Language adds to the increasing body of evidence that we process words in the same way as we do the concepts represented by the words; speaking (or reading) is, neutrally speaking, the same as doing.

Perhaps we should start thinking of language less as some specialized process and more as one approach to thought. A study involving native signers of American Sign Language (which has the helpful characteristic that subject-object relationships can be expressed in either of the two ways languages usually use: word order or inflection) has revealed that there are distinct regions of the brain that are used to process the two types of sentences: those in which word order determined the relationships between the sentence elements, and those in which inflection was providing the information. These brain regions are the ones designed to accomplish tasks that relate to the type of sentence they are trying to interpret. Word order sentences activated areas involved in working memory and lexical access, including the dorsolateral prefrontal cortex, the inferior frontal gyrus, the inferior parietal lobe, and the middle temporal gyrus. Inflectional sentences activated areas involved in building and analyzing combinatorial structure, including bilateral inferior frontal and anterior temporal regions as well as the basal ganglia and medial temporal/limbic areas. In other words, as an increasing body of evidence tells us, we process words in the same way as we do the concepts represented by the words; speaking (or reading) is, neutrally speaking, the same as doing.

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[453] Newman, A. J., Supalla T., Hauser P., Newport E. L., & Bavelier D.
(2010).  Dissociating neural subsystems for grammar by contrasting word order and inflection.
Proceedings of the National Academy of Sciences. 107(16), 7539 - 7544.

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Human working memory is based on dynamic interaction networks in the brain

April, 2010

Visual working memory, which can only hold three of four objects at a time, is thought to be based on synchronized brain activity across a network of brain regions. Now a new study has allowed us to get a better picture of how exactly that works.

Visual working memory, which can only hold three of four objects at a time, is thought to be based on synchronized brain activity across a network of brain regions. Now a new study has allowed us to get a better picture of how exactly that works. Both the maintenance and the contents of working memory were connected to brief synchronizations of neural activity in alpha, beta and gamma brainwaves across frontoparietal regions that underlie executive and attentional functions and visual areas in the occipital lobe. Most interestingly, individual VWM capacity could be predicted by synchrony in a network centered on the intraparietal sulcus.

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[458] Palva, M. J., Monto S., Kulashekhar S., & Palva S.
(2010).  Neuronal synchrony reveals working memory networks and predicts individual memory capacity.
Proceedings of the National Academy of Sciences. 107(16), 7580 - 7585.

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