Explaining the Flynn Effect an IQ Decreases
For around a century, average IQ in wealthier nations increased about 3 points per decade (see Flynn effect, p 383 of the text). But in the past few years a handful of papers have reported a decline; the decreases are small, translating to a point or less per decade, but it has researchers' attention. By tracking three decades of data from Norwegian military recruits, researchers concluded that both the increase and decrease in IQ can be explained by within-family variation (environmental effects), ruling out between-family differences as well as genes (Proceedings of the National Academy of Sciences, Vol 115, 6674-6678). Robin Morris of King's College London looked at tests from 1972 forward and concluded that the decline is due to an increase in people 60 years old or older taking the tests. Working memory is known to decrease with aging, while short-term memory remains stable, and he found that both occurred in the data from his sample. Intelligence, Vol 64, 71-80. A Chinese analysis of 32,000 students' test scores has identified environmental pollution as a possible contributor to cognitive decline. A 17% increase in pollution was associated with a 6% decrease in verbal skills and a 2% decrease in math performance. Previous studies indicated that air pollution can affect the brain through toxins, decreased oxygen, and neurological inflammation and disease. The team calculated that lowering pollution in China to levels recommend in the U.S. could increase verbal test scores by 13% and math scores by 3.7%. Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.1809474115.

Brain Implant Boosts Memory
According to a paper presented at the Society for Neuroscience meeting, scientists were able to improve learning performance by stimulating the hippocampus in humans (who already had electrodes implanted to treat epilepsy). As the volunteers practiced learning tasks, the scientists recorded each person's activity patterns in the hippocampus. Then while the subjects learned new tasks, the researchers stimulated the hippocampus with the pattern that corresponded to each person's best performance. Compared to their own performance without stimulation, they did 15% better on short term memory tasks (requiring the person to remember a shape for 5 to 10 seconds) and 25% better on working memory (with a delay of 10 to 40 minutes). Random pattern stimulation decreased performance. There are few instances in which the procedure would be practical until a less invasive method is found, but in the meantime the ability to duplicate and use the patterns has potential for studying the neural process of learning and for restoring lost functions, such as controlling paralyzed limbs. New Scientist, Nov 18, 2017, p 8.

Up to Half of Developmental Disorders Due to New Mutations
Developmental disorders, often called learning disorders, typically begin in childhood; they include, among others, intellectual disability, autism spectrum disorder, and ADHD. In an attempt to determine the role of recessive genes, a team from the UK studied 6000 European and 300 Pakistani children with developmental disorders. In Europe, 3.6 of the cases were due to recessive genes, while 50% were due to new mutations occurring in the sperm or egg of one parent; the remainder were of unknown origin. In the Pakistani group, among whom marriage of cousins is common, the effect of recessive genes rose to 31%. Science, DOI: 10.1126/science.aar6731 . A recent study found that 80% of gene mutations are passed on by the father. This makes sense, because women are thought to be born with all the eggs they will ever have while men's sperm are made throughout life and the chance of forming mutations during cell division increases with age (in both sexes). Nature, DOI: 10/1038/nature24018.


Fasting Increases Brain Derived Neurotrophic Factor
Alternate-day feeding has been reported to improve learning performance and brain health in mice, and some people using intermittent fasting (e.g., reducing calories two days a week) to lose weight say they experience greater mental sharpness. In a study presented at the annual meeting of the Society for Neuroscience, mice fed on alternate days (without calorie reduction) had a 50% increase in brain derived neurotrophic factor; BDNF promotes growth of snapses and increases the number of mitochondria, which provide a cell's energy. The researchers are currently studying humans who reduce their calorie intake two days a week to see if it improves cognitive function. New Scientist, Dec 11, 2017.

Court Orders EPA to Ban Farm Use of Chlorpyrifos
Household use of the pesticide chlorpyrifos (in products such as RAID) has been prohibited in the U.S. since 2000, due to evidence it can cause neurodevelopmental damage (see p 385 of the text). Under court order to make a decision about farm use, the Environmental Protection Agency ruled in 2017 that a broader ban was not warranted. Now, in response to a lawsuit brought by public health groups and state attorneys general, a federal court has ordered the EPA to ban all use of chlorpyrifos within 60 days. CNNPolitics, Aug 9, 2018.

EEG Uncoupling in Old Brains and Forgetting
There is considerable evidence that slow-wave, non-rapid-eye-movement (NREM) sleep supports memory consolidation, and synchrony between sleep spindles and the slow waves has been proposed as the mechanism. A study of young and older adults demonstrated that the quality of this coordination correlates with overnight memory retention. In the older subjects, atrophy within the medial frontal cortex was associated with loss of slow wave-spindle coupling, impaired overnight memory consolidation, and forgetting. Neuron, Vol 97, 221-230.e4.


THC May Improve Cognitive Performance in the Elderly
Another contribution to cognitive performance decline is age-related reduction of activity in the endocannabinoid system, which modulates the physiological processes underlying aging. When researchers administered small amounts of THC (delta9-tetrahydrocannabinol) to eldely mice (12 months old) for a month, their performance on cognitive tasks (maze learning, recognizing other individuals, etc.) not only was better than that of same-age controls, but matched that of THC-free 2-month-olds. Young rats given THC declined in performance, suggesting there there is an optimum level of endocannabinoid activity. The behavioral improvement was accompanied by enhanced protein activity at synapses and, in the hippocampus, increased synaptic spine density and restoration of gene activity. Blocking CB1 cannabinoid receptors eliminated the benefits, indicating that improvement relies on restoration of CB1 signalling and suggesting this as a target for cognitive improvement therapies. Nature Medicine, Vol 23, 782-787.

Bigger Cells, Smarter Brains?
Scientists who removed small samples of temporal lobe tissue from patients undergoing brain surgery found that those with higher IQs had larger neurons. The neurons also had more and longer dendrites, and they were able to conduct at higher rates. These properties accounted for about one-fourth of the patients' differences in IQ. The increased size could have a biological origin, but it might also be the result of experience (see the London taxi driver study, p 376 of the text). bioRxiv, DOI: https://doi.org/10.1101/296343.