A part of the brain first affected by Alzheimer's disease is thinner in youth with a risk gene for the disorder, a brain imaging study has found. A thinner entorhinal cortex may render these youth more susceptible to degenerative changes and mental decline later in life. This learning and memory hub is thinner in youth with the Alzheimer's-releated ApoE4 variant of the apolipoprotein gene, perhaps lowering the threshold for adverse consequences with aging-related tissue loss.

Chronic depression may cause diabetes in older adults, according to a new study. This is the first national study to suggest that depression alone -- and not lifestyle factors like being overweight -- can trigger diabetes in adults 65 and older, a population with a high prevalence of diabetes and depression. A high level of the stress hormone cortisol -- common in people who are depressed and which can decrease insulin sensitivity -- may be triggering the disease.

In the recently concluded first quarter, both the NYSE and the NASDAQ saw more IPOs than in any other quarter since the last bubble. All told, 64 companies, including many that are far from profitability, raised $12.1 billion during the period. This stands in stark contrast to the stock market a year ago, which saw relatively few IPOs, despite the fact that there was plenty of activity in terms of startups and young companies. At the time, one of the popular reasons given for the lack of IPOs was the Sarbanes-Oxley "tax", which was seen as an undue burden on small companies. This view, a popular one among venture capitalists, was bolstered by the fact that a number of companies, which in the past would have probably listed on the NASDAQ, were opting to go public in London, where they could escape Sarbanes-Oxley. Also, the rise of private equity and management-led buyouts gave credence to the idea that Sarbanes-Oxley made it not worthwhile to be public. So, then, does the resurgent IPO market discredit the Sarbanes-Oxley complaints at all? Certainly, Sarbanes-Oxley still represents a significant cost for small companies, and there's almost no other explanation for why American companies would list in London rather than their home market. But, seeing as the IPO comeback coincides with record highs for the stock market, it would appear that economic cycles must be playing a pretty significant factor. This doesn't dismiss the Sarbanes-Oxley explanation, but it does suggest that it's just one of a number of factors, rather than the dominant one.

Memorizing a series of facts is one thing, understanding the big picture is quite another. Now a new study demonstrates that relational memory -- the ability to make logical "big picture" inferences from disparate pieces of information -- is dependent on taking a break from studies and learning, and even more important, getting a good night's sleep.