Note that this is a study on a high-fructose diet, not a high-fructose corn syrup diet. A major source of fructose is sucrose, which when cooked with is often already broken down into glucose and fructose before consumption.
Note also that this was a study on rats, not humans.
If we cut through the press release (which was already amended to be less sensationalist), this was actually a study showing that omega-3 fatty acids improved the rats' memories of a maze after six weeks. That a high-fructose diet would "sabotage learning, memory" is merely supposition on the part of the researcher (and he says so, explicitly). There is no evidence from this study that that is the case. Why they wouldn't have a control group not receiving the high-fructose diet is not apparent.
Metabolism results in rats are notoriously bad at generalizing to humans. You can get rats to live much longer by restricting their calories; live 30% shorter lives by giving them small doses of caffeine; we can cure obesity, spinal injuries, get them to regenerate nerves.. and none of it has been shown to generalize to humans.
Note also that this was a study on rats, not humans.
If we cut through the press release (which was already amended to be less sensationalist), this was actually a study showing that omega-3 fatty acids improved the rats' memories of a maze after six weeks. That a high-fructose diet would "sabotage learning, memory" is merely supposition on the part of the researcher (and he says so, explicitly). There is no evidence from this study that that is the case. Why they wouldn't have a control group not receiving the high-fructose diet is not apparent.