Jonah Lehrer, has an article in this week’s Nature News, (find a PDF here) , regarding 30 or so cognitively enhanced mice strains that have been bred and genetically engineered. As Lehrer very elaborately documents, all these have enhanced LTP as an intervening mechanism that leads to improvements in learning and memory. Most of the genes involved affcet the LTP mechanism in one way or the other to breed super mnemonist mice. However, from the time of Luria, t has been well known that those who have enhanced memory also suffer from some of its disadvantages and that the ability to forget is also very important.
Little is known about the side effects and tradeoffs of both the current usage or the drugs in development, but initial clues offered by smart mice raise concerns. The Hras strain developed in Silva’s lab might be good at learning, but its fear response for a relatively benign stimulus would be counterproductive for a wild mouse. Its enhanced memory is both a blessing and a burden. Silva cites other strains of smart mice that excel at solving complex exercises, such as the Morris water maze, but that struggle with simpler mazes. “It’s as if they remember too much,” he says — possibly taking in irrelevant information such as the position of windows or lights but missing the big clues.
Farah sees a parallel between these mice and one of the few case studies of an individual with profoundly enhanced memory. In the early 1920s, the Russian neurologist Alexander Luria began studying the learning skills of a newspaper reporter called Solomon Shereshevsky, who had been referred to the doctor by his editor. Shereshevsky had such a perfect memory that he often struggled to forget irrelevant details. After a single read of Dante’s Divine Comedy, he was able to recite the complete poem by heart. Although this flawless memory occasionally helped Shereshevsky at work — he never needed to take notes — Luria also documented the profound disadvantages of such a capacious memory. Shereshevsky, for instance, was almost entirely unable to grasp metaphors, as his mind was so fixated on particulars. When he tried to read poetry, for example, “the obstacles to his understanding were overwhelming”, Luria wrote in his book The Mind of a Mnemonist. “Each expression gave rise to a remembered image; this, in turn, would conflict with another image that had been evoked.”
For Luria, Shereshevsky’s struggles were a powerful reminder that the ability to forget is as important as the ability to remember. Enhancing human memory in individuals without severe cognitive defects might prove counterproductive.
It is interesting to pause here and note that many savants who have excellent memory are also autistic and that schizophrenics on the opposite end of the spectrum are characterized by too much reliance of metaphors and too much generalizations and abstractions. Further Martha Farah notes the following:
Many scientists are concerned that the animal models of enhanced cognition might obscure subtle side effects, which can’t be studied in rodents or primates. Farah is currently looking at the trade-off between enhanced attention — she gives human subjects a mild amphetamine — and performance on creative tasks. Other researchers have used computer models to show that memory is actually optimized by slight imperfections, as they allow one to see connections between different but related events9. “The brain seems to have made a compromise in that having a more accurate memory interferes with the ability to generalize,” Farah says. “You need a little noise in order to be able to think abstractly, to get beyond the concrete and literal.”
Again, one can easily see the correlations with Autism and Schizophrenia- one end marked by too narrow a focus , while the other marked by too much noise and divergent creativity. I would have been happy to incorporate the more LTP as autistic and less LTP as schizophrenics, but it flies in face of my earlier findings regarding experience dependent plasticity in autism and schizophrenia where the conclusions were just the revers. Yet, it is clear that synaptic plasticity is a majo mechanism involved in the autism/psychosis differentiation. Do let me know if you can reconcile the new findings with the older ones to come up with the right LTP and psychosis/autism relationship.