Have you seen the movie Inception? If not you should. It is all about a group of people high jacking the dreams of company bosses to steal useful information from their memory to sell them to their rivals. Anyway the Holy Grail of these “being in other peoples head and manipulating things” – trips is not the stealing but rather the INCEPTION of a new memory.
Now a study from the Mark Mayford lab (Garner et al 2012) has shown a way to generate a synthetic memory in rodents by a smart combination of genetic tricks and behavioral assay. They used double transgenic mice in which they can switch on and off the activity dependent expression (regulated by a c-fos promoter) of an hM3Dq-receptor. Activating this receptor by the injection of its agonist (CNO) induced neural activity.
They took these mice, switched on the activity regulated expression of the receptor and put them into a novel context (ctxA). Consequently they assume that the receptor will be expressed in those neurons activated throughout ctxA exploration. On the consecutive day, when the receptor expression is switched off, they fear conditioned the animals in a second context (ctxB) under the influence of the receptor agonist CNO. By injecting CNO the authors claim that they fire the neurons active in the pre exposure of ctxA while fear conditioning ctxB. In the following retrieval test the mere ctxB exposure could not elicit fear response (freezing). Nevertheless when animals were treated with CNO and tested in ctxB, freezing was on the level of the control animals. Since no fear response was observed in ctxA irrespectively of CNO injection the authors postulate that a “…hybrid representation incorporating both CNO-induced artificial stimulation and natural sensory cues…” was learned. Additional control experiments showed that the effect on the memory formation is specific for the pre exposed context. Further the authors demonstrated that if CNO was not injected during training but during retrieval memory retention for ctxB is reduced suggesting CNO is inducing a competing signal.
In sum Garner et al produced a synthetic memory trace by adding specific neural activity to the neural activity caused by sensory input in the presence of reinforcement. Despite the promising title: “Generation of a Synthetic Memory Trace” it seems to be a long way to a complete INCEPTION of a memory trace. Anyway the work might be an important step towards understanding of the role of internal generated neural activity during the formation of a memory produced by external stimuli.
Garner AR, Rowland DC, Hwang SY, Baumgaertel K, Roth BL, Kentros C, & Mayford M (2012). Generation of a synthetic memory trace. Science (New York, N.Y.), 335 (6075), 1513-6 PMID: 22442487
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