The memory experiments
The experiments ask for different accomplishments: retaining an avoidance response, recognising an object or navigating a maze.
Experimental cortical injury
The cortical-infarction experiment reported that intranasal Semax reduced the volume of damaged cortex and improved retention of a conditioned passive-avoidance response in rats. The model used focal photoinduced ischemia in the prefrontal cortex. Both the injury and the learning task matter to the result.
Preservation earns my enthusiasm here: an experimentally injured animal retained something it had learned, while the tissue measurement also moved in a favourable direction. That is enough to make the paper interesting. An unresolved question follows: how much of the behavioural result followed from preserving the tissue, and how much reflected a more specific effect on memory?
The reported outcomes leave those explanations entangled. An experiment designed to distinguish them would add something more useful than another broad description of a “nootropic” effect.
Transgenic mice and recognition tasks
In APPswe/PS1dE9 transgenic Alzheimer’s-model mice, Semax and a derivative improved cognitive performance and reduced amyloid inclusions in cortex and hippocampus. The reported testing included novel-object recognition and the Barnes maze. The paper therefore offers behavioural and tissue findings in another animal model.
The objects are an appealingly ordinary interruption in a molecular story. The task of recognition feels concrete beside a sweeping claim about cognition. Still, the transgenic model is the setting in which these findings occurred. Its name carries a disease hypothesis into the experiment; it cannot settle whether a treatment would help people with Alzheimer’s disease.
The derivative also deserves to remain visible in the account. A fuller comparison of the compounds and tasks could clarify how much of that encouraging description applies to Semax alone.
An injured and a healthy comparison
I’d like the same memory question carried through an injured model and a healthy comparison, with the task and tissue outcomes reported separately. That is a wish for another experiment, rather than a description of one already completed.
A persuasive result ought to survive a serious attempt to explain it another way. For these papers, a clear account of retention, recognition and the contribution of tissue protection would do more than a larger collection of favourable adjectives. The molecular findings give possible leads to investigate; they do not finish that experiment.