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Stress is part of our everyday lives โ while some thrive on it, it makes others sick. But what does stress do to ourย senses?
When we train them, we can sharpen our senses thereby improve our perceptual performance. The stress hormone cortisol completely blocks this important ability. In the current issue of โPsychoneuroendocrinologyโ neuroscientists of the Ruhr University Bochum (RUB) report on thisย finding.
โPrevious research has already shown that stress can prevent the retrieval of memories. But now we have discovered that it also has a major effect on our perception and perceptual learning,โ explains Dr Hubert Dinse, one of the authors of theย study.
Tactile sense inย training
In their study, researchers investigated how the sense of touch of 30 study participants could be changed after a training phase. Half of them received a medium dose of the stress hormone cortisol, while the other half received a placeboย drug.
To make training comparable across all participants, the researchers employed the well-established approach of passive finger stimulation. Previous studies and several therapy approaches have shown that this method leads to an improved tactileย acuity.
Tactile performance was assessed using the so-called โtwo-point discrimination thresholdโ. This marker indicates how far apart two stimuli need to be, to be discriminated as two separate sensations โ the closer they are, the better the sense ofย touch.
No learning effect afterย cortisol
The placebo group improved their tactile acuity, as expected, by about 15 percent. In contrast, the cortisol given to the other group blocked almost all the stimulation-induced improvement. Cognitive psychologist Prof Dr Oliver T. Wolf explains:โ Our data show that a single dose of cortisol not only disrupts memory in the hippocampus, but it also has a substantial effect on the plasticity of sensory areas of theย brain.โ
Cortisol blocks synapticย connections
In previous studies on a cellular level, neuroscientists have demonstrated that cortisol suppresses the strengthening of synaptic connections, and therefore the plasticity of the brain โ its ability to learn. The team led by Hubert Dinse therefore suggests, their results could also explain by cortisol-induced suppression of synapticย plasticity.
Effects on clinicalย treatments
The results of the study could also affect clinical treatments. Corticosteroids, of which cortisol is one, are often used in the treatment of immunological and neurological diseases. However, the effects on perceptual learning observed in this study may counteract rehabilitation efforts, which rely on just these mechanisms. It is therefore necessary to find out which effects the clinical treatment with these substances has on learning mechanisms in theย brain.
Original Research:ย Full open access research for โThe stress hormone cortisol blocks perceptual learning in humansโ by Hubert R. Dinse, Jan-Christoph Kattenstroth, Melanie Lenz, Martin Tegenthoff, and Oliver T. Wolf in Psychoneuroendocrinology. Published online December 9 2016ย doi:10.1016/j.psyneuen.2016.12.002