To do this, they took 35 rats and divided them into five groups of 7, each of which was fed dark chocolate while experiencing chronic isolation stress, with each group following a different dietary pattern. The three dark chocolate dietary patterns they tested were dubbed stress-compulsory, stress-optional and stress-restricted.

"The stressed rats on a compulsory diet only received DC and the ones on an optional diet received unlimited chow and/or DC," the researchers wrote in their paper. "Also, the stressed rats on a restricted diet each received chow freely and only 4 g DC daily. Subsequently, the slope and amplitude of field excitatory postsynaptic potentials (fEPSPs) were assessed based on the Input-Output (I/O) curves and after the long-term potentiation (LTP)."

The researchers also measured the food intake and body weight of the rats they tested on at the beginning and end of their experiment. Interestingly, they found that all the dark chocolate dietary patterns reduced both the rats' food intake and their body weight. The strongest effects, however, were those caused by compulsory and restricted dietary patterns.

"The fEPSP slope and amplitude in the I/O curves and after LTP decreased significantly in the stress group compared to the control group," the researchers wrote in their paper. "Although the slope and amplitude both enhanced non-significantly in the optional DC diet, these parameters changed significantly in both compulsory and restricted DC dietary patterns compared to the stress group. Also, food intake and body weight decreased significantly in all DC groups."

Overall, the experiments carried out by this team of researchers suggest that the systematic consumption of dark chocolate could reverse the adverse effects of chronic isolation stress on the synaptic potency and plasticity of the hippocampal CA1 area. This would in turn have beneficial effects on both memory and learning.

As their study was carried out in rats, however, to be applicable to humans, their findings would need to be validated on a human sample of participants. If their results were confirmed in future studies involving humans, their work would offer evidence of the positive effects of cocoa on the brain and on cognitive abilities.

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