A rat study has demonstrated that cytokines (immune system signaling molecules) impair communication among neurons in the hippocampus. The increased cytokine levels affected complex discrimination memory, that is, the ability to differentiate among generally similar experiences.
In the study, the rats were exposed to two similar environments, one of which was associated with a mild foot shock, making them reluctant to enter that environment. When some rats were then given a low dose of a bacterial agent to induce a neuroinflammatory response, leading to cytokine release in the brain, they became no longer able to distinguish between the two environments.
Analysis of changes in the activity patterns of hippocampal neurons suggested that cytokines impaired recall by disrupting the function of specific neuron circuits, taking the neural network that had learned the discrimination back to the state it had been before learning took place.
The finding may help explain "chemobrain", and suggests that an intervention aimed at reducing inflammation might be effective approach.
Czerniawski, J., & Guzowski, J. F. (2014). Acute Neuroinflammation Impairs Context Discrimination Memory and Disrupts Pattern Separation Processes in Hippocampus. The Journal of Neuroscience, 34(37), 12470–12480. http://doi.org/10.1523/JNEUROSCI.0542-14.2014