Relationship between sodium and diffusion MRI metrics in multiple sclerosis.

Sodium MRI can measure sodium concentrations in people with multiple sclerosis, but the extent to which these alterations reflect metabolic dysfunction in the absence of tissue damage or neuroaxonal loss remains uncertain. Increases in total sodium concentration and extracellular sodium concentration are believed to be indicative of tissue disruption and extracellular space expansion. Conversely, increase in intracellular sodium concentration may represent early and transient responses to neuronal insult, preceding overt tissue damage.

Pharmacological modulation of dopamine receptors reveals distinct brain-wide networks associated with learning and motivation in non-human primates.

The neurotransmitter dopamine (DA) has a multifaceted role in healthy and disordered brains through its action on multiple subtypes of dopaminergic receptors. How modulation of these receptors influences learning and motivation by altering intrinsic brain-wide networks remains unclear. Here we performed parallel behavioral and resting-state functional MRI experiments after administration of two different DA receptor antagonists in male and female macaque monkeys.

Ventrolateral prefrontal cortex in macaques guides decisions in different learning contexts.

Flexibly adjusting our behavioral strategies based on the environmental context is critical to maximize rewards. Ventrolateral prefrontal cortex (vlPFC) has been implicated in both learning and decision-making for probabilistic rewards, although how context influences these processes remains unclear. We collected functional neuroimaging data while rhesus macaques performed a probabilistic learning task in two contexts: one with novel and another with familiar visual stimuli.