Divergent opioid-mediated suppression of inhibition between hippocampus and neocortex across species and development.

Opioid receptors within the CNS regulate pain sensation and mood and are key targets for drugs of abuse. Within the adult rodent hippocampus (HPC), µ-opioid receptor agonists suppress inhibitory parvalbumin-expressing interneurons (PV-INs), thus disinhibiting the circuit. However, it is uncertain if this disinhibitory motif is conserved in other cortical regions, species, or across development. We observed that PV-IN mediated inhibition is robustly suppressed by opioids in HPC but not neocortex in mice and nonhuman primates, with spontaneous inhibitory tone in resected human tissue also following a consistent dichotomy. This hippocampal disinhibitory motif was established in early development when immature PV-INs and opioids already influence primordial network rhythmogenesis. Acute opioid-mediated modulation was partially occluded with morphine pretreatment, with implications for the effects of opioids on hippocampal network activity during circuit maturation as well as learning and memory. Together, these findings demonstrate that PV-INs exhibit a divergence in opioid sensitivity across brain regions that is remarkably conserved across evolution and highlights the underappreciated role of opioids acting through immature PV-INs in shaping hippocampal development.

The visual prefrontal cortex of anthropoids: interaction with temporal cortex in decision making and its role in the making of "visual animals".

The ventral prefrontal cortex (PFC) of primates-a region strongly implicated in decision making-receives highly processed visual sensory inputs from the inferior temporal cortex (ITC) and perirhinal cortex (PRC) and can therefore be considered visual PFC. Usually, the functions of temporal cortex and visual PFC have been discussed in separate literatures. By considering them together, we aim to clarify the ways in which fronto-temporal networks guide decision making. After discussing the ways in which visual PFC interacts with temporal cortex to promote decision making, we offer specific predictions about the selective roles of the ITC- and PRC-based fronto-temporal networks. Finally, we suggest that an increased reliance on visual PFC in anthropoid primates led to our emergence as 'visual' animals.