Neuronal Population Encoding of Identity in Primate Prefrontal Cortex.

The ventrolateral prefrontal cortex (VLPFC) shows robust activation during the perception of faces and voices. However, little is known about what categorical features of social stimuli drive neural activity in this region. Since perception of identity and expression are critical social functions, we examined whether neural responses to naturalistic stimuli were driven by these two categorical features in the prefrontal cortex. We recorded single neurons in the VLPFC, while two male rhesus macaques (Macaca mulatta) viewed short audiovisual videos of unfamiliar conspecifics making expressions of aggressive, affiliative, and neutral valence. Of the 285 neurons responsive to the audiovisual stimuli, 111 neurons had a main effect (two-way ANOVA) of identity, expression, or their interaction in their stimulus-related firing rates; however, decoding of expression and identity using single-unit firing rates rendered poor accuracy. Interestingly, when decoding from pseudo-populations of recorded neurons, the accuracy for both expression and identity increased with population size, suggesting that the population transmitted information relevant to both variables. Principal components analysis of mean population activity across time revealed that population responses to the same identity followed similar trajectories in the response space, facilitating segregation from other identities. Our results suggest that identity is a critical feature of social stimuli that dictates the structure of population activity in the VLPFC, during the perception of vocalizations and their corresponding facial expressions. These findings enhance our understanding of the role of the VLPFC in social behavior.

[Treatment of orthostatic hypotension with metoclopramide]. / Tratamento da hipotensão ortostática com metoclopramida.

A 38 year-old woman, with orthostatic hypotension secondary to autonomic dysfunction accompanied by sympathetic hyperactivity and excess of dopamine, was treated with an antagonistic dopaminergic drug, metoclopramide, 30 mg/day, with good tolerance. Support intervention as well as the use of various drugs (beta-blockers, caffeine, fludrocortisone, haloperidol) showed no effect. The answer to metoclopramide both subjective and objective were remarkable. The way in which metoclopramide acts has not yet been fully clarified. Being a widely used drug, well tolerated, its use must be considered in cases of severe orthostatic hypotension, especially those with an excess of dopamine.