Programa de Neuroimmunología - IDIBAPS


"Posterior Parietal and Prefrontal cortex involvement in a rat auditory parametric working memory task"

By Athena Akrami, Princeton University

Abstact: Parametric Working Memory (PWM) is the short-term storage of graded stimuli to guide behavior, and its neural correlates have been studied in primates, but until recently, there has been no demonstration of this capacity in rodents. To extend this understanding to rodents and improve our knowledge about the neural mechanisms of PWM, we have developed the first parametric delayed comparison task in rats, using vibratory stimuli applied on whiskers. We have further devised an auditory version of this task, in which rats compare two sequential auditory stimuli, ‘f1’ and ‘f2’, separated by a variable delay. Stimuli consist of broadband noise (2K-20K Hz), generated as a series of Sound Pressure Level (SPL) values sampled from a zero-mean normal distribution. Rats should judge which of f1 and f2 had greater SPL standard desviation. They show a remarkable ability to hold information about f1 stimulus in their memory for up to 9s (the longest tested).

Where and how is this information held in the brain? The prefrontal and posterior parietal cortices (mPFC and PPC) have been proposed to be involved in working memory, but no inactivation experiments probing whether these areas are necessary for parametric working memory have been performed. Here, for the first time we show that activity in PPC and mPFC is necessary for a PWM behavior. Using a logistic regresión analysis to analyze the specific task components impacted by inactivations, together with electrophysiological recordings, our data suggest distinct roles played by PPC and mPFC in auditory PWM. 

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