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FUNCTIONAL STATES OF RATS CORTICAL CIRCUITS DURING UNPREDICTABLE AVAILABILITY OF A REWARD-RELATED CUE

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2016-11-21
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Nature Publishing Group
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Proper performance of acquired abilities can be disturbed by the unexpected occurrence of external changes. Rats trained with an operant conditioning task (to press a lever in order to obtain a food pellet) using a fixed-ratio (1:1) schedule were subsequently placed in a Skinner box in which the lever could be removed randomly. Field postsynaptic potentials (fPSPs) were chronically evoked in perforant pathway-hippocampal CA1 (PP-CA1), CA1-subiculum (CA1-SUB), CA1- medial prefrontal cortex (CA1-mPFC), mPFC-nucleus accumbens (mPFC-NAc), and mPFC-basolateral amygdala (mPFC-BLA) synapses during lever IN and lever OUT situations. While lever presses were accompanied by a significant increase in fPSP slopes at the five synapses, the unpredictable absence of the lever were accompanied by decreased fPSP slopes in all, except PP-CA1 synapses. Spectral analysis of local field potentials (LFPs) recorded when the animal approached the corresponding area in the lever OUT situation presented lower spectral powers than during lever IN occasions for all recording sites, apart from CA1. Thus, the unpredictable availability of a reward-related cue modified the activity of cortical and subcortical areas related with the acquisition of operant learning tasks, suggesting an immediate functional reorganization of these neural circuits to address the changed situation and to modify ongoing behaviors accordingly.
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MINECO-BFU2014-56692-R
BIO122/P07-CVI-02686
BIO122/CVI 2487
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En este trabajo los potenciales de campo locales (LFPs) se registraron simultáneamente desde dos nodos estructurales del circuito del hipocampo (CA1, “Cormu Ammonis area 1” y SUB, Subiculum”), así como desde otros tres nodos ubicados extrínsecamente (NAc, “Nucleus Accumbens”; BLA, “Basolateral Amygdala”; y PFC, “Prefrontal Cortex”) que se han relacionado, en menor o mayor medida, con el aprendizaje asociativo, y en particular con el condicionamiento operante. La idea fue comprender cómo esta pequeña red de nodos estructurales y las sinapsis subyacentes pueden verse afectadas por la aparición inesperada de cambios externos. Para ello se diseñaron dos tipos de ensayos en uno de los cuales la palanca siempre estaba disponible (Lever IN) y en el otro se retiraba aleatoriamente (Lever OUT). Los resultados mostraron que el hipocampo no cambiaba su eficacia sináptica ni se alteraba la potencia espectral de los LFPs, sin embargo, en los nodos extrínsecos si se encontraron cambios estadísticamente significativos entre estas variables cuando se compararon las dos situaciones. Concluimos que la disponibilidad impredecible de una señal relacionada con la recompensa modificó la actividad de las áreas corticales y subcorticales relacionadas con la adquisición de tareas de aprendizaje operante, lo que sugiere una reorganización funcional inmediata de estos circuitos neuronales para abordar la situación impredecible, y en consecuencia, modificar los comportamientos en curso.
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Scientific Reports, vol 6, 37650, p. 1-17
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