Abstract
Decision-making and other cognitive processes are assumed to take place in the prefrontal cortex. In particular, the medial prefrontal cortex (mPFC) is identified in rodents by its dense connectivity with the mediodorsal (MD) thalamus, and because of its inputs from other sites, such as hippocampus and amygdala (Amyg). The aim of this study was to find a putative relationship between the behavior of mice during the performance of decision-making tasks that involve penalties as a consequence of induced actions, and the strength of field postsynaptic potentials (fPSPs) evoked in the prefrontal cortex from its thalamic, hippocampal, and amygdalar afferents. Mice were chronically implanted with stimulating electrodes in the MD thalamus, the hippocampal CA1 area, or the basolateral amygdala (BLA), and with recording electrodes in the prelimbic/infralimbic area of the prefrontal cortex. Additional stimulating electrodes aimed at evoking negative reinforcements were implanted on the trigeminal nerve. FPSPs evoked at the mPFC from the three selected projecting areas during the food/shock decision-making task decreased in amplitude with shock intensity and animals’ avoidance of the reward. FPSPs collected during the operant task also decreased in amplitude (but that evoked by amygdalar stimulation) when lever presses were associated with a trigeminal shock. Results showed a general decrease in the strength of these potentials when animals inhibited their natural or learned appetitive behaviors, suggesting an inhibition of the prefrontal cortex in these conflicting situations.
Highlights
When an animal has to select one out of two or more actions, a conjunction of cognitive processes is developed in order to take the most appropriate decision
FPSPs collected during the operant task decreased in amplitude when lever presses were associated with a trigeminal shock
We studied the electrophysiological properties of the three mentioned synapses by determining their input/output curves (I-O), paired-pulse facilitation (P-P), and long-term potentiation (LTP) through a high-frequency-stimulation (HFS) protocol
Summary
When an animal has to select one out of two or more actions, a conjunction of cognitive processes is developed in order to take the most appropriate decision. Among the main connections of the prefrontal cortex are afferents from the hippocampal CA1 area (Thierry et al, 2000; Takita et al, 2007; Parent et al, 2010), and the two bidirectional connections with the mediodorsal (MD) thalamic nucleus (Rose and Woolsey, 1948; Herry et al, 1999; Herry and Garcia, 2002), and the Amyg (Gabbott et al, 2005, 2012; Cressman et al, 2010). Varicose fibers and terminal hippocampal arborizations are present in layers II–VI of the ventral portion, while the innervation is less dense in the deep layers (V–VI) of the dorsal prelimbic area. Synaptic contacts between MD thalamocortical terminals and GABAergic interneurons have been described in the prelimbic cortex and between GABAergic terminals and corticothalamic neurons projecting to the MD (Kuroda et al, 2004). Neurons in the BLA projects monosinaptically onto corticospinal neurons in the mPFC that, at the same time, projects to the thoracic spinal cord and to subcortical regions, as the lateral hypothalamus (Gabbott et al, 2012)
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