Deep layer prefrontal cortex unit discharge in a cue-controlled open-field environment in the freely-moving rat.

The activity of single units in prefrontal cortex (prelimbic and anterior cingulate subregions) was recorded as rats performed a 'pellet-chasing' task in a cue-controlled, open-field environment in which the position of a single salient cue card was manipulated. Spike train analyses revealed three different types of unit. The first type was characterized by rhythmic bursts of spiking with inter-burst intervals of approximately 200 ms (66% of units), the second by bursts with inter-burst intervals of approximately 80 ms (33% of units), and the third by non-rhythmic firing characteristics (33% of units). None of the units had spatially-selective firing characteristics, nor were their discharge patterns affected by manipulation of the cue card. Instead, the firing of the units had multiple behavioural correlates that occurred as the rat explored the environment. These results are in line with previous studies that suggest that prefrontal cortex unit discharge is not related to spatial processing but to behaviours necessary for exploration.