Prevalence and modulation of rat off-track head-scanning on linear tracks: possible implications for representational and dynamical properties of hippocampal place cells

(Re)mapping of different environments by hippocampal place cells is thought to reflect incidental learning. Rat "head scanning" is a spontaneous and presumed investigatory behavior that can trigger the onset of firing locations in place cells. This behavior was studied on (quasi-)circular tracks, and it was speculated that off-track head scans might have been overlooked or inadvertently discouraged in studies employing more common apparatus. To better understand the general prevalence and significance of off-track scanning, we investigated it in rats running laps on linear tracks in rooms featuring visual landmarks. Scanning spanned the length of the track, even in highly familiar conditions and in rats rewarded only at the two ends of the track. Thus, co-localized rewards are not necessary for the occurrence of this behavior. Scanning rate increased markedly in a novel room and then declined steeply during each daily session in this room over 3 days. Transient increases at the beginning of each daily session partially counteracted this decline, producing a "seesaw" profile that is reminiscent of previous observations on place cell plasticity. Therefore, the remapping that place cells are known to undergo in similar contextual changes could conceivably be facilitated by the putative surge of new place fields induced by increased scanning. Investigatory behaviors could thus be causally involved in the representational and dynamic properties of hippocampal representations. Addressing these possibilities offers insight into the incidental creation and update of a cognitive map. HIGHLIGHTSO_LIRat head scanning is known to trigger the onset of firing locations in place cells C_LIO_LIOff-track scanning occurs on linear tracks in familiar and novel conditions C_LIO_LICo-localized rewards are not necessary for scanning events C_LIO_LIResponse to a novel room resembles that seen in place cell dynamics C_LIO_LIRelationships between head scanning and place field formation could help uncover the incidental process of map making C_LI