Neural Correlates of Novel Object and Novel Location Recognition Behavior in the Mouse 1 Anterior Cingulate Cortex

11 The anterior cingulate cortex (ACC) is a component of the limbic system implicated in a wide variety of functions 12 spanning motor and sensory information processing, memory, attention, novelty detection, and comparisons of 13 expectation versus outcome. It remains unclear how much of this functional diversity stems from differences in 14 methodology or interpretation versus truly reflecting the range of processes in which the ACC is involved. In the 15 present study, ACC neuronal activity was examined in freely behaving mice (C57BL6/J) under conditions allowing 16 investigation of many of the above functions in conditions free from externally applied rules: tests of novel object 17 and novel location recognition memory. Behavioral and neuronal activity was recorded first in the open field, during 18 the initial exposure and subsequent familiarization to two identical objects, and finally during the recognition 19 memory tests. No discernible stable firing correlates of ACC neurons were found in the open field, but the addition 20 of objects led to lasting changes in the firing patterns of many ACC neurons around one or both of the object 21 locations. During the novel location test, some neurons followed the familiar object to its new location, others fired 22 exclusively where the object had been, and yet others fired to both current and former object locations. Many of 23 these same features were observed during tests of object recognition memory. However, the magnitude of the 24 neuronal preference for the novel or the familiar object was markedly greater than that observed during either the 25 tests of location recognition or novel object preferences in animals that did not exhibit the expected behavior. The 26 present study reveals, for the first time, single neuron correlates of object and location recognition behaviors in the 27 rodent ACC, and suggests that neurons of the ACC provide a distributed representation of all of the salient features 28 of a task.