Differential Cortical c-Fos and Zif-268 Expression after Object and Spatial Memory Processing in a Standard or Episodic-Like Object Recognition Task

Abstract

Episodic memory reflects the capacity to recollect what, where, and when a specific event happened in an integrative manner. Animal studies have suggested that the medial temporal lobe and the medial pre-frontal cortex are important for episodic-like memory (ELM) formation. The goal of present study was to evaluate whether there are different patterns of expression of the immediate early genes c-Fos and Zif-268 in these cortical areas after rats are exposed to object recognition (OR) tasks with different cognitive demands. Male rats were randomly assigned to five groups: home cage control, empty open field (CTR-OF), open field with one object (CTR-OF + Obj), novel OR task, and ELM task and were killed 1 h after the last behavioral procedure. Rats were able to discriminate the objects in the OR task. In the ELM task, rats showed spatial (but not temporal) discrimination of the objects. We found an increase in the c-Fos expression in the dorsal dentate gyrus (DG) and in the perirhinal cortex (PRh) in the OR and ELM groups. The OR group also presented an increase of c-Fos expression in the medial prefrontal cortex (mPFC). Additionally, the OR and ELM groups had increased expression of Zif-268 in the mPFC. Moreover, Zif-268 was increased in the dorsal CA1 and PRh only in the ELM group. In conclusion, the pattern of activation was different in tasks with different cognitive demands. Accordingly, correlation tests suggest the engagement of different neural networks in the tasks used. Specifically, perirhinal-DG co-activation was detected after the what-where memory retrieval, but not after the novel OR task. Both regions correlated with the respective behavioral outcome. These findings can be helpful in the understanding of the neural networks underlying memory tasks with different cognitive demands.

Role of the anterior cingulate cortex in the retrieval of novel object recognition memory after a long delay

“…Interestingly, using early-gene activation techniques, Barbosa and co-workers analysed the correlation between cognitive demand in object recognition variants (discrimination between novel and familiar object and spatiotemporal discrimination of familiar object) and activation of the mPFC including the ACgx. They found that the number of c-Fos and Zif-268-positive neurons in the mPFC was significantly increased compared with the control condition after retrieval of a NOR task (Barbosa et al 2013). These data suggest that activity within the mPFC is associated with successful retrieval of NOR.…”

D2 dopamine receptor regulation of learning, sleep and plasticity

“…Since Zif-268 levels in the hippocampus are increased 1-2 h after a novel stimulus (Barbosa et al, 2013), we believe that a 6 h increase in vehicle-injected animals could be related to a second wave of Zif-268 transcription and translation. This re-induction is probably related to the occurrence of REM sleep in vehicleinjected animals, but not in haloperidol-injected animals, during the 4 h interval following object exposure.…”

Memory of Occasional Events in Rats: Individual Episodic Memory Profiles, Flexibility, and Neural Substrate

“…Animal studies have to our knowledge never evaluated neural network recruitment in episodic-like memory, and in investigations of other forms of memories, distinct patterns of expression of different IEGs were often observed (Tse et al, 2011;Barbosa et al, 2013), probably because these IEGs have different functions (Davis et al, 2003). c-Fos is generally believed to reflect eventinduced neuronal activation, while the transcription factor Zif268 more likely reflects synaptic activation and plasticity mechanisms involved in long-term memory (Jones et al, 2001;Veyrac et al, 2014).…”