Insular cortex is involved in consolidation of object recognition memory

Abstract

Previous findings indicate that the insular cortex (IC) is involved in conditioned taste aversion and taste recognition. Here we report evidence that the IC is not uniquely dedicated to taste learning but plays a more general role in consolidating recognition memories. Immediate post-training infusions of the muscarinic cholinergic receptor antagonist scopolamine administered into the IC produced locus-specific and time-dependent impairment of object recognition memory.Extensive evidence indicates that the IC, also termed gustatory cortex, is critically involved in conditioned taste aversion and taste recognition memory (Bermudez-Rattoni 2004). Although most studies of the involvement of the IC in memory have investigated taste, there is some evidence that the IC is involved in memory that is not based on taste Paller et al. 2003;Reed et al. 2004). Converging evidence from animal and human studies suggests that a network of temporal cortical regions participates in recognition memory (Tang et al. 1997;Aggleton and Brown 1999;Malkova and Mishkin 2003;Reed et al. 2004). However, there is little information on the role of the IC in visual recognition memory. Therefore, the present study examined the involvement of the IC in the consolidation of object recognition memory, a task based on the tendency of rodents to explore a novel object more than a familiar one (Ennaceur and Delacour 1988). As microdialysis studies have shown that the release of acetylcholine in the IC in response to a novel, but not a familiar, taste stimulus (Miranda et al. 2000) and cortical cholinergic activity is involved in the acquisition of object recognition memory (Tang et al. 1997;Warburton et al. 2003), the present study examined whether the muscarinic cholinergic receptor antagonist scopolamine infused into the IC immediately after training impairs the consolidation of object recognition memory. To control for site specificity, other rats received posttraining infusions of scopolamine into the frontoparietal cortex (FPC), dorsomedial but adjacent to the IC. All experimental procedures were in compliance with NIH guidelines and approved by the UC Irvine's Institutional Animal Care and Use Committee.Adult male Sprague-Dawley rats (280-320 g at time of surgery) from Charles River Laboratories were implanted under sodium pentobarbital anesthesia (50 mg/kg, ip) with bilateral guide cannulae (23-ga.) aimed either at the IC [coordinates of the infusion sites from bregma (Paxinos and Watson 1986): anteroposterior (AP), +1.2 mm; mediolateral (ML), ‫5.5ע‬ mm; dorsoventral (DV), ‫5.6מ‬ mm] or the FPC (AP, +1.2 mm; ML, ‫0.4ע‬ mm; DV, ‫0.3מ‬ mm). Histological examination revealed that the injection needle tips were placed in the granular and agranular divisions of the IC, from ‫3.0מ‬ to +1.7 mm from bregma (Fig. 1A). Needles aimed at the FPC were found in the dorsal FPC from ‫8.0מ‬ to +1.7 mm from bregma (Fig. 1B). Three animals with cannulae misplacements were excluded from analyses, leaving 8-11 animals per group.After recovery, the rats were trai...

Subregion-specific p300 conditional knock-out mice exhibit long-term memory impairments

“…However, it remains to be investigated whether full deletion of p300 in the hippocampus induces long-term object recognition memory deficits. Cortical regions such as the perirhinal and insular cortices have been implicated in the consolidation of object recognition memory (Bermudez-Rattoni et al 2005;Winters and Bussey 2005;Barker et al 2007;Balderas et al 2008;Winters et al 2008;Roozendaal et al 2010) and p300 conditional knock-out mice lack p300 in cells within these regions. Importantly, acetylation of histone H3 is reduced in the caudal perirhinal cortex in p300 conditional knock-out mice, and lesions of this region have been correlated with recognition memory deficits (Albasser et al 2009).…”

Modulation of long-term memory for object recognition via HDAC inhibition

“…1. This evidence suggests that brain regions required for long-term memory for object recognition (9)(10)(11)(12)(13)(14)(15)(16) may be particularly sensitive to alterations in CBP activity and histone acetylation. The results from Cbp mutant mice with regard to long-term memory for object recognition suggest that this type of memory may be well suited for studying the role of histone modifying enzymes in memory formation.…”

Differential roles for Nr4a1 and Nr4a2 in object location vs. object recognition long-term memory

“…We chose to examine regions involved in object location memory and object recognition memory, as the training for these tasks is the same, but the testing depends on different brain regions. (Bermudez-Rattoni et al 2005;Balderas et al 2008;Roozendaal et al 2010;Haettig et al 2011). We performed immunohistochemistry on 20-mm coronal sections of formaldehyde fixed brain tissue from adult male mice to examine expression of NR4A1 and NR4A2 in the hippocampus as well as the insular, perirhinal, and entorhinal cortices.…”