The Intralaminar Thalamic Nuclei Contribute to Remote Spatial Memory

Abstract

Recent studies have shown that the anterior (ATN) and lateral thalamic nuclei (including the intralaminar nuclei; ILN/LT) play different roles in memory processes. These nuclei have prominent direct and indirect connections with the hippocampal system and/or the prefrontal cortex and may thus participate in the time-dependent reorganization of memory traces during systems-level consolidation. We investigated whether ATN or ILN/LT lesions in rats influenced acquisition and subsequent retrieval of spatial memory in a Morris water maze. Retrieval was assessed with a probe trial after a short (5 d, recent memory) or a long (25 d, remote memory) postacquisition delay. The ATN group showed impaired acquisition compared with the Sham controls and ILN/LT groups, which did not differ during acquisition, and exhibited no preference for the target quadrant during the recent or remote memory probe trials. In contrast, probe trial performance in rats with ILN/LT lesions differed according to the age of the memory, with accurate spatial retrieval for the recent memory probe trial but impaired retrieval during the remote memory one. These findings confirm that ATN but not ILN/LT lesions disrupt the acquisition of spatial memory and provide new evidence that the ILN/LT region contributes to remote memory processing. Thus, the lateral thalamus may modulate some aspects of remote memory formation and/or retrieval during the course of systems-level consolidation.

Facilitation of Hippocampal Synaptogenesis and Spatial Memory by C-Terminal Truncated Nle1-Angiotensin IV Analogs

“…This "probe" trial assesses the time each rat spends searching for the missing platform in its original target quadrant and is considered a gauge of the strength of the learned response (Lopez et al, 2009), thus providing a second measure of the cognitive-enhancing properties of these Nle 1 -AngIV-related peptides. Figure 2A offers a comparison between control rats and those impaired by scopolamine application.…”

“…Persistence to remain in the target quadrant during probe trials has been used to assess the relative strength of the learning achieved during maze training (Lopez et al, 2009). Results from probe trials indicated that sequential removal of amino acids from the C terminus of Nle 1 -AngIV progressively reduced the search time in the target quadrant, thus reflecting the overall level of water maze learning.…”

The Ventral Midline Thalamus (Reuniens and Rhomboid Nuclei) Contributes to the Persistence of Spatial Memory in Rats

“…Our understanding of the neuroanatomical bases of diencephalic amnesia is complicated by the fact that KS or stroke usually affects a relatively large number of thalamic and sometimes even extrathalamic nuclei (Van der Werf et al, 2000, 2003aCarlesimo et al, 2011). Approaches in animals, which enable better circumscribed damage, suggest that intralaminar (ILN) and/or anterior thalamic nuclei lesions could be among the critical alterations accounting for diencephalic amnesia (Aggleton and Brown, 1999;Gold and Squire, 2006;Lopez et al, 2009). Thalamic nuclei that received much less attention are the reuniens (Re) and rhomboid (Rh) nuclei.…”

Remote spatial memory and the hippocampus: Effect of early and extensive training in the radial maze

“…The absence of a hippocampal gradient in some of the aforementioned studies, however, does not mean that brain circuits involved in water-or radial-maze memories are not reorganized over time during systems-level consolidation, as other studies have shown in nonspatial paradigms (Takehara et al 2003;Ross and Eichenbaum 2006). For example, in the Morris water maze test, the anterior cingulate cortex and the intralaminar thalamic nuclei are necessary for the expression of remote, but not of recent, memory (Teixeira et al 2006;Lopez et al 2009). Similarly, in place discrimination experiments using a radial maze, lesions to the anterior cingulate cortex and to the retrosplenial cortex disrupt the expression of remote, but not of recent, memory (Maviel et al 2004;Haijima and Ichitani 2008).…”