Long-term effects of neonatal hippocampal lesions on novelty preference in monkeys

Abstract

In a recent longitudinal study to assess the development of incidental recognition memory processes in monkeys, we showed that the effects of neonatal hippocampal lesions did alter incidental recognition memory only when the animals reached the juvenile period (Zeamer et al., 2010). The current follow-up study tested whether this incidental memory loss was long-lasting, i.e. present in adulthood, or only transitory, due to functional compensation with further brain maturation. The same animals with neonatal hippocampal lesions and their sham-operated controls were re-tested in the visual paired-comparison task when they reached adulthood (48 months). The results demonstrated that, at least for easily discriminable color pictures of objects, the involvement of the hippocampus was only transitory, given that when re-tested as adults, animals with neonatal hippocampal lesions performed as well as sham-operated controls at all delays. Yet, significant recognition memory impairment was re-instated when the discriminability of the stimuli was made more difficult (Black/White pictures of similar objects). The data demonstrate profound functional remodeling within the hippocampus and its interactions with different medial temporal lobe structures from the juvenile period to adulthood, which is substantiated by a parallel morphological maturation of hippocampal intrinsic circuits (Lavenex et al., 2007a; Jabès et al., 2011).

Alterations of hippocampal projections in adult macaques with neonatal hippocampal lesions: A Diffusion Tensor Imaging study

“…Details of the MRI-guided surgical procedures, lesion evaluation and rearing conditions were reported previously (Goursaud and Bachevalier, 2007; Zeamer et al, 2010). Development of cognitive functions was evaluated in the same cohorts of animals at different time points during development and included measures of object recognition memory (Heuer and Bachevalier, 2011a; Zeamer and Bachevalier, 2013; Zeamer et al, 2010), memory for location and object/place associations (Blue et al, 2013), memory for food/place associations (Glavis-Bloom et al, 2013) and working memory (Heuer and Bachevalier, 2011b, 2013). …”

“…Pearson’s correlation analysis in the Neo-Hibo group was carried out to evaluate the relation between with the memory scores in recognition and working memory tasks (Heuer and Bachevalier, 2013; Zeamer and Bachevalier, 2013) and the DTI-derived measures with significant group difference revealed by TBSS analysis, volume-of-interest analysis, and tracts-defined analysis, as stated above. For the incidental object recognition task (Zeamer and Bachevalier, 2013), memory scores were represented by the percent looking at novel black-white pictures at delays of 120-s collected at 48 months of age ( n = 4).…”

“…For the incidental object recognition task (Zeamer and Bachevalier, 2013), memory scores were represented by the percent looking at novel black-white pictures at delays of 120-s collected at 48 months of age ( n = 4). In the 4-objects serial order working memory task (SMOT) (Heuer and Bachevalier, 2013), memory scores were ratio scores measuring cumulative correct responses on the inner object discrimination (2 vs 3) divided by the number of correct responses on the outer discrimination (1 vs 4) across the three-day probe sessions collected at 6 and 8 years of age ( n = 5).…”

“…These deficits include impairment in object recognition memory (Zeamer and Bachevalier, 2013; Zeamer et al, 2010), memory for food/place associations (Glavis-Bloom et al, 2013), and memory for spatial locations and object/place associations (Blue et al, 2013). Interestingly, the neonatal hippocampal lesions appeared to have altered widespread neural systems given that the same animals also presented with loss of working memory processes (Heuer and Bachevalier, 2011a, 2013) thought to be mediated by the lateral prefrontal cortex (Curtis and D'Esposito, 2004; Owen, 2000; Petrides, 2005).…”

Increased anxiety-like behaviors, but blunted cortisol stress response after neonatal hippocampal lesions in monkeys

“…Our previous studies have demonstrated that neonatal lesion of the hippocampus critically alter the development of memory processes, including visual recognition memory (Zeamer et al, 2010; Zeamer & Bachevalier, 2013), spatial memory (Blue et al, 2013; Glavis-Bloom et al, 2013), and working memory processes (Heuer & Bachevalier, 2011, 2013). These studies provide strong evidence that damage to the hippocampus has a deleterious and long-lasting effect on the development of memory as it does in adult subjects (Nemanic, et al, 2004; Alvarado & Bachevalier, 2005; Bachevalier & Nemanic, 2008).…”