Long-term effects of neonatal medial temporal ablations on socioemotional behavior in monkeys (Macaca mulatta).

Abstract

Socioemotional abnormalities, including low levels of social interaction and high levels of selfdirected activity, were reported when rhesus monkeys with neonatal ablations of either the medial temporal lobe (AH) or the inferior temporal cortex (TE) were paired with unoperated peers at two and six months of age, though these abnormalities were more severe in the AH group (Bachevalier et al., 2001). As they reached adulthood (Experiment 1), the same monkeys were re-evaluated in the same dyads and their reactivity to novel toys, social status, and reactions to separation from age-matched peers were also assessed. Group TE now showed few if any of the abnormal behaviors observed when they were infants. By contrast, Group AH continued to display low levels of social interaction, high levels of self-directed activity and submissive behavior, and reduced responses to separation, although they reacted normally to novel toys. To determine whether this degree of socioemotional impairment was less severe than that produced by the same damage in adulthood, we assessed dyadic social interactions of monkeys raised until adulthood in laboratory conditions similar to those of the earlier groups and then given the AH ablation (Experiment 2). Two months postoperatively these adult-lesioned monkeys showed a small reduction in social interactions that became more pronounced six months postoperatively, yet remained less severe than that seen in the infant-lesioned monkeys. Also, except for an increase in food and water consumption throughout this 6-month period, they showed no other socioemotional effects. The finding that neonatal AH lesions produce more severe socioemotional disturbances than the same lesion in adulthood is the reverse of the effect commonly reported for other cognitive functions after cerebral damage.

The Impact of Early Amygdala Damage on Juvenile Rhesus Macaque Social Behavior

“…Other laboratories that have conducted similar experiments, but that have isolate-reared or peer-reared (rather than mother-reared) their subjects, have found that early perturbations in social behavior persist across the developmental trajectory (e.g., Thompson et al, 1969; Thompson & Towfighi, 1976; Bachevalier, Málková, & Mishkin, 2001; Málková, Mishkin, Suomi, & Bachevalier, 2010). Similarly, social isolation exacerbates the impact of neonatal damage to the rat amygdala, such that amygdala-lesioned animals that spend time socially isolated when they were young spent less time interacting with peers than amygdala-lesioned animals raised socially later in life (Diergaarde et al, 2004).…”

Growing pains and pleasures: how emotional learning guides development

“…In fact the low levels of fear exhibited by the juvenile-lesioned animals along with other differences in social behavior suggest deficits in completely different domains of behavior (such as wariness and dominance) which are typically acquired during adolescence 77, 79 . Moreover, although the magnitude of these effects diminished over the course of development in both groups of monkeys distinct patterns in most functions did persist into adulthood suggesting that amygdala modulated social behavior in development has persistent effects 78, 80 …”

The Cerebellum, Sensitive Periods, and Autism

“…Adult lesion of this structure leads to face blindness and behavioral abnormalities such as hyperorality and decreased aggression, but if the lesion is done neonatally, these signs fade considerably over time (Málková et al, 2010). Thus inferior temporal cortex, which is well studied in ASD patients, might be regarded as a structure whose contributions to core social capacity are compensatable.…”