Early life adversity: Lasting consequences for emotional learning

Abstract

The early postnatal period is a highly sensitive time period for the developing brain, both in humans and rodents. During this time window, exposure to adverse experiences can lastingly impact cognitive and emotional development. In this review, we briefly discuss human and rodent studies investigating how exposure to adverse early life conditions – mainly related to quality of parental care - affects brain activity, brain structure, cognition and emotional responses later in life. We discuss the evidence that early life adversity hampers later hippocampal and prefrontal cortex functions, while increasing amygdala activity, and the sensitivity to stressors and emotional behavior later in life. Exposure to early life stress may thus on the one hand promote behavioral adaptation to potentially threatening conditions later in life –at the cost of contextual memory formation in less threatening situations- but may on the other hand also increase the sensitivity to develop stress-related and anxiety disorders in vulnerable individuals.

Chronic early life stress induced by limited bedding and nesting (LBN) material in rodents: critical considerations of methodology, outcomes and translational potential

“…While hippocampal dependent learning and memory processes are generally hampered, LBN in fact enhances contextual aspects of conditioned fear as described above (Arp, et al, 2016; Krugers, et al, 2016). In particular, LBN reduces the ability to discriminate between tone-on and tone-off periods in an auditory fear-conditioning paradigm (Arp, et al, 2016).…”

“…maternal separation during the entire postnatal period, it was reported that stressed females, but not males had increased infralimbic mPFC apical dendritic branch number and length at PND40 compared to controls (Farrell, Holland, Shansky, & Brenhouse, 2016). Together, these studies suggest that ELS, and in particular LBN, tends to hamper higher order cognitive functions while enhancing the emotional aspects, in particular expression of conditioned fear (Krugers, et al, 2016). …”

“…The models of ELS discussed here using both intermittent and continuous exposure to ELS have documented long term effects on fear and anxiety, allowing probing of the mechanisms by which ELS increases vulnerability to these pathologies (Krugers et al, 2016). As is documented here, the LBN paradigm produces an animal that shows increased fear but also decreased responses to safety.…”

Stress early in life leads to cognitive impairments, reduced numbers of CA3 neurons and altered maternal behavior in adult female mice

“…Many studies show the critical importance of the postnatal period for individual development because stress in this period can have delayed effects on cognition, individual behavior, neuronal plasticity and epigenetics . Nevertheless, the mouse and rat studies on MS and HD effects on cognition in adult females are limited.…”

Bushmeat trade consequences predict higher anxiety, restraint, and dominance in chimpanzees

“…In the same line, other authors noted that early maternal rejection predicted increases in child fear and irritability (Lengua, ) and infants of postpartum depressed mothers expressed more negative emotions (Whiffen & Gotlib, ). Parental separation, the quality of parental behavior, childhood trauma, high stress exposure, and abuse may thus be specific vulnerability factors for several mental disorders such as post‐traumatic stress disorder (Pratchett & Yehuda, ), major depressive episodes (Aguilera et al, ; Cai et al, ), anxiety (Krugers et al, ), cognitive impairment (Barzilay et al, ), risk for phobia (Kendler, Neale, Kessler, Heath, & Eaves, ), violent aggression (Mitjans et al, ), and psychotic experiences (Alemany et al, ), among others. The increased risks of personality disorders were particularly characteristic of individuals separated from mothers before the age of five and more prevalent in men (Lahti et al, ), and the development of some of these disorders are mediated by personality organization (Fuchshuber, Hiebler‐Ragger, Kresse, Kapfhammer, & Unterrainer, ).…”