Early life experiences affect the formation of neuronal networks, which can have a profound impact on brain function and behavior later in life. Previous work has shown that mice exposed to excessive sensory stimulation during development are hyperactive, novelty-seeking and display impaired cognition compared to controls. In this study, we addressed the issue of whether excessive sensory stimulation during development could alter behaviors related to addiction and underlying circuitry in CD-1 mice. We found that the reinforcing properties of cocaine were significantly enhanced in mice exposed to excessive sensory stimulation. Moreover, although these mice displayed hyperactivity that became more pronounced over time, they showed impaired persistence of cocaine-induced locomotor sensitization. These behavioral effects were associated with alterations in glutamatergic transmission in the nucleus accumbens and amygdala. Together, these findings suggest that excessive sensory stimulation in early life significantly alters drug reward and the neural circuits that regulate addiction and attention-deficit hyperactivity. These observations highlight the consequences of early-life experiences and may have important implications for children growing up in today’s complex technological environment.
Significance Statement: Environmental stimulation in the form of enrichment has been shown to be beneficial for brain development and behavior. Although this has been broadly interpreted as stimulating the developing brain is positive, recent work demonstrates that sensory stimulation can in fact have negative consequences, particularly if it is non-normative, extensive and presented during development. This research adds to existing knowledge on the impact of early-life experiences and provides fundamental insights into how environmental factors during development can shape the brain and behavior. At a point where childhood and adolescence is increasingly dominated by exposure to audio-visual media, we believe our findings build the case for further investigation on the effects of extended exposure to sensory experiences in early life.
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