Environmental noise degrades hippocampus-related learning and memory

Abstract

The neural mechanisms underlying the impacts of noise on nonauditory function, particularly learning and memory, remain largely unknown. Here, we demonstrate that rats exposed postnatally (between postnatal days 9 and 56) to structured noise delivered at a sound pressure level of ∼65 dB displayed significantly degraded hippocampus-related learning and memory abilities. Noise exposure also suppressed the induction of hippocampal long-term potentiation (LTP). In parallel, the total or phosphorylated levels of certain LTP-related key signaling molecules in the synapses of the hippocampus were down-regulated. However, no significant changes in stress-related processes were found for the noise-exposed rats. These results in a rodent model indicate that even moderate-level noise with little effect on stress status can substantially impair hippocampus-related learning and memory by altering the plasticity of synaptic transmission. They support the importance of more thoroughly defining the unappreciated hazards of moderately loud noise in modern human environments.

Hippocampal Proteomic Analysis in Male Mice Following Aggressive Behavior Induced by Long-Term Administration of Perampanel

“… 15 The hippocampus is a key anatomical brain region involved in learning and memory, anxiety, and depression. 16 It is highly susceptible to drugs and environmental toxins. 17 A structural magnetic resonance imaging study found that a decreased volume of the hippocampal cortex and structural brain abnormalities were strongly associated with aggressive behavior.…”

Altered synaptic plasticity of the longitudinal dentate gyrus network in noise-induced anxiety

“…This is closely associated with anxiety-like behavior but not with short-term memory impairment. Given that previous reports have shown memory impairment following either 3 months of post-acute noise exposure ( Liu et al., 2018 ) or chronic repetitive noise exposure ( Zhang et al., 2021 ), the 2-week observation period following acute noise exposure in our animal model may not be sufficient to reveal the development of a memory deficit. This difference between our study and previous studies presumably arises from disparities in the animal species (rats vs. mice), noise levels (circumstantial vs. traumatic), age (young vs. mature), and laterality (bilateral vs. unilateral).…”

“…The hippocampus is susceptible to changes in response to noise exposure, irrespective of whether the noise is benign or traumatic. Long-term environmental noise exposure during the postnatal period (65 dB SPL) diminishes LTP in the perforant path (PP)-DG synapses and impairs hippocampus-dependent memory function ( Zhang et al., 2021 ). Traumatic noise exposure (110–120 dB) also diminishes LTP in the CA3-CA1 and PP-DG networks, although the behavioral effects of such changes have not yet been studied ( Cunha et al., 2015 ; De Deus et al., 2017 ).…”

Noise-induced hippocampal damage: potential mechanisms

“…In addition, the age of exposure seems to be a determining factor of how noise can affect the HC: it has been shown that noiseinduced hippocampal oxidative alterations in postnatal day 7 animals, should be generated through the activation of an auditoryindependent pathway, such as the mechanical vibration of the tissues (Molina et al, 2016a(Molina et al, , 2019, given that the auditory system of rats matures and becomes susceptible to sounds at approximately postnatal day 12. Finally, Zhang et al (2020) observed hippocampal and behavioral disturbances after chronic exposure to noise of about 65 dB, intensity considered non-stressful and not harmful to the auditory system. It should be noted that exposed animals were going through critical periods for development of the HC, which would make them more vulnerable to the noxious effects of noise.…”

“…It should be noted that the auditory pathway is considered the main route through which loud noise can induce oxidative stress or excitotoxicity in HC; nevertheless, it is still not entirely clear how it occurs. On the one hand, it has been suggested that hearing loss would drive hippocampal dysfunctions (Nadhimi and Llano, 2020;Zhang et al, 2020). Indeed, in addition to HC damage, different alterations have been reported in the circuits that run between the auditory system and the HC.…”