The hippocampus may be more susceptible to environmental noise than the auditory cortex

Abstract

Noise exposure can cause structural and functional problem in the auditory cortex (AC) and hippocampus, the two brain regions in the auditory and non-auditory systems respectively. The aim of the present study was to explore which one of these two brain regions may be more susceptible to environmental noise. The AC and hippocampus of mice were separated following 1 or 3 weeks exposure to moderate noise (80 dB SPL, 2 h/day). The levels of oxidative stress and tau phosphorylation were then measured to evaluate the effects by noise. Results showed significant peroxidation and tau hyperphosphorylation in the hippocampus with 1 week of noise exposure. However, the AC did not show significant changes until exposure for 3 weeks. These data suggest that although the hippocampus and AC were affected by moderate noise exposure, the hippocampus in the non-auditory system may have been more vulnerable to environmental noise than the AC.

Loud Noise Exposure Produces DNA, Neurotransmitter and Morphological Damage within Specific Brain Areas

“…For instance, in rodents exposed to loud noise persistent cognitive and memory impairment were observed in association with tau phosphorylation and neuronal apoptosis both in dentate gyrus (DG) and CA of the hippocampus. This hippocampal pathology was related to altered monoamine and amino-acidic hippocampal innervation (Cui et al, 2013; Busceti et al, 2015; Cheng et al, 2016). …”

“…In noise-exposed rats, impairment in spatial and associative memory is accompanied by an imbalance between pro- and anti-oxidants in the hippocampus and cerebellum (Uran et al, 2010; Cheng et al, 2016; Sikandaner et al, 2017). Remarkably, the hippocampus, despite not belonging to the auditory pathways, was recently shown to be more vulnerable than the auditory cortex to environmental noise (Cheng et al, 2016).…”

“…Remarkably, the hippocampus, despite not belonging to the auditory pathways, was recently shown to be more vulnerable than the auditory cortex to environmental noise (Cheng et al, 2016). In particular, Cheng et al (2011, 2016) hypothesized that noise-induced oxidative stress can be transmitted to hippocampus via ascendant lemniscal and inferior colliculus, thus causing memory impairment and pathological tau hyperphosphorylation.…”

“…Remarkably, the hippocampus, despite not belonging to the auditory pathways, was recently shown to be more vulnerable than the auditory cortex to environmental noise (Cheng et al, 2016). In particular, Cheng et al (2011, 2016) hypothesized that noise-induced oxidative stress can be transmitted to hippocampus via ascendant lemniscal and inferior colliculus, thus causing memory impairment and pathological tau hyperphosphorylation. Manikandan et al (2006) also reported that cognitive impairment related to noise-induced stress is associated with altered hippocampal neuronal dendritic function and abnormal tau phosphorylation, which in turn, might depend on the loss of cytoskeleton integrity.…”

“…In particular, due to a massive involvement of the hippocampus in the effects of loud noise, we focused on the potential noise-induced hippocampal alterations. It is reported that loud noise exposure induces hippocampal damage such as apoptosis (Säljö et al, 2002; Cui et al, 2013; Kim et al, 2013), and tau-phosphorylation (Cui et al, 2012, 2013; Cheng et al, 2016). …”