Han Ji-Hye, Lee Hyo-Jeong, Kang Hyejin, Oh Seung-Ha, Lee Dong Soo
Laboratory of Brain & Cognitive Sciences for Convergence Medicine, Hallym University College of Medicine, Chuncheon, South Korea.
Department of Otorhinolaryngology-Head and Neck Surgery, Hallym University College of Medicine, Chuncheon, South Korea.
Front Hum Neurosci. 2019 Feb 19;13:38. doi: 10.3389/fnhum.2019.00038. eCollection 2019.
Sensory plasticity, which is associated with deafness, has not been as thoroughly investigated in the adult brain as it has in the developing brain. In this study, we examined the brain reorganization induced by auditory deprivation in people with adult-onset deafness and its clinical relevance by measuring glucose metabolism before cochlear implant (CI) surgery. F-18 fluorodeoxyglucose positron emission tomography (F-FDG-PET) scans were performed in 37 postlingually deafened patients during the preoperative workup period, and in 39 normal-hearing (NH) controls. Behavioral CI outcomes were measured at 1 year after implantation using a phoneme identification test with auditory cueing only. In the deaf individuals, areas involved in the auditory pathway such as the inferior colliculus and bilateral superior temporal gyri were hypometabolic compared to the NH controls. The hypometabolism observed in the deaf auditory cortices gradually returned to levels similar to the controls as the duration of deafness increased. However, contrary to our previous findings in congenitally deaf children, this metabolic recovery failed to have a significant prognostic value for the recovery of the speech perception ability in adult CI patients. In a broad occipital area centered on the primary visual cortices, glucose metabolism was higher in the deaf patients than the controls, suggesting that the area had become visually hyperactive for sensory compensation immediately after the onset of deafness. In addition, a negative correlation between the metabolic activity and behavioral speech perception outcomes was observed in the visual association areas. In the medial frontal cortices, cortical metabolism in most patients decreased, but patients who had preserved metabolic activities showed better speech performance. These results suggest that the auditory cortex in people with adult-onset deafness is relatively resistant to cross-modal plasticity, and instead, individual traits in late-stage visual processing and cognitive control seem to be more reliable prognostic markers for adult-onset deafness.
与耳聋相关的感觉可塑性在成人大脑中的研究不如在发育中的大脑中深入。在本研究中，我们通过测量人工耳蜗（CI）植入手术前的葡萄糖代谢，研究了成人后天性耳聋患者因听觉剥夺引起的大脑重组及其临床相关性。对37例语后聋患者在术前检查期间进行了F-18氟脱氧葡萄糖正电子发射断层扫描（F-FDG-PET），并与39例听力正常（NH）的对照者进行了比较。植入后1年，仅使用听觉提示的音素识别测试来测量CI的行为结果。与NH对照组相比，耳聋个体中涉及听觉通路的区域，如下丘和双侧颞上回，代谢减低。随着耳聋持续时间的增加，在耳聋听觉皮层中观察到的代谢减低逐渐恢复到与对照组相似的水平。然而，与我们之前在先天性耳聋儿童中的发现相反，这种代谢恢复对成人CI患者言语感知能力的恢复没有显著的预后价值。在以初级视觉皮层为中心的广泛枕叶区域，耳聋患者的葡萄糖代谢高于对照组，这表明在耳聋发生后，该区域立即因感觉补偿而视觉活动增强。此外，在视觉联合区观察到代谢活动与行为言语感知结果之间呈负相关。在内侧额叶皮层，大多数患者的皮层代谢降低，但代谢活动保留的患者言语表现更好。这些结果表明，成人后天性耳聋患者的听觉皮层对跨模态可塑性相对不敏感，相反，晚期视觉处理和认知控制中的个体特征似乎是成人后天性耳聋更可靠的预后标志物。
