【摘要】：老年人的視覺系統(tǒng)存在多種多樣的功能衰退,例如空間對比度分辨,視覺信息處理速度,視覺運(yùn)動(dòng)知覺等。這些視覺功能障礙嚴(yán)重影響了老年人的日常生活、工作,例如閱讀,以及駕駛等。 前人的研究表明,老年人的視覺功能障礙不能單由眼睛光學(xué)系統(tǒng)的退化介導(dǎo),提示老化過程中存在視覺中樞神經(jīng)系統(tǒng)的衰退。與此一致的是,本實(shí)驗(yàn)室以往的研究發(fā)現(xiàn),以老年猴和老年貓為動(dòng)物模型,神經(jīng)元的反應(yīng)在多個(gè)方面、多個(gè)視覺皮層均受到了老化的影響,具體表現(xiàn)為：反應(yīng)潛伏期增長(老年猴V1區(qū)、V2區(qū))、對重復(fù)刺激的反應(yīng)變異性增大(老年猴V1區(qū)、MT區(qū))、方位方向選擇性降低(老年猴V1區(qū)、MT區(qū),老年貓V1區(qū))、對比敏感度降低(老年猴V1區(qū)、MT區(qū))等。 本研究旨在進(jìn)一步探索老化引起視覺功能衰退的神經(jīng)元反應(yīng)機(jī)制。在視覺研究領(lǐng)域,基于視覺圖像可以被大腦以不同的傅里葉成分進(jìn)行解碼處理的假說,視覺研究工作者對神經(jīng)元的空間、時(shí)間頻率反應(yīng)特性的探索由來已久。本研究使用了兩種動(dòng)物模型——獼猴(Macaca Mulatta)和貓(Falis Catus),在麻醉麻痹的狀態(tài)下,使用胞外單細(xì)胞記錄的方法,研究了視覺系統(tǒng)神經(jīng)元的空間頻率、時(shí)間頻率反應(yīng)特性。 獼猴中顳葉皮層(MT區(qū)/V5)在視覺信息處理通路中位于初級視覺皮層的下游,是運(yùn)動(dòng)視覺信息處理的關(guān)鍵皮層。我們檢測了MT區(qū)神經(jīng)元的空間和時(shí)間頻率反應(yīng)調(diào)諧特性,結(jié)果顯示：相對于青年獼猴,老年獼猴MT區(qū)神經(jīng)元的最優(yōu)空間頻率降低,最優(yōu)時(shí)間頻率降低,空間分辨率降低,時(shí)間頻率高頻截止頻率降低,同時(shí)空間頻率調(diào)諧帶寬增寬,自發(fā)放增大,信噪比降低。這些結(jié)果表明老化顯著改變了MT區(qū)神經(jīng)元的空間和時(shí)間頻率反應(yīng)調(diào)諧特性。 我們在貓視覺通路多個(gè)級別(LGN、A17區(qū)、A18區(qū)、PMLS區(qū))檢測了老化對神經(jīng)元空間頻率反應(yīng)特性的影響模式。結(jié)果顯示,位于丘腦的外側(cè)膝狀體的神經(jīng)元,其空間頻率調(diào)諧特性并未受老化的影響；而位于皮層區(qū)域(A17區(qū)、A18區(qū)、PMLS區(qū))的神經(jīng)元,其偏好的最優(yōu)空間頻率雖未受老化影響,但其空間頻率調(diào)諧帶寬均表現(xiàn)為不同程度地增寬。這一結(jié)果表明老化降低了貓視覺皮層神經(jīng)元的空間頻率選擇性。 我們的研究為老化引起的視覺功能衰退,尤其是視覺信息的空間和時(shí)間處理能力的衰退,提供了新的生理學(xué)依據(jù)。
[Abstract]:There are a variety of functional degradation in the visual system of the elderly, such as spatial contrast resolution, visual information processing speed, visual motion perception and so on. These visual disorders severely affect the elderly's daily life, work, such as reading, and driving. Previous studies have shown that the visual dysfunction of the elderly can not only be mediated by the degeneration of the optical system of the eyes, suggesting that there is a decline in the visual central nervous system during aging. Consistent with this, previous studies in our laboratory have found that the responses of neurons to aging are affected by aging in many ways, using old monkeys and cats as animal models. The specific manifestations were as follows: increased latency (V1 / V2), increased response variability to repeated stimulation (V1 / MT), and decreased azimuth selectivity (V1 / MT). In elderly cats, the contrast sensitivity was decreased (V 1 area and MT area), and so on. The aim of this study was to further explore the mechanism of neuronal response to visual impairment induced by aging. In the field of visual research, based on the hypothesis that visual images can be decoded by different Fourier components of the brain, visual researchers have been exploring the spatial and time-frequency response characteristics of neurons for a long time. In this study, two animal models, rhesus monkey (Macaca Mulatta) and cat (Falis Catus), were used to study the spatial frequency and time-frequency response of neurons in the visual system under anesthetic paralysis using extracellular single cell recording. The middle temporal cortex (MT / V 5) is located downstream of the primary visual cortex in the visual information processing pathway, and is the key cortex in the motor visual information processing. We examined the spatial and temporal response tuning characteristics of neurons in the MT region. The results showed that the optimal spatial frequency, the optimal time frequency and the spatial resolution of the neurons in the MT region of the old macaque were lower than those of the young macaque. The high frequency cutoff frequency of time and frequency is decreased, while the bandwidth of spatial frequency tuning is widened, the self-broadcasting is increased, and the signal-to-noise ratio is decreased. These results indicate that aging significantly changes the spatial and temporal response tuning characteristics of neurons in the MT region. We examined the effects of aging on the spatial frequency response of neurons at multiple levels of the visual pathway in cats (the A18 region of the LGN,A17 region). The results showed that the spatial frequency tuning characteristics of the neurons located in the lateral geniculate body of the thalamus were not affected by aging, while the preferred spatial frequency of the neurons located in the cortical region (A17 / A18 / PMLS) was not affected by aging. However, the spatial frequency tuning bandwidth is widened to some extent. These results suggest that aging reduces spatial frequency selectivity of visual cortical neurons in cats. Our research provides a new physiological basis for the decline of visual function caused by aging, especially the decline of spatial and temporal processing ability of visual information.
【學(xué)位授予單位】：中國科學(xué)技術(shù)大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2014
【分類號】：Q42

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