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Effects of Intracochlear High-Rate Electrical Stimulation on the Spontaneous Activity of the Higher Auditory Pathway
蜗内高速率电刺激对高级听觉通路的自发活动的影响
Dietmar Basta, Ph.D.[1]/[2]博士
Romy Goetze, M.Sc.[2]医学硕士
Moritz Groeschel, M.Sc.[2]硕士
Oliver Janke, M.D.[2]医学博士
Patrick Boyle, M.Sc.[3]医学硕士
Arne Ernst, M.D.[1]医学博士
[1] Unfallkrankenhaus Charité Medical School, Berlin, Germany 德国柏林慈善医科学院
[2] Humboldt University, Berlin, Germany 德国柏林洪堡大学
[3] Advanced Bionics, Europe美国AB人工耳蜗公司欧洲分部
The advantage of high-rate stimulation up to 5000
pulses per second per channel (pps/ch) for speech
perception in cochlear implant recipients has been
well demonstrated. The neurophysiological consequences
of stimulation rates above 800 pps (i.e., the
expected maximum firing rate of a single auditory
nerve fiber) also have been observed (Oertel et al,
2002). For example, higher rates can decrease the
amplitudes of electrical evoked compound action
potentials and lengthen their latencies. Some studies
indicate that increasing stimulation rates abolishes
EABR responses for several hours and prolonged
stimulation at higher rates increases EABR thresholds
(Tykocinski et al, 1995; Xu et al, 1997). In
contrast, other studies demonstrate that EABR
thresholds and survival rate of spiral ganglion cells
do not depend on stimulation rate (Cords et al,
1997; Reuter et al, 1997).
每个通道5000脉冲每秒的高速率刺激对人工耳蜗植入者的言语感知的好处已经得到了很好的实证。高于800脉冲每秒刺激速率（也就是说，预期的单根听神经的最大触发率）的神经生理学结论也已经被观测到（Oertel et al, 2002）。例如：更高的刺激速率能增强电诱发化合行为的振幅，并增加它们的反应时间。一些研究显示高刺激速率让EABR反应好消失了几个小时，还有结果显示高刺激速率的长时刺激提高了EABR的阈值。（Tykocinski et al, 1995; Xu et al, 1997）。相反地，另有研究证明EABR阈值和螺旋神经节细胞的存活率和刺激速率的高低无甚关联。（Cords et al, 1997; Reuter et al, 1997）.
Because the data concerning the effects of stimulation
rate are inconsistent, the upper rate limit for
safe and physiologically acceptable electrical stimulation
is not clear. Another important point is that
earlier studies primarily used summating potentials,
which are not sufficiently sensitive to monitor minor
cellular or synaptic changes—indicating the initiation
of long-term physiological changes following
high-rate electrical stimulation. Thus, it is important
to investigate the electrophysiological consequences
of chronic high-rate electrical stimulation
on the auditory pathway at a cellular level—that is,
the effect of stimulation on spontaneous neuronal
activity. Moreover, because a change in spontaneous
activity in the neuronal network of higher auditory
centers could contribute to a change in the auditory
perception of cochlear implant users, this information
is clinically relevant.
因为有关刺激速率效果的数据相互矛盾，电刺激的安全上限和神经生理学上可接受阈值尚不清楚。另外一个关键之处在于早期研究主要使用总和电位法，这一方法不能足够敏感地检测次级细胞或神经突触的变化——这些都标志着高速率电刺激产生的长期生理学变化的伊始。因此，在细胞水平下，即对自发性神经活动的影响进行研究，探知听觉通路在长期高速率电刺激下的电生理学结果是很重要的。此外，因为在高级听觉中心的听觉网络中，自发活动的变化能够有助于改变人工耳蜗植入者的听觉感知，所以这一信息具有临床意义。
Therefore, this study investigated the effect of chronic
intracochlear high-rate stimulation on the spontaneous
activity in living brain slices of the medial
geniculate body (MGB) and primary auditory cortex
(AC). Sixteen guinea pigs were implanted unilaterally
with a HiRes 90K implant and HiFocus electrode
array. After recovery from surgery, the implants
were activated in eight animals with a stimulation
rate of 5000 pps/ch and a pulse duration of 11 μs
per phase using the HiRes strategy. The other eight
animals were not activated and served as controls.
The speech processor parameters were set based on
NRI data and behavioral reactions to sound. After
12 weeks of daily use (16 hours per day) in a standardized
species-relevant acoustical environment,
single-unit recordings were made in living brain
slices of the MGB and AC.
因此，本项研究从内侧膝状体和主要听觉皮层的的活体切片入手，研究了长期蜗内高速率电刺激对自发活动的影响。16只豚鼠被单侧植入了拥有HiFocus平板高聚焦预弯电极的HiRes 90K植入体。手术恢复之后，其中8只豚鼠激活使用5000脉冲每秒刺激速率且每个相位的脉冲周期为11微秒的HiRes高分辨率言语编码策略。另外8只豚鼠没有激活使用这种言语编码策略但依然受控。根据神经反应成像（NRI）数据和对声音的行为反应，我们设置好声音处理器的参数。在一个标准化的物种相关听觉环境下，经过了12周的日常使用（每天16个小时），受验动物作为单组记录，制出了内侧膝状体和主要听觉皮层的的活体切片。
Based on recordings from 334 neurons, no statistically
significant differences were found in spontaneous
activity between the implanted and
nonimplanted sides of the MGB or AC in the
activated animals. There also were no differences in
spontaneous activity between the study and control
animals on the implanted sides. This finding indicates
that there were no negative effects of high-rate
electrical stimulation found in the higher auditory
system. Subsequent to these data, the effects of
chronic intracochlear high-rate electrical stimulation
on the lower auditory pathway now is under investigation.
The results of these studies together will
improve understanding of the safety and efficacy of
stimulation parameters (rate, duration) for cochlear
implant users.
基于对334个神经元细胞的记录，激活使用了HiRes高分辨率言语编码策略的动物的植入侧和未植入侧的内侧膝状体和主要听觉皮层的神经元细胞之间在自发活动方面未见任何明显不同。未使用HiRes高分辨率言语编码策略的动物的植入侧和未植入侧的内侧膝状体和主要听觉皮层的神经元细胞之间在自发活动方面也未见任何明显不同。这一发现显示：在高级听觉系统中，高速率电刺激的负面影响未见发现。根据这些数据，在更低的听觉通道中，长期蜗内高频率电刺激的影响正在研究中。这些研究结果将会一同提高对人工耳蜗使用者的刺激参数（频率，周期）的安全性和功效性的理解。
References参考条目
Cords SM, Reuter G, Issing P, Lenarz T. (1997) Development of the evoked auditory
brain stem response amplitude peak IV during chronic electrical, intracochlear,
multichannel high-rate stimulation. Am J Otol 18(6 Suppl.):S22-S23.
Oertel D, Fay RR, Popper AN. eds. (2002) Integrative Functions in the Mammalian
Auditory Pathway, Springer Handbook of Auditory Research, Vol. 15, New York:
Springer.
Reuter G, Cords SM, Issing P, Lenarz T. (1997) Acute and chronic effects of electrical
intracochlear multichannel high rate stimulation on the auditory brainstem response
in neonatally deafened kittens. Adv Otorhinolaryngol 52:46-51.
Tykocinski M, Shepherd RK, Clark GM. (1995) Reduction in excitability of the
auditory nerve following electrical stimulation at high stimulus rates. Hear Res
88(1-2):124-142.
Xu J, Shepherd RK, Millard RE, Clark GM. (1997) Chronic electrical stimulation
of the auditory nerve at high stimulus rates: a physiological and histopathological
study. Hear Res 105(1-2):1-29. |
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发表于 2010-12-29 00:35
发表于 2010-12-29 10:00
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