CORTICAL AND BEHAVIORAL RESPONSES TO COCHLEAR IMPLANTS

临床经验和心理物理学研究表明，人工耳蜗每个通道上的电流配置对语音和其他信号的识别有很大影响。该研究项目的目标是阐明与正常听力和假体听力相关的机制，以指导临床刺激策略的发展。所提出的实验将比较由各种耳蜗电流配置确定的听觉皮层中的刺激表征的质量。单极和其他配置，假定产生弥漫性神经激活将与双极和其他配置认为产生更多的局灶性激活进行比较。实验将在豚鼠中进行。具体目标1是表征响应于单个耳蜗通道刺激的跨皮层位置和刺激后时间的单位活动的分布。多通道皮质记录探头将允许在16个皮质部位同时进行单位记录。人工神经网络技术将测试根据皮层活动模式识别耳蜗刺激通道的准确性。刺激电流水平将相对于个体受试者评估的心理物理阈值来表示。具体目标2将使用单脉冲和调幅脉冲串测试耳蜗通道之间的相互作用。将量化刺激调制的皮质锁相，然后评估第二耳蜗通道上出现的同时或交错掩蔽脉冲串的影响。具体目标3中的动物心理物理实验将测量第二耳蜗通道上存在和不存在掩蔽物的调制检测阈值。刺激条件将进行比较，在皮层实验中，最大限度地减少或最大限度地增加耳蜗通道之间的相互作用。具体目标4是确定特别适合于各种耳聋和刺激病史的电流配置。结果将被用来检查中枢机制，耳聋和刺激的持续时间的影响。这些结果将被用来检查中枢机制，耳聋的持续时间对假体功能的影响。

Clinical experience and psychophysical research indicate that the configuration of electrical currents on each channel of a cochlear prosthesis can have great impact on recognition of speech and other signals. The goal of this research program is to elucidate mechanisms relevant to normal and prosthetic hearing that can guide development of clinical stimulation strategies. The proposed experiments will compare the quality of stimulus representation in the auditory cortex determined by various cochlear current configurations. Monopolar and other configurations that are presumed to produce diffuse neural activation will be compared with bipolar and other configurations thought to produce more focal activation. Experiments will be conducted in guinea pigs. Specific Aim 1 is to characterize the distribution of unit activity across cortical location and post-stimulus time in response to stimulation of a single cochlear channel. Multi-channel cortical recording probes will permit simultaneous unit recording at 16 cortical sites. Artificial neural-network techniques will test the accuracy with which cochlear stimulation channels can be identified on the basis of patterns of cortical activity. Stimulus current levels will be expressed relative to psychophysical thresholds assessed in individual subjects. Specific Aim 2 will test interactions between cochlear channels, using single pulses and amplitude-modulated pulse trains. Cortical phase locking to stimulus modulation will be quantified, then the influence of a simultaneous or interleaved masking pulse train presented on a second cochlear channel will be assessed. Animal psychophysical experiments in Specific Aim 3 will measure thresholds for modulation detection in the presence and absence of a masker on a second cochlear channel. Stimulus conditions will be compared that, in the cortical experiments, either minimize or maximize interaction between cochlear channels. Specific Aim 4 is to identify current configurations that are particularly suited to various histories of deafness and stimulation. The results will be used to examine the central mechanisms that underlie effects of duration of deafness and stimulation. These results will be used to examine the central mechanisms that underlie effects of duration of deafness on prosthesis function.