CORTICAL AND BEHAVIORAL RESPONSES TO COCHLEAR IMPLANTS

临床经验和心理物理研究表明，人工耳蜗各通道的电流配置对语音和其他信号的识别有很大影响。本研究计划的目标是阐明与正常听力和假肢听力相关的机制，从而指导临床刺激策略的发展。所提出的实验将比较不同耳蜗电流配置决定的听觉皮层刺激表征的质量。单极和其他被认为产生弥漫性神经激活的结构将与双极和其他被认为产生更多局灶性激活的结构进行比较。实验将在豚鼠身上进行。具体目的1是表征单个耳蜗通道刺激后单位活动在皮质位置和刺激后时间的分布。多通道皮质记录探头将允许在16个皮质部位同时进行单元记录。人工神经网络技术将测试在皮层活动模式的基础上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达。具体目标2将测试耳蜗通道之间的相互作用，使用单脉冲和调幅脉冲序列。刺激调制的皮质锁相将被量化，然后同时或交错掩蔽脉冲序列对第二耳蜗通道的影响将被评估。特定目标3中的动物心理物理实验将测量在第二耳蜗通道上存在和不存在掩蔽物时调制检测的阈值。刺激条件将比较，在皮质实验中，最小化或最大化耳蜗通道之间的相互作用。具体目标4是确定当前的配置，特别适合各种耳聋和刺激的历史。研究结果将用于研究耳聋和刺激持续时间影响的核心机制。这些结果将用于研究耳聋持续时间对假体功能影响的核心机制。

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.