Faculty Bibliography

Hand manipulation neurons in areas 5 and 7b/anterior intraparietal area (AIP) of posterior parietal cortex were analyzed in three macaque monkeys during a trained prehension task. Digital video recordings of hand kinematics synchronized to neuronal spike trains were used to correlate firing rates of 128 neurons with hand actions as the animals grasped and lifted rectangular and round objects. We distinguished seven task stages: approach, contact, grasp, lift, hold, lower, and relax. Posterior parietal cortex (PPC) firing rates were highest during object acquisition; 88% of task-related area 5 neurons and 77% in AIP/7b fired maximally during stages 1, 2, or 3. Firing rates rose 200-500 ms before contact, peaked at contact, and declined after grasp was secured. 83% of area 5 neurons and 72% in AIP/7b showed significant increases in mean rates during approach as the fingers were preshaped for grasp. Somatosensory signals at contact provided feedback concerning the accuracy of reach and helped guide the hand to grasp sites. In error trials, tactile information was used to abort grasp, or to initiate corrective actions to achieve task goals. Firing rates declined as lift began. 41% of area 5 neurons and 38% in AIP/7b were inhibited during holding, and returned to baseline when grasp was relaxed. Anatomical connections suggest that area 5 provides somesthetic information to circuits linking AIP/7b to frontal motor areas involved in grasping. Area 5 may also participate in sensorimotor transformations coordinating reach and grasp behaviors and provide on-line feedback needed for goal-directed hand movements

OBJECTIVE: Perimodiolar electrode arrays were developed in an attempt to improve stimulation of specific neural populations and to decrease electrical thresholds, thereby decreasing power consumption. Postoperative radiographs show that coiling of the arrays is variable. Our previous study explored the relationship between the angle of coiling, threshold levels, and functional outcomes using the Nucleus Contour electrode array. This study compares coiling angle, electrical threshold levels, and speech perception measures with the Nucleus Contour Advance electrode array implanted using the new advance off stylet technique versus the Nucleus Contour electrode array implanted using the standard technique. STUDY DESIGN: Retrospective review. SETTING: University medical center. PATIENTS: Forty-two adults and children with normal cochlear anatomy implanted with the Nucleus CI24RCA electrode using the advance off stylet technique with at least 1-year follow-up. INTERVENTION: Therapeutic. MAIN OUTCOME MEASURES: Computer-aided radiographic analysis of perimodiolar electrode placement, electrical threshold measurements, and speech perception outcome measures at 1 year postimplantation. RESULTS: The degree of modiolar coiling was tighter using the new electrode and technique in comparison with standard insertion technique using the Nucleus Contour electrode array. The tighter coiling tended to result in higher electrical thresholds. Lower speech perception outcome measures tended to correlate with a higher degree of coiling. CONCLUSION: The Nucleus Contour Advance electrode array combined with the advance off stylet technique resulted in a more consistent perimodiolar position. However, the tighter coiling resulted in statistically significant increased electrical thresholds and decreased speech perception outcomes. This finding may be secondary to multiple factors, not just coiling angle

OBJECTIVE: Perimodiolar electrode arrays were developed to improve stimulation of specific neural populations and to decrease power consumption. Postoperative radiographs suggest that some arrays are more tightly coiled than others. The purpose of this study was to evaluate whether the degree of modiolar coil correlates with electrical threshold and/or performance measures postimplantation with the Nucleus CI24RCS (Contour) device. STUDY DESIGN: Retrospective review. SETTING: Cochlear implant center and a tertiary care hospital. PATIENTS: Twenty-eight adult cochlear implant recipients with normal cochlear anatomy who underwent implantation with the Nucleus C124RCS perimodiolar electrode and are at least 1 year postimplantation. INTERVENTIONS: Therapeutic. MAIN OUTCOME MEASURES: Radiologic degree of perimodiolar electrode placement (determined by a computer algorithmic analysis) compared with electrical thresholds and standard speech perception outcome measures at 1 year postcochlear implantation. RESULTS: No significant correlations were found between the degree of modiolar coiling of the electrode array and electrical thresholds and speech perception outcome measures at 1 year postcochlear implantation. CONCLUSIONS: The degree of coiling of a modiolar hugging electrode array was not directly correlated with the level of electrical thresholds or postoperative speech perception outcome measures. Appearance of coil tightness on postoperative radiographs could reflect either differences in array placement or intrinsic variations in cochlear anatomy, and variations in speech perception performance can be influenced by other factors, including length of deafness