SPATIAL SPREAD MEASUREMENTS IN HR 90K USERS Birgit Philips, Paul Corthals, Eddy De Vel, Ingeborg Dhooge Ghent University, ENT-department, Ghent, Belgium Background Ideally, in multi-channel cochlear implants (CI), each electrode should selectively activate a distinct group of neurons in the cochlea. In reality, the same neurons are stimulated by multiple electrodes because the injected current spreads through the cochlear tissue. If two or more electrodes stimulate overlapping neural populations, whether simultaneously or in sequence, then channel interaction may occur. Consequently, perception with the CI might be affected. Objectives Feasibility of two spatial measurement techniques. Gaining insight in obtained width values with respect to electrode location (El 3, El 7, El 11) and spatial measurement technique (SOE-VR and SOE-VM). Evaluating the possible correlations between spatial profiles and speech perception in quiet and noise. Methods SOE-Variable Recording SOE-Variable Masker RSPOM (research studies platform – objective measures) v.1.3.0 Eight HR 90K adult recipients, Platinum Speech Processor Three electrode (El) stimulation locations: one apical (El 3), one mid (El 7) and one basal (El 11) Two spatial measurement techniques: SOE-Variable Recording and SOE-Variable Masker Symmetric biphasic pulses, pulse width of 32 μs (cathodic pulse first) Stimuli were given at patient’s Most Comfortable Level Two-sided exponential decay curve Width values at 80% of the peak of each fitted curve Results Both spatial measurement techniques were found applicable to measure spatial spread within HR 90K users. A two-way ANOVA revealed a statistical significant main effect for spatial measurement technique (p<.05), but not for electrode location (p>.05). No significant correlations could be found between spatial measurements and speech perception in quiet nor noise. Conclusions Well-known speech materials give no or only restricted frequency-specific information. Possibly, the usage of a detailed phonological test can reveal a correlation with spatial measurements tests. Musical tuning and melody identification tasks could also be included to gain insight in the relationship between the perception of spectrally rich signals and spatial measurements.