Clinical Applications of Evoked Potential Continuous Loop Averaging Deconvolution (CLAD)

Abstract

Using the new Continuous Loop Averaging Deconvolution (CLAD) acquisition technique, it is now possible to record evoked potentials at very high stimulation rates. The CLAD technique allows the experimenter to tailor the stimulation sequences to fit his specific application to unwrap overlapping responmses at high rates. CLAD sequences can be designed to reduce physiological adaptation effects and to control the noise shaping effect of the deconvolution process. This study shows examples of promising clinical applications of CLAD using Electrocochleograms (ECochGm), Auditory Brainstem Responses (ABR), Auditory Middle Latency Responses (AMLR): In the first example CLAD was applied to record TransTympanic (TT) ECochGm at conventional and high rates in Meniere’s patients. These high-rate ECochGs revealed distinctive physiological patterns not previously observed at conventional rates. Regarding the ABRs, custom CLAD sequences were designed to simultaneously provide high Signal to Noise Ratio (SNR) ABRs and 80-Hz Auditory Steady State Responses (ASSR). The use of these sequences enabled the investigators to assess the hearing in guinea pigs exposed to cochlear implant electrode insertion trauma. A similar technique was applied in normal human subjects to unveil the generation mechanisms of amplitude modulated ASSR. CLAD was also used to record 40-Hz MLRs in normal awake subjects and patients under anesthesia; the ASSR showed to be a composite of the evoked, transient waveforms. Thus CLAD was able to explain the inability of 5- or 10-Hz AMLRs to predict the 40-Hz ASSR in anesthesia.