Altered attentional filters in subjects with graded levels of sensorineural hearing loss
Near-threshold tones (targets) in noise that are preceded by cues of the same frequency or occur with a high probability are detected better than tones of other frequencies that may occur with a lower probability (probes); the better detection of targets than probes defines the attentional filter. We measured attentional filters using a cued probe-signal procedure with a two-interval forced-choice (2IFC) method in normal-hearing subjects (N = 15) and subjects with sensorineural hearing loss (SNHL; N = 14) with a range of hearing levels. Attentional filters were altered in SNHL subjects, who detected low-frequency probes as well as targets at all hearing levels and who detected high-frequency probes increasingly well with increasing hearing level. These effects were present in both intervals of the 2IFC procedure. As auditory filters measured psychophysically are typically asymmetric in subjects with SNHL, these results suggest that the signal frequencies affected by the attentional filter are governed by the shapes of the auditory filters at and around the cue frequency. The normal-hearing subjects showed the expected attentional filters in the first interval and shallower filters in the second interval, suggesting that the cue-evoked attentional process is transient. In the first interval, both low- and high-frequency probes were detected better as hearing level increased over a narrow range (from −5 to 10 dB at the target frequency), with a resultant loss of attentional filtering. This finding adds to observations of variable auditory function in individuals with clinically normal hearing thresholds established by audiometry.