Using spatial release from masking to estimate the magnitude of the familiar-voice intelligibility benefit

Executive functions in relapsing-remitting multiple sclerosis

Some studies suggest that patients with relapsing-remitting multiple sclerosis have problems in the functioning of working memory, and more specifically in executive functions, but the available results are still inconsistent. The aim of the present study was to examine executive functioning in multiple sclerosis using classical and representative tasks for divided attention, updating, attentional shifting, and inhibition. The sample was composed of 48 participants aged between 18 and 59 years (24 persons living with multiple sclerosis and 24 healthy participants matched in age and education level). The executive functions of divided attention, updating, attentional shifting, and inhibition were analyzed through the Dual-Task Paradigm, the N-Back task, the Trail Making Test (TMT), and the Stroop test, respectively. The analyses of the data showed that the functioning of working memory was impaired in multiple sclerosis in the executive functions of divided attention and updating when the group of persons living with MS and the control group were compared. In addition, the performance in the four executive functions analyzed did not show the same profile across the persons living with MS in the sample, as no deficit in attentional shifting or inhibition was observed. It can be concluded that the presence of deficits was observed only in the executive functions of divided attention and updating under the condition of greater cognitive demand. The clinical implications of these results are underlined due to their impact on daily life.

Intelligibility benefit for familiar voices is not accompanied by better discrimination of fundamental frequency or vocal tract length

Speech is more intelligible when it is spoken by familiar than unfamiliar people. If this benefit arises because key voice characteristics like perceptual correlates of fundamental frequency or vocal tract length (VTL) are more accurately represented for familiar voices, listeners may be able to discriminate smaller manipulations to such characteristics for familiar than unfamiliar voices. We measured participants' (N = 17) thresholds for discriminating pitch (correlate of fundamental frequency, or glottal pulse rate) and formant spacing (correlate of VTL; 'VTL-timbre') for voices that were familiar (participants' friends) and unfamiliar (other participants' friends). As expected, familiar voices were more intelligible. However, discrimination thresholds were no smaller for the same familiar voices. The size of the intelligibility benefit for a familiar over an unfamiliar voice did not relate to the difference in discrimination thresholds for the same voices. Also, the familiar-voice intelligibility benefit was just as large following perceptible manipulations to pitch and VTL-timbre. These results are more consistent with cognitive accounts of speech perception than traditional accounts that predict better discrimination.

Discriminating spatialised speech in complex environments in multiple sclerosis

People with multiple sclerosis (pwMS) frequently present with deficits in binaural processing used for sound localization. This study examined spatial release from speech-on-speech masking in pwMS, which involves binaural processing and additional higher level mechanisms underlying streaming, such as spatial attention. 26 pwMS with mild severity (Expanded Disability Status Scale score <3) and 20 age-matched controls listened via headphones to pre-recorded sentences from a standard list presented simultaneously with eight-talker babble. Virtual acoustic techniques were used to simulate sentences originating from 0°, 20°, or 50° on the interaural horizontal plane around the listener whilst babble was presented continuously at 0° azimuth, and participants verbally repeated the target sentence. In a separate task, two simultaneous sentences both containing a colour and number were presented, and participants were required to report the target colour and number. Both competing sentences could originate from 0°, 20°, or 50° on the azimuthal plane. Participants also completed a series of neuropsychological assessments, an auditory questionnaire, and a three-alternative forced-choice task that involved the detection of interaural time differences (ITDs) in noise bursts. Spatial release from masking was observed in both pwMS and controls, as response accuracy in the two speech discrimination tasks improved in the spatially separated conditions (20° and 50°) compared with the co-localised condition. However, pwMS demonstrated significantly less spatial release (18%) than controls (28%) when discriminating colour/number coordinates. At 50° separation, pwMS discriminated significantly fewer coordinates (77%) than controls (89%). In contrast, pwMS had similar performances to controls when sentences were presented in babble, and for the basic ITD discrimination task. Significant correlations between speech discrimination performance and standardized neuropsychological scores were observed across all spatial conditions. Our findings suggest that spatial hearing is likely to be implicated in pwMS, thereby affecting the perception of competing speech originating from various locations.