Categorization and timbre perception of environmental sounds in schizophrenia

Abstract

Perception of environmental sounds from impacted materials (Wood, Metal and Glass) was examined by conducting a categorization experiment. Stimuli consisted of sound continua evoking progressive transitions between material categories. Results highlighted shallower response curves in subjects with schizophrenia than healthy participants, and are discussed in the framework of Signal Detection Theory and in terms of impaired perception of specific timbre features in schizophrenia.

Introduction

Schizophrenia is associated with complex cognitive (Frith, 1987) and perceptual (Holzman, 1972) impairments. An extensive literature analyzed perceptual impairments that were mainly interpreted as consequences of sensory processing dysfunctions (Javitt, 2009a, Javitt, 2009b). In the auditory modality (Rabinowicz et al., 2000), anomalies were found in tone matching (Javitt et al., 1997), pitch identification (Holcomb et al., 1995), or sound duration discrimination (Todd et al., 2003). Leitman et al. (2008) evaluated the contribution of these underlying dysfunctions, especially tone matching, to emotion recognition from vocal expressions in schizophrenia. Further on, Bach et al. (2009) suggested that perceptual impairments can be related to a more general dysfunction in cortical brain networks according to the Signal Detection Theory (SDT) that allowed the authors to explain the shallower response curves in Schizophrenia found by Kee et al. (2006) in an identification task on emotional facial continua (i.e., two facial expressions morphed into each other).

However, perceptual impairments in schizophrenia have not been thoroughly investigated for the perception of environmental sounds, which is an essential way to perceive the surrounding world (Gaver, 1993). We here aim at examining disturbances of sound categorization in schizophrenia by using impact sounds from different material categories (Wood, Glass, and Metal) which present the following advantages: i) they afford relevant information to perceive surrounding objects in a very concise way, which is important in everyday situations, ii) the parametric manipulation of these sounds was previously explored by creating sound continua (impacted sounds morphed between two material categories) with analysis–synthesis and interpolation methods and iii) the relevancy of specific acoustic features for material perception, i.e., damping and spectral complexity (roughness), was previously highlighted (Aramaki et al., 2011). With a reduced sound corpus from this previous study, we used the same experimental protocol based on a forced-choice categorization task of the perceived material and measured the response curve for these transitions. We compared group data between patients with schizophrenia (SCZ) and control participants (CTL).

Analogous to results from Kee et al.'s (2006) study based on emotional facial continua, we expect disturbances of the sound categorization reflected by shallower response curves in SCZ than in CTL. Going further, based on the knowledge of acoustic features responsible for the material perception, we expect to identify the effect of specific timbre-related features on the possible disturbances in SCZ.