Effects of Perceptual Sonic Features on the Affective States of Dementia Patients 1 Running head : SONIC FEATURES AND AFFECTIVE STATES Effects of Sonic Features on the Affective States of Dementia Patients : A Pilot Study

Although music is widely used in therapeutic settings, the precise relationship between musical parameters and affective states is not clear. To address this issue in the context of Alzheimer disease (AD) we developed an automated test procedure that assesses the correlation between the timbre, spectral content, intensity, tempo and consonance of a set of parametrized sound samples with the self-reported emotional state of AD patients. Our results show that the control and patient groups had significantly different emotional reactions to the sound samples, suggesting possible applications in automatic AD diagnosis. We found that the timbre characteristic of a sound had a direct impact on the reported emotional state of the patients. Synthetic sounds and voices were reported to be sad and relaxing while the voice was perceived as unpleasant. Higher levels in the sound features entailed a more stressful response from the patients. Since specific characteristics of the sound seem to trigger specific emotional response, we could use those correlations as a means to induce soothing emotional states in AD patients. Effects of Perceptual Sonic Features on the Affective States of Dementia Patients 3 Effects of Sonic Features on the Affective States of Dementia Patients: A Pilot Study Dementia can be defined as a progressive loss of mental function which results in a restriction of daily activities and in most cases leads in the long term to the need for care (Kurz, 2007). Given the increased life expectancy in the western world, the total number of Alzheimer Disease (AD) patients will increase while also their fraction will increase due to a decreased population growth. Although the most common type of dementia is Alzheimer’s disease (6070% of the cases), there are other known types of dementia like the vascular dementia, dementia with Lewy bodies, frontotemporal dementia and the Creutzfeldt-Jakob disease. The common symptoms of dementia are cognitive impairments such as memory impairment, aphasia, apraxia, disorientation and mental slowing accompanied with non-cognitive deficits and behavioral problems (Alzheimer ́s association, 2006). The latter are common in more advanced phases of AD including: depression (60-98% of patients), anxiety and agitation (80% of dementia patients), sleeping problems (70% of dementia), and wandering. These behavioral problems appear to be the main cause of carer burden (Coen et al., 1997;Lyketsos et al., 2002;Tremont et al, 2006) and currently the use of restraints is one of the most common choices to deal with problem behavior (Testad et al., 2005). These disorders have a great impact on the duration of inpatient treatment, reduction of self-care and the probability of nursing home placement (Wancata, et al., 2003). However, the pharmacological treatment of these non-cognitive symptoms is only of limited effect (Sink et al., 2005) and is considered inappropriate due to an increased risk of mortality (www.fda.gov/cder/drug/advisory/antipsychotics.htm). Hence, non-pharmacological interventions to combat the behavioral and psychiatric symptoms of AD are urgently needed. However, currently it is not clear what alternative approaches such as sensory interventions, Effects of Perceptual Sonic Features on the Affective States of Dementia Patients 4 social contact (real or simulated), behavior therapy, staff training, structured activities, environmental interventions, medical/nursing care interventions, and combination therapies have to offer (Cohen-Mansfield, 2001). Here we investigate the effect of sound properties on the emotional state of AD patients. The effect of music on stress and anxiety has been established using a variety of selfreport, physiological, and observational means (Hanser, 1985; Khalfa et al., 2003). Music therapy can have physiological and psychological benefits on patients with a variety of diagnoses and undergoing differing medical treatments (Standley, 2000), while the effect of music on stress induced arousal has shown consistent results using physiological, behavioral and self-report measures (Pelletier, 2004). Interestingly enough this analysis also suggested that specific musical properties including slow tempo, low pitches, primarily based on string composition excluding lyrics and regular rhythmic patterns without extreme changes in dynamics are more effective than the subject’s preferred music. Music and music therapy has been shown to affect, at different time scales, a number of neuromodulatory and neurohormonal systems that are correlated with depression including 5HT and melatonin (Kumar et al., 1999; Evers et al., 2000). Although these results show great promise, a more recent meta-analysis has shown that strong conclusions cannot be drawn from the literature on music therapy due to a number of methodological problems (Sung & Chang, 2005). The same conclusion was drawn from a metaanalysis of the effect of music therapy on agitation treatment in AD patients (Lou, 2001). In this paper we focus on the study of a parameterized set of sound samples. We propose to study the effect of subtle sound properties such as timbre, spectral content, tempo, consonance and intensity on the subject’s emotional state. We propose a quantitative psychoacoustic study Effects of Perceptual Sonic Features on the Affective States of Dementia Patients 5 using self-report measures with well-diagnosed and monitored patient groups to define a foundation on which sonic based therapy can be applied to AD. Method Subjects A total of 65 subjects ranging from 51 to 92 years of age attending two day-care centers in Barcelona participated in this study. Criteria for inclusion in the study included the following: (a) a neurologist diagnosis of dementia, (b) verbal ability sufficient to answer simple social and verbal instructions, and (c) signed consent form to participate in the study. Also 8 healthy adults from the university with an age range from 23 to 30 years old served as control subjects. Experimental Set-Up In our experiment, each subject was seated in front of a computer and interacted with custom-made stimulus delivery and data acquisition software, called Zblast . When the experiment started, the subject was exposed to a number of sounds to calibrate the sound level. Subsequently, a number of sound samples with specific sonic characteristics were presented together with a dialog (Fig 1). The subject had to rate each in terms of their emotional content (valence, arousal, anger, pleasantness) using a percentage scale by moving a slider on the screen. The subject was given the possibility to skip samples and a music therapist was available for subjects who had difficulty manipulating the mouse. Each sample was looped for a maximum of 30 seconds or until the subject had responded to all four dialog boxes. Effects of Perceptual Sonic Features on the Affective States of Dementia Patients 6 Figure 1: The stimulus delivery and data acquisition system’s Graphical User Interface: The user rates the sound sample 1 on a scale from happy to sad based on his/her self-reported emotional state. The user can click the box “no lo se” (I do not know) or “pasar al siquiente” (pass to the next) to skip the next dialog. The blue bar at the top indicates the duration that the sample has played and will play. Procedure We investigated a parameterization of musical space by distinguishing a number of sonic categories and their parameters (see Figure 2). Central to this structure is the, so-called, critical band theory of the perception of consonance and dissonance that defines these musical parameters as objective biophysical properties (Fishman et al., 2001; Schreiner et al., 2000). Effects of Perceptual Sonic Features on the Affective States of Dementia Patients 7 Figure 2: Parametric tree defining the first level musical space that will be explored. See text for further explanation. We have investigated the influence of different sound features on the emotional state of the patients using a fully automated and computer based stimulus presentation and response registration system. The sound database comprised 75 different sound samples that covered the parameter space depicted in Figure 2. After listening to each sound the patients were asked to give ratings for four main emotional states: happy/sad (Valence from 0 to 100%), relaxed/stressed (Arousal from 0 to 100%), fear/anger, like/dislike (Pleasantness from 0 to 100%). Preliminary Results Global Distributions The observation of global distribution histograms for the control group and the patients shows that the dementia patients have a tendency to be more extreme in their ratings than the controls (See Figure 3 and 4) . We confirm this observation by a multivariate (four emotional Effects of Perceptual Sonic Features on the Affective States of Dementia Patients 8 state variables) ANOVA analysis on the control and patient groups that yields a value p<0.05. The distribution of responses significantly differs between the patient and control groups. Figure 3: Frequency distribution of the emotional ratings (scale from 0 to 100%) from the control group (N=8). Dark blue stands for valence rating, light blue stands for Arousal, Yellow is Anger and red is pleasantness. Effects of Perceptual Sonic Features on the Affective States of Dementia Patients 9 Figure 4: Frequency distribution of the emotional rating ratings (scale from 0 to 100%) from the dementia patients (N=65). Dark blue stands for valence rating, light blue stands for Arousal, Yellow is Anger and red is pleasantness. Another interesting observation concerns the emotional states themselves. The boxplot of the different emotional states for the control and patient groups suggest that the axis Fear/Anger is perceived as confusing for both the controls and the patients (See Figure 5). It appears that the Fear/Anger state has no correlation with the musical properties. Consequently, in our future anal