Musical Structural Determinants of Emotional Judgments in Dementia ...

Neuropsychology 2009, Vol. 23, No. 1, 90 –97

© 2009 American Psychological Association 0894-4105/09/$12.00 DOI:10.1037/a0013790

Musical Structural Determinants of Emotional Judgments in Dementia of the Alzheimer Type Lise Gagnon

Isabelle Peretz

Universite´ de Sherbrooke

Universite´ de Montreál

Tama`s Fu¨lo¨p

This document is copyrighted by the American Psychological Association or one of its allied publishers. This article is intended solely for the personal use of the individual user and is not to be disseminated broadly.

Universite´ de Sherbrooke People with dementia of the Alzheimer type (DAT) may well be emotionally soothed by listening to music. However, very few systematic studies have been conducted to support the anecdotal evidence. DAT does damage certain cerebral structures that subsume emotional processing, and some studies have demonstrated deficits affecting emotional judgments of facial expression and prosody in DAT. Accordingly, this study addressed the question of whether DAT might leave musical emotional judgment intact. Twelve early DAT participants and 12 healthy elderly participants took part in this study. Emotional judgments were examined in relation to mode and tempo, two important structural properties that contribute to the happy-sad distinction in music. Their respective contributions were assessed in four different experimental conditions. The DAT participants’ responses were similar to those of healthy elderly participants, showing spared ability to employ tempo and mode as cues for emotional interpretation. The DAT participants’ performance was not correlated with their global cognitive functioning. These results constitute a preliminary empirical demonstration that, in early DAT, musical emotional judgments appear to be based on normal structural analysis of musical input. Keywords: dementia, music, emotion, recognition

Music as a medium for communication with DAT patients is interesting because its nonverbal nature bypasses the language and semantic deficits that characterize DAT. However, many other cognitive deficits occur during the course of DAT. Accordingly, one important question arises in relation to music: how might DAT affect the emotional judgment of music? In its early stages, Alzheimer’s disease damages some of the most important cerebral structures that subserve emotional processing, such as the hippocampus and the posterior association areas (Kemper, 1984). Most systematic studies that have examined emotional judgments in this disease have concluded that there is some evidence of impairment for emotional judgments of facial expression and prosody (Allen & Brosgole, 1993; Allender & Kaszniak, 1989; Hargrave, Maddock, & Stone, 2002; Kohler et al., 2005; Roudier et al., 1998; Shimokawa et al., 2000, 2001; Testa, Beatty, Gleason, Orbelo, & Ross, 2001; see Kohler et al., 2005 for a review). However, those studies included groups of mixed early (or mild) and moderate DAT participants. Studies that clearly distinguished early and moderate DAT participants did not find such impairment. Lavenu, Pasquier, Lebert, Petit, & Van der Linden (1999) found preserved emotional recognition for facial expressions of happiness, sadness, surprise, disgust, anger, and contempt, with a limited deficit for the recognition of fear. However, when the same participants reached a moderate level of DAT (3 years later) and were assigned the same tests, they showed a decline in the recognition of all emotions except for happiness, sadness, and contempt (Lavenu & Pasquier, 2005). Roberts, Ingram, Lamar, and Green (1996) compared early and moderate DAT participants for comprehension of emotional prosody, and found a significant impairment only with the moderate DAT participants (for surprise, sadness, anger, or neutral—the

The use of music as a clinical tool with people who have dementia of the Alzheimer type (DAT) has grown impressively in the last two decades. Many anecdotal reports describe music as having the power to release DAT patients’ emotions and also to cognitively stimulate even severe cases of DAT. Accordingly, systematic reviews have been published on music therapy for people with dementia (Gibbons, 1988; Kneafsey, 1997; Koger & Brotons, 2000; Sherratt, Thornton, & Hatton, 2004; Vink, Birks, Bruinsma, & Scholten, 2004, 2006), with many reference works on the subject appearing since 1996 (see, e.g., Aldridge, 2000; Clair, 1996; Hanser, 1999). Although musical interventions really do seem to be beneficial for DAT patients, systematic proof of their efficacy is still lacking. The very few studies that have been conducted on this topic have used poor experimental methodologies (Vink et al., 2006).

Lise Gagnon and Tama`s Fu¨lo¨p, Research Center on Aging, Universite´ de Sherbrooke; Isabelle Peretz, Department of Psychology, Universite´ de Montreál. We are grateful to all the participants, to Stephanie Louveaux for her help in testing them, and to Lise Trottier for her help with the statistical analysis. We are also grateful to Francine Fontaine, Brigitte Gilbert, and Marie Robitaille for their clinical advice, and to Zofia Laubitz and Linda Bergeron for copy-editing this article. We particularly wish to acknowledge the insightful and constructive comments of Nathalie Gosselin. This research was supported by a fellowship from the Fonds de la Recherche en Sante´ du Que´bec and from the Re´seau provincial de recherche en adaptation-reádaptation (REPAR) to the first author. Correspondence concerning this article should be addressed to Lise Gagnon, Research Center on Aging, 1036 Belve´de`re Sud, Sherbrooke, Que´bec J1H 4C4, Canada. E-mail: [email protected] 90

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MUSIC, EMOTION, AND DEMENTIA OF THE ALZHEIMER TYPE

only emotional intonations to identify). Kohler et al. (2005) did find impairment for the recognition of happy and sad facial expressions with early DAT participants. However, the task was to identify intensity of facial expressions by ranging them on a 7-point Likert scale, ranging from Very Happy to Neutral to Very Sad; this is quite a difficult procedure even for early DAT patients. Only one study has systematically examined emotional judgments of music in patients suffering from dementia (Allen & Brosgole, 1993). Participants were asked to listen to 18 popular musical excerpts lasting 10 seconds each and expressing happy, sad, or angry emotions. They had to point to a picture of the happy, sad, or angry face of an animal, in association with each musical selection. In a second condition, participants had to listen to each excerpt and say whether it was happy, sad, or angry. Demented patients’ overall performance showed deficits affecting the recognition of happy, sad, and angry musical expressions. However, the clinical descriptions of patients were unclear, and no specific type or severity of dementia was mentioned. Most of the experimental studies of music and DAT have examined music perception and memory or musical performance by musicians. Some studies of music perception and memory have concluded that those abilities are relatively spared in DAT (Bier, Provencher, Gagnon, Van der Linden, & Desrosiers, 2008; Cowles et al., 2003; Cuddy & Duffin, 2005; White & Murphy, 1998). As well, the preservation of instrumental playing of music in DAT has been demonstrated in some case studies (Beatty, Brumback, & Vonsattel, 1997; Beatty et al., 1999, 1988; Crystal, Grober, & Masur, 1989). However, long-term recognition of familiar or unfamiliar melodies may be compromised (Bartlett, Halpern, & Dowling, 1995; Crystal et al., 1989; Halpern & O’Connor, 2000), even implicitly, through emotional ratings of pleasantness (Halpern & O’Connor, 2000). Contradictory results were obtained by Quoniam et al. (2003), however, who demonstrated normal priming effects on preference judgments for unfamiliar melodies with a group of 10 DAT participants, even though the participants’ explicit recognition of the same melodies was severely impaired. In conclusion, it is still not exactly clear how DAT affects music perception and memory. More studies, with a similar methodology, are needed to answer that question. Besides, even though music recognition may deteriorate in DAT, it might be dissociated from emotional judgments of music. The system for the analysis of emotional expression by music is isolable from music memory (Peretz & Gagnon, 1999; Peretz, Gagnon, & Bouchard, 1998). The study of a case of amusia demonstrated that the ability to distinguish between happy and sad music may be spared by brain damage, even when the recognition of specific pieces of music is impaired (Peretz & Gagnon, 1999). Accordingly, even though DAT may affect music memory, might it leave emotional judgments of music intact? This is the question addressed in the present study, which constitutes the first systematic exploration of musical emotional judgments in early DAT. Since it has previously been demonstrated that instrumentation and interpretation are not major determinants of emotional judgments (Peretz et al., 1998), such judgments were examined in relation to structural characteristics that are relevant in this respect. Two structural properties that are known to convey important information with regard to the happy-sad distinction are the tempo and the mode of a piece (e.g., Gagnon & Peretz, 2003; Hevner, 1935, 1937). Slow tempi, or few beats per minute, tend to evoke

sad moods, whereas fast tempi, or many beats per minute, tend to evoke happy moods. Mode is related to the subset of pitches selected in a given musical segment: the minor mode is associated with a sad tone, whereas the major mode is associated with a happy tone. To assess the respective contributions of tempo and mode to the emotional evaluation of musical stimuli, we manipulated these characteristics orthogonally, in three different experimental conditions, in our earlier study of an amusic patient, I.R. (Peretz et al., 1998). Normal controls and I.R. all proved to be sensitive to characteristics of mode and tempo. Those results were generalized to a sample of 24 university students (Dalla Bella, Peretz, Rousseau, & Gosselin, 2001). In the present study, we aimed to use the same materials as Peretz et al. (1998) and Dalla Bella et al. (2001) to investigate whether early DAT patients and normal elderly persons would also be sensitive to mode and tempo as determinants of musical emotional judgments.

Method Participants A group of 12 participants who met the NINCDS-ADRDA (McKhann et al., 1984) or DSM–IV criteria (American Psychiatric Association, 1994) for probable Alzheimer’s disease participated in this study. Their characteristics are presented in Table 1. They were recruited either by the multidisciplinary team of the memory clinic of the Sherbrooke Geriatric University Institute (SGUI), from the SGUI archives, or by the Eastern Townships Alzheimer Society in Sherbrooke. They had received a diagnosis of DAT based on complete geriatric and neuropsychological investigations conducted at the SGUI memory clinic. The exclusion criteria were: (1) cognitive deficits that could interfere with the course of the procedure (such as comprehension deficits) and major auditory deficits; (2) major depression or anxiety; (3) behavior problems; and (4) any other dementia (vascular, semantic, alcoholic, etc.). A comparison group of 12 healthy elderly participants also took part in this study. All were Canadian. They were recruited by word of mouth and by advertisements distributed via the SGUI Research Center on Aging’s newsletter sent to Sherbrooke seniors. Exclusion criteria included dementia of all kinds, memory complaints, history of head injury, depression, or a Mini Mental State Evaluation (MMSE; Folstein, Folstein, & McHugh, 1975) score abnormal for the age and level of education. The two groups did not differ according to age or years of education. As expected, they differed significantly in general cognitive functioning, as assessed by the MMSE (see Table 1). Table 1 Demographic Characteristics of Participants and Level of General Cognitive Functioning

Characteristics

DAT participants

Healthy elderly participants

Age 74.3 (56–85) 71.3 (64–84) Sex (number of women) 7 11 Years of education 9 (6–18) 8.83 (5–15) MMSE (/30) 23.08 (16–27) 27.75 (25–30) a

Mann-Whitney U-tests.

Differences between groups (level of significance)a 0.132 — 0.555 ⬍0.001


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¨ LO ¨P GAGNON, PERETZ, AND FU

Eleven of the 12 DAT participants also received a standardized neuropsychological evaluation. This was done so that only early DAT participants would be included. The results are shown in Table 2. The DAT group as a whole presented mainly episodic memory, semantic memory, and inhibition deficits, in accordance with the general cognitive profile of early DAT (Collette, Van der Linden, Juillerat, & Meulemans, 2003; Hodges & Patterson, 1995). Also, as a group, they obtained a mean score of 23.08 on the MMSE, which is defined as minimal to mild DAT (Hodges, 2000).1 Musical experience was assessed through a brief questionnaire, to include only nonmusicians. Among both healthy elderly and DAT participants, if anyone had received a musical education, it could be for no more than 5 years and on an instrument that they had not played for at least 15 years. All participants were given $15 compensation for their participation. The project was approved by the Research Ethics Committee of the Research Center on Aging (SGUI). Informed consent was obtained from the participants, and the consent form was signed by the participants, the researcher in charge of the project, and a witness. Participants were tested at the Research Center on Aging or at home.

Materials and Procedure Materials. The same set of 32 musical excerpts was used throughout the experiments. This set, which was previously used in one of our studies done with an amusic patient (Peretz et al., 1998, which presents the set of musical selections in the Appendix) and in a developmental study including young adults (Dalla Bella et al., 2001), very effectively assessed the effect of tempo and mode manipulation regarding the happy-sad distinction. All the excerpts were instrumental in that they were not originally sung with lyrics; as well, the excerpts were drawn from the corpus of Western music and were composed for purposes other than experimentation. The excerpts were chosen from the classical corpus because it was considered important to use musical material that is sufficiently complex and engaging to guarantee its processing as a meaningful structure rather than as a simple sequence of tones. The selections were drawn from the baroque (e.g., Bach, Albinoni), classical (e.g., Mozart), romantic (e.g., Verdi), and contemporary (e.g., Ravel) periods. These excerpts were selected so that half evoked a sense of happiness and the other half, a sense of sadness. The original instrumentation was generally orchestral (22 excerpts) or for solo piano (8 excerpts). The excerpts lasted from 7 seconds to 33 seconds (mean: 15.8 seconds). The computer-generated versions were created on a microcomputer running a MIDI sequencing program (Sequencer Plus Gold) and controlling a sample playback digital synthesizer (Roland Sound Canvas SC 50) by entering the original scores manually. Each tone occupied its precise value in terms of pitch and duration, keeping intensity and velocity constant. The pedal was used in the piano renditions. The excerpts contained structural characteristics that determine emotional judgments. Two structural properties known to convey important information regarding the happy-sad distinction are the tempo and mode of the piece (e.g., Hevner, 1935, 1937). As mentioned above, slow tempi tend to evoke sad moods, whereas fast tempi evoke happy moods. Moreover, minor mode is associ-

ated with sadness, whereas major mode is associated with happiness (see Crowder, 1984; Gagnon & Peretz, 2003). The musical excerpts used in the present study generally followed these principles: the happy excerpts were mostly played in a fast tempo (the quarter note value varied from 80 to 255, conventionally written as M.M. for Metronome Marking) and were all in a major mode; most of the sad excerpts were played at a slow tempo (between 20 and 100 M.M.) and were in the minor mode. Therefore, it is likely that both tempo and mode are structural characteristics of the pieces that contributed to the happy-sad discrimination. The piano-synthesized version was used, mainly because such a version is easier to manipulate with a computer program. A baseline condition, referred to as the original condition, included the 32 original piano-synthesized excerpts. To assess the respective contributions of tempo and mode to the emotional evaluation of the musical stimuli, we manipulated these characteristics orthogonally, in three different conditions. In the tempo change condition, all tempi were set to a single neutralized value (with the quarter note ⫽ 84 M.M.) that corresponded to the median of the original tempi (because inversions from fast to slow, or from slow to fast tempi were too drastic and resulted in excerpts that sounded unnatural or ill-formed). In the mode change condition, the pieces were transcribed in the opposite mode to the original. The procedure used for the mode transcription was conventional and identical to that used by Hevner (1935). Finally, to examine the joint influence of mode and tempo, the two modifications applied in isolation in the mode and tempo change conditions were combined in the mode ⫹ tempo change condition. Sample stimuli can be heard at www.brams.umontreal.ca/plab in relation to the Dalla Bella et al. (2001) publication. Procedure. All stimuli were recorded on compact disks and played on a CD player in free field at a loudness level that was comfortable and customary for the listener. Each participant was tested individually. The four conditions were always presented in the same order: (1) Original, (2) Mode change, (3) Tempo change, and (4) Mode ⫹ tempo change. The sequence was designed to respect the fact that tempo is generally a more salient determinant of happy-sad judgments (Gagnon & Peretz, 2003; Peretz et al., 1998, for the same stimuli); thus, the experiment was made easier as participants could move on from the second to the fourth conditions, thus bypassing any fatigue effect. (Although Dalla Bella et al., 2001, controlled for potential biases because of order of presentation, they found no effect of this variable.) Participants were never informed of the nature of the changes applied to the stimuli. 1 Participant 1’s cognitive profile requires further clarification. He scored 27 on the MMSE but showed significant episodic memory deficits. He had a university degree, the highest educational level of all participants. He had received a diagnosis of dementia based on three complete geriatric and neuropsychological investigations (from 2002 to 2005; for details, see Bier et al., 2008). His isolated memory problems and functional difficulties suggested a diagnosis of a possible, slowly isolated progressive memory disorder (Della Salla & Spinnler, 1999) or possible Alzheimer’s disease (McKhann et al., 1984). It is worth noting that Participant 1’s very high educational level made the neuropsychological tests less sensitive, thereby making a more specific diagnosis hazardous.

0ⴱ 5ⴱ 0ⴱ 0ⴱ 13ⴱ

0ⴱ 4ⴱ 0ⴱ 0ⴱ 7ⴱ NA

10ⴱ 26

6ⴱ 23 111⬙ (1/1) 65⬙ (2/0)ⴱ NT 94⬙ⴱ 488⬙ⴱ (1) 105ⴱ

98⬙ (0/1) 46⬙ (0/0) 196⬙ (5/9) 161⬙ⴱ 428⬙ⴱ (4) NA

17 30 64⬙ (0/2) 52⬙ (0/1) 119⬙ (0/4)ⴱ 38⬙ 91⬙ (0) 132

41⬙ 238⬙ (6) 116

95⬙ (0/1) 58⬙ (0/0) 335⬙ⴱ (8/4)

9ⴱ 28

4

ⴱ

8ⴱ 19 3ⴱ 5 15

6/2 4 9

73 (9) 24

5

128⬙ⴱ 765⬙ⴱ (0) 119

80⬙ (0/1) 56⬙ (0/0) 241⬙ (9/7)ⴱ

8ⴱ 27

6

3ⴱ 18 0ⴱ 8 16

4/3 4 3

79 (7) 22

6

7ⴱ 28

11

5ⴱ 9 0ⴱ 1 8ⴱ

4/3 4 10

85 (8) 24

7

159⬙ⴱ NT 91ⴱ

87⬙ (2/0) 63⬙ (0/1) 188⬙ (61/3)ⴱ

DAT participants

NA

10 27 NA

9

4ⴱ 0ⴱ 0ⴱ 0ⴱ 15

4/4 NA NA

83 (8) 21

8

44⬙ 200⬙ (0) 120

NT NT NT

14 30

18

2ⴱ 8 0ⴱ 3 10ⴱ

5/5 5 5

76 (8) 24

9

97⬙ⴱ 308⬙ⴱ (2) 128

95⬙ (0/1) 74⬙ (0/0) 231⬙ (1/3)

108⬙ⴱ (5/3)ⴱ 112⬙ⴱ (5/4)ⴱ NT 445⬙ⴱ NT 97ⴱ

8ⴱ 27

9

4ⴱ 14 1ⴱ 7 16

6/3 4 9

76 (6) 26

11

5ⴱ 28

2

ⴱ

5ⴱ 11 2ⴱ 1 12ⴱ

4/2 4 NA

56 (8) 16

10

NA

NA

NA

NA

68 (11) 19 NA

12

Note. SD ⫽ standard deviation; SS ⫽ scaled score from raw score; NT ⫽ could not complete task; NA ⫽ not available; ⬙ ⫽ seconds. References for the tests as follows: Digit span and letter-number sequencing tests–WAIS III (Wechsler, 1997a); Visuo-spatial block tapping test–WMS-III (Wechsler, 1997b); French version of the Selective and Cued Reminding Test (SCRT) (Calisis, Wyns, Van der Linden, & Coyette, 1994); Verbal fluency–French version (Joanette, Ska, Poissant, Belleville, Lecours, et al., 1995); Association match task from the Birmingham Object Recognition Battery (BORB) (Riddoch & Humphreys, 1993)” Benton’s face discrimination test (Benton, Hamsher, Varney, & Spreen, 1983); Stroop test (Golden, 1978); Trail Making Test A and B (Partington & Leiter, 1949; as cited in Spreen & Strauss, 1998); DRS (Mattis Dementia Rating Scale: French version; Mattis, 1976). ⴱ ⫽ two standard deviations below the mean performance, adjusted for age and education.

79⬙ⴱ 329⬙ⴱ (3) 121

89⬙ (0/0) 73⬙ⴱ (2/0)ⴱ 660⬙ⴱ (12/13)

9

8

14ⴱ 16 9 4 15

6/3 5 3

73 (11) 25

4

14

12 21 5ⴱ 6 14ⴱ

7/4 3 4

6/4 4 NA

8/5 6 13

72 (7) 24

75 (7) 25

75 (18) 27

3

Age (years of education) MMSE Working memory Digit span forward/backward Spatial span (Block-tapping test) Letter-number sequencing: SS Episodic memory Selective cued reminding test: Immediate free recall (total/48) Immediate cued recall (total/48) Delayed free recall (total/16) Delayed cued recall (total/16) Delayed recognition (total/16) Language and semantic memory Verbal fluency (number of words): Letter (mean for P, T, and/or L) Semantic (mean for animals, clothes, vegetables, and/or tools) Association match task (/30) Executive functions Stroop: Color naming (errors/corrected errors) Reading (errors/corrected errors) Interference (errors/corrected errors) Trail Making Test: Trail A Trail B (errors) DRS (total/144)

2

1

Neuropsychological testing

Table 2 Neuropsychological Profile of the DAT Group



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To keep the procedure used in our previous experiment (Peretz et al., 1998), participants were asked to judge, on a 10-point scale, whether each excerpt sounded happy or sad, with 1 meaning very sad and 10 meaning very happy. However, this procedure was too difficult for the DAT participants. For example, they frequently gave a rating of 10 and said “very sad.” They seemed to find it very difficult to conceptualize a score of 1 as indicating maximum intensity. A pilot group of five DAT participants confirmed the need to adapt the procedure to their cognitive functional level. The chosen procedure was to ask participants (1) to judge whether each excerpt sounded happy or sad, and (2) to judge the intensity of the identified emotion on a 5-point scale where 1 meant not much and 5 meant very much.

Results and Comments The ratings provided by the DAT participants were converted to correspond to the original 10-point scale. Accordingly, “happy” ratings of 1, 2, 3, 4, and 5 were converted into ratings of 6, 7, 8, 9, and 10, respectively, and “sad” ratings of 1, 2, 3, 4, and 5 were converted into ratings of 5, 4, 3, 2, and 1, respectively. The mean ratings given by DAT participants and by healthy elderly participants, in each condition for the “happy” and “sad” excerpts, are presented in Table 3. The mean ratings obtained for each excerpt were evaluated with an analysis of variance (ANOVA), with participants as the random variable, Group (DAT vs. healthy elderly) as the between-participants variable, and Emotional Category (happy vs. sad) and Condition (original vs. tempo vs. mode vs. tempo ⫹ mode) as the within-participants variables. The analyses revealed a tendency toward a three-way interaction with the Group, Condition, and Emotional Category variables with F(3, 20) ⫽ 2.79, p ⫽ .067. Because this interaction was almost significant, a comparison between the two groups was performed using separate ANOVAs for each condition, considering Group (DAT vs. healthy elderly) as the between-participants variable, and Emotional Category (happy vs. sad) as a within-participant variable. The analyses did not reveal an interaction of the Group and Emotional Category variables (F(1, 22) ⫽ 2.63 for original, 1.17 for mode, 3.43 for tempo, and .54 for tempo ⫹ mode, ns) nor any effect of Group. Those analyses confirm the absence of significant differences in sensitivity to mode and tempo between our groups for the emotional classification of musical excerpts. As can be seen in Figure 1, means were relatively homogeneous from one subject to another. The mean ratings obtained from DAT participants for excerpts of tempo ⫹ mode condition seemed to differ from the one of healthy elderly participants, moreover indicating a change of category from sad to happy judgments. However, this appears to be the result of one subject’s extreme happy ratings for sad excerpts. In fact, this participant, in his statements, clearly judged the sad excerpts as being relaxing and, accordingly, happy.2 To examine each group’s sensitivity to the structural manipulations, separate ANOVAs on the ratings were performed. ANOVAs still considered Emotional Category (happy vs. sad) and Condition (original vs. tempo vs. mode vs. mode ⫹ tempo) as the withinparticipants variables. The ratings given by each group were significantly influenced by the condition presented; the Emotional Category by Condition interaction is significant in both DAT and healthy elderly participants’ data, with F(3, 9) ⫽ 105.98 and 41.14,

respectively, ps ⬍ .001. Comparisons between conditions were performed two by two, with separate ANOVAs, considering the same factors as in the overall ANOVAs. These subsequent analyses indicate that each modification of the original version significantly affects the response pattern. When compared to the original version, the tempo condition yields a significant interaction between Condition and Emotional Category (with F(1, 11) ⫽ 33.94 and 49.58, ps ⬍ .001, for DAT and healthy elderly, respectively), as does the mode condition (with F(1, 11) ⫽ 7.71, p ⬍ .05, and 10.44, p ⬍ .01, for DAT and healthy elderly, respectively) and the mode ⫹ tempo condition (with F(1, 11) ⫽ 281.04 and 124.88, ps ⬍ .001, for DAT and healthy elderly, respectively). Note that in the latter condition, where the manipulation has the greatest impact, ratings are still significantly higher for the happy than the sad excerpts, t(11) ⫽ 2.54, p ⫽ .027 and 3.67, p ⫽ .004 by bilateral tests, for DAT and healthy elderly, respectively. Thus, despite the change of both mode and tempo applied to the stimuli, even DAT participants were still able to discriminate happy from sad excerpts.

Correlation Between AD Participants’ Performance and Their Cognitive Profile The purpose of this analysis was to explore a possible relationship between DAT severity and performance on musical emotion recognition. Bivariate Spearman correlations were carried out between the following general cognitive measures and the DAT group’s mean ratings obtained on the mode condition (this being the most difficult experimental condition): (1) global functioning, measured by the Dementia Rating Scale (DRS); and (2) the Mini Mental State Examination (MMSE). The mean ratings obtained in the mode condition by DAT participants were not correlated with global cognitive functioning as measured by the DRS (rs(9) of .07 and .32 for happy and sad categories, respectively, ns); nor were they correlated with the MMSE (rs(12) of .46 and .07 for happy and sad categories, respectively, ns).

Discussion The objective of this study was to examine the perceptual basis of emotional judgments of music in early DAT. Accordingly, we investigated whether early DAT patients and healthy elderly participants showed the same sensitivity to the principal determinants of musical emotional judgments—mode and tempo—in four dif2 The mean differences obtained as a change in ratings from original to mode, from mode to tempo, and from tempo to mode ⫹ tempo were also evaluated with an analysis of variance (ANOVA), with participants as the random variable, Group (DAT vs. healthy elderly) as the between-participants variable, and Emotional Category (happy vs. sad) and Change in mean ratings (original to mode, mode to tempo, and tempo to mode ⫹ tempo) as the within-participants variables. These analyses revealed no interaction between Group, Change, and Emotional Category variables ( p ⬎ .1). They revealed a main group effect, with F(1, 22) ⫽ 8.023, with p ⫽ .01. Simple comparisons between groups revealed a tendency toward a significant difference for the Change from tempo to mode ⫹ tempo, but only for the Happy excerpts, t(22) ⫽ 1.88, p ⫽ .07 by bilateral tests, with DAT showing the largest difference.

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Table 3 Mean Ratings (and Standard Errors) for DAT and Healthy Elderly Participants in the Different Conditions as Defined by the Type of Modification Applied to the Musical Excerpts DAT participants Condition

Happy

Sad

Happy

Sad

Original Mode change Tempo change Mode ⫹ tempo change

8.8 (0.5) 8.3 (0.9) 7.9 (0.8) 6.7 (1.1)

4.4 (1) 4.7 (1.1) 5.2 (1.2) 6.1 (1.2)

8.2 (0.9) 7.6 (1.1) 7.0 (1.1) 6.3 (0.9)

4.4 (0.8) 4.5 (0.9) 5.1 (1) 5.4 (1)

ⴱ


Healthy elderly participants ⴱ

Effect sizes

.60 (⫺0.20, 1.60) .44 (⫺0.51, 1.62) .67 (⫺0.09, 1.61) .30 (⫺0.99, 0.47)

Effect sizes for the comparisons between groups for each condition (with Confidence Intervals at 95%).

ferent experimental conditions previously used in two studies by our group (Dalla Bella et al., 2001; Peretz et al., 1998). For both DAT and healthy elderly participants, mode and tempo modifications changed participants’ performances, particularly when the musical excerpts presented incorporated both kinds of modifications. Moreover, DAT participants’ responses were similar to those of healthy elderly, showing spared ability to employ tempo and mode as cues for emotional interpretation. These results constitute a preliminary empirical demonstration that early DAT patients’ musical emotional judgments appear to reveal normal structural analysis of musical input. In other respects, DAT ratings for the Original condition happy excerpts were higher than healthy elderly ratings (despite the absence of a significant interaction between Groups and Emotional Category for the Original condition). This could be the result of the different procedure used by DAT participants. They had to rate from a simpler 5-point scale, and conversions of their ratings to the original 10-point scale may have resulted in an apparent better recognition of happiness. It is also interesting to note that DAT participants’ ratings seemed to suggest less sensitivity to mode than those of healthy

elderly (at least for the happy excerpts). However, the analyses performed on differences obtained as a change in ratings from original to mode did not confirm such a conclusion. Instead, they revealed that DAT participants were really sensitive to mode, inasmuch as they showed, for happy excerpts, the largest mean difference of ratings from tempo to mode ⫹ tempo conditions. Besides, despite the changes of both mode and tempo applied to the stimuli in mode ⫹ tempo condition, even DAT participants were still able to discriminate happy from sad excerpts. This suggests that, like healthy elderly and young adults (Dalla Bella et al., 2001; Peretz et al., 1998), early DAT patients are sensitive to determinants other than tempo and mode that play a role in the emotional classification of the stimuli (such as pitch level; Gabrielsson & Juslin, 2003). Another determinant of performance in DAT might be the level of cognitive decline. The longitudinal study of Lavenu and Pasquier (2005), which demonstrated a specific decrease in the recognition of facial emotional expressions in DAT as dementia progressed, concluded that the results might be related to the progressive degeneration of the structures involved in emotional processing. Such a conclusion is also supported by the results obtained in the

Figure 1. Mean ratings obtained for the happy and sad excerpts in each experimental condition as presented for each participant from the DAT and healthy elderly groups.


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study of Roberts et al. (1996), which examined the comprehension of emotional prosody by early and moderate DAT participants. Even if the present study specifically included early DAT participants, there might be some variability between subjects of the same cognitive level (e.g., Bier, Gagnon, & Desrosiers, 2005; Joanette, Ska, Poissant, Belleville, Bellavance, et al., 1995). Accordingly, we addressed the question of whether the DAT participants’ performance in our study might be correlated with the severity of the general cognitive decline. In fact, the DAT participants’ performance in the mode condition (the most difficult condition) was not correlated with their global cognitive functioning, as measured by either the MMSE or the DRS. In fact, these results may be simply consistent with our description of DAT participants as constituting a homogeneous group with a general cognitive profile of early DAT. It would therefore be of great interest to explore sensitivity to mode and tempo in moderate to severe forms of DAT. Contradictory results obtained by Allen and Brosgole (1993) may also be explained by severity of cognitive decline. In their study, demented participants showed deficits affecting the recognition of happy, sad, and angry musical expressions. Although the authors did not provide measures of cognitive level, they described demented participants as nursing home residents; thus, the participants were probably showing moderate to severe cognitive deficits. Participants in the present study were clearly showing a mild level of deficit, for they were all still living at home (with minimal assistance). Finally, the Allen and Brosgole (1993) study may also have included other types of dementia, such as frontotemporal dementia, that also involve emotional recognition deficits, even earlier than DAT (Lavenu et al., 1999). Because the majority of studies on the emotional judgment of facial expressions and prosody include more than two categories of emotions, the negative findings in our study may be partly due to the fact that we examined the emotional judgment of music for only happiness and sadness. Alzheimer’s disease, even in its early stages, damages the amygdala (Chow & Cummings, 2000). This is in accordance with results from the study of Lavenu et al. (1999) that found deficits in emotional recognition only for facial expression of fear in early DAT. Moreover, the amygdala has already been demonstrated to be necessary for the emotional processing of fear in music (Gosselin, Peretz, Johnsen, & Adolphs, 2007). Accordingly, further studies of the emotional judgment of music in DAT should also include fearful music. Finally, the negative findings obtained in the present study— mainly the absence of any differences between healthy elderly and DAT participants’ performances—may also be the result of a limited statistical power because of the small sample sizes. This is also suggested by some effect sizes obtained for the comparisons between groups for each condition (see Table 3). However, results regarding emotional recognition were relatively homogeneous, as can be seen in Figure 1. Nonetheless, the present study suggests that early DAT does spare some aspects of the emotional appreciation of music. This conclusion suggests that further studies should be done to provide more empirical support for the use of music as an emotional medium to improve the quality of life of people who suffer from DAT.

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Received January 17, 2008 Revision received July 10, 2008 Accepted July 16, 2008 䡲