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Instrumental and vocal music effects on EEG and EKG in neonates of depressed and non-depressed mothers
Infant Behavior & Development 29 (2006) 518–525
Instrumental and vocal music effects on EEG and EKG in neonates of depressed and non-depressed mothers Maria Hernandez-Reif ∗ , Miguel Diego, Tiffany Field University of Miami School of Medicine, United States Received 28 September 2005; received in revised form 21 April 2006; accepted 12 July 2006
Abstract Neonates (M age = 16 days) born to depressed and non-depressed mothers were randomly assigned to hear an audiotaped lullaby of instrumental music with vocals or without vocals. Neonatal EEG and EKG were recorded for 2 min (baseline) of silence and for 2 min of one or the other music presentation. Neonates of non-depressed mothers showed greater relative right frontal EEG asymmetry to both types of music, suggesting a withdrawal response. Neonates of depressed mothers on the other hand showed greater relative left frontal EEG asymmetry to the instrumental without vocal segment, suggesting an approach response, and greater relative right frontal EEG asymmetry to the instrumental with vocal segment, suggesting a withdrawal response. Heart rate decelerations occurred following the music onset for both groups of infants, however, compared to infants of non-depressed mothers, infants of depressed mothers showed a delayed heart rate deceleration, suggesting slower processing and/or delayed attention. These findings suggest that neonates of depressed and non-depressed mothers show different EKG and EEG responses to instrumental music with versus without vocals. © 2006 Published by Elsevier Inc. Keywords: Neonates; Depressed and non-depressed mothers; Instrumental music
Young infants respond to music in ways similar and different from adults (Trehub, 2003). For example, just like adults, infants detect pitch changes and distance between tones (Trehub, Schellenberg, & Kamenetsky, 1999) and show memory for songs (Saffran, Lomam, & Robertson, 2000). Further, they are able to detect subtle variations in simple melodies, not discernable to most adults (Lynch, Eilers, Oller, & Urbano, 1990). Infants also show musical preferences for different types of music. For example, they prefer “motherese” lullabies over “adult-directed” songs (Masataka, 1999; Trainor, 1996), and they favor consonant music (e.g., harmonic music such as in a nursery rhyme) over dissonant music (e.g., certain types of jazz music) (Trainor & Heinmiller, 1998; Zentner & Kagan, 1996). These findings suggest that infants are sensitive to critical features of music (see Trehub, 2001, 2003 for reviews). Few studies exist on neonatal music perception and no studies were found on infants’ preference for instrumental versus vocal music. In the present study, we examined physiological responses to instrumental versus instrumental plus vocal music in newborn infants. We also examined responses to music stimuli in infants of depressed mothers inasmuch as research shows that infants of depressed mothers exhibit different responses to sensory stimuli than infants born to non-depressed mothers. For example, shortly after birth, infants of depressed mothers take longer to habituate their
∗ Corresponding author at: Touch Research Institutes, Department of Pediatrics, University of Miami School of Medicine, P.O. Box 016820 (D-820), Miami, FL 33101, United States.
0163-6383/$ – see front matter © 2006 Published by Elsevier Inc. doi:10.1016/j.infbeh.2006.07.008
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mothers’ face-voice (Hernandez-Reif, Field, Diego & Largie, 2002), and at 3–5 months of age take longer to habituate a stranger’s face-voice (Hernandez-Reif, Field, Diego, Vera, & Pickens, 2006), suggesting that they are less attentive to female voices/faces and habituate them more slowly. Similarly, newborn infants of depressed mothers spend less time mouthing novel objects (Hernandez-Reif, Field, del Pino & Diego, 2000), and take longer to habituate objects by hand, suggesting that they are less exploratory or attentive. Based on these findings, we hypothesized that neonates of depressed mothers would be less attentive and take longer to respond to music stimuli. To test the above hypotheses, we measured heart rate and frontal EEG asymmetry responses to instrumental with versus without vocal music in newborns of depressed versus non-depressed mothers. Heart rate deceleration/acceleration was measured as an index of arousal and attention. Newborns show heart rate deceleration when attending to a stimulus and heart rate acceleration following an aversive stimulus or when aroused (Morrongiello & Clifton, 1984). EEG asymmetry responses served as an index of affective responses to the music stimuli. Greater relative right frontal EEG asymmetry has been associated with behavioral withdrawal and negative affect (fear, sadness and disgust), while greater relative left frontal EEG asymmetry has been associated with behavioral approach and positive affect in both adults and infants (Davidson & Fox, 1989; Fox, 1994). 1. Method 1.1. Participants Fifty-three full term neonates (n = 27 born to non-depressed mothers) were recruited for this study from a longitudinal study on the effects of maternal depression on infants. The mothers’ depression status was based on their score on the Center for Epidemiological Depression Scale (CES-D; Radloff, 1977 see below) and a diagnostic classification of depression on the Structured Clinical Interview for DSM-IV—research version (SCID; First, Spitzer, Gibbon, & Williams, 2002). The infants averaged 16-days-old (S.D. = 8.2), and 52% were boys. Exclusion criteria for the mothers included self-reported perinatal complications or medical conditions during pregnancy (e.g., gestational diabetes, preeclampsia, drug use and HIV). Exclusion criteria for the newborns included prematurity, low birthweight, surgery, postnatal complications and Apgar scores less than 7 at 1 and 5 min. Mothers were on an average 26-years-old (S.D. = 5.86), came from predominantly lower-middle SES families (M = 3.8, S.D. = 1.11 on the Hollingshead, 1975), and were ethnically distributed 52% White-Hispanic, 42% AfricanAmerican, 4% Non-Hispanic White, and 2% Asian. Depressed mothers were on an average younger (depressed M age = 24, S.D. = 3.6 versus non-depressed M age = 28, S.D. = 6.9, F (1, 51) = 7.04, p < 0.05) and were lower socioeconomic status (depressed M Hollingshead SES = 4.2, S.D. = 0.7, versus non-depressed M Hollingshead SES = 3.4, S.D. = 1.3, F (1, 51) = 8.31, p < 0.05) than the non-depressed mothers. The groups did not differ on the other demographic variables. None of the depressed mothers were receiving treatment or medication for their depression. 1.2. Procedure 1.2.1. Center for epidemiological depression scale (CES-D; Radloff, 1977) and the structural clinical interview for depression (SCID) The mothers were assessed for depression on the CES-D when they were pregnant and when their infants were born. The CES-D is a 20-item scale, rated on a Likert Scale of 0 (0 or 1 day) to 3 (nearly every day), that assesses symptoms of depression such as appetite, sleep difficulty, and feeling blue over the past 7 days. Infants whose mothers scored 16 (cutpoint) or higher on the CES-D were assigned to the depressed group, and those whose mothers scored 3–12 on the CES-D were assigned to the non-depressed group. Mothers were not recruited for the study if their scores fell in the “faking good” (0–2) or “borderline” (13–15) range or if they shifted from depressed to non-depressed (or vice-versa) from pregnancy to birth. The CES-D has been validated with pregnant women as well as with women from different ethnic and socioeconomic status groups (Myers & Weissman, 1980). Women who scored at or above the CES-D cutpoint (>16) were subsequently interviewed by a graduate-level trained researcher to determine the women’s depression diagnosis using the Structural Clinical Interview for DSM-IV (SCIDresearch version). The SCID, which was adapted for depression only diagnosis, is a semi-structured interview in which the presence or absence of symptoms that comprise a depressive mood disorder are noted for a diagnosis of major depressive disorder (acute depression) or dysthmia (chronic depression). Women who met a depression diagnosis were
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recruited for the depressed group, and those who scored less than 12 on the CES-D were recruited for the non-depressed group after meeting the inclusion/exclusion criteria. 1.2.2. Laboratory session The mothers were scheduled to bring their newborn infants to our laboratory for testing as soon as possible after delivering their infants and within the first month of life. After arriving, the mothers and neonates were taken to a quiet room, and the mothers were asked to feed and change their infants 30 min before testing. The neonates were subsequently swaddled using a cotton blanket and tested while resting in a reclined infant seat. EEG and EKG were recorded throughout the procedure (see Sections 2.1.1 and 2.1.2 below). 1.2.3. Music stimuli The music score was a version of “Dream a Little Dream” and consisted of two segments: an instrumental only (instrumental) and an instrumental plus vocal (vocal) segment. The instrumental segment featured a coronet playing the melody in the same pitch as the vocalist. The vocal segment started with the same instrumental music as in the instrumental condition, and 8 s later, a female vocalist was featured singing the melody in the same mid-range pitch. The tone quality of the coronet and the vocalist was very similar. This music score was selected because it allowed us to compare infants’ physiological responses to instrumental music with and without a vocalist. The music was presented on a Lennox Sound Stereo AM/FM Cassette Recorder (Model# CT-731/BP-731), which was filtered to a small headphone placed inside a cushioned head cradle, which nested the neonate’s head. The volume level was marked on the cassette recorder and checked before each testing to ensure that all infants were presented with the music stimuli at the same volume. After a 2-min baseline quiet period, each infant was presented with the instrumental only or the instrumental plus vocal segments for 2 min. 1.2.4. EEG recordings The infant’s EEG was recorded from the mid-frontal (F3 and F4) region and referenced to the vertex (Cz) according to the International 10–20 placement system. Prior to electrode attachment, electrode sites were marked, wiped with alcohol and gently abraded with Omni-prep gel. Electrodes were then affixed to the scalp using Ten20 conductive EEG paste (D.O. Weaver & Co., Aurora, CO). Impedances were less than 10 k or the site was re-abraded until optimal impedances were obtained. After the electrodes were in place, gauze was wrapped around the newborn’s head to secure the electrodes. EEG was only recorded from midfrontal sites as frontal EEG asymmetry was the only EEG measure of interest in the present study. The vertex reference location was used because this reference site has been shown to produce comparable results to other reference sites (Tomarken, Davidson, Wheeler, & Kinney, 1992), and it is the least invasive location for infants this age. EOG was also obtained from the outer canthus and the supra-orbit position of one eye using Beckman mini-electrodes. The EEG signals were obtained using a Grass Model 12 Neurodata Acquisition System with filters set at 1 Hz high pass and 100 Hz low pass and a gain of 20,000. Prior to data collection, the signal for each channel was calibrated. The output was directed to a personal computer fitted with an Analog Devices RTI-815 A/D board at a rate of 512 samples per second and saved to a hard disk using data acquisition software (Snapstream, v. 3.21, HEM Data Corp. 1991). Newborn EEGs were recorded with the mother outside the EEG recording room. The EEG data were scored for eye and motor movement artifact using the EOG channels as cues, and the datacontaining artifact were underscored and eliminated from each channel. The data were submitted to a discrete Fourier Transform using a 1-s Hanning Window with 50% overlap. The analyses produced power for the 3–6, 6–9 and 9–12 Hz frequency bands in picowatt ohms (one microvolt squared) for each channel. A minimum of 10 artifact free windows per epoch was required for analysis. Frontal asymmetry scores were then computed using the natural log power scores. The asymmetry score is a difference score reflecting the power in one hemisphere relative to the power in the contralateral hemisphere (Ln (right) − Ln (left)), with negative scores reflecting greater relative right frontal EEG activation and positive scores reflecting greater relative left frontal EEG activation. 1.2.5. EKG recordings EKG was recorded by placing three neonatal disposable electrodes on the infant’s chest and back. EKG signals were obtained using a Grass Model 12 Neurodata Acquisition System with filters set at 1 Hz high pass and 100 Hz low pass and a gain of 2000. The output was directed to a personal computer fitted with an analog devices RTI-815 A/D board at a rate of 512 samples per second and saved to a hard disk using data acquisition software (Snapstream, v. 3.21,
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HEM Data Corp. 1991). EKG data were manually scored for movement artifact, and the data-containing artifact were underscored and eliminated. Mean heart rate in beats per minute (BPM) was then computed for the 20 s immediately preceding and the 20 s immediately following the music presentation using data acquisition and analysis software (AcqKnowledge software V.3.5, Biopac Systems Inc., 1999). Heart rate decelerations/accelerations were coded as any instance that heart rate exceeded the confidence intervals computed across the 20-s baseline. Of the 53 infant recordings 34 infants (n = 17 depressed) had usable EEG data and 35 infants (n = 17 depressed) had usable EKG data. Excluded data derived from movement artifact or crying (n = 9 depressed and n = 7 non-depressed) and equipment problems (n = 1 depressed and n = 2 non-depressed). 2. Results The first set of analyses examined neonatal (infants of non-depressed mothers) physiological responses to vocal versus instrumental music. The second set of analyses compared the responses for neonates of depressed mothers to those of neonates of non-depressed mothers. 2.1. EEG and EKG responses to music by infants of non-depressed mothers 2.1.1. EKG Instrumental versus vocal ANOVAs computed on mean baseline heart rate, heart rate variability following music onset, heart rate deceleration, magnitude and lagtime failed to reveal any significant differences in infants’ EKG responses to instrumental versus the instrumental plus vocal segments (Table 1). 2.1.2. EEG To address the question of whether EEG responses differed by music type for typical newborns (i.e., of non-depressed mothers), instrumental versus instrumental plus vocal ANOVAs were conducted on the different band frontal EEG asymmetry change scores. These analyses failed to reveal any significant effects, suggesting that typical neonates (born to non-depressed mothers) had similar EEG responses to the instrumental and the instrumental plus vocal segments (Table 1). However it is interesting to note that, both groups showed a shift towards greater relative right frontal EEG asymmetry, suggesting they showed inhibited behavior to both music types. 2.2. Differences in EEG and EKG responses to music by infants of depressed and non-depressed mothers 2.2.1. EKG Group (depressed/non-depressed) by music condition (instrumental/vocal) ANOVAs computed on mean baseline heart rate, heart rate variability following music onset, heart rate deceleration and heart rate deceleration lagtime revealed the following: (1) no differences on baseline heart rate; (2) greater heart rate variability by neonates of depressed Table 1 Means and standard deviations (in parentheses under means) for EEG and EKG measures for infants of non-depressed mothers Vocal
Instrumental
EEG asymmetry change 3–6 Hz Asymmetry 6–9 Hz Asymmetry 9–12 Hz Asymmetry
−0.01a (0.10) −0.03a (0.16) −0.07a (0.10)
−0.07a (0.11) −0.06a (0.05) −0.02a (0.03)
EKG Baseline heart rate (BPM) Heart rate variability following music onset
151.25a (13.18) 4.46a (1.26)
148.45a (16.95) 3.94a (1.37)
First heart rate deceleration Magnitude (BPM) Lagtime (s)
−16.46a (10.36) 1.06a (0.63)
−10.64a (4.91) 1.11a (0.33)
Different letter superscripts (a, b) indicate significant differences between means at * p < 0.05.
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Table 2 Means and standard deviations (in parentheses under means) for heart rate measures Depressed
Non-depressed
Vocal
Instrumental
Vocal
Instrumental
Baseline heart rate (BPM) Heart rate variability following music onset
152.15a (13.58) 5.83a (1.75)
148.95a (20.21) 6.77a (2.66)
151.25a (13.18) 4.46b (1.26)
148.45a (16.95) 3.94b (1.37)
First heart rate deceleration Magnitude (BPM) Lagtime (s)
−11.24a (4.73) 1.56a (0.90)
−12.33a (8.15) 1.56a (0.73)
−16.46a (10.36) 1.06b (0.63)
−10.64a (4.91) 1.11b (0.33)
Second heart rate deceleration Magnitude (BPM) Lagtime (s)
6.38a (9.13) 9.38a (1.30)
13.67a (10.33) 8.11b (0.60)
Different subscripts (a and b) indicate significant differences between means at * p < 0.05.
mothers, F (1, 31) = 11.20, p < 0.01 (see Table 2); (3) infants of depressed mothers showed a longer lagtime to heart rate deceleration than infants of non-depressed mothers during both music conditions, F (1, 31) = 1.98, p < 0.05 (see Table 2); (4) further examination of heart rate responses revealed for all infants (1) a mean 13 BPM heart rate deceleration following the instrumental music onset (see Fig. 1) and (2); in the instrumental plus vocal condition (vocal) a second heart rate deceleration that coincided with the onset of the female vocalist, approximately 8 s (S.D. = 1.1) following the onset of the vocal/instrumental condition (see Fig. 1). ANOVAs computed to analyze for group (depressed/non-depressed) heart rate deceleration differences for the vocal condition revealed a greater lagtime in heart rate deceleration for the neonates of depressed mothers compared to neonates of non-depressed mothers in responding to the vocal segment, F (1, 15) = 6.87, p < 0.05 (see Table 2). 2.2.2. EEG EEG gender differences have been previously reported for young infants by our group (Diego, Jones, Field, & Hernandez-Reif, in press). Therefore, group (depressed/non-depressed) by gender (male/female) ANOVAs were first conducted on baseline frontal EEG asymmetry. The ANOVAs revealed significant group by gender baseline frontal EEG asymmetry interaction effects for 3–6 Hz, F (1, 30) = 10.37, p < 0.01, 6–9 Hz, F (1, 30) = 9.13, p < 0.01, and 9–12 Hz, F (1, 30) = 4.50, p < 0.05 (see Fig. 2). Subsequent post hoc Bonferroni t-tests were conducted to assess the interaction effects. These analyses revealed that at baseline, female infants of depressed mothers exhibited greater relative right frontal EEG asymmetry within the 3–6 Hz (p < 0.05), the 6–9 Hz (p < 0.05) and the 9–12 Hz (p < 0.05) bands than the other groups. Music type (instrumental versus instrumental plus vocal) by group (depressed/non-depressed), ANCOVAs were then conducted on the different band frontal EEG asymmetry change scores with music condition and group as the grouping factors. Inasmuch as male and female infants exhibited different frontal EEG asymmetry scores at baseline, gender was entered as a covariate. These analyses revealed a significant music by group interaction effect for only the 9–12 Hz band, F (1, 28) = 4.33, p < 0.05 (Fig. 3). Subsequent post hoc Bonferroni t-tests revealed that the EEG patterns for the group of neonates of depressed mothers who listened to the instrumental music differed from the group of newborns of depressed mothers who were presented with the instrumental plus vocal music (M difference = 0.21, p < 0.05). Specifically, the neonates of depressed mothers who listened to the instrumental music exhibited greater relative left frontal EEG asymmetry or approach behaviors, whereas neonates of depressed mothers who listened to the instrumental plus vocal music showed greater relative right frontal EEG asymmetry or withdrawal responses. 3. Discussion This study assessed frontal EEG asymmetry and heart rate responses to instrumental music with and without a vocal component. Inasmuch as infants of depressed mothers have been shown to exhibit different responses to sensory stimuli than infants born to non-depressed mothers (Hernandez-Reif et al., 2000, 2002, 2003) neonates of depressed mothers were expected to be less attentive to the vocal music.
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Fig. 1. Mean heart rate (BPM) 20-s baseline and mean heart rate (BPM) during the 20-s music condition (instrumental or instrumental and vocal). The first vertical line denotes the onset of the instrumental.
The heart rate deceleration exhibited by both groups of infants immediately after the music onset suggests that both groups of neonates were attentive to the music, as heart rate deceleration in response to a stimulus is considered to be an index of neonatal attention (Morrongiello & Clifton, 1984). However, as expected, neonates of depressed mothers showed a greater lagtime in heart rate deceleration, suggesting slower responding or attending by this group. The neonates of depressed mothers also showed greater heart rate variability following the music onset, suggesting that they may have difficulty modulating arousal. The less attending and poorer arousal suggested by the physiological findings reported in this study might explain the slower habituation of faces and voices by infants of depressed mothers previously reported (Hernandez-Reif et al., 2000; Hernandez-Reif et al., 2003). Newborns of non-depressed mothers exhibited greater relative right frontal EEG asymmetry during both the instrumental and vocal conditions, suggesting a withdrawal response. It is possible that this withdrawal response to both music stimuli is an adaptive response in reaction to an unfamiliar situation inasmuch as these were newborn infants who probably had little or no previous exposure to vocal and/or instrumental music. Neonates of depressed mothers
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Fig. 2. Baseline frontal EEG asymmetry (LN(right) − LN(left)) in male and female newborns of depressed (black bars) and non-depressed (white bars) mothers.
also showed a withdrawal response (i.e., greater relative right frontal EEG asymmetry) during the vocal condition; however, they unexpectedly exhibited an approach response (i.e., greater relative left frontal EEG activation) during the instrumental condition. The negative EEG response by all neonates to the vocal music (i.e., less approach/more withdrawal) is compelling and may relate to a greater difficulty processing voices, especially singing voices. Further study is needed to confirm this provocative finding and perhaps to determine if similar results would occur for other vocal conditions, such as the mother singing or a child singing. A confound in the design of the study was that the instrumental plus vocalist condition contained both music types. Thus, future research is needed to examine neonates’ physiological responding to vocal music alone (e.g., singing without instruments) to better assess newborn infants’ response to singing. As in a previous study (Diego et al., in press) young infant girls born to depressed mothers showed a baseline pattern of greater relative right frontal EEG asymmetry, a pattern which has been associated with depression in adults. The
Fig. 3. Baseline to music condition change in frontal EEG asymmetry values (9–12 Hz).
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small sample size in our study did not allow us to examine whether gender differences by music type might exist for those girls born to depressed versus non-depressed mothers. Future research on this topic is also necessary. In summary, the findings from this study support the view that newborns attend to music stimuli evident by the heart rate changes, and that instrumental and vocal music have different effects on neonates of depressed versus nondepressed mothers. In particular, neonates of depressed mothers show approach behaviors to instrumental music. Future studies might examine the effects of varying music types on older infants of depressed versus non-depressed mothers to examine how infants’ responses to music types develop over time and to establish which music types might have calming effects or be more positively perceived by infants. Acknowledgements We thank the mothers and infants who participated in this study. We also thank Julia Beutler, Mercedes Fernandez, Karla Gil, Amparo Roca, Chris Sanders and Yanexy Vera for their assistance with recruitment and data collection. This research was supported by an NIMH Senior Research Scientist Award (#MH00331) and an NIMH Merit Award (#MH46586) to Tiffany Field, an NIH/NCCAM grant (AT 000370) to Maria Hernandez-Reif, an NIH/NCCAM supplemental grant (AT 000370-S2) to Miguel Diego and funding from Johnson & Johnson Pediatric Institute to the Touch Research Institutes. References Clifton, R. (1974). Heart rate conditioning in the newborn infant. Journal of Experimental Child Psychology, 18, 9–21. Davidson, R., & Fox, N. (1989). Frontal brain asymmetry predicts infants’ response to maternal separation. Journal of Abnormal Psychology, 98, 127–131. Diego, M., Jones, N., Field, T., & Hernandez-Reif, M. (in press). Frontal EEG asymmetry gender differences in infants of depressed and non-depressed mothers. Developmental Psychobiology. First, M., Spitzer, R., Gibbon, M., & Williams, J. (2002). Structured clinical interview for DSM-IV-TR axis I disorders, research version, Non-patient Edition. (SCID-I/NP) New York: Biometrics Research, New York State Psychiatric Institute. Fox, N. (1994). If it’s not left, it’s right. Electroencephaolograph asymmetry and the development of emotion. American Psychologist, 46, 863–872. Hernandez-Reif, M., Field, T., del Pino, N., & Diego, M. (2000). Less exploring by mouth occurs in newborns of depressed mothers. Infant Mental Health Journal, 21, 204–210. Hernandez-Reif, M., Field, T., Diego, M., & Largie, S. (2002). Depressed mothers’ newborns show longer habituation and fail to show face/voice preference. Infant Mental Health Journal, 23, 643–653. Hernandez-Reif, M., Field, T., Diego, M., & Largie, S. (2003). Haptic habituation to temperature is slower in infants of depressed mothers. Haptic habituation to temperature is slower in newborns of depressed mothers. Infancy, 4, 47–63. Hernandez-Reif, M., Field, T., Diego, M., Vera, Y., & Pickens, J. (2006). Happy faces are habituated more slowly by infants of depressed mothers. Infant Behavior and Development, 29, 131–135. Hollingshead, A. (1975). Four factor index of social status. New Haven, CT, Yale University. Lynch, M., Eilers, R., Oller, D., & Urbano, R. (1990). Innateness, experience and music perception. Psychological Science, 1, 272–276. Masataka, N. (1999). Preference for infant-directed singing in 2-day old hearing infants of deaf parents. Developmental Psychology, 35, 1001–1005. Morrongiello, B., & Clifton, R. (1984). Effects of sound frequency on behavioral and cardiac orienting in newborn and five-month-old infants. Journal of Experimental Child Psychology, 38, 429–446. Myers, J., & Weissman, M. (1980). Use of a self-report symptoms scale to detect depression in a community sample. American Journal of Psychiatry, 137, 1081–1084. Radloff, L. (1977). The CES-D Scale: A self-report depression scale for research in the general population. Journal of Applied Psychological Measures, 1, 385–401. Saffran, J., Loman, M., & Robertson, R. (2000). Infant memory for musical experiences. Cognition, 77, 15–23. Tomarken, A., Davidson, R., Wheeler, R., & Kinney, L. (1992). Psychometric properties of resting anterior EEG asymmetry. Temporal stability and internal consistency. Psychophysiology, 29, 576–592. Trainor, L. (1996). Infant preferences for infant-directed versus non-infant-directed play songs and lullabies. Infant Behavior and Development, 19, 83–92. Trainor, L., & Heinmiller, B. (1998). The development of evaluative responses to music: Infants prefer to listen to consonance over dissonance. Infant Behavior and Development, 21, 77–88. Trehub, S. (2001). Musical predispositions in infancy. Annals New York Academy of Sciences, 930, 1–16. Trehub, S., Schellenberg, E., & Kamenetsky, S. (1999). Infants’ and adults’ perception of scale structure. Journal of Experimental Psychology: Human Perception and Performance, 25, 965–975. Trehub, S. (2003). The developmental origins of musicality. Nature Neuroscience, 6, 669–673. Zentner, M., & Kagan, J. (1996). Perception of music by infants. Nature, 383, 29.
Instrumental and vocal music effects on EEG and EKG in neonates of depressed and non-depressed mothers Maria Hernandez-Reif ∗ , Miguel Diego, Tiffany Field University of Miami School of Medicine, United States Received 28 September 2005; received in revised form 21 April 2006; accepted 12 July 2006
Abstract Neonates (M age = 16 days) born to depressed and non-depressed mothers were randomly assigned to hear an audiotaped lullaby of instrumental music with vocals or without vocals. Neonatal EEG and EKG were recorded for 2 min (baseline) of silence and for 2 min of one or the other music presentation. Neonates of non-depressed mothers showed greater relative right frontal EEG asymmetry to both types of music, suggesting a withdrawal response. Neonates of depressed mothers on the other hand showed greater relative left frontal EEG asymmetry to the instrumental without vocal segment, suggesting an approach response, and greater relative right frontal EEG asymmetry to the instrumental with vocal segment, suggesting a withdrawal response. Heart rate decelerations occurred following the music onset for both groups of infants, however, compared to infants of non-depressed mothers, infants of depressed mothers showed a delayed heart rate deceleration, suggesting slower processing and/or delayed attention. These findings suggest that neonates of depressed and non-depressed mothers show different EKG and EEG responses to instrumental music with versus without vocals. © 2006 Published by Elsevier Inc. Keywords: Neonates; Depressed and non-depressed mothers; Instrumental music
Young infants respond to music in ways similar and different from adults (Trehub, 2003). For example, just like adults, infants detect pitch changes and distance between tones (Trehub, Schellenberg, & Kamenetsky, 1999) and show memory for songs (Saffran, Lomam, & Robertson, 2000). Further, they are able to detect subtle variations in simple melodies, not discernable to most adults (Lynch, Eilers, Oller, & Urbano, 1990). Infants also show musical preferences for different types of music. For example, they prefer “motherese” lullabies over “adult-directed” songs (Masataka, 1999; Trainor, 1996), and they favor consonant music (e.g., harmonic music such as in a nursery rhyme) over dissonant music (e.g., certain types of jazz music) (Trainor & Heinmiller, 1998; Zentner & Kagan, 1996). These findings suggest that infants are sensitive to critical features of music (see Trehub, 2001, 2003 for reviews). Few studies exist on neonatal music perception and no studies were found on infants’ preference for instrumental versus vocal music. In the present study, we examined physiological responses to instrumental versus instrumental plus vocal music in newborn infants. We also examined responses to music stimuli in infants of depressed mothers inasmuch as research shows that infants of depressed mothers exhibit different responses to sensory stimuli than infants born to non-depressed mothers. For example, shortly after birth, infants of depressed mothers take longer to habituate their
∗ Corresponding author at: Touch Research Institutes, Department of Pediatrics, University of Miami School of Medicine, P.O. Box 016820 (D-820), Miami, FL 33101, United States.
0163-6383/$ – see front matter © 2006 Published by Elsevier Inc. doi:10.1016/j.infbeh.2006.07.008
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mothers’ face-voice (Hernandez-Reif, Field, Diego & Largie, 2002), and at 3–5 months of age take longer to habituate a stranger’s face-voice (Hernandez-Reif, Field, Diego, Vera, & Pickens, 2006), suggesting that they are less attentive to female voices/faces and habituate them more slowly. Similarly, newborn infants of depressed mothers spend less time mouthing novel objects (Hernandez-Reif, Field, del Pino & Diego, 2000), and take longer to habituate objects by hand, suggesting that they are less exploratory or attentive. Based on these findings, we hypothesized that neonates of depressed mothers would be less attentive and take longer to respond to music stimuli. To test the above hypotheses, we measured heart rate and frontal EEG asymmetry responses to instrumental with versus without vocal music in newborns of depressed versus non-depressed mothers. Heart rate deceleration/acceleration was measured as an index of arousal and attention. Newborns show heart rate deceleration when attending to a stimulus and heart rate acceleration following an aversive stimulus or when aroused (Morrongiello & Clifton, 1984). EEG asymmetry responses served as an index of affective responses to the music stimuli. Greater relative right frontal EEG asymmetry has been associated with behavioral withdrawal and negative affect (fear, sadness and disgust), while greater relative left frontal EEG asymmetry has been associated with behavioral approach and positive affect in both adults and infants (Davidson & Fox, 1989; Fox, 1994). 1. Method 1.1. Participants Fifty-three full term neonates (n = 27 born to non-depressed mothers) were recruited for this study from a longitudinal study on the effects of maternal depression on infants. The mothers’ depression status was based on their score on the Center for Epidemiological Depression Scale (CES-D; Radloff, 1977 see below) and a diagnostic classification of depression on the Structured Clinical Interview for DSM-IV—research version (SCID; First, Spitzer, Gibbon, & Williams, 2002). The infants averaged 16-days-old (S.D. = 8.2), and 52% were boys. Exclusion criteria for the mothers included self-reported perinatal complications or medical conditions during pregnancy (e.g., gestational diabetes, preeclampsia, drug use and HIV). Exclusion criteria for the newborns included prematurity, low birthweight, surgery, postnatal complications and Apgar scores less than 7 at 1 and 5 min. Mothers were on an average 26-years-old (S.D. = 5.86), came from predominantly lower-middle SES families (M = 3.8, S.D. = 1.11 on the Hollingshead, 1975), and were ethnically distributed 52% White-Hispanic, 42% AfricanAmerican, 4% Non-Hispanic White, and 2% Asian. Depressed mothers were on an average younger (depressed M age = 24, S.D. = 3.6 versus non-depressed M age = 28, S.D. = 6.9, F (1, 51) = 7.04, p < 0.05) and were lower socioeconomic status (depressed M Hollingshead SES = 4.2, S.D. = 0.7, versus non-depressed M Hollingshead SES = 3.4, S.D. = 1.3, F (1, 51) = 8.31, p < 0.05) than the non-depressed mothers. The groups did not differ on the other demographic variables. None of the depressed mothers were receiving treatment or medication for their depression. 1.2. Procedure 1.2.1. Center for epidemiological depression scale (CES-D; Radloff, 1977) and the structural clinical interview for depression (SCID) The mothers were assessed for depression on the CES-D when they were pregnant and when their infants were born. The CES-D is a 20-item scale, rated on a Likert Scale of 0 (0 or 1 day) to 3 (nearly every day), that assesses symptoms of depression such as appetite, sleep difficulty, and feeling blue over the past 7 days. Infants whose mothers scored 16 (cutpoint) or higher on the CES-D were assigned to the depressed group, and those whose mothers scored 3–12 on the CES-D were assigned to the non-depressed group. Mothers were not recruited for the study if their scores fell in the “faking good” (0–2) or “borderline” (13–15) range or if they shifted from depressed to non-depressed (or vice-versa) from pregnancy to birth. The CES-D has been validated with pregnant women as well as with women from different ethnic and socioeconomic status groups (Myers & Weissman, 1980). Women who scored at or above the CES-D cutpoint (>16) were subsequently interviewed by a graduate-level trained researcher to determine the women’s depression diagnosis using the Structural Clinical Interview for DSM-IV (SCIDresearch version). The SCID, which was adapted for depression only diagnosis, is a semi-structured interview in which the presence or absence of symptoms that comprise a depressive mood disorder are noted for a diagnosis of major depressive disorder (acute depression) or dysthmia (chronic depression). Women who met a depression diagnosis were
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recruited for the depressed group, and those who scored less than 12 on the CES-D were recruited for the non-depressed group after meeting the inclusion/exclusion criteria. 1.2.2. Laboratory session The mothers were scheduled to bring their newborn infants to our laboratory for testing as soon as possible after delivering their infants and within the first month of life. After arriving, the mothers and neonates were taken to a quiet room, and the mothers were asked to feed and change their infants 30 min before testing. The neonates were subsequently swaddled using a cotton blanket and tested while resting in a reclined infant seat. EEG and EKG were recorded throughout the procedure (see Sections 2.1.1 and 2.1.2 below). 1.2.3. Music stimuli The music score was a version of “Dream a Little Dream” and consisted of two segments: an instrumental only (instrumental) and an instrumental plus vocal (vocal) segment. The instrumental segment featured a coronet playing the melody in the same pitch as the vocalist. The vocal segment started with the same instrumental music as in the instrumental condition, and 8 s later, a female vocalist was featured singing the melody in the same mid-range pitch. The tone quality of the coronet and the vocalist was very similar. This music score was selected because it allowed us to compare infants’ physiological responses to instrumental music with and without a vocalist. The music was presented on a Lennox Sound Stereo AM/FM Cassette Recorder (Model# CT-731/BP-731), which was filtered to a small headphone placed inside a cushioned head cradle, which nested the neonate’s head. The volume level was marked on the cassette recorder and checked before each testing to ensure that all infants were presented with the music stimuli at the same volume. After a 2-min baseline quiet period, each infant was presented with the instrumental only or the instrumental plus vocal segments for 2 min. 1.2.4. EEG recordings The infant’s EEG was recorded from the mid-frontal (F3 and F4) region and referenced to the vertex (Cz) according to the International 10–20 placement system. Prior to electrode attachment, electrode sites were marked, wiped with alcohol and gently abraded with Omni-prep gel. Electrodes were then affixed to the scalp using Ten20 conductive EEG paste (D.O. Weaver & Co., Aurora, CO). Impedances were less than 10 k or the site was re-abraded until optimal impedances were obtained. After the electrodes were in place, gauze was wrapped around the newborn’s head to secure the electrodes. EEG was only recorded from midfrontal sites as frontal EEG asymmetry was the only EEG measure of interest in the present study. The vertex reference location was used because this reference site has been shown to produce comparable results to other reference sites (Tomarken, Davidson, Wheeler, & Kinney, 1992), and it is the least invasive location for infants this age. EOG was also obtained from the outer canthus and the supra-orbit position of one eye using Beckman mini-electrodes. The EEG signals were obtained using a Grass Model 12 Neurodata Acquisition System with filters set at 1 Hz high pass and 100 Hz low pass and a gain of 20,000. Prior to data collection, the signal for each channel was calibrated. The output was directed to a personal computer fitted with an Analog Devices RTI-815 A/D board at a rate of 512 samples per second and saved to a hard disk using data acquisition software (Snapstream, v. 3.21, HEM Data Corp. 1991). Newborn EEGs were recorded with the mother outside the EEG recording room. The EEG data were scored for eye and motor movement artifact using the EOG channels as cues, and the datacontaining artifact were underscored and eliminated from each channel. The data were submitted to a discrete Fourier Transform using a 1-s Hanning Window with 50% overlap. The analyses produced power for the 3–6, 6–9 and 9–12 Hz frequency bands in picowatt ohms (one microvolt squared) for each channel. A minimum of 10 artifact free windows per epoch was required for analysis. Frontal asymmetry scores were then computed using the natural log power scores. The asymmetry score is a difference score reflecting the power in one hemisphere relative to the power in the contralateral hemisphere (Ln (right) − Ln (left)), with negative scores reflecting greater relative right frontal EEG activation and positive scores reflecting greater relative left frontal EEG activation. 1.2.5. EKG recordings EKG was recorded by placing three neonatal disposable electrodes on the infant’s chest and back. EKG signals were obtained using a Grass Model 12 Neurodata Acquisition System with filters set at 1 Hz high pass and 100 Hz low pass and a gain of 2000. The output was directed to a personal computer fitted with an analog devices RTI-815 A/D board at a rate of 512 samples per second and saved to a hard disk using data acquisition software (Snapstream, v. 3.21,
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HEM Data Corp. 1991). EKG data were manually scored for movement artifact, and the data-containing artifact were underscored and eliminated. Mean heart rate in beats per minute (BPM) was then computed for the 20 s immediately preceding and the 20 s immediately following the music presentation using data acquisition and analysis software (AcqKnowledge software V.3.5, Biopac Systems Inc., 1999). Heart rate decelerations/accelerations were coded as any instance that heart rate exceeded the confidence intervals computed across the 20-s baseline. Of the 53 infant recordings 34 infants (n = 17 depressed) had usable EEG data and 35 infants (n = 17 depressed) had usable EKG data. Excluded data derived from movement artifact or crying (n = 9 depressed and n = 7 non-depressed) and equipment problems (n = 1 depressed and n = 2 non-depressed). 2. Results The first set of analyses examined neonatal (infants of non-depressed mothers) physiological responses to vocal versus instrumental music. The second set of analyses compared the responses for neonates of depressed mothers to those of neonates of non-depressed mothers. 2.1. EEG and EKG responses to music by infants of non-depressed mothers 2.1.1. EKG Instrumental versus vocal ANOVAs computed on mean baseline heart rate, heart rate variability following music onset, heart rate deceleration, magnitude and lagtime failed to reveal any significant differences in infants’ EKG responses to instrumental versus the instrumental plus vocal segments (Table 1). 2.1.2. EEG To address the question of whether EEG responses differed by music type for typical newborns (i.e., of non-depressed mothers), instrumental versus instrumental plus vocal ANOVAs were conducted on the different band frontal EEG asymmetry change scores. These analyses failed to reveal any significant effects, suggesting that typical neonates (born to non-depressed mothers) had similar EEG responses to the instrumental and the instrumental plus vocal segments (Table 1). However it is interesting to note that, both groups showed a shift towards greater relative right frontal EEG asymmetry, suggesting they showed inhibited behavior to both music types. 2.2. Differences in EEG and EKG responses to music by infants of depressed and non-depressed mothers 2.2.1. EKG Group (depressed/non-depressed) by music condition (instrumental/vocal) ANOVAs computed on mean baseline heart rate, heart rate variability following music onset, heart rate deceleration and heart rate deceleration lagtime revealed the following: (1) no differences on baseline heart rate; (2) greater heart rate variability by neonates of depressed Table 1 Means and standard deviations (in parentheses under means) for EEG and EKG measures for infants of non-depressed mothers Vocal
Instrumental
EEG asymmetry change 3–6 Hz Asymmetry 6–9 Hz Asymmetry 9–12 Hz Asymmetry
−0.01a (0.10) −0.03a (0.16) −0.07a (0.10)
−0.07a (0.11) −0.06a (0.05) −0.02a (0.03)
EKG Baseline heart rate (BPM) Heart rate variability following music onset
151.25a (13.18) 4.46a (1.26)
148.45a (16.95) 3.94a (1.37)
First heart rate deceleration Magnitude (BPM) Lagtime (s)
−16.46a (10.36) 1.06a (0.63)
−10.64a (4.91) 1.11a (0.33)
Different letter superscripts (a, b) indicate significant differences between means at * p < 0.05.
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Table 2 Means and standard deviations (in parentheses under means) for heart rate measures Depressed
Non-depressed
Vocal
Instrumental
Vocal
Instrumental
Baseline heart rate (BPM) Heart rate variability following music onset
152.15a (13.58) 5.83a (1.75)
148.95a (20.21) 6.77a (2.66)
151.25a (13.18) 4.46b (1.26)
148.45a (16.95) 3.94b (1.37)
First heart rate deceleration Magnitude (BPM) Lagtime (s)
−11.24a (4.73) 1.56a (0.90)
−12.33a (8.15) 1.56a (0.73)
−16.46a (10.36) 1.06b (0.63)
−10.64a (4.91) 1.11b (0.33)
Second heart rate deceleration Magnitude (BPM) Lagtime (s)
6.38a (9.13) 9.38a (1.30)
13.67a (10.33) 8.11b (0.60)
Different subscripts (a and b) indicate significant differences between means at * p < 0.05.
mothers, F (1, 31) = 11.20, p < 0.01 (see Table 2); (3) infants of depressed mothers showed a longer lagtime to heart rate deceleration than infants of non-depressed mothers during both music conditions, F (1, 31) = 1.98, p < 0.05 (see Table 2); (4) further examination of heart rate responses revealed for all infants (1) a mean 13 BPM heart rate deceleration following the instrumental music onset (see Fig. 1) and (2); in the instrumental plus vocal condition (vocal) a second heart rate deceleration that coincided with the onset of the female vocalist, approximately 8 s (S.D. = 1.1) following the onset of the vocal/instrumental condition (see Fig. 1). ANOVAs computed to analyze for group (depressed/non-depressed) heart rate deceleration differences for the vocal condition revealed a greater lagtime in heart rate deceleration for the neonates of depressed mothers compared to neonates of non-depressed mothers in responding to the vocal segment, F (1, 15) = 6.87, p < 0.05 (see Table 2). 2.2.2. EEG EEG gender differences have been previously reported for young infants by our group (Diego, Jones, Field, & Hernandez-Reif, in press). Therefore, group (depressed/non-depressed) by gender (male/female) ANOVAs were first conducted on baseline frontal EEG asymmetry. The ANOVAs revealed significant group by gender baseline frontal EEG asymmetry interaction effects for 3–6 Hz, F (1, 30) = 10.37, p < 0.01, 6–9 Hz, F (1, 30) = 9.13, p < 0.01, and 9–12 Hz, F (1, 30) = 4.50, p < 0.05 (see Fig. 2). Subsequent post hoc Bonferroni t-tests were conducted to assess the interaction effects. These analyses revealed that at baseline, female infants of depressed mothers exhibited greater relative right frontal EEG asymmetry within the 3–6 Hz (p < 0.05), the 6–9 Hz (p < 0.05) and the 9–12 Hz (p < 0.05) bands than the other groups. Music type (instrumental versus instrumental plus vocal) by group (depressed/non-depressed), ANCOVAs were then conducted on the different band frontal EEG asymmetry change scores with music condition and group as the grouping factors. Inasmuch as male and female infants exhibited different frontal EEG asymmetry scores at baseline, gender was entered as a covariate. These analyses revealed a significant music by group interaction effect for only the 9–12 Hz band, F (1, 28) = 4.33, p < 0.05 (Fig. 3). Subsequent post hoc Bonferroni t-tests revealed that the EEG patterns for the group of neonates of depressed mothers who listened to the instrumental music differed from the group of newborns of depressed mothers who were presented with the instrumental plus vocal music (M difference = 0.21, p < 0.05). Specifically, the neonates of depressed mothers who listened to the instrumental music exhibited greater relative left frontal EEG asymmetry or approach behaviors, whereas neonates of depressed mothers who listened to the instrumental plus vocal music showed greater relative right frontal EEG asymmetry or withdrawal responses. 3. Discussion This study assessed frontal EEG asymmetry and heart rate responses to instrumental music with and without a vocal component. Inasmuch as infants of depressed mothers have been shown to exhibit different responses to sensory stimuli than infants born to non-depressed mothers (Hernandez-Reif et al., 2000, 2002, 2003) neonates of depressed mothers were expected to be less attentive to the vocal music.
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Fig. 1. Mean heart rate (BPM) 20-s baseline and mean heart rate (BPM) during the 20-s music condition (instrumental or instrumental and vocal). The first vertical line denotes the onset of the instrumental.
The heart rate deceleration exhibited by both groups of infants immediately after the music onset suggests that both groups of neonates were attentive to the music, as heart rate deceleration in response to a stimulus is considered to be an index of neonatal attention (Morrongiello & Clifton, 1984). However, as expected, neonates of depressed mothers showed a greater lagtime in heart rate deceleration, suggesting slower responding or attending by this group. The neonates of depressed mothers also showed greater heart rate variability following the music onset, suggesting that they may have difficulty modulating arousal. The less attending and poorer arousal suggested by the physiological findings reported in this study might explain the slower habituation of faces and voices by infants of depressed mothers previously reported (Hernandez-Reif et al., 2000; Hernandez-Reif et al., 2003). Newborns of non-depressed mothers exhibited greater relative right frontal EEG asymmetry during both the instrumental and vocal conditions, suggesting a withdrawal response. It is possible that this withdrawal response to both music stimuli is an adaptive response in reaction to an unfamiliar situation inasmuch as these were newborn infants who probably had little or no previous exposure to vocal and/or instrumental music. Neonates of depressed mothers
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Fig. 2. Baseline frontal EEG asymmetry (LN(right) − LN(left)) in male and female newborns of depressed (black bars) and non-depressed (white bars) mothers.
also showed a withdrawal response (i.e., greater relative right frontal EEG asymmetry) during the vocal condition; however, they unexpectedly exhibited an approach response (i.e., greater relative left frontal EEG activation) during the instrumental condition. The negative EEG response by all neonates to the vocal music (i.e., less approach/more withdrawal) is compelling and may relate to a greater difficulty processing voices, especially singing voices. Further study is needed to confirm this provocative finding and perhaps to determine if similar results would occur for other vocal conditions, such as the mother singing or a child singing. A confound in the design of the study was that the instrumental plus vocalist condition contained both music types. Thus, future research is needed to examine neonates’ physiological responding to vocal music alone (e.g., singing without instruments) to better assess newborn infants’ response to singing. As in a previous study (Diego et al., in press) young infant girls born to depressed mothers showed a baseline pattern of greater relative right frontal EEG asymmetry, a pattern which has been associated with depression in adults. The
Fig. 3. Baseline to music condition change in frontal EEG asymmetry values (9–12 Hz).
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small sample size in our study did not allow us to examine whether gender differences by music type might exist for those girls born to depressed versus non-depressed mothers. Future research on this topic is also necessary. In summary, the findings from this study support the view that newborns attend to music stimuli evident by the heart rate changes, and that instrumental and vocal music have different effects on neonates of depressed versus nondepressed mothers. In particular, neonates of depressed mothers show approach behaviors to instrumental music. Future studies might examine the effects of varying music types on older infants of depressed versus non-depressed mothers to examine how infants’ responses to music types develop over time and to establish which music types might have calming effects or be more positively perceived by infants. Acknowledgements We thank the mothers and infants who participated in this study. We also thank Julia Beutler, Mercedes Fernandez, Karla Gil, Amparo Roca, Chris Sanders and Yanexy Vera for their assistance with recruitment and data collection. This research was supported by an NIMH Senior Research Scientist Award (#MH00331) and an NIMH Merit Award (#MH46586) to Tiffany Field, an NIH/NCCAM grant (AT 000370) to Maria Hernandez-Reif, an NIH/NCCAM supplemental grant (AT 000370-S2) to Miguel Diego and funding from Johnson & Johnson Pediatric Institute to the Touch Research Institutes. References Clifton, R. (1974). Heart rate conditioning in the newborn infant. Journal of Experimental Child Psychology, 18, 9–21. Davidson, R., & Fox, N. (1989). Frontal brain asymmetry predicts infants’ response to maternal separation. Journal of Abnormal Psychology, 98, 127–131. Diego, M., Jones, N., Field, T., & Hernandez-Reif, M. (in press). Frontal EEG asymmetry gender differences in infants of depressed and non-depressed mothers. Developmental Psychobiology. First, M., Spitzer, R., Gibbon, M., & Williams, J. (2002). Structured clinical interview for DSM-IV-TR axis I disorders, research version, Non-patient Edition. (SCID-I/NP) New York: Biometrics Research, New York State Psychiatric Institute. Fox, N. (1994). If it’s not left, it’s right. Electroencephaolograph asymmetry and the development of emotion. American Psychologist, 46, 863–872. Hernandez-Reif, M., Field, T., del Pino, N., & Diego, M. (2000). Less exploring by mouth occurs in newborns of depressed mothers. Infant Mental Health Journal, 21, 204–210. Hernandez-Reif, M., Field, T., Diego, M., & Largie, S. (2002). Depressed mothers’ newborns show longer habituation and fail to show face/voice preference. Infant Mental Health Journal, 23, 643–653. Hernandez-Reif, M., Field, T., Diego, M., & Largie, S. (2003). Haptic habituation to temperature is slower in infants of depressed mothers. Haptic habituation to temperature is slower in newborns of depressed mothers. Infancy, 4, 47–63. Hernandez-Reif, M., Field, T., Diego, M., Vera, Y., & Pickens, J. (2006). Happy faces are habituated more slowly by infants of depressed mothers. Infant Behavior and Development, 29, 131–135. Hollingshead, A. (1975). Four factor index of social status. New Haven, CT, Yale University. Lynch, M., Eilers, R., Oller, D., & Urbano, R. (1990). Innateness, experience and music perception. Psychological Science, 1, 272–276. Masataka, N. (1999). Preference for infant-directed singing in 2-day old hearing infants of deaf parents. Developmental Psychology, 35, 1001–1005. Morrongiello, B., & Clifton, R. (1984). Effects of sound frequency on behavioral and cardiac orienting in newborn and five-month-old infants. Journal of Experimental Child Psychology, 38, 429–446. Myers, J., & Weissman, M. (1980). Use of a self-report symptoms scale to detect depression in a community sample. American Journal of Psychiatry, 137, 1081–1084. Radloff, L. (1977). The CES-D Scale: A self-report depression scale for research in the general population. Journal of Applied Psychological Measures, 1, 385–401. Saffran, J., Loman, M., & Robertson, R. (2000). Infant memory for musical experiences. Cognition, 77, 15–23. Tomarken, A., Davidson, R., Wheeler, R., & Kinney, L. (1992). Psychometric properties of resting anterior EEG asymmetry. Temporal stability and internal consistency. Psychophysiology, 29, 576–592. Trainor, L. (1996). Infant preferences for infant-directed versus non-infant-directed play songs and lullabies. Infant Behavior and Development, 19, 83–92. Trainor, L., & Heinmiller, B. (1998). The development of evaluative responses to music: Infants prefer to listen to consonance over dissonance. Infant Behavior and Development, 21, 77–88. Trehub, S. (2001). Musical predispositions in infancy. Annals New York Academy of Sciences, 930, 1–16. Trehub, S., Schellenberg, E., & Kamenetsky, S. (1999). Infants’ and adults’ perception of scale structure. Journal of Experimental Psychology: Human Perception and Performance, 25, 965–975. Trehub, S. (2003). The developmental origins of musicality. Nature Neuroscience, 6, 669–673. Zentner, M., & Kagan, J. (1996). Perception of music by infants. Nature, 383, 29.