Cortical Plasticity in 4-Month-Old Infants: Specific Effects of Experience with Musical Timbres

Animal models suggest that the brain is particularly neuroplastic early in development, but previous studies have not systematically controlled the auditory environment in human infants and observed the effects on auditory cortical representations. We exposed 4-month-old infants to melodies in either guitar or marimba timbre (infants were randomly assigned to exposure group) for a total of?~160?min over the course of a week, after which we measured electroencephalogram (EEG) responses to guitar and marimba tones at pitches not previously heard during the exposure phase. A frontally negative response with a topography consistent with generation in auditory areas, peaking around 450?ms, was significantly larger for guitar than marimba tones in the guitar-exposed group but significantly larger for marimba than guitar tones in the marimba-exposed group. This indicates that experience with tones in a particular timbre affects representations for that timbre, and that this effect generalizes to tones not previously experienced during exposure. Furthermore, mismatch responses to occasional small 3% changes in pitch were larger for tones in guitar than marimba timbre only for infants exposed to guitar tones. Together these results indicate that a relatively small amount of passive exposure to a particular timbre in infancy enhances representations of that timbre and leads to more precise pitch processing for that timbre.     

EFFECTS OF A TASK-RELEVANT RESPONSE ON PUPIL SIZE

This experiment examined the effects on pupil size of the relevance of an overt response to a cognitive task. Sixteen Ss were assigned to two experimental groups. In one group Ss were required to judge the pitch equality of tones and, subsequently, indicate their decision by pressing or not pressing a telegraph key. In the other group Ss were required to make the pitch-discriminations, but the key press response was unrelated to the preceding cognitive task. Continuous photographs of each S's pupil were taken during the experiment. Results showed that a small amount of pupillary dilation occurred during the discrimination task in the group where the key press was irrelevant to the pitch-discrimination. In the group where S's behavior indicated task fulfillment, however, a significantly greater increase in pupil size occurred, the amount of dilation being larger when task completion was indicated by the key press response than when fulfillment was indicated by no key press. The findings were discussed in terms of arousal associated with apprehension about evaluation, and muscle tension from anticipation of making the overt response.     

An early perceptual locus of absolute pitch

Absolute pitch (AP) refers to the naming of musical tone without external reference. The influential two-component model states that AP is limited by the late-emerging pitch labeling process only and not the earlier perceptual and memory processes. Over the years, however, support for this model at the neural level has been mixed with various methodological limitations. Here, the electroencephalography responses of 27 AP possessors and 27 non-AP possessors were recorded. During both name verification and passive listening, event-related potential analyses showed a difference between AP and non-AP possessors at about 200 ms in their response toward tones compared with noise stimuli. Multivariate pattern analyses suggested that pitch naming was subserved by a series of transient processes for the first 250 ms, followed by a stage-like process for both AP and non-AP possessors with no group differences between them. These findings are inconsistent with the predictions of the two-component model, and instead suggest the existence of an early perceptual locus of AP.     

Impaired perception of harmonic complexity in congenital amusia: A case study

This study investigates whether congenital amusia (an inability to perceive music from birth) also impairs the perception of musical qualities that do not rely on fine-grained pitch discrimination. We established that G.G. (64-year-old male, age-typical hearing) met the criteria of congenital amusia and demonstrated music-specific deficits (e.g., language processing, intonation, prosody, fine-grained pitch processing, pitch discrimination, identification of discrepant tones and direction of pitch for tones in a series, pitch discrimination within scale segments, predictability of tone sequences, recognition versus knowing memory for melodies, and short-term memory for melodies). Next, we conducted tests of tonal fusion, harmonic complexity, and affect perception: recognizing timbre, assessing consonance and dissonance, and recognizing musical affect from harmony. G.G. displayed relatively unimpaired perception and production of environmental sounds, prosody, and emotion conveyed by speech compared with impaired fine-grained pitch perception, tonal sequence discrimination, and melody recognition. Importantly, G.G. could not perform tests of tonal fusion that do not rely on pitch discrimination: He could not distinguish concurrent notes, timbre, consonance/dissonance, simultaneous notes, and musical affect. Results indicate at least three distinct problems—one with pitch discrimination, one with harmonic simultaneity, and one with musical affect—and each has distinct consequences for music perception.     

Timbre-independent extraction of pitch in newborn infants

The ability to separate pitch from other spectral sound features, such as timbre, is an important prerequisite of veridical auditory perception underlying speech acquisition and music cognition. The current study investigated whether or not newborn infants generalize pitch across different timbres. Perceived resonator size is an aspect of timbre that informs the listener about the size of the sound source, a cue that may be important already at birth. Therefore, detection of infrequent pitch changes was tested by recording event-related brain potentials in healthy newborn infants to frequent standard and infrequent pitch-deviant sounds while the perceived resonator size of all sounds was randomly varied. The elicitation of an early negative and a later positive discriminative response by deviant sounds demonstrated that the neonate auditory system represents pitch separately from timbre, thus showing advanced pitch processing capabilities.     

Re-evaluation of tropicamide in the pupillary response test for Alzheimer's disease

In 1994, a pupillary response test using very dilute (0.01%) tropicamide, a cholinergic antagonist, evoked remarkable pupil dilation in subjects with Alzheimer's disease (AD) and has since been considered a diagnostic tool for AD. However, since this test was first reported, there have been studies suggesting it cannot provide a differential diagnosis of AD. Thus, the present study re-evaluated the pupillary dilation of AD (n=17) and non-AD (n=20) subjects at a 0.01% concentration of tropicamide and found that non-AD subjects, including young subjects, showed the same extent of pupil dilation as AD subjects. Furthermore, there was no significant difference between the average dilation rate of the two groups (P>0.05). When the tropicamide concentration was diluted to half of the initial concentration and performed for AD (n=14), vascular dementia (VD) (n=14), and young (n=16) subjects, the AD subjects showed a large dilation (mean pupil dilation rate: 133.8+/-15%) while the non-AD subjects did not show hypersensitivity to the new concentration of eye drops (105.4+/-9%). These differences in pupillary dilation between AD and non-AD patients were statistically significant (P<0.001). Based on these results, the most effective cutoff point of 0.005% tropicamide for differential diagnosis was 114.5% of the average pupil dilation rate for 60 min.     

Saltation in pitch perception

Sensory saltation is a spatiotemporal illusion in which the location of a brief stimulus is displaced towards a subsequent one following closely in time and space. This study investigated in three experiments whether or not saltation is present in spectral pitch, a non-spatial dimension. Employing the “symmetrical-rabbit” paradigm, listeners judged the continuity of sequences of six short tones, differing in pitch (Exp. 1). Furthermore, the “reduced-rabbit” paradigm consisting of only three short tones was used in combination with an objective two-alternative forced-choice task (Exp. 2) and a subjective judgment task (Exp. 3). All findings indicated displacements in pitch towards subsequent tones when the interstimulus interval between the tones was short, and the frequency separation was small. This suggests a saltation-like illusion for non-spatial stimulus parameters. Possible explanations are discussed in view of the supramodal characteristic of the phenomenon.     

People with absolute pitch process tones with producing P300

We recorded a P300 component of event-related potentials associated with auditory oddball tasks in nine absolute pitch (AP) possessors and seven non-AP possessors. The previous studies demonstrated that AP possessors did not appear to employ working memory during auditory oddball tasks because they have a fixed tonal template in their memories. However, the present findings showed that the AP possessors exhibited similar P300 as the non-AP possessors and did update the tonal context in the auditory oddball tasks. This result suggests that the AP possessors do not always refer to the fixed tonal template in their memories when executing the oddball tasks and they employ working memory properly according to the difficulty of the auditory tasks.     

Pupillary responses and attentional allocation problems on the backward masking task in schizophrenia.

Early visual information processing impairment has consistently been found on the backward masking task in patients with schizophrenia, but the nature of this impairment remains unclear. Pupillometry was used to measure attentional allocation during visual backward masking task performance in patients with schizophrenia (n=16) and nonpsychiatric controls (n=16). The extent of pupil dilation recorded during a cognitive task reflects the processing load placed on the nervous system by the task. Schizophrenia patients detected significantly fewer targets than controls only when the stimulus onset asynchrony (SOA) between targets and masks reached 317 ms. For both groups, peak pupil dilation responses were also significantly larger in the 317 ms SOA condition relative to a no-mask condition, suggesting that the processing load of the 317 SOA masking condition was greater than the no-mask condition. In addition, a principal components analysis of pupillary response waveforms identified time-related factors that appeared to differentially index attentional allocation to targets vs. masks. Patients with schizophrenia showed less dilation than controls on a middle factor that appeared to index attentional allocation to targets, but patients showed greater dilation than controls on a late factor that appeared to index attentional allocation to masks. That is, controls attended more to targets than to masks, but patients attended more to masks than to targets. These findings suggest that masking impairments at SOA intervals greater than 100-200 ms may be due abnormalities in attentional allocation mechanisms.     

Processing of pitch and time sequences in music

Pitch and duration -- either as written symbols or in auditory form -- are the basic structural properties in tones that form a melodic sequence. From the cognitive perspective, it is still a matter of debate whether, and at which processing stage, these two factors are processed independently or interdependently. The present study addresses this issue from the neuroscientist's point of view by measuring event-related potentials (ERPs) in musicians and non-musicians. Either the pitches or the durations of the tones, or both, were permuted randomly over a set of melodies in order to remove all sequential ordering with respect to these factors. Effects of both, pitch and time order, on the peak amplitudes of the P1-N1-P2 complex were observed. ANOVA revealed that sequential processing may depend on the different levels of skill in analytical hearing. For musicians, strong interaction effects for all three ERP components corroborated the interdependence of pitch and time processing. Musicians also seem to rely on coherent time structure more than non-musicians and showed enlarged P1 and P2 components whenever tone duration, either with or without preserved pitch, was at random. Non-musicians tend to use ordered pitch relations for perceptual orientation, and main effects without any interactions might indicate some kind of independent processing of both dimensions at some processing stages.     

Representation of harmonic frequencies in auditory memory: a mismatch negativity study

Most natural sounds are composed of a mixture of frequencies, which activate separate neurons in the tonotopic auditory cortex. Nevertheless, we perceive this mixture as an integrated sound with unique acoustic properties. We used the Mismatch Negativity (MMN), a marker of auditory change detection, to determine whether individual harmonics are represented in sensory memory. The MMN elicited by duration and pitch deviations were compared for harmonic and pure tones. Controlled for acoustic differences between standards and deviants and their relative probabilities, the MMN was larger for harmonic than pure tones for duration but not for pitch deviance. Because the magnitude of the MMN reflects the number of concurrent changes in the acoustic input relative to a preexistent acoustic representation, these results suggest that duration is represented and compared separately for individual frequencies, whereas pitch comparison occurs after integration.     

Pupillary assessment and computational modeling of the Stroop task in depression.

Depressed individuals frequently display disruptions in selective attention, but the time course and specificity of these difficulties are not well-understood. To better understand the nature of attentional disruptions in depression, 28 healthy adults and 23 unmedicated depressed adults completed a Stroop color-naming task using a long inter-stimulus interval and pupil dilation was recorded as a measure of cognitive load. Both groups took longer to name the color for incongruent than congruent trials. Pupil dilation was also larger for incongruent trials than for congruent trials across groups, which suggested that pupil dilation reflected cognitive load on the task. Though the groups did not differ in the magnitude of Stroop effect in pupil dilation, depressed individuals displayed decreased pupil dilation in the seconds following stimuli relative to controls. Computational neural network modeling further suggested that observed effects were consistent with decreased prefrontal cortex activity, associated with decreased cognitive control.     

Neuroticism and the pupillary response to a brief exposure to noise

'Neurotic' and 'stable' groups (n = 8) were formed by means of the Finnish version of the Eysenck Personality Inventory. Subjects were exposed individually to 80-100 dBA broadband noise. No overt response was made. The dependent variable was the pupil dilation. The louder the noise, the larger the pupil was. At each level of noise intensity, the dilation was largest immediately after the change of intensity. In general, the pupil size decreased in the course of the experiment, indicating habituation. The 'neurotic' subjects displayed the largest relative dilation as a function of noise intensity. Results are discussed in terms of the arousing effects of auditory stimulus intensity.     

Musical training and language-related brain electrical activity in children

This experiment aimed at testing whether 8 weeks of musical training affect the ability of 8-year-old children to detect pitch changes in language. Twenty nonmusician children listened to linguistic phrases that ended with prosodically congruous words or with weak or strong pitch incongruities. We recorded reaction times, error rates, and event-related brain potentials to the final words. Half of the children followed music training and the other half painting training, and all children were retested following training. For both groups, the weak incongruity was the most difficult to detect, but performance was not significantly different between groups. However, the amplitude of a late positive component was largest to strong incongruities and was reduced after training only in the music group. These results suggest that a relatively short exposure to pitch processing in music exerts some influence on pitch processing in language.     

Auditory Evoked Potentials to Unpredictable Shifts in Pitch

Auditory evoked potentials (EPs) were recorded from subjects presented with a regular series of tone pips at one of three rates (1/sec, 2/sec, or 4/sec). Occasionally one of the pips was 5%, 25%, or 100% (an octave) different in pitch from the repetitive background pips. These “mismatch” tones occurred at random with a mean interval of 12 sec (range 1–24 sec) for all of the repetition rates. This determined an average sequential probability = 0.083, 0.042, 0.021 that a tone would be a mismatch. On different runs, subjects either responded with a button press each time they heard a mismatch or they read a book. The amplitude of a large negative component (N2 at 154 msec) evoked after mismatch tones was unrelated to degree of mismatch but was larger to all the mismatch tones than to the background pip. Instructions to attend did not affect N2. A subsequent positive peak at 277 msec (P3), recorded during reading, did increase in amplitude with increasing mismatch, as did a P3 at 330 msec recorded during responding. Sequential probability had no main effect on N2 or P3. This lack of an effect on P3 suggests that the well-known influence of stimulus uncertainty on P3 may be determined by the temporal rather than sequential uncertainty of events, or that our range of probabilities was too narrow to obtain the effect.     

Pupil Size, Information Overload, and Performance Differences

As a test of the hypothesis that pupil dilation during performance is partially due to a task related anxiety component, pupillary patterns were measured while subjects (Ss) processed digit strings of various lengths for immediate recall. Information overload resulted in a leveling of the dilation pattern which suggested a momentary suspension of processing effort. In addition, significant correlations were observed between individual differences in pupil size and recall performance.     

Vocal analysis related to changes in frequency of pure tone auditory feedback

Purpose

Many studies have shown that subjects show a change of vocal fundamental frequency (F0) when phonating subjects hear their vocal pitch feedback shifted upward or downward. This study was performed to demonstrate whether vocal parameters [F0, intensity, jitter, shimmer, and noise to harmonic ratio (NHR)] in normal males respond to changes in frequency of pure tone masking.

Materials and Methods

Twenty healthy male subjects participated in this study. Subjects vocalized /a/ vowel sounds while listening to a pitch-shift pure tone through headphones (upward pitch-shift in succession: 1kHz to 2 kHz and 1 kHz to 4 kHz at 50 dB or 80 dB, respectively, downward pitch-shift in succession: 1 kHz to 250 Hz and 1 kH to 500 Hz at 50 dB or 80 dB, respectively).

Results

Vocal intensity, F0, was increased, whereas jitter was decreased as the pitch of pure tone was shifted upward. However, there was no correlation between shimmer and NHR with pitch-shift feedback for pure tones. Unlike vocal pitch-shift feedback in other studies, upward pitch-shift feedback of pure tones caused the vocal F0 and intensity to change in the same direction as pitch-shift.

Conclusion

The results of this study demonstrated that auditory kinesthetic feedback is affected by pitch-shift in pure tone.     

Memory load and the cognitive pupillary response in aging

The effect of memory load on the cognitive pupillary response among 16 young adults and 16 older adults was investigated. Mean pupil dilation and reaction time were measured during a Sternberg memory-search task, which involved six levels of memory load. A classic interaction pattern was obtained in which the reaction times of the elderly participants increased more as a function of memory load than the reaction times of the young participants. In the encoding phase of the experiment, mean dilation increased with memory load. No age differences were observed here. In the search phase of the experiment, however, mean pupil dilation was considerably greater in the young than in the elderly participants. Moreover, mean dilation of the older participants was not sensitive to memory load, whereas mean dilation increased as a function of memory load in the young participants. The results suggest that the usefulness of the pupillary response as a correlate of subtle fluctuations in memory load diminishes with old age.     

Relationships between affect, vigilance, and sleepiness following sleep deprivation

This pilot study examined the relationships between the effects of sleep deprivation on subjective and objective measures of sleepiness and affect, and psychomotor vigilance performance. Following an adaptation night in the laboratory, healthy young adults were randomly assigned to either a night of total sleep deprivation (SD group; n = 15) or to a night of normal sleep (non-SD group; n = 14) under controlled laboratory conditions. The following day, subjective reports of mood and sleepiness, objective sleepiness (Multiple Sleep Latency Test and spontaneous oscillations in pupil diameter, PUI), affective reactivity/regulation (pupil dilation responses to emotional pictures), and psychomotor vigilance performance (PVT) were measured. Sleep deprivation had a significant impact on all three domains (affect, sleepiness, and vigilance), with significant group differences for eight of the nine outcome measures. Exploratory factor analyses performed across the entire sample and within the SD group alone revealed that the outcomes clustered on three orthogonal dimensions reflecting the method of measurement: physiological measures of sleepiness and affective reactivity/regulation, subjective measures of sleepiness and mood, and vigilance performance. Sleepiness and affective responses to sleep deprivation were associated (although separately for objective and subjective measures). PVT performance was also independent of the sleepiness and affect outcomes. These findings suggest that objective and subjective measures represent distinct entities that should not be assumed to be equivalent. By including affective outcomes in experimental sleep deprivation research, the impact of sleep loss on affective function and their relationship to other neurobehavioral domains can be assessed.     

Pupillometric investigation into the speed-accuracy trade-off in a visuo-motor aiming task

Convergent lines of evidence suggest that fluctuations in the size of the pupil may be associated with the trade-off between the speed (adrenergic, sympathetic) and accuracy (cholinergic, parasympathetic) of behavior across a variety of task contexts. Here, we explored whether pupil size was related to this trade-off during a visuospatial motor aiming task. Participants were shown visual targets at random locations on a screen and were instructed and incentivized to move a computer mouse-controlled cursor to the center of the targets, either as fast as possible, as accurately as possible, or to strike a balance between the two. Behavioral results showed that these instructions led to typical speed-accuracy trade-off effects on movement reaction times and hit distances to target centers. Pupillometric analyses revealed that movements were faster and less accurate when participants had relatively large baseline pupil sizes, as measured before target onset. Furthermore, trial-evoked pupil dilation was related specifically to a bias toward speed in the trade-off and the speed of the ballistic and error-correction phases of the motor responses such that larger pupils predicted shorter latencies and higher movement speeds. Pupil responses were also associated with performance in a manner that may reflect the combined influence of a number of factors, including the generation of dynamic urgency and an arousal response to negative feedback. Our results generally support a role for pupil-linked arousal in regulating the trade-off between speed and accuracy, while also highlighting how the trial-related pupil response can exhibit multifaceted, temporally discrete associations with behavior.