Intertone Interval Research Articles

Attentional modulation of startle in psychosis-prone college students.

Attentional modulation of startle eyeblink was studied in college students putatively at risk for psychosis and in normal controls. At-risk subjects had extreme scores on scales for either anhedonia or perceptual aberration-magical thinking (per-mags). Subjects were presented with to-be-attended and to-be-ignored tones; white noise startle probes were presented at lead intervals of 60, 120, 240, or 2,000 ms following the onset of attended and ignored tones and during intertone intervals. Controls showed greater inhibition of startle blink at 120 ms and greater facilitation at 2,000 ms during to-be-attended than to-be-ignored tone, demonstrating attentional modulation of prepulse inhibition and facilitation. Both at-risk groups showed normal overall levels of early inhibition and late facilitation. However, per-mags failed to show attentional modulation of either inhibition at 120 ms or facilitation at 2,000 ms; anhedonics showed no modulation of inhibition and modulation of facilitation was delayed in development. The results for the per-mags are strikingly similar to those observed in schizophrenic patients and suggest that these deficits index a trait-linked vulnerability to disorders in the schizophrenic spectrum.

Developmental increase in the duration of memory for tone pitch.

This research examined developmental change in the duration of memory for tome pitch. In Experiment 1, the persistence of memory for pitch was examined with a 2-tone comparison task in children 6-7 and 10-12 years old and in adults. Because pitch perception differences could contaminate the measure of memory, the frequency difference between tones was adjusted for each subject until a criterion level of performance was reached. In a subsequent test phase, the resulting frequency difference was maintained but the time between tones was varied. Performance deteriorated across the intertone interval more quickly in younger than in older subjects. Experiment 2 demonstrated that the developmental difference in pitch memory persistence is unlikely to be based on the development of strategic processing

Interaction of excitation and inhibition in processing of pure tone and amplitude-modulated stimuli in the medial superior olive of the mustached bat

1. In mammals with good low-frequency hearing, the medial superior olive (MSO) processes interaural time or phase differences that are important cues for sound localization. Its cells receive excitatory projections from both cochlear nuclei and are thought to function as coincidence detectors. The response patterns of MSO neurons in most mammals are predominantly sustained. In contrast, the MSO in the mustached bat is a monaural nucleus containing neurons with phasic discharge patterns. These neurons receive projections from the contralateral anteroventral cochlear nucleus (AVCN) and the ipsilateral medial nucleus of the trapezoid body (MNTB). 2. To further investigate the role of the MSO in the bat, the responses of 252 single units in the MSO to pure tones and sinusoidal amplitude-modulated (SAM) stimuli were recorded. The results confirmed that the MSO in the mustached bat is tonotopically organized, with low frequencies in the dorsal part and high frequencies in the ventral part. The 61-kHz region is overrepresented. Most neurons tested (88%) were monaural and discharged only in response to contralateral stimuli. Their response could not be influenced by stimulation of the ipsilateral ear. 3. Only 11% of all MSO neurons were spontaneously active. In these neurons the spontaneous discharge rate was suppressed during the stimulus presentation. 4. The majority of cells (85%) responded with a phasic discharge pattern. About one-half (51%) responded with a level-independent phasic ON response. Other phasic response patterns included phasic OFF or phasic ON-OFF, depending on the stimulus frequency. Neurons with ON-OFF discharge patterns were most common in the 61-kHz region and absent in the high-frequency region. 5. Double tone experiments showed that at short intertone intervals the ON response to the second stimulus or the OFF response to the first stimulus was inhibited. 6. In neuropharmacological experiments, glycine applied to MSO neurons (n = 71) inhibited any tone-evoked response. In the presence of the glycine antagonist strychnine the response patterns changed from phasic to sustained (n = 35) and the neurons responded to both tones presented in double tone experiments independent of the intertone interval (n = 5). The effects of strychnine were reversible. 7. Twenty of 21 neurons tested with sinusoidally amplitude-modulated (SAM) signals exhibited low-pass or band-pass filter characteristics. Tests with SAM signals also revealed a weak temporal summation of inhibition in 13 of the 21 cells tested.(ABSTRACT TRUNCATED AT 400 WORDS)

Probing the orienting response with startle modification and secondary reaction time.

Current models of orienting suggest a relationship between the orienting response and attentional processing. This relationship was examined using two independent probe techniques to index attentional processing: secondary reaction time and startle eyeblink modification. Twenty-eight college-age subjects received intermixed presentations of to-be-attended and to-be-ignored tones. Skin conductance orienting responses were obtained during a subset of the tones. Each of the remaining tones contained either a secondary reaction time probe at lead intervals of 150 or 2,000 ms or a startle eyeblink probe presented at lead intervals of 120 or 2,000 ms. In addition, reaction time and startle probes also were presented during selected intertone intervals, and responses to these stimuli served as the baselines from which to compare changes in reaction time and blink amplitude produced by the attended and ignored tones. The results revealed that, compared with the ignored tones, the attended tones were associated with larger skin conductance orienting responses, greater blink inhibition at the 120-ms lead interval, greater blink facilitation at the 2,000-ms lead interval, and greater reaction time slowing at the 2,000-ms lead interval. Consistent with previous findings, the ignored tone was associated with greater reaction time slowing than was the attended tone at the 150-ms lead interval. The results support a relationship between elicitation of the skin conductance orienting response and attentional processes and suggest that the secondary reaction time and blink modification techniques may provide unique information regarding this relationship.

Serial position effects in temporal pattern discrimination

Observers were presented with two successive 8-tone sequences; the task was to discriminate between the temporal patterns defined by the inter-tone intervals in each sequence (average inter-tone interval=50 ms, tone duration=25 ms, tone frequency=1000 or 2500 Hz). The observers had to indicate whether the two patterns on each trial were the same or different. A conditional-on-a-single-stimulus (COSS) technique [B. C. Berg, J. Acoust. Soc. Am. 86, 1743–1746 (1991)] was used to evaluate the salience of each temporal position. The probability of responding DIFFERENT is computed given the magnitude of ‖t1,i−t2,i‖, the absolute difference between the inter-tone intervals at each serial position (i=1,2,...,7). The temporal information in the first and last positions had the greatest influence on the observer’s response. These results have implications for models of temporal pattern discrimination. [Work supported by AFOSR.]

Auditory event-related dynamics of the EEG spectrum and effects of exposure to tones

A new measure of event-related brain dynamics, the event-related spectral perturbation (ERSP), is introduced to study event-related dynamics of the EEG spectrum induced by, but not phase-locked to, the onset of the auditory stimuli. The ERSP reveals aspects of event-related brain dynamics not contained in the ERP average of the same response epochs. Twenty-eight subjects participated in daily auditory evoked response experiments during a 4 day study of the effects of 24 h free-field exposure to intermittent trains of 89 dB low frequency tones. During evoked response testing, the same tones were presented through headphones in random order at 5 sec intervals. No significant changes in behavioral thresholds occurred during or after free-field exposure. ERSPs induced by target pips presented in some inter-tone intervals were larger than, but shared common features with, ERSPs induced by the tones, most prominently a ridge of augmented EEG amplitude from 11 to 18 Hz, peaking 1–1.5 sec after stimulus onset. Following 3–11 h of free-field exposure, this feature was significantly smaller in tone-induced ERSPs; target-induced ERSPs were not similarly affected. These results, therefore, document systematic effects of exposure to intermittent tones on EEG brain dynamics even in the absence of changes in auditory thresholds.

Temporally directed attention in the detection and discrimination of auditory pattern components

Thresholds for detection and frequency discrimination were determined for tones that occurred at unexpected temporal locations within 12-tone sequences. Expectancies were established by repeated presentations of a standard pattern on each trial. Temporal deviations were introduced in comparison patterns by advancing or delaying the onset of a single ‘‘target’’ tone while maintaining its serial position within the pattern. Rhythmic patterns consisting of 350- and 150-ms intertone intervals were used to allow for a large range of temporal displacements. Thresholds were determined for target tones that were advanced (‘‘early’’ targets) or delayed (‘‘late’’ targets) by various degrees. Thresholds for displaced targets were elevated with respect to nondisplaced targets for both detection and discrimination. However, for most listeners, there was little or no effect of temporal displacement on detection except when targets were advanced by 200 ms or more. Temporal deviations had more consistent effects on frequency discrimination for both early and late targets. The results are consistent with the view that, when presented with an auditory pattern, a listener’s attention is dynamically allocated in time in response to the temporal structure of the pattern. [Work supported by NIH.]

Event-related potentials in auditory backward recognition masking: a new way to study the neurophysiological basis of sensory memory in humans.

Task-irrelevant pairs of short tones were presented to healthy human subjects while electric potentials were recorded from their scalp ('event-related brain potential', ERP). Infrequent increments in the frequency of the first tone of the repetitive tone-pair elicited an extra ERP component termed 'mismatch negativity' (MMN) when the silent interval between the first and second tone of the pair ('inter-tone interval') was long (150, 300, or 400 ms) but not when this interval was short (20 or 50 ms). This effect did not depend on whether the two tones of the tone-pair were presented to the same or to different ears. The present inter-tone interval effect is consistent with the effects of backward-masking on recognition performance in audition, suggesting that the MMN reflects the neurophysiological basis of echoic memory.

Sensorimotor synchronization: Motor responses to regular auditory patterns

Subjects (N = 32) were asked to synchronize a motor response with tones in auditory patterns. These patterns were created from six tones and six intertone intervals of equal duration. The pitch of the first tone differed from the others. It was found that subjects used three types of timing in their motor response: (1) the first intertone interval was prolonged and the second interval was shortened, (2) the second intertone interval was prolonged and the first interval was shortened, and/or (3) the first interval and the second interval were of approximately the same length. The prolongation of the fifth interval was observed during all three types of timing. The results are explained using the concept of suprasegmental control of timing, which explains a prolongation of intervals at critical control point of the patterns. The occurrence of three different strategies of timing is discussed in connection with similar principles in musical performance.

The effects of demanding temporal accuracy on the programming of simple tapping sequences

This experiment was undertaken in order to determine the effects of movement complexity and the demand for temporal accuracy on simple reaction time (SRT). Subjects listened to 2 to 5 tones separated by intertone intervals of 400 msec and attempted to initiate as quickly as possible, after an imperative stimulus, an accurate temporal reproduction of these tones by tapping on a single response key. Half of the subjects were allowed to vary from the 400 msec criterion without penalty (lenient temporal demands); and half were required to be within ±10% of the 400 msec criterion (360–440 msec) (stringent temporal demands). Increasing the number of taps within a sequence had no effect on SRT when the demands for temporal accuracy were lenient; but caused a nonlinear increase in SRT when stringent temporal demands were imposed. The results indicate that the additional requirement of accuracy had an effect on the manner in which the subjects prepared and initiated their responses. A rule-based approach is suggested as a possible explanation for the differences which occured.

Behavioral responsiveness in sleeping older adults

The control of behavior by stimuli presented during sleep, and related effects on sleep and daytime sleepiness, were investigated in 17 older (age = 60–74 years) adults. Experimental subjects ( N = 8) were trained while awake to terminate tone presentations by taking a deep breath. Tones were then presented following sleep onset for four consecutive nights with a mean intertone interval of 4 min. Control subjects ( N = 9) slept in the laboratory but did not receive tones. The daytime sleepiness of both groups was assessed by recording latency to sleep onset in a morning and afternoon nap test. It was found that the experimental subjects responded reliably to the tones. Responding, however, was almost invariably accompanied by disruption of sleep and overall sleep structure was markedly altered. Surprisingly, the daytime sleepiness of experimental subjects was not reliably greater than that of control subjects.

Alcohol effects on variability of timing responses to single-ear or dual-ear stimulation

University students were given timing tasks after a 30-min ingestion period of alcohol (0.4 g/kg). Intertone intervals to be matched were presented either to both ears or to the left ear only. Compared with controls, subjects receiving alcohol were found to show reduced timing variability (time estimate variance and Fourier transforms of the estimates) when tones were presented to both ears, but not to the left ear only. Control subjects displayed a smaller variability of timing responses for tones presented to the left ear than for tones presented to both ears, but these differences were either reversed or eliminated by alcohol. The results are discussed in terms of a variability hypothesis of alcohol effects.

Timing in auditory perception

Recognition of sequential patterns of sound is basic to speech recognition, music perception, and identification of environmental sounds from birdsong to thunderclaps. While we define these sound patterns as sequences of brief sounds, the usual acoustical description has principally been the spectrum. For some 30 years, work has been reported on fusion and successivity, duration discrimination, perceived order, and the influence of temporal variables on more traditional psychoacoustic dimensions. At Central Institute, with colleagues Divenyi, Lauter, Grant, Singh, and Monahan, our emphasis has been on listeners' sensitivity to changes in order and timing, and influence of nontemporal features on such perception. Here, some experiments are described that address interval perception in a series. In an isochronous series of three, six, or ten tones with intertone intervals of 200 ms or more, listeners can detect a temporal offset or “jitter” of between 5% and 10%, irrespective of the position of offset. For ...

Auditory sensory storage in relation to the growth of sensation and acoustic information extraction.

A brief, vivid phase of auditory sensory storage that outlasts the stimulus could be used in perception in two ways: First, all of the neural activity resulting from the stimulus, including that of the sensory store, could contribute to a sensation of growing loudness; second, the sensory store could permit the continued extraction of information about the sound's acoustic properties. This study includes a task for which these two processes lead to different predictions; a third prediction is based on the two processes combined. The task required loudness judgments for two brief tones presented with a variable intertone interval. The results of Experiments 1-3 were as one would expect if both the growth of sensation and information extraction contributed to the pattern of loudness judgments. Experiment 4 strengthened the two-process account by demonstrating the separability of the two processes. Approaches to mathematical modeling of these results are discussed.

Sleep disturbances due to exposure to tone pulses throughout the night.

Sleep electroencephalograms (EEGs) and subjective reports data were obtained from six subjects (male college students) during 2 nights of baseline observation and 5 experimental nights of exposure to a 90-100 dB, 25 ms, 1,000 c/s tone pulse with various interstimulus intervals. The first of the 5 experimental nights started with an intertone interval of 80 s. On each of the following 4 nights, the intertone interval was fixed at 40-, 10-, 2.5-, or 1-s intervals, respectively. With the intensification of noise stimulus by shortening the intervals of tone pulses, a progressive disruption of nightly EEG sleep patterns was observed as follows: (a) increased frequency of awakenings and sleep stage changes during the night, (b) prolonged sleep latency, and (c) increased percentage of time spent in stage 1 sleep. However, total sleep time, REM latency, inter-REM intervals, and the percentages of time in stages 2, 3, 4, and REM sleep did not change significantly. The degree of subjective sleep disturbance was highly associated with objective measures of nightly EEG sleep patterns.

Inferior colliculus of the house mouse

1. Single unit responses were recorded from the dorsal cortex (DC), dorsomedial nucleus (DM) and central nucleus (CN) of the inferior colliculus (IC) of chlorprothixene anesthetized house mice. Tone and noise thresholds, spontaneous activities, frequency tuning curves, tone response patterns, spike rate-intensity functions, and tone-innoise response patterns were determined within a 40 dB sound intensity range above the units' thresholds. 2. Single unit thresholds were often lower than the average lowest behavioral thresholds, however, the envelope of the neural data resembled the behavioral curve in most of the frequency range (Fig. 2). 3. Spontaneous activity ranged from 0 to 62 spikes/s with a peak of the distribution at 1–3 spikes/s (Fig. 3). 4. About 35% of CN excitatory tuning curves were primary-like (resembling those of auditory nerve fibers). The remaining 65% were variable including broad, constant width, closed, tilted and complex shapes. The proportion of tuning curve shapes in the DC was similar to that in the CN, however the DM distribution, in which tuning curves with steep flanks and closed ones dominated, differed significantly from both (Figs. 4, 5). 5. Tonic, primary-like tone response patterns were found at least at some intensities in nearly 55% of units from all three nuclei (Fig. 8). The other response patterns observed were phasic, phasic with some tonic components, pauser, long latency, spontaneous activity inhibited, and no tone response (Figs. 7, 8). 6. With increasing sound intensity 60% of the units changed their tone response pattern, most frequently to pauser responses (Fig. 9). 7. Neurons from the three nucleus areas had significantly different shapes of rate-intensity functions (Fig. 10). Monotonic functions dominated in the CN, peaked ones in the DC and peaked and complex ones in the DM (Fig. 11). 8. Averaged spike rates of all IC units studied and averaged tendencies for rate increases or decreases changed little with increasing tone level from 10 to 40 dB above the units' tone thresholds. 9. Nine distinct tone-in-noise response patterns were seen when unit responses as a function of noise level were examined. Noise can have facilitating, enhancing, inhibitory, or little influence on the response patterns in tone intervals. In the intertone (noise only) intervals noise can have excitatory, inhibitory or no effects on the unit responses (Figs. 13, 14). Tone-in-noise response patterns depended both on tone and noise intensities and shifted frequently with changing stimulus intensity. Occurrence rates of the different tone-in-noise response patterns differed significantly between the DC and the DM or CN (Fig. 14). 10. Averaged across the different nuclei of the IC, about half of tone-in-noise responses differed from those described for the auditory nerve and ventral cochlear nucleus. 11. Tuning curve shapes correlated significantly with the forms of rate-intensity functions (primarylike tuning curves — non-peaked functions; higher order tuning curves — peaked or complex functions). There were also statistically significant relations between tone response patterns and tone-innoise response patterns. 12. Temporal response patterns of the neurons (PSTH patterns) were not related to tuning curve shapes and to forms of rate-intensity functions. 13. Results are discussed with regard to sound intensity effects on the processing of auditory information in the three IC nuclei and in comparison with studies on other mammals.

Inferior colliculus of the house mouse

1. Single unit responses were recorded from the dorsal cortex (DC), dorsomedial nucleus (DM) and central nucleus (CN) of the inferior colliculus (IC) of chlorprothixene anesthetized house mice. Tone and noise thresholds, spontaneous activities, frequency tuning curves, tone response patterns, spike rate-intensity functions, and tone-innoise response patterns were determined within a 40 dB sound intensity range above the units' thresholds. 2. Single unit thresholds were often lower than the average lowest behavioral thresholds, however, the envelope of the neural data resembled the behavioral curve in most of the frequency range (Fig. 2). 3. Spontaneous activity ranged from 0 to 62 spikes/s with a peak of the distribution at 1–3 spikes/s (Fig. 3). 4. About 35% of CN excitatory tuning curves were primary-like (resembling those of auditory nerve fibers). The remaining 65% were variable including broad, constant width, closed, tilted and complex shapes. The proportion of tuning curve shapes in the DC was similar to that in the CN, however the DM distribution, in which tuning curves with steep flanks and closed ones dominated, differed significantly from both (Figs. 4, 5). 5. Tonic, primary-like tone response patterns were found at least at some intensities in nearly 55% of units from all three nuclei (Fig. 8). The other response patterns observed were phasic, phasic with some tonic components, pauser, long latency, spontaneous activity inhibited, and no tone response (Figs. 7, 8). 6. With increasing sound intensity 60% of the units changed their tone response pattern, most frequently to pauser responses (Fig. 9). 7. Neurons from the three nucleus areas had significantly different shapes of rate-intensity functions (Fig. 10). Monotonic functions dominated in the CN, peaked ones in the DC and peaked and complex ones in the DM (Fig. 11). 8. Averaged spike rates of all IC units studied and averaged tendencies for rate increases or decreases changed little with increasing tone level from 10 to 40 dB above the units' tone thresholds. 9. Nine distinct tone-in-noise response patterns were seen when unit responses as a function of noise level were examined. Noise can have facilitating, enhancing, inhibitory, or little influence on the response patterns in tone intervals. In the intertone (noise only) intervals noise can have excitatory, inhibitory or no effects on the unit responses (Figs. 13, 14). Tone-in-noise response patterns depended both on tone and noise intensities and shifted frequently with changing stimulus intensity. Occurrence rates of the different tone-in-noise response patterns differed significantly between the DC and the DM or CN (Fig. 14). 10. Averaged across the different nuclei of the IC, about half of tone-in-noise responses differed from those described for the auditory nerve and ventral cochlear nucleus. 11. Tuning curve shapes correlated significantly with the forms of rate-intensity functions (primarylike tuning curves — non-peaked functions; higher order tuning curves — peaked or complex functions). There were also statistically significant relations between tone response patterns and tone-innoise response patterns. 12. Temporal response patterns of the neurons (PSTH patterns) were not related to tuning curve shapes and to forms of rate-intensity functions. 13. Results are discussed with regard to sound intensity effects on the processing of auditory information in the three IC nuclei and in comparison with studies on other mammals.

Discrimination and Generalization of Rhythmic and Arrhythmic Sound Patterns by European Starlings (Sturnus vulgaris)

European starlings (Sturnus vulgaris) learned to discriminate patterns of 2000-Hz tones organized into rhythmic as compared with random, arrhythmic temporal structures, and the perceptual processes underlying the discrimination were then analyzed. Two rhythmic patterns were constructed, for different birds, according to a linear rule in which tones and intertone intervals of equal duration alternated or according to a hierarchical rule in which two subpatterns alternated. The arrhythmic pattern was a sequence of tone and intertone intervals each of random duration. The birds were required to peck at one key in the presence of a rhythmic pattern and at another key in the presence of the arrhythmic pattern to obtain food reward. All birds learned the rhythmic–arrhythmic discrimination, and discrimination accuracy was the same for both the linear and hierarchical rhythmic structures. In a series of transfer tests that followed, discrimination performance was tested when the temporal structure of the rhythmic stimulus patterns was transformed and when their pitch was shifted up or down an octave. For temporal transformations, performance was well maintained under (a) a log transformation which, from test to test, changed the absolute duration of tones and intertone intervals but kept their ratios constant (a simple tempo transformation); (b) an additive transformation which kept either tone duration or intertone interval constant from test to test while their counterparts changed in duration; and (c) a pattern interchange in which, for the appropriate birds, the linear was substituted for the hierarchical pattern, or the hierarchical was substituted for the linear pattern. Performance deteriorated (but remained above chance), however, when rhythmic patterns were degraded by holding tone (or intertone) duration constant while intertone (or tone) durations varied randomly within a test session. Performance was also well maintained when the baseline temporal patterns were shifted an octave in pitch, but the data do not necessarily force the conclusion that the birds showed true octave generalization. The results suggest the birds solved the rhythmic–arrhythmic discrimination on the basis of a nominal, qualitative pattern attribute, rhythmicity. Patterns are high in rhythmicity if pattern components are of constant duration within a test session, and if they reoccur periodically. Rhythmicity deteriorates as pattern components vary in duration within a test session and reoccur at varying time intervals. The results also show that the human capacity for discrimination among complex temporal patterns of sound is shared with at least one other species and may, therefore, represent a perceptual process that is—within limits yet to be determined—phylogenetically general.

Prolonged auditory processing time in the elderly: evidence from a backward recognition-masking paradigm.

The rate of processing pure-tone stimuli was measured in 10 elderly subjects and 10 young controls using an auditory backward recognition-masking paradigm. Experimental trials consisted of the presentation of either a 770- or 870-Hz target stimulus (TS) followed by an 820-Hz masking stimulus (MS), separated by a variable silent intertone interval (ITI). For both groups, the mean percent correct recognition scores for TS identification improved systematically with increases in ITIs, reaching an asymptote followed by an apparent plateau. The mean recognition scores at each ITI were lower for the elderly subjects than for the controls; however, equivalence between groups was observed at prolonged ITIs. The elderly group's mean asymptote was observed at a longer ITI (360 ms) relative to that of the controls (248 ms), a statistically significant difference. The findings suggest an age-associated slowing in auditory processing time.

The effects of prior inputs on auditory perceptual processing

Two experiments are reported on subjects’ ability to attend to an auditory channel (i.e., ear of input). The subjects’ task was to identify the last tone (target) in a sequence of tones as “sharp ” or “dull. ” The results indicated that when all tones of a given sequence were presented in the same ear, the target was more easily and rapidly identified than when half of the tones were randomly presented to each ear. For sequences in which half of the tones were presented to each ear, the greater the number of successive tones in the same ear as the target, the better or faster the target was identified. Differences were generally greater with a shorter intertone interval (250 msec) than with a longer one (600 msec). The results show that “attentional ” effects can occur when prior inputs are present on a given auditory channel.