Development of neuronal responsiveness in the mediorostral neostriatum/hyperstriatum ventrale during auditory filial imprinting in domestic chicks

Chronic electrophysiological recordings of slow field potentials from tone-imprinted chicks show significantly enhanced fast Fourier transform (FFT) power during playback of rhythmic 400-Hz imprinting tone stimuli in the presence of a surrogate mother. The FFT power was already significantly higher during the very first imprinting session, when the chick was exposed to the imprinting tone stimuli in the presence of the surrogate mother compared to spontaneous activity (EEG recordings). During discrimination tests, where individual chicks were exposed to the imprinting tone stimuli in alternation to rhythmic 700-Hz tone stimuli (discrimination tone stimuli), the FFT power was significantly higher during playback of the imprinting tone stimuli than the FFT power during playback of the discrimination tone stimuli. Chicks which were imprinted in the absence of the surrogate mother also show enhanced FFT power in the course of the imprinting sessions; however, in contrast to the first group, they did not show significant differences in the FFT power during playback of either the imprinting or discrimination tone stimuli in the discrimination tests. Our results suggest that the high FFT power of a potential imprinting stimulus or situation, which is expressed in newborn (still naive) chicks, is maintained only when the chicks form an association between the tone stimuli and a positive emotional situation (represented by the surrogate mother).     

Intramodal and crossmodal pairing and anchoring in comparisons of successive stimuli

Two experiments were conducted to study effects of modality, temporal position, and their interaction on comparisons of successive stimuli. In Experiment 1, intramodal (tone–tone and line–line) and crossmodal (tone–line and line–tone) stimulus pairs, with two interstimulus intervals (ISIs), 400 and 2,000 ms, were presented. Participants indicated which stimulus was the “stronger.” Time-order errors (TOEs) were assessed using the D% measure and were found in all types of pairs. Variation in TOEs across conditions was well accounted for by changes in parameters (stimulus weights, reference levels) in an extended version of Hellström’s sensation weighting (SW) model. With an ISI of 2,000 ms, the first stimulus had a lower weight (less impact on the response) than did the second stimulus. More negative TOEs were found with the longer ISI in all pair types except tone–line. In Experiment 2, participants indicated which of two lines was the longer or which of two tones was the louder. An intra- or crossmodal anchor, or no anchor, was interpolated between the stimuli. Anchoring tended to reduce the weight of the first stimulus, suggesting interference with memory, and to yield negative TOEs. Intramodal anchors yielded reduced weights of both stimuli, most dramatically for tones, suggesting an additional effect of stimulus interference. Response times decreased with crossmodal anchors. For line–line pairs, strong negative TOEs were found. In both experiments, the variation in TOE across conditions was well accounted for by the SW model.     

Stimulus control of heart rate by auditory frequency and auditory pattern in pigeons

A new method was used to investigate auditory discrimination in pigeons. Basically, the method involves the repeated presentation of one stimulus preceding the single presentation of a different stimulus that is followed by shock. Stimulus control is assessed by the increase in heart rate that accompanies the presentation of the second stimulus. In Experiment 1, the efficiency of the method was explored by determining the frequency difference thresholds of pigeons at 500, 1000, 2000, and 4000 Hz. Weber fractions comparable to those reported in an earlier study using the conditioned suppression method were obtained. Experiment 2 demonstrated that, contrary to results of earlier studies, auditory temporal patterns can exercise differential stimulus control in pigeons. One stimulus consisted of the presentation (once per second) of a 1000-Hz pure tone of 150 msec duration followed by a 2000-Hz pure tone of equal duration; the other was the same except for the reversed order of the frequency components. Results indicated that the frequency pattern and not the loudness pattern of the stimuli was the cue controlling heart-rate changes.     

The slippery context effect in psychophysics: Intensive,extensive, and qualitative continua

When subjects gave magnitude estimates of 500- and 2500-Hz tones at various SPLs, they judged a 500-Hz tone of 60 dB to be as loud as a 2500-Hz tone of 57 dB in one context (low SPLs at 500 Hz, high SPLs at 2500 Hz), but as loud as a 2500-Hz tone at 40 dB in another context (high SPLs at 500 Hz, low at 2500 Hz) (Marks, 1988). Such shifts in matches derived from judgments of multi-dimensionally varying stimuli are termedslippery context effects. The present set of seven experiments showed that slippery effects were absent from judgments of pitch of tones at different loudnesses, duration of tones at different pitches, and length of lines at different colors, though a small effect emerged in judgments of duration of tones and lights. Slippery context effects were substantial when subjects gave magnitude estimates of loudness of 500- and 2500-Hz tones under conditions in which the pitch at each trial either was cued visually beforehand or could be known through the regular stimulus sequence, and with instructions to make absolute magnitude estimates. The results are consistent with the view that slippery context effects occur automatically and “preattentively.”     

The slippery context effect in psychophysics: intensive, extensive, and qualitative continua.

When subjects gave magnitude estimates of 500- and 2500-Hz tones at various SPLs, they judged a 500-Hz tone of 60 dB to be as loud as a 2500-Hz tone of 57 dB in one context (low SPLs at 500 Hz, high SPLs at 2500 Hz), but as loud as a 2500-Hz tone at 40 dB in another context (high SPLs at 500 Hz, low at 2500 Hz) (Marks, 1988). Such shifts in matches derived from judgments of multidimensionally varying stimuli are termed slippery context effects. The present set of seven experiments showed that slippery effects were absent from judgments of pitch of tones at different loudnesses, duration of tones at different pitches, and length of lines at different colors, though a small effect emerged in judgments of duration of tones and lights. Slippery context effects were substantial when subjects gave magnitude estimates of loudness of 500- and 2500-Hz tones under conditions in which the pitch at each trial either was cued visually beforehand or could be known through the regular stimulus sequence, and with instructions to make absolute magnitude estimates. The results are consistent with the view that slippery context effects occur automatically and "preattentively."     

Is auditory discrimination mature by middle childhood? A study using time‐frequency analysis of mismatch responses from 7 years to adulthood

Behavioural and electrophysiological studies give differing impressions of when auditory discrimination is mature. Ability to discriminate frequency and speech contrasts reaches adult levels only around 12 years of age, yet an electrophysiological index of auditory discrimination, the mismatch negativity (MMN), is reported to be as large in children as in adults. Auditory ERPs were measured in 30 children (7 to 12 years), 23 teenagers (13 to 16 years) and 32 adults (35 to 56 years) in an oddball paradigm with tone or syllable stimuli. For each stimulus type, a standard stimulus (1000 Hz tone or syllable [ba]) occurred on 70% of trials, and one of two deviants (1030 or 1200 Hz tone, or syllables [da] or [bi]) equiprobably on the remaining trials. For the traditional MMN interval of 100–250 ms post-onset, size of mismatch responses increased with age, whereas the opposite trend was seen for an interval from 300 to 550 ms post-onset, corresponding to the late discriminative negativity (LDN). Time-frequency analysis of single trials revealed that the MMN resulted from phase-synchronization of oscillations in the theta (4–7 Hz) range, with greater synchronization in adults than children. Furthermore, the amount of synchronization was significantly correlated with frequency discrimination threshold. These results show that neurophysiological processes underlying auditory discrimination continue to develop through childhood and adolescence. Previous reports of adult-like MMN amplitudes in children may be artefactual results of using peak measurements when comparing groups that differ in variance.     

The locus of the emotional Stroop effect: A study with the PRP paradigm

Stimuli that are clearly positive or negative (hence valence-laden stimuli) have the potential to interrupt unrelated task processing. A typical example is the emotional Stroop effect (ESE) in which responding to a certain task feature (e.g., color) is delayed by the presentation of task-irrelevant valent stimuli (e.g., negative pictures) compared to valence-neutral stimuli. Here we scrutinize which processes are slowed down by irrelevant but valent stimulation. In Experiment 1, participants performed in a Psychological Refractory Period (PRP) experiment with tone discrimination as Task 1 and color discrimination as Task 2. Importantly, colors in Task 2 were accompanied by valent or neutral pictures. Valent pictures delayed responding in Task 2 (thus an ESE) and this delay was additive to the time interval between tasks. In Experiment 2, task order was reversed and the ESE in Task 1 fully propagated to the Task 2 tone discrimination. These results imply that irrelevant valence-laden stimulation delays capacity-limited processes, and we suggest that this is a late perceptual process acting on stimulus categorization.     

The anchor effects on the judgment of loudness using reaction time as an index of loudness

The present study was designed to investigate anchor effects on loudness judgments, using reaction time (RT) as an index of loudness. In Experiment 1, anchor effects were reexamined using verbal categories. Two kinds of anchor stimuli, 60- and 90-dB SPL 1,000-Hz pure tones, and four kinds of series stimuli, 60-, 70-, 80-, and 90-dB tones, were used. In this experiment, clear anchor effects were found just the same as in our previous experiment. Experiment 2 was conducted using RT as an index of loudness with stimulus conditions similar to those in Experiment 1. The same anchor effects could be seen in this experiment too. As RT is quite free from the limitations inevitably accompanying the verbal responses, it may be concluded that the anchor effects reflect the shift in perception.     

The effect of skin temperature on vibrotactile sensitivity

The effect of skin temperature on detection of vibrotactile stimuli was measured for vibrations of 30 and 250 Hz. Data for the 250-Hz stimulus supported the results of Weitz (1941), who found that thresholds for 100-, 256-, and 900-Hz vibration varied as a If-shape function of skin temperature with a minimum at about 37°C. Temperature had a negligible effect on sensitivity at 30 Hz. A second experiment examined a range of frequencies between 30 and 250 Hz. Cooling greatly lowered sensitivity only to 150- and 250-Hz stimuli. Warming reduced sensitivity less, but more uniformly across frequencies. It was concluded that cooling may affect vibrotactile thresholds by decreasing the sensitivity of Pacinian corpuscles; the reason for the decrease in sensitivity due to warming is unclear.     

Stimulus sequence and the exponent of the power function for loudness

In two experiments, 15 and 13 subjects estimated the loudness of 12 sound-pressure levels (38-104 dB; 6-dB intervals) of a 1000-Hz tone by the method of magnitude estimation with a modulus assigned to the first stimulus presented. The tone duration was 1 sec. and the interstimulus interval was 6 sec. The presentation order was systematically ascending-descending in one experiment and balanced-irregular in the other. The results indicate that (1) loudness is a power function of sound pressure with an exponent of 0.60 for the systematic order and 0.29 for the irregular order. (2) For both the irregular and systematic orders, a large step-size (12 or 18 dB) between the stimulus on Trial n and on Trial n-1 (or n-3) results in a slight assimilation effect. This also occurs for the small step-size (6 dB) in the irregular order. (3) The size of momentary exponents (based on two points, Trials n and n-1 or n-3) depends on the sound pressures of successive stimuli, whether the steps are positive or negative, and whether the stimuli have been presented in systematic or irregular order. For positive steps, the momentary exponent is lower for a soft tone (Trial n) than for a loud tone, whereas for negative steps the momentary exponent is lower for a loud tone than for a soft tone. These effects ar more pronounced when these stimuli are presented in an irregular order. A relative judgment model is offered for magnitude estimation. It assumes that subjects judge the loudness of a stimulus in terms of three reference markers: the minimum and maximum sound pressures as well as the sound pressure of the previous stimulus.     

The ontogeny of auditory frequency generalization in the chicken.

To determine if there is an ontogenetic change in stimulus coding, chickens between the day of hatching and 9-10 days old were tested using a habituation-generalization paradigm. Experiment 1 indicated that 1 day-old and 3--4-day-old chicks show similar habituation of an eye-opening response to auditory stimuli in the 800--1,200-Hz range. In Experiment 2 the eye-opening response to a 1,000-Hz stimulus was habituated and then immediately tested using stimuli which varied between 800 and 1,200 Hz. Each age-group (1 day, 3--4 days, and 9--10 days) showed a symmetrical stimulus generalization gradient around the 1,000-Hz stimulus and the 1-day-old chicks displayed a reliably flatter gradient than either of the older groups, which did not differ. In a third experiment, the position of the gradients relative to the baseline was shifted without altering the relative shapes. These results allow general arousal, general auditory responsiveness, overall error rate, and metric characteristics of the independent and dependent variables to be eliminated as possible sources of the age differences in gradient shape. The changes in stimulus generalization, therefore, support the view that during normal development there is a sharpening of perceptual coding processes.     

Measuring human aversion to sound without verbal descriptors

High school students tapped rapidly on a telegraph key to reduce the intensity of a continuous acoustic stimulus presented through earphones. Failure to respond resulted in an intensity increase of 1 dB every 4 sec. In Experiment 1, a group of 19 students responded to three pure tones (125, 1,000, and 8,000 Hz) and a white noise. The different asymptotic levels observed after 4 min were taken as a measure of equal aversion levels for the stimuli. In Experiment 2, the effect of the starting intensity level (45, 70, and 90 dB SPL) was determined for a 1,000-Hz tone. Differences in the asymptotic intensity levels observed after 6 rain were not significant. In Experiment 3, no significant effect was found upon varying the number of responses required to produce a 1-dB intensity decrement in a 1,000-Hz tone. Together, the experiments demonstrated the feasibility of determining equal-aversion levels for sounds.     

Auditory generalization gradients for response latency in the monkey

Two monkeys were trained to press and hold a response key in the presence of a light and to release it at the onset of a pure tone. Initially, all responses with latencies shorter than 1 sec were reinforced without regard to the frequency of the pure tone, and the intensity of the pure tone that resulted in equal latencies at each frequency was determined. The second stage of the experiment consisted of discrimination training, during which releases to one pure-tone frequency (positive stimulus) were reinforced and releases to a second frequency (negative stimulus) were extinguished. Median latencies to the negative stimulus slowly increased as did the variability of the latency distribution for the negative stimulus. There was no evidence of a concurrent decrease in latencies to the positive stimulus indicative of behavioral contrast. The third part of the experiment consisted of determining maintained generalization gradients by increasing the number of nonreinforcement stimuli. The gradients that eventually resulted showed approximately equal latencies to all frequencies of the negative stimulus and shorter latencies to the positive stimulus frequency.     

Effects of auditory frequency-shifts on zero and below-zero SCR habituation

The purpose of the present experiment was to test a procedure for the measurement of effects of zero- and below-zero habituation (BZH) on responding to frequency shifts in auditory stimuli. The present procedure avoided some of the drawbacks of other procedures, that is, long duration, ambiguity in the definition of BZH, and inadequate control procedures. Two groups received 18 stimulus presentations each; group 1 received first a tone of 1000 Hz 12 times, then 1400 Hz (test stimulus 1) 3 times, and 1850 Hz (test stimulus 2) 3 times. Group 2 received the same stimuli, but 3, 12, and 3 times, respectively. The procedure had the advantages of short duration of the experiment, zero habituation and BZH were operationally defined (as 3 and 12 stimulus presentations, respectively), and there were adequate control conditions since a control group that did not receive stimulus change on the relevant trial was employed. The results showed no effects of stimulus shifts on responding to the test stimuli. Group 2 responded significantly less than group 1 across trials, though, and this may be explained by an inhibitory process elicited by changes in weak stimulation during the habituation process.     

On the processing of simple visual and auditory stimuli at distinct levels

Two RT studies explored the possibility that identification of a single stimulus can take place through more than one perceptual route. In the first experiment, mean RT to color was systematically changed by varying type of catch stimulus. In the second experiment, the form of the RT distribution to a tone was changed by varying type of catch stimulus. Considerations of distribution means and shapes led to the conclusion that detection and discrimination are two of the alternative levels of perceptual processing which can be evoked in rapid identification of these stimuli.     

Reliability of electrodermal habituation measures under two conditions of stimulus intensity

The present study investigated test-retest reliability of habituation of the evoked skin conductance response. Subjects received 20 presentations of a 1000-Hz, 3-sec tone at the same time of day on two separate occasions, separated by an interval of 97–160 days. Thirteen subjects received stimuli of 90 dB, while for 24 subjects, stimulus intensity was 70 dB. Interstimulus interval was 21 sec for both groups. Both absolute rate of habituation and trials to criterion displayed moderate reliability, and the relationships between habituation measures and other aspects of electrodermal activity were in agreement with previous findings.     

Vibrotactile frequency discrimination at short durations

This experiment investigated how frequency discrimination of a sinusoidal, mechanical vibration applied to the tip of the right index finger is affected by shortening the duration of the stimuli from 200 ms to 30 ms. Using a standard stimulus of 100 Hz at 30 dB above threshold, seven comparison frequencies (at intervals of 10 Hz) were judged as higher or lower in frequency according to the method of constant differences. Vibrotactile stimuli were matched for subjective intensity across both frequency and duration. Difference limens for vibrotactile frequency were found to decline slightly from 200 ms to 50 ms (attributable to practice) and to increase noticeably at 30 ms. This result is discussed in relation to the seemingly contradictory results for auditory pitch discrimination.     

Summation of punishment suppression

In two experiments, eight rats were trained to lever press with food on a variable-interval schedule. Bar pressing produced shock on a variable-interval schedule in the presence of two independently presented stimuli, a light and a tone. Two rats in each experiment received alternative presentations of the light and the tone and were consequently always in the presence of a stimulus that signalled variable-interval punishment. The other two rats in each experiment were treated similarly except that they received periods in which neither light nor tone was present. During these periods, bar pressing was not punished. The two stimuli that signalled punishment were then presented simultaneously to evaluate the effect of stimulus compounding on response suppression. The subjects trained without punishment-free periods did not show summation to the compound stimulus; the subjects trained with punishment-free periods showed summation of suppression. The major difference between the two experiments was the longer mean interval of variable-interval punishment used in the second experiment. This manipulation made the summation effect more resistant to extinction and thus increased its magnitude.     

Frequency recognition in temporal interference tasks: A comparison among four psychophysical procedures

The frequency discrimination of a 20-msec test tone was measured for the same subjects in four psychophysical paradigms: a single-interval procedure, a two-alternative forced-choice procedure, a same-different procedure, and a method-of-adjustment procedure. In each paradigm, the 20-msec test tone was preceded or followed by a 500-msec, 800-Hz interfering tone. The interfering tone occurred 50 or 5 msec before the onset of the test tone (forward interference) or 100 or 5 msec after the offset of the test tone (backward interference). In each of the four paradigms and for each of the interference conditions the value of Δf for the test tone was varied symetrically around 800 Hz to obtain an estimate of the frequency discrimination thresholds. In all psychophysical paradigms except for the single-interval procedure, there were small or no significant differences in observers’ frequency discrimination behavior among the interference conditions. The thresholds for Δf from these conditions were approximately the same as those obtained without an interfering tone. In the single-interval task, when the test tone preceded the interfering tone (backward interference) by 5 msec, an increase in the value of Δf required for discrimination over that required in the other conditions was measured. These results suggest that the effect of backward interference on a target tone does depend on psychophysical procedure.     

Inhibition of acoustic startle using different mechanoreceptive channels

In this experiment, we investigated the impact of vibrotactile prepulse frequency and intensity on the acoustically elicited startle response in humans. Mechanoreceptive channels differing in their sensitivity to transient stimulation have been identified in the skin. The Pacinian channel is optimally sensitive to vibrations at approximately 300 Hz and is specialized for the detection of stimulus transients, whereas the non-Pacinian I and III channels are optimally sensitive to vibrations at approximately 30 Hz. Vibrotactile prepulses with frequencies of 30 and 300 Hz and intensities of 95 and 130 mV were presented for 50 msec to the dominant hand of college students (N = 31), followed on some trials by a 95-dB broadband acoustic startle stimulus. The 300-Hz prepulses resulted in significantly more pronounced inhibition of startle magnitude, amplitude, and probability, whereas only the 30-Hz prepulses significantly facilitated blink latency. These results support the idea that the inhibition of acoustic startle is determined more by transient than by sustained aspects of vibrotactile prepulse stimuli. This study also demonstrates that different aspects of the startle response differentially reflect stimulus characteristics of the prepulse.