Intensity effects of the auditory evoked brain response to stimulus onset and cessation

Average evoked brain responses (EBR) to the onset (ON) and cessation (OFF) of 1-kHz pure-tone stimuli were computed from human scalp recordings. Stimuli of 2,000 msec duration were presented binaurally at 10 intensity levels. The waveform of the OFF EBR is similar to the ON EBR. The ON response is in general larger than the OFF response. Comparable ON and OFF amplitude response measures are both sensitive to changes in stimulus intensity which may be fit by a linear function. Significant differences in slope between ON and OFF amplitude intensity functions were demonstrated, which suggests different physiological systems for these responses.     

Auditory streaming: Competition among alternative organizations

It has been suggested that the ON and OFF components of the auditory evoked potential (AEP) may be mediated by independent physiological mechanisms and that the response to a brief tone consists of overlapping ON and OFF responses. Two experiments were performed to evaluate these proposals. First, AEPs were recorded to tonebursts of various durations presented at a fixed rate. As the tonebursts were made longer, they evoked smaller ON responses and larger OFF responses, particularly when either response followed the other by less than 5 sec. This indicates that ON and OFF responses are not physiologically independent. Second, the AEP to a 25-msec tone was compared with the ON response to a 2,000-msec tone. At an interstimulus interval of 4 sec, the difference wave formed by subtracting the latter AEP from the former contained clear N₁ (ca. 100 msec) and P₂ (ca. 180 msec) components, which have been interpreted as an OFF response by some authors. These components in the difference wave were greatly reduced or even inverted at 10-sec interstimulus intervals, however, where interactions between ON and OFF responses to successive stimuli were minimized. This result indicates that any residual OFF response in the AEP to a brief tone is very small in amplitude, if present at all.     

Orienting responses as a function of age and task complexity.

Aged-related differences in the elicitation and habituation of orienting responses to the onset and offset of stimuli have been suggested by several authors. Electrodermal and cardiac orienting responses to the onset and offset of a visual stimulus were measured in three age groups (4 yr., 7 yr., and undergraduate). Each S made one of three judgments: non-signal (observe stimulus), content (color of stimulus), and duration (length of time stimulus presented). Few age differences were found in elicitation or habituation of orienting responses to stimulus onset or offset. There was a trend for elicitation of orienting responses to stimulus offset to be age-related, but the failure to find any other age-related changes made this difference somewhat questionable. Instructions as to the judgement to be made by S were the primary determinants of orienting responses to stimulus onset and offset across all age groups.     

Saccade latency and warning signals: Stimulus onset,offset, and change as warning events

Two experiments investigated saccade latency to a peripheral target under various warning signal conditions. In Experiment I, the effects of warning stimulus onset, change, and two offset conditions were compared at warning intervals of 0, 100, 300, and 600 msec. Warning stimulus onset, change, and offset were all effective in reducing saccade latency as compared to a no-warning control condition, but warning stimulus offset resulted in shorter saccade latency than onset or change at all warning intervals. Experiment 2 compared onset and offset warning conditions at ?300-, ?250-, ?200-, ?150-, ?100-, ?50-, 0-, and 50-msec intervals. Responses following onset were slower than those following offset at the latter five intervals, while warning onset resulted in slower saccades than no-warning control conditions at ?150-, ?100-, and ?50-msec intervals. These results indicate that the onset of a visual warning signal can have an interfering effect on the programming or execution of a saccade.     

Spatial correspondence between onsets and offsets of stimuli and responses

The Simon effect denotes faster responses when the task-irrelevant stimulus position corresponds to response position than when it does not. A common explanation is that a spatial stimulus code is formed automatically and activates a spatially corresponding response code. Previous research on stimulus–response (S–R) compatibility has focused on the ability to initiate movements to stimulus onsets. The present study investigates spatial-compatibility effects (i.e., the Simon effect) in the ability to initiate and to terminate actions both to stimulus onsets and to stimulus offsets. There were four major results. Firstly, offset stimuli produced normal Simon effects suggesting that stimulus offsets can automatically produce spatial codes. Secondly, onset stimuli produced larger Simon effects than offset stimuli, which is consistent with the attention-shift account of spatial coding. Thirdly, Simon effects were also observed in action termination. Fourthly, Simon effects in action initiation and in action termination were of similar size.     

Effect of stimulus duration on perceptual onset and offset latencies

The effects of stimulus duration on perceptual onset and offset latency were compared in vision and audition. It was found that perceptual onset latency was independent of stimulus duration but that the perceptual offset latency was longer for brief stimuli than for stimuli that exceeded a critical duration. For stimuli longer than the critical duration, the perceptual onset and offset latencies were equal: The same temporal relationships were found in both modalities. The results indicate that for any specific stimulus parameters, reduction of stimulus duration results, ultimately, in a perception of fixed duration.     

Cardiac deceleration in newborns: habituation, dishabituation, and offset responses.

Twenty healthy, 1–4 day-old infants were selected from a sample of 135 neonates on the basis of alertness during testing. The infants were presented mild intensity colored light with gradual onset and offset while heart rate was monitored. Half the infants received six exposures to blue light followed by two exposures to blue-green light, whereas remaining subjects received colors in reverse order. Stimulus duration was 20 sec and variable periods between stimuli averaged 30 sec. Results of trend analysis of variance of the second-by-second cardiac data indicated that for infants older than the median age, the decelerative responses to both stimulus onset and offset were significant. Further, these subjects' onset decelerations significantly habituated within the six stimulus repetitions and significantly dishabituated with change in the stimulus color. Offset decelerations incremented over habituation trials and decremented with change in stimulus color. Responses of younger subjects were more variable which probably reflects their less complete recovery from the effects of maternal medication and the birth process.     

Electrodermal measures of attention and effort to stimulus onset and offset for intramodal and intermodal tasks.

Two experiments were designed to assess the relationship between task difficulty and arousal. Electrodermal measures of tonic and phasic arousal to four levels of task difficulty at stimulus onset and offset were studied in college students for intramodal and intermodal tasks. The students were presented for 18 trails with visual-auditory or visual-visual stimuli with either 2.0-, 0.2-, or 0.02-sec difference between stimuli onset or offset, and asked to judge which stimulus came on or went off first or merely to observe the stimuli. Both frequency and amplitude of skin conductance responses reliably differentiated the levels of task difficulty for both the intramodal and the intermodal task. None of the measures of tonic level of arousal was reliable. Electrodermal measures of phasic responses accurately reflected the task demands.     

Visual recognition as a function of stimulus offset asynchrony and duration

The stimuli consisted of two complementary dot patterns that formed a bigram when they were flashed simultaneously; impairment of letter recognition developed when one of the patterns was briefly extended beyond the termination of the other (stimulus offset asynchrony). However, if the ratio of stimulus offset asynchrony to bigram duration remained constant, the probability of a correct recognition response also remained constant as duration varied over a 50- to 100-msec interval. When percent stimulus asynchrony increased, the impairment increased. An interaction between bigram letter position and each of bigram duration and percent stimulus asynchrony was observed with recognition accuracy greater in general for the letter in the left half of the field.     

Differential redundancy gain in onset detection versus offset detection

In a visual simple reaction time paradigm with attention divided between the left and right visual fields, redundancy gain refers to the finding of faster responses to stimuli presented in both fields than to single stimuli. The present study investigated whether the effects of low-level perceptual processing affect the redundancy gain by comparing the detection of onsets versus offsets. In different blocks, participants responded to left and right visual field stimuli that either appeared (onset) or disappeared (offset), with a single stimulus change in some trials and two redundant stimulus changes in others. With onset stimuli, the results replicated previous redundancy gain effects. In contrast, there was much less redundancy gain when participants responded to stimulus offsets. This finding suggests that redundancy gain is sensitive to low-level perceptual characteristics, such as onset versus offset presentation of stimuli.     

Providing a sensory basis for models of visual information acquisition

Our major goal is to account for some simple digit-recall data with a theory that integrates two models from two scientific traditions. Therandom-sampling model, founded in the memory and attention literature, holds that (1) stimulus features are randomly sampled throughout the course of stimulus presence and (2) proportion correct recall is equal to the ratio of sampled features to total features.The linear-filter model, founded in the vision and sensation literature, holds that the initial stages of the visual system act as a low-pass temporal filter on the input stimulus, resulting in a time-varyingsensory response in the nervous system. We report two experiments in which a variable-duration, masked, four-digit string had to be immediately recalled. Experiment 1 was designed principally to replicate past data confirming the basic random-sampling model. Like others, we were able to confirm the model only by endowing it with an additionalprocessing-delay assumption: that feature sampling does not begin until the stimulus has been physically present for some minimal duration. Experiment 2 was an extension of Experiment 1 in which the target stimulus was preceded, 250 msec prior to its onset, by a 50-msec pre-presentation ofthe same stimulus called aprime. The Experiment 2 results allowed the following conclusions. First, the initial processing delay found in Experiment 1 is immutably tied to stimulus onset; that is, if there are two stimulus onsets, separated even briefly in time, there are two associated processing delays. Second, processing rate is essentially unaffected by the prime’s presentation. Third, being presented with a 50-msec prime is equivalent, in terms of memory performance, to increasing unprimed stimulus duration by approximately 30 msec; the prime can thus said to beworth 30 msec of additional exposure duration. This third conclusion seems superficially paradoxical, in the sense that one would expect that having seen a 50-msec prime would be equivalent to increasing exposure duration byat least the same 50 msec. However, both the initial processing delays and the 30-msec prime’s worth are natural consequences of our theory that conjoins the random-sampling model with the linear-filter model.     

Enhancement,extension, and reversal of the frequency selectivity effect

The influence of a frequency cue on judgments of whether or not a subsequent target incorporated a brief silent gap was examined. In Experiment 1, there was no predictive frequency relation and evidence of auditory inhibition of return was obtained with frequency repetitions, producing a facilitative effect at 175-msec stimulus onset asynchrony (SOA) and an inhibitory effect at 775-msec SOA. Relative to this baseline performance pattern, increasing the probability of a frequency match to .75 (Experiment 2) served to generate a beneficial effect of frequency repetitions at lengthy SOAs and to enlarge its magnitude at 175-msec SOA. In contrast, a reduction in the probability of a frequency match to .25 (Experiment 3) resulted in the elimination of any facilitative effect of repetition at 175-msec SOA and the development of an inhibitory effect at 475- and 1,075-msec SOA. These results establish that a frequency cue may engage both exogenous and endogenous attentional processes within 175 msec following its presentation.     

Auditory evoked brain responses: Intensity functions from bipolar human scalp recordings

Average evoked brain responses were computed from four simultaneous recordings during binaural tone stimulation at 10 intensity levels. Amplitudes and latencies were measured for the prominent components, and linear regression coefficients were computed. The results indicate that the sensitivity of the evoked response to stimulus intensity is dependent upon the selection of the appropriate measure. Linear amplitude functions were demonstrated. Additional research relating these responses to psychophysical measures is suggested.     

STIMULUS EFFECTS ON LOCAL PREFERENCE: STIMULUS—RESPONSE CONTINGENCIES,STIMULUS—FOOD PAIRING,AND STIMULUS—FOOD CORRELATION

Four pigeons were trained in a procedure in which concurrent‐schedule food ratios changed unpredictably across seven unsignaled components after 10 food deliveries. Additional green‐key stimulus presentations also occurred on the two alternatives, sometimes in the same ratio as the component food ratio, and sometimes in the inverse ratio. In eight experimental conditions, we varied the contingencies surrounding these additional stimuli: In two conditions, stimulus onset and offset were noncontingent; in another two, stimulus onset was noncontingent, and offset was response contingent. In four conditions, both stimulus onset and offset were contingent, and in two of these conditions the stimulus was simultaneously paired with food delivery. Sensitivity to component food ratios was significantly higher when stimulus onset was response contingent compared to when it was noncontingent. Choice changes following food delivery were similar in all eight conditions. Choice changes following stimuli were smaller than those following food, and directionally were completely determined by the food‐ratio:stimulus‐ratio correlation, not by the stimulus contingency nor by whether the stimulus was paired with food or not. These results support the idea that conditional reinforcers may best be viewed as signals for next‐food location rather than as stimuli that have acquired hedonic value, at least when the signals are differential with respect to future conditions.     

Interaction between visually and kinesthetically triggered voluntary responses

A voluntary motor response that is prepared in advance of a stimulus may be triggered by any sensory input. This study investigated the combination of visual and kinesthetic inputs in triggering voluntary torque responses. When a visual stimulus was presented alone, subjects produced a fast and accurate increase in elbow flexion torque. When a kinesthetic stimulus was presented instead of the visual stimulus, subjects produced a similar response with a reduced response latency. When a visual stimulus was presented in combination with a kinesthetic stimulus, subjects initiated their responses after either a visual or a kinesthetic response latency, depending on the relative timing of the two stimuli. An analysis of response amplitude suggested that when visual and kinesthetic stimuli were combined, both stimuli triggered a response. The results are more consistent with a simple behavioral model of addition of visual and kinesthetic responses (which predicts that the response to combined stimuli should be the sum of individual responses) than with a model of exclusion of one response (which predicts that the response to combined stimuli should be identical to either the visual or the kinesthetic response). Because addition of visually and kinesthetically triggered responses produced a response with an erroneously large amplitude, it is suggested that visual and kinesthetic inputs are not always efficiently integrated.     

The role of tone duration in dichotic temporal order judgment

Over the past two decades, a number of studies have been based on the dichotic temporal order judgment (TOJ) paradigm, to compare auditory temporal processing in various subpopulations to that of young, normal controls. The reported estimates of dichotic TOJ thresholds, expressed as the interstimulus intervals (ISIs) for 75 % accuracy among the controls, have varied. In the present study, we examined the influence of tone duration, within the 10- to 40-msec range, on dichotic TOJ accuracy and threshold. The results indicated that increases in either ISI or tone duration increased dichotic TOJ accuracy similarly, implying that changes in tone duration may affect dichotic TOJs simply by adding to the delay between onset of the tone at the lead ear and onset of the tone at the lag ear. The dichotic TOJ thresholds from three published studies that had used tones as stimuli and the dichotic thresholds from the present study all fell within 0.5 standard deviations from the theoretical line of a 10-msec reduction in threshold for every 10-msec increase in tone duration. When the dichotic TOJ threshold data from the present study and from the published studies were converted to stimulus onset asynchronies (SOAs) and plotted as a function of tone duration, they fell very close to or on a zero-slope line, indicating that when ISI and duration are summed to yield an SOA, dichotic TOJ thresholds are invariant to tone duration within the range of 10–40 msec.     

Time course of chord priming

The time course of chord priming was explored in four experiments. In chord priming, a chord (a typical combination of simultaneously sounded tones) primes other chords that are musically related. In the present study, the prime duration and the stimulus onset asynchrony (SOA) between the prime chord and the chord to be judged were varied. Priming occurred at an SOA and prime duration as short as 50 msec, the shortest tested. When the prime duration was held constant at 50 msec, priming occurred at an SOA as long as 2,500 msec, the longest tested, and the magnitude of the priming effect did not diminish. To eliminate a possible role of sensory memory in maintaining the priming effect during the silence following the prime, a 250-msec noise mask was presented immediately following the 50-msec prime. The interpolated noise mask did not eliminate priming, thereby supporting the view that chord priming is the consequence of associative activation.     

Time course of chord priming.

The time course of chord priming was explored in four experiments. In chord priming, a chord (a typical combination of simultaneously sounded tones) primes other chords that are musically related. In the present study, the prime duration and the stimulus onset asynchrony (SOA) between the prime chord and the chord to be judged were varied. Priming occurred at an SOA and prime duration as short as 50 msec, the shortest tested. When the prime duration was held constant at 50 msec, priming occurred at an SOA as long as 2,500 msec, the longest tested, and the magnitude of the priming effect did not diminish. To eliminate a possible role of sensory memory in maintaining the priming effect during the silence following the prime, a 250-msec noise mask was presented immediately following the 50-msec prime. The interpolated noise mask did not eliminate priming, thereby supporting the view that chord priming is the consequence of associative activation.     

The role of duration and rapid temporal processing on the lateral perception of consonants and vowels

This study explored the extent to which rapid temporal processing and duration contribute to the right-ear advantage (REA) and presumably left-hemisphere processing for stop consonants and the lack of clear-cut laterality effects for vowels. Three sets of synthetic stimuli were constructed: consonant vowel stimuli [ba da ga bi di gi bu du gu] of 300 msec duration (full stimuli) and two shortened stimuli consisting either of a noise burst and 40-msec transitions (40-msec stimuli), or a noise burst and 20-msec transitions (20-msec stimuli). Stimuli were presented dichotically for consonant, vowel, and syllable identification. Results indicated a significant REA for consonants in the full and 40-msec conditions and a non-significant REA in the 20-msec condition. Nevertheless, the magnitude of laterality did not change across the three conditions. These results suggest that although transition information including duration contributes to lateralization for stop consonants, it is the presence of abrupt onsets which crucially determines lateralized processing. For vowels, there was a significant REA only in the full stimulus condition, and a significant decrement in the magnitude of the laterality effect in the two shortened stimulus conditions. These results suggest that for vowel perception, it is the nature of the acoustic cue used for phonetic identification and not duration that seems to be the critical determinant of lateralization effects.     

THE DISCRIMINATION OF STIMULUS DURATION BY PIGEONS1

Pigeons were trained to discriminate the duration of a stimulus. One response in a psychophysical choice situation was reinforced, given the immediately prior presentation of a stimulus duration in one class of durations called short durations, and the other response was reinforced given the immediately prior presentation of a stimulus duration in a second class called long durations. Durations of equal logarithmic difference from the cutoff, whether in the short or long class, yielded equal accuracy. Accuracy was a function not only of the properties of the stimuli to be discriminated, but also of the experimental contingencies used. Accuracy was greater in variable-ratio than in fixed-ratio schedules of reinforcement of the discriminative responses, and was lower at the beginning than later in individual fixed ratios. Proportion of short or long responses (response bias) was affected by sequential dependencies among long and short durations and was effectively controlled through the use of asymmetric reinforcement and fixed-ratio contingencies.