Adaptation to auditory motion in the horizontal plane: Effect of prior exposure to motion on motion detectability

Thresholds for auditory motion detectability were measured in a darkened anechoic chamber while subjects were adapted to horizontally moving sound saurces of various-velocities. All stimuli were 500-Hz lowpass noises presented at a level of 55 dBA. The threshold measure employed was the minimum audible movement angle(MAMA)—that is, the minimum angle a horizontally moving sound must traverse to be just discriminable from a stationary sound. In an adaptive, two-interval forced-choice procedure, trials occurred every 2-5 sec (Experiment 1) or every 10–12 sec (Experiment 2). Intertrial time was “filled” with exposure to the adaptor—a stimulus that repeatedly traversed the subject’s front hemifield at ear level (distance: 1.7 m) at a constant velocity (?150°/secto + 150°/sec)during a run. Average MAMAs in the control condition, in which the adaptor was stationary (0°/sec), were 2.4° (Experiment 1) and 3.0° (Experiment 2). Three out of 4 subjects in each experiment showed significantly elevated MAMAs (by up to 60%), with some adaptors relative to the control condition. However, there were large intersubject differences in the shape of the MAMA versus adaptor velocity functions. This loss of sensitivity to motion that most subjects show after exposure to moving signals is probably one component underlying the auditory motion aftereffect (Grantham, 1989), in which judgmentsof the direction-afmoving sounds are biased in the direction opposite to that of a previously presented adaptor.     

Aging effect on detectability,criticality and urgency under various auditory conditions

The objective of the study was to investigate the relationship between different components of an auditory warning signal and determine elderly driver’s detection, criticality and urgency perceptions under varied auditory warning conditions. A laboratory study was conducted involving 28 younger and 28 older adults. A pure-tone audiogram was administered for quantification of the participant’s hearing level (in dBHL) prior to the test protocols. Audiogram was conducted in a sound isolated booth. The main experiment investigated the effects of frequency, temporal characteristics, aging, and noise on detectability, caution and perceived urgent levels. Method of adjustment was used by the subjects to adjust the sound pressure level (dBA) till they detected, or felt caution or urgent. Overall, the results indicated that elderly had higher sound pressure threshold than younger individuals in all the sessions (i.e., detectability, caution and urgency). Elderly were found to have higher hearing thresholds especially at 4000 Hz. Higher frequencies were also seen to require less sound pressure thresholds to convey feeling of caution and urgency. Sound pressure threshold to convey the feeling of urgency was the lowest for 2000 Hz and 4000 Hz with 1000 Hz requiring the highest threshold intensity. In conclusion, current study findings suggest frequency, temporal and spectral components to influence a person’s criterion. We would recommend the use of complex tones (multi-components) having high frequency around 2000 Hz for detection, warning and urgent conditions.     

Visual detectability gradients: effect of illiteracy.

When subjects are required to detect a target pattern presented simultaneously with a number of similar non-target patterns in a brief exposure, marked differences of target detectability are observed as a function of the spatial location of the target (Efron, Yund, & Nichols, 1987, 1990a, b, c; Yund, Efron & Nichols, 1990a, b, c). These differences in detectability as a function of retinal locus, referred to collectively as a "detectability gradient," have been attributed to a central serial processing mechanism, which scans the decaying neural representation of the image. There also is evidence suggesting that, at least in some circumstances, this gradient may be influenced by the direction in which subjects normally read (Heron, 1957; Mishkin & Forgays, 1952; Efron et al., 1987). The object of the present experiment was to determine whether the detectability gradient obtained with the non-linguistic stimuli used in our previous experiments would differ as a function of previous reading experience. The experiment was performed on a group of 60 illiterate subjects and on a socioeconomic-matched group of 60 literate subjects. While the overall accuracy of target detection was identical in the two groups, there were significant differences between the detectability gradients of the literate and illiterate subjects. The nature of these differences indicates that reading, or learning to read, causes the scanning mechanisms of literate subjects to adopt more consistent scan paths, from subject to subject, than they would have adopted without this reading experience.     

Adaptation in motion perception: Alteration of induced motion

Prolonged exposure to a condition that causes induced motion was found to diminish this effect. The extent of a horizontal induced motion was measured by obtaining estimates of the direction of the apparent oblique path that resulted when a spot was visible on a horizontally moving pattern and was therefore in horizontal induced motion and, at the same time, moved vertically. Because the horizontal component of the perceived motion path represented the induced motion, the slope of the path measured the extent of the induced motion. After a 10-min exposure to induced motion, the apparent motion path was steeper; the mean change corresponded to a 15% smaller extent of the induced motion. Results were obtained that argue that this effect is not due to a diminished horizontal motion of the pattern but amounts to a smaller motion-inducing effect. The experiments were meant to support the view that the perceptual process that underlies induced motion is learned.     

The effect of brief auditory stimuli on visual apparent motion

When two discrete stimuli are presented in rapid succession, observers typically report a movement of the lead stimulus toward the lag stimulus. The object of this study was to investigate crossmodal effects of irrelevant sounds on this illusion of visual apparent motion. Observers were presented with two visual stimuli that were temporally separated by interstimulus onset intervals from 0 to 350 ms. After each trial, observers classified their impression of the stimuli using a categorisation system. The presentation of short sounds intervening between the visual stimuli facilitated the impression of apparent motion relative to baseline (visual stimuli without sounds), whereas sounds presented before the first and after the second visual stimulus as well as simultaneously presented sounds reduced the motion impression. The results demonstrate an effect of the temporal structure of irrelevant sounds on visual apparent motion that is discussed in light of a related multisensory phenomenon, 'temporal ventriloquism', on the assumption that sounds can attract lights in the temporal dimension.     

Experimental disorientation in the horizontal plane

Twenty-eight subjects were examined on a visual matching task for their ability to maintain an orientation with respect to a particular direction in the horizontal plane following a voluntary rotary body movement through 180 degrees. Each subject was examined with respect to eight different directions.

Numerous gross errors occurred when visual information was reduced to the display of an arrow indicating a direction and a second arrow manipulated by the subject. The magnitude and distribution of the errors suggest that, under the conditions of this experiment, visual information as to direction in the horizontal plane is analysed according to the two horizontal dimensions defined by the sagittal and coronal planes of the head. In correcting for the rotary body movement, failure may occur with respect to either or both of these two dimensions. The frequency of a failure to make any correction at all (i.e. 180-degree errors) is consistent with independent failure in each of the two horizontal dimensions.

Failure is markedly more frequent in the fore-aft dimension than in the left-right dimension. It is suggested that this may be explained in terms of the ambiguous spatial significance of vertical disposition on the retina and the possibility of contamination between the two systems of conceptual analysis which identify the vertical and the fore-aft dimensions of visual space.

It is demonstrated that when minimal “landmarks” are provided they tend to be utilized as reference points in attempts to maintain orientation, even when the subject is aware that the “landmarks” are misleading. Such a use of “landmarks” does not suppress the previously mentioned mechanism of dimensional orientation.

The relevance of these results to normal human orientation is discussed.     

Adaptation to spiral motion in crowding condition

When a single, moving stimulus is presented in the peripheral visual field, its direction of motion can be easily distinguished, but when the same stimulus is flanked by other similar moving stimuli, observers are unable to report its direction of motion. In this condition, known as 'crowding', specific features of visual stimuli do not access conscious perception. The aim of this study was to investigate whether adaptation to spiral motion is preserved in crowding conditions. Logarithmic spirals were used as adapting stimuli. A rotating spiral stimulus (target spiral) was presented, flanked by spirals of the same type, and observers were adapted to its motion. The observers' task was to report the rotational direction of a directionally ambiguous motion (test stimulus) presented afterwards. The directionally ambiguous motion consisted of a pair of spirals flickering in counterphase, which were mirror images of the target spiral. Although observers were not aware of the rotational direction of the target and identified it at chance levels, the direction of rotation reported by the observers during the test phase (motion aftereffect) was contrarotational to the direction of the adapting spiral. Since all contours of the adapting and test stimuli were 90 degrees apart, local motion detectors tuned to the directions of the mirror-image spiral should fail to respond, and therefore not adapt to the adapting spiral. Thus, any motion aftereffect observed should be attributed to adaptation of global motion detectors (ie rotation detectors). Hence, activation of rotation-selective cells is not necessarily correlated with conscious perception.     

Ontogeny of the adrenal response to (+)-methamphetamine in neonatal rats: the effect of prior drug exposure

We examined the ontogeny of the corticosterone response to (+)-methamphetamine in neonatal rats. In experiment-1, animals were injected with 10 mg/kg of (+)-methamphetamine or saline and plasma corticosterone levels were examined in separate groups 30 or 105 min later on postnatal day (P) 1, 3, 5, 7, 9, 11, 13, 15, 17, or 19. The adrenal response to methamphetamine was best described by a U-shaped function with the nadir of corticosterone release occurring between P7 and P13. Experiment-2 was similar except that the effect of four consecutive days of exposure to (+)-methamphetamine (four times daily at 2 h intervals with 10 mg/kg) was assessed with a single final dose early on the fifth day (i.e. P1-5, 3-7, 5-9, 7-11, 9-13, 11-15, 13-17, 15-19). The 30 min corticosterone response after multiple methamphetamine doses was augmented compared to single exposures, with the exception of the two earliest dosing intervals ending on P5 and P7, where the responses were lower. In addition, at 105 min, the levels of corticosterone were attenuated relative to a single drug administration. With the exception of animals receiving methamphetamine from P15 to P19, thymus weights were unaffected. The data demonstrate that (+)-methamphetamine is a robust activator of corticosterone release in developing animals and this release is extensively modified by age and previous drug exposure.     

Visual detectability gradients: effect of high-speed visual experience.

The detectability of a target pattern presented briefly with a number of similar nontarget patterns varies as a function of the spatial location of the target. Previous work attributes these detectability gradients to a visual search process--a non-eye movement serial scan--that examines a decaying neural representation of the image. (Heron, 1957; Efron, Yund, & Nichols, 1987, 1990a,b,c; Yund, Efron, & Nichols, 1990a,b,c). The results reported in the companion paper (Ostrosky-Solis, Efron, & Yund, 1991) indicated that literacy did not affect overall performance levels but did influence scanning behavior: "...reading, or learning to read, caused the scanning mechanisms of literate subjects to adopt more consistent scan paths, from subject to subject, than they would have adopted without this reading experience." The purpose of the present experiment was to determine the effect on this scanning mechanism, if any, of an entirely different type of visual experience--the high-speed visual processing required of tennis players. Unlike reading which requires the linguistic interpretation of a highly structured visual input, tennis skill requires rapid target detection and tracking in three-dimensional visual space as well as large scale visual-motor coordination. As in the previous experiments, subjects were required to detect a vertical stripe pattern among a number of similar non-target patterns. The experiment was performed on a group of 52 tennis players and on an age- and sex-matched group of 52 non-tennis players. The overall accuracy of target detection was greater among the tennis players than among the non-tennis players and, of more interest, there was a significant difference in the detectability gradients. The detection advantage of the tennis group seemed to reach its maximum in the first half of the scan and then to deteriorate as the scan proceeded. These results indicate that visual experience other than reading can affect the habitual activity of the scanning mechanism.     

The effect of timing and spatial separation on the velocity of auditory apparent motion

Previously, it was shown that the minimum conditions for the illusion of auditory apparent motion (AAM) depend on stimulus timing but not spatial separation. In the present experiment, the effects of stimulus timing and source separation on the perceived velocity of AAM were examined. Eight listeners estimated the velocity, duration, and distance traveled of AAM, using a no-modulus, magnitude estimation procedure. Four burst durations (25, 50, 100, and 300 msec), 10 stimulus onset asynchronies (SOAs; 30, 40, 50, 60, 70, 80, 90, 100, 110, and 120 msec) and two separations (10° and 40°) were tested. Perceived velocity estimates were related to the total duration (burst duration + SOA) of the stimulus sequence. The effect of separation on velocity was extremely small but statistically significant. These results are similar to those obtained previously on the minimum conditions for AAM. Duration estimates were related only to total duration, but separation estimates were related to both separation and total duration. These results suggest that velocity is possibly a primary dimension of AAM that is independent of source separation.     

Adaptation in motion perception: Alteration of motion evoked by ocular pursuit

A new perceptual adaptation, an alteration in the perceived direction of motion given by ocular pursuit, is reported. When an object starts to move on a straight path, its displacement is initially given by a shift of its image on the retinas of the stationary eyes; then, after about 200 msec, the eyes start to track the moving object. The perception of motion that results from ocular pursuit was altered by causing ocular pursuit of a moving object to be preceded regularly by a displacement of the object’s image whose direction differed from the direction of the pursuit movement. This was arranged by changing the direction of the given motion at approximately the moment when image displacement changed into tracking. Prolonged exposure to such conditions resulted in a change of the tracked motion’s apparent direction, which became somewhat more like the direction of the preceding motion phase that was given by image displacement.     

Visual detectability gradients: the effect of distractors in contralateral field

A number of studies involving recognition of tachistoscopically presented words have reported that the typical right visual field performance superiority associated with linguistic stimuli is enhanced by bilateral presentations (simultaneous stimuli in both visual half-fields) compared to unilateral presentations (stimuli in only one half-field on a trial). We have reported the same phenomenon, however, using visual spatial patterns in a search paradigm (E. W. Yund, R. Efron, & D. R. Nichols, 1990c. Brain and Cognition, 12, 117-127) and have accounted for it in terms of the operating characteristics of a visual scanning mechanism which serially examines a decaying neural representation of the stimuli. In the present experiment we attempted to exploit these operating characteristics to influence this difference between unilateral and bilateral presentations. The results not only are consistent with the assumptions of the scanning hypothesis but they also provide new information pertinent to the operating characteristics of this mechanism.     

Effects of laterality and pitch height of an auditory accessory stimulus on horizontal response selection: The Simon effect and the SMARC effect

In the present article, we investigated the effects of pitch height and the presented ear (laterality) of an auditory stimulus, irrelevant to the ongoing visual task, on horizontal response selection. Performance was better when the response and the stimulated ear spatially corresponded (Simon effect), and when the spatial—musical association of response codes (SMARC) correspondence was maintained—that is, right (left) response with a high-pitched (low-pitched) tone. These findings reveal an automatic activation of spatially and musically associated responses by task-irrelevant auditory accessory stimuli. Pitch height is strong enough to influence the horizontal responses despite modality differences with task target.     

Temporal constraints on apparent motion in auditory space

The hypothesis that the extent of spatial separation between successive sound events directly affects the perception of time intervals between these events was tested using an apparent motion paradigm. Subjects listened to four-tone pitch patterns whose individual tones were sounded alternately at one of two loudspeaker positions, and they adjusted the alternation rate until they could no longer distinguish the four-tone ordering of the pattern. Four horizontal and two vertical loudspeaker separations were tested. Results indicate a direct relation between horizontal separation and the critical stimulus onset asynchrony (SOA) between successive tones within a pattern. At the critical SOA, subjects reported hearing not a four-tone pattern, but two pairs of two-note groups overlapping in time. The findings are discussed in the context .of auditory spatial processing mechanisms and possible sensory-specific representational constraints.     

Influences on the Simon effect of prior practice with spatially incompatible mappings: Transfer within and between horizontal and vertical dimensions

The Simon effect refers to the fact that for tasks in which stimulus location is irrelevant and a nonspatial attribute is relevant, responses are typically faster when stimulus and response locations correspond than when they do not. Two experiments examined the influence of prior practice with an incompatible relevant spatial mapping on the Simon effect as a function of the dimension (vertical or horizontal) along which the stimuli and responses varied in practice and transfer sessions. With 72 practice trials, the Simon effect in the transfer session was eliminated only when the spatial dimension was horizontal for both practice and transfer. With 600 practice trials, the Simon effect was eliminated for all combinations of practice and transfer dimensions, with noncorresponding responses showing an advantage when the dimension was horizontal for both practice and transfer. Within-dimension transfer effects for the horizontal dimension after a small amount of practice can be attributed to reactivation of specific stimulus-response associations defined for the practice task. However, the between-dimension transfer effects evident after a larger amount of practice cannot be explained in this manner and suggest that the subjects acquired a general procedure of responding opposite to the stimulus location.     

Nicotinic modulation of tone-evoked responses in auditory cortex reflects the strength of prior auditory learning

Nicotinic acetylcholine receptors (nAChRs) contribute to sensory-cognitive function, as demonstrated by evidence that nAChR activation enhances, and nAChR blockade impairs, neural processing of sensory stimuli and sensory-cognitive behavior. To better understand the relationship between nAChR function and behavior, here we compare the strength of nAChR-mediated physiology in individual animals to their prior auditory behavioral performance. Adult rats were trained on an auditory-cued, active avoidance task over 4 days and classified as “good,” “intermediate” or “poor” performers based on their initial rate of learning and eventual level of performance. Animals were then anesthetized, and tone-evoked local field potentials (LFPs) recorded in layer 4 of auditory cortex (ACx) before and after a test dose of nicotine (0.7 mg/kg, s.c.) or saline. In “good” performers, nicotine enhanced LFP amplitude and decreased response threshold to characteristic frequency (CF) stimuli, yet had opposite effects (decreased amplitude, increased threshold) on responses to spectrally distant stimuli; i.e., cortical receptive fields became more selective for CF stimuli. In contrast, nicotine had little effect on LFP amplitude in “intermediate” or “poor” performing animals. Nicotine did, however, reduce LFP onset latency in all three groups, indicating that all received an effective dose of the drug. Our findings suggest that nicotinic regulation of cortical receptive fields may be a distinguishing feature of the best-performing animals, and may facilitate sensory-related learning by enhancing receptive field selectivity.     

A facilitative effect of prior punishments on: II. Subsequent resistance to simple extinction

The facilitative effect of interspered shock was studied by removing shocks and allowing simple extinction, i.e. no shock and no food. There were five groups with five rats in each group. Ten shocks wer interspersed in IP-10, 40 shocks in IP-40, and 40 nonrewards were interspersed in IR. The number of rewarded trials was constant in all 5 groups - i.e. 140. The R group was given only 140 rewards consistently and the R-P group was given 140 rewards consistently followed by 10 consistent shocks. The findings were that the interspersed shock groups (especially IP-10) pressed many more times during extinction than R, or R-P or even IR. The counterconditioning hypothesis in contrast to alternative notions was seen to provide a satisfactory explanation of the findings.     

Lessons learned: the effect of prior technology use on Web-based interventions.

This study examined the role of regular prior technology use in treatment response to an online family problem-solving (OFPS) intervention and an Internet resource intervention (IRI) for pediatric traumatic brain injury (TBI). Participants were 150 individuals in 40 families of children with TBI randomly assigned to OFPS intervention or an IRI. All families received free computers and Internet access to TBI resources. OFPS families received Web-based sessions and therapist-guided synchronous videoconferences focusing on problem solving, communication skills, and behavior management. All participants completed measures of depression, anxiety, and computer usage. OFPS participants rated treatment satisfaction, therapeutic alliance, and Web site and technology comfort. With the OFPS intervention, depression and anxiety improved significantly more among technology using parents (n = 14) than nontechnology users (n = 6). Technology users reported increasing comfort with technology over time, and this change was predictive of depression at followup. Satisfaction and ease-of-use ratings did not differ by technology usage. Lack of regular prior home computer usage and nonadherence were predictive of anxiety at followup. The IRI was not globally effective. However, controlling for prior depression, age, and technology at work, there was a significant effect of technology at home for depression. Families with technology experience at home (n = 11) reported significantly greater improvements in depression than families without prior technology experience at home (n = 8). Although Web-based OFPS was effective in improving caregiver functioning, individuals with limited computer experience may benefit less from an online intervention due to increased nonadherence.