Beverly A. Wright’s research while affiliated with Northwestern University and other places

In many non-human species, learning retention decreases temporarily following training. This has led to the suggestion that these lapses reflect a fundamental component of memory formation. If so, transient memory lapses should also be prevalent in humans, and should occur for all types of learning. In line with these predictions, we report two cases of transient memory lapses in humans that occur 1-3 h after training on a perceptual-discrimination task. The results indicate that the occurrence of transient memory lapses extends to perceptual learning, a form of skill learning, and suggest that transient memory lapses may be a common but overlooked facet of memory formation in humans.

Perceptual learning is the process by which experience alters how incoming sensory information is processed by the brain to give rise to behavior—it is critical for how humans educate children, train experts, treat diseases, and promote health and well-being throughout the lifespan. Knowledge of perceptual learning requires basic and applied research in humans and nonhuman animal models, which informs strategic targets for advancing applications. Commercial products to induce perceptual learning are proliferating rapidly with limited regulation (e.g., for rehabilitation), while at the same time basic science is increasingly restricted by changing regulations (such as new granting-agency definitions of clinical trials). Realizing the full potential of perceptual learning requires balancing basic and translational science to advance new knowledge, while serving and protecting consumers. Reforms can promote open, accessible, and representative research, and the translation of this research to applications across different sectors of society.

Training on one task (task A) can disrupt learning on a subsequently trained task (task B), illustrating anterograde learning interference. We asked whether the induction of anterograde learning interference depends on the learning stage that task A has reached when the training on task B begins. To do so, we drew on previous observations in perceptual learning in which completing all training on one task before beginning training on another task (blocked training) yielded markedly different learning outcomes than alternating training between the same two tasks for the same total number of trials (interleaved training). Those blocked versus interleaved contrasts suggest that there is a transition between two differentially vulnerable learning stages that is related to the number of consecutive training trials on each task, with interleaved training presumably tapping acquisition, and blocked training tapping consolidation. Here, we used the blocked versus interleaved paradigm in auditory perceptual learning in a case in which blocked training generated anterograde—but not its converse, retrograde—learning interference (A→B, not B←A). We report that anterograde learning interference of training on task A (interaural time difference discrimination) on learning on task B (interaural level difference discrimination) occurred with blocked training and diminished with interleaved training, with faster rates of interleaving leading to less interference. This pattern held for across-day, within-session, and offline learning. Thus, anterograde learning interference only occurred when the number of consecutive training trials on task A surpassed some critical value, consistent with other recent evidence that anterograde learning interference only arises when learning on task A has entered the consolidation stage.

Dave Green had an enormous influence on auditory research via signal-detection theory. A major contribution of signal-detection theory is the concept and application of the ideal detector, which establishes the absolute optimal detection performance. To bridge between the ideal performance and the less-than-ideal human performance, Green and Swets (1966) described an energy detector. The energy-detector model relaxed assumptions of the ideal detector to account for the phase insensitivity and limited frequency selectivity of humans, but it retained the assumption that the time window is matched to the signal duration. However, the time-window assumption had no clear support from human data. To help fill this gap, we examined the detectability of signals with expected versus unexpected temporal properties. The results of experiments and signal-detection analyses suggest that listeners listen selectively to signal duration, implying that they match the time window to the overall signal duration as was assumed in the energy-detector model. Additional results suggest that listeners do not also listen selectively to the temporal structure of the signal, implying that the temporal constraint is based on overall signal duration. We are grateful for the opportunity to have worked with Dave.

The two primary cues to sound-source location on the horizontal plane are interaural time differences (ITDs) and interaural level differences (ILDs). Here we asked whether the ability to discriminate small changes in each of these interaural cues differs between the sexes. We tested one group of males (n = 43) and females (n = 94) on ITD discrimination at 0.5 kHz and a separate group of males (n = 80) and females (n = 166) on ILD discrimination at 4 kHz. None of the participants had any prior experience with psychoacoustic tasks. Testing of each participant was completed in a single testing session of 4-5 blocks of 60 trials. For ILD discrimination, the overall mean threshold, as well as the mean threshold for each block, was statistically significantly lower for males than for females. Despite that, males and females learned at an equal rate over the course of testing. For ITD discrimination, in contrast, thresholds did not differ significantly between the sexes for the overall mean or for any block. There also was no statistically significant learning across blocks for either sex. For both tasks and both sexes, the individual thresholds spanned a wide range. The presence of a statistically significant sex difference and learning for ILD but not for ITD discrimination, along with a larger effect size for ILD than for ITD discrimination, suggests that the factors responsible for these outcomes acted upon an ILD-specific neural pathway, and not upon an ITD-specific pathway, nor any pathway common to the two cues. Because the ILD and ITD specific pathways are most separable initially, the factors associated with sex and learning may have acted upon the ILD-specific pathway at an early stage.

No PDF available ABSTRACT The two primary cues to sound-source location on the horizontal plane are interaural differences in time (ITDs) and in level (ILDs). Here, we asked whether the ability to discriminate small changes in each of these interaural cues differs between the sexes. We tested males and females who had no prior experience with any psychoacoustic task on either ILD discrimination at 4 kHz or ITD discrimination at 0.5 kHz. For ILD discrimination, the overall mean threshold, as well as the threshold for each 50-trial block, was significantly lower for males (n = 80) than for females (n = 166). Both males and females learned over the course of testing, but there was no sex difference in learning rate. In contrast, for ITD discrimination, thresholds did not differ significantly between the sexes for the overall mean or for any block (n = 43M/94F). There also was no learning across blocks for either group. For both tasks, the individual thresholds spanned a wide range in each group. The presence of sex differences and learning for ILD but not ITD discrimination suggests that the factors responsible for these outcomes influenced a relatively peripheral ILD-specific pathway, and not an ITD-specific pathway, or a more central locus that is not cue specific.

Distinguishing between regular and irregular heartbeats, conversing with speakers of different accents, and tuning a guitar-all rely on some form of auditory learning. What drives these experience-dependent changes? A growing body of evidence suggests an important role for non-sensory influences, including reward, task engagement, and social or linguistic context. This review is a collection of contributions that highlight how these non-sensory factors shape auditory plasticity and learning at the molecular, physiological, and behavioral level. We begin by presenting evidence that reward signals from the dopaminergic midbrain act on cortico-subcortical networks to shape sound-evoked responses of auditory cortical neurons, facilitate auditory category learning, and modulate the long-term storage of new words and their meanings. We then discuss the role of task engagement in auditory perceptual learning and suggest that plasticity in top-down cortical networks mediates learning-related improvements in auditory cortical and perceptual sensitivity. Finally, we present data that illustrates how social experience impacts sound-evoked activity in the auditory midbrain and forebrain and how the linguistic environment rapidly shapes speech perception. These findings, which are derived from both human and animal models, suggest that non-sensory influences are important regulators of auditory learning and plasticity and are often implemented by shared neural substrates. Application of these principles could improve clinical training strategies and inform the development of treatments that enhance auditory learning in individuals with communication disorders.

Most sounds fluctuate in amplitude, but do listeners attend to the temporal structure of those fluctuations when trying to detect the mere presence of those sounds? This question was addressed by leading listeners to expect a faint sound with a fixed temporal structure (pulse train or steady-state tone) and total duration (300 ms) and measuring their ability to detect equally faint sounds of unexpected temporal structure (pulse train when expecting steady state) and/or total duration (<300 ms). Detection was poorer for sounds with unexpected than with expected total durations, replicating previous outcomes, but was uninfluenced by the temporal structure of the expected sound. The results disagree with computational predictions of the multiple-look model, which posits that listeners attend to both the total duration and temporal structure of the signal, but agree with predictions of the matched-window energy-detector model, which posits that listeners attend to the total duration but not the temporal structure of the signal. Moreover, the matched-window energy-detector model could also account for previous results, including some that were originally interpreted as supporting the multiple-look model. Taken together, at least when detecting faint sounds, listeners appear to attend to the total duration of expected sounds but to ignore their detailed temporal structure.

Extended high frequencies (EHF), above 8 kHz, represent a region of the human hearing spectrum that is generally ignored by clinicians and researchers alike. This article is a compilation of contributions that, together, make the case for an essential role of EHF in both normal hearing and auditory dysfunction. We start with the fundamentals of biological and acoustic determinism - humans have EHF hearing for a purpose, for example, the detection of prey, predators, and mates. EHF hearing may also provide a boost to speech perception in challenging conditions and its loss, conversely, might help explain difficulty with the same task. However, it could be that EHF are a marker for damage in the conventional frequency region that is more related to speech perception difficulties. Measurement of EHF hearing in concert with otoacoustic emissions could provide an early warning of age-related hearing loss. In early life, when EHF hearing sensitivity is optimal, we can use it for enhanced phonetic identification during language learning, but we are also susceptible to diseases that can prematurely damage it. EHF audiometry techniques and standardization are reviewed, providing evidence that they are reliable to measure and provide important information for early detection, monitoring and possible prevention of hearing loss in populations at-risk. To better understand the full contribution of EHF to human hearing, clinicians and researchers can contribute by including its measurement, along with measures of speech in noise and self-report of hearing difficulties and tinnitus in clinical evaluations and studies.