Listening for the Norm: Adaptive Coding in Speech Categorization

Perceptual aftereffects have been referred to as “the psychologist’s microelectrode” because they can expose dimensions of representation through the residual effect of a context stimulus upon perception of a subsequent target. The present study uses such context-dependence to examine the dimensions of representation involved in a classic demonstration of “talker normalization” in speech perception. Whereas most accounts of talker normalization have emphasized talker-, speech-, or articulatory-specific dimensions’ significance, the present work tests an alternative hypothesis: that the long-term average spectrum (LTAS) of speech context is responsible for patterns of context-dependent perception considered to be evidence for talker normalization. In support of this hypothesis, listeners’ vowel categorization was equivalently influenced by speech contexts manipulated to sound as though they were spoken by different talkers and non-speech analogs matched in LTAS to the speech contexts. Since the non-speech contexts did not possess talker, speech, or articulatory information, general perceptual mechanisms are implicated. Results are described in terms of adaptive perceptual coding

How may the basal ganglia contribute to auditory categorization and speech perception?

Listeners must accomplish two complementary perceptual feats in extracting a message from speech. They must discriminate linguistically-relevant acoustic variability and generalize across irrelevant variability. Said another way, they must categorize speech. Since the mapping of acoustic variability is language-specific, these categories must be learned from experience. Thus, understanding how, in general, the auditory system acquires and represents categories can inform us about the toolbox of mechanisms available to speech perception. This perspective invites consideration of findings from cognitive neuroscience literatures outside of the speech domain as a means of constraining models of speech perception. Although neurobiological models of speech perception have mainly focused on cerebral cortex, research outside the speech domain is consistent with the possibility of significant subcortical contributions in category learning. Here, we review the functional role of one such structure, the basal ganglia. We examine research from animal electrophysiology, human neuroimaging, and behavior to consider characteristics of basal ganglia processing that may be advantageous for speech category learning. We also present emerging evidence for a direct role for basal ganglia in learning auditory categories in a complex, naturalistic task intended to model the incidental manner in which speech categories are acquired. To conclude, we highlight new research questions that arise in incorporating the broader neuroscience research literature in modeling speech perception, and suggest how understanding contributions of the basal ganglia can inform attempts to optimize training protocols for learning non-native speech categories in adulthood

Tuned with a Tune: Talker Normalization via General Auditory Processes

Voices have unique acoustic signatures, contributing to the acoustic variability listeners must contend with in perceiving speech, and it has long been proposed that listeners normalize speech perception to information extracted from a talker’s speech. Initial attempts to explain talker normalization relied on extraction of articulatory referents, but recent studies of context-dependent auditory perception suggest that general auditory referents such as the long-term average spectrum (LTAS) of a talker’s speech similarly affect speech perception. The present study aimed to differentiate the contributions of articulatory/linguistic versus auditory referents for context-driven talker normalization effects and, more specifically, to identify the specific constraints under which such contexts impact speech perception. Synthesized sentences manipulated to sound like different talkers influenced categorization of a subsequent speech target only when differences in the sentences’ LTAS were in the frequency range of the acoustic cues relevant for the target phonemic contrast. This effect was true both for speech targets preceded by spoken sentence contexts and for targets preceded by non-speech tone sequences that were LTAS-matched to the spoken sentence contexts. Specific LTAS characteristics, rather than perceived talker, predicted the results suggesting that general auditory mechanisms play an important role in effects considered to be instances of perceptual talker normalization

Differences in Nursery Pigs’ Behavior on the Day of Vaccination

Swine industry feed suppliers are continually striving to develop techniques and tools to reduce the additive stressors imposed on the weanling piglet, to increase advantageous behaviors (feeding and drinking) and to reduce aggressive interactions. One product on the market designed to ease the transition from a liquid diet (sow\u27s milk) to a dry ration is a gel-based feed supplement that was incorporated in this trial as a means to positively affect feeding and drinking behaviors. The objectives of this study were to determine if there were differences in the nursery pigs’ behavior on the day of vaccination when provided a gel supplement. A total of 29 d crossbred pigs (5.94 kg) were housed in Double L® confinement nursery buildings. Four treatments were compared. No vaccine and no gel (control n = 4) defined as unvaccinated and without supplemental gel at days 8 to 10. No vaccine and gel (n = 4) defined as pigs that were provided supplemental gel at days 8 to 10 without vaccination. Vaccinated and no gel (n = 4) defined as pigs that were vaccinated but did not receive supplemental gel at days 8 to 10. Vaccinated and gel (n = 4) defined as pigs that were provided supplemental gel at days 8 to 10 and were vaccinated. The group of four pigs housed together in a pen was considered the experimental unit for data analysis. Definitions for the behaviors and postures recorded and summarized for the trial included the following: Active was defined as standing, this included any upright postures. Inactive posture was defined as sitting or lying postures (both lateral and sternal). Time at drinker was defined as when an individual pig’s mouth was around the water nipple. Time at feeding stations was defined as the time when the individual pig’s head was inside the creep (that contained gel) or the three hole feeder (dry pelleted feed). Nursery aged pigs were less active (P \u3c 0.05; Figure 1) and spent less time (P \u3c 0.05; Figure 2) at the feeding stations 1- h after receiving Mycoplasma hyopneumoniae vaccination, indicating a short term behavioral response to this stressor. These behavioral alterations continued for approximately 6- h (or 5:00 PM the vaccination day afternoon). After this time, all nursery pigs regardless of treatment engaged in the same behavioral repertoire. However, the behavioral repertoire of these nursery pigs were not different over the 3-d trial (previously published worked by Johnson et al., 2008) suggesting that the effects of this vaccination stressor and product were not long lasting

Subthalamic Nucleus and Sensorimotor Cortex Activity During Speech Production

The sensorimotor cortex is somatotopically organized to represent the vocal tract articulators such as lips, tongue, larynx, and jaw. How speech and articulatory features are encoded at the subcortical level, however, remains largely unknown. We analyzed LFP recordings from the subthalamic nucleus (STN) and simultaneous electrocorticography recordings from the sensorimotor cortex of 11 human subjects (1 female) with Parkinson´s disease during implantation of deep-brain stimulation (DBS) electrodes while they read aloud three-phoneme words. The initial phonemes involved either articulation primarily with the tongue (coronal consonants) or the lips (labial consonants). We observed significant increases in high-gamma (60?150 Hz) power in both the STN and the sensorimotor cortex that began before speech onset and persisted for the duration of speech articulation. As expected from previous reports, in the sensorimotor cortex, the primary articulators involved in the production of the initial consonants were topographically represented by high-gamma activity. We found that STN high-gamma activity also demonstrated specificity for the primary articulator, although no clear topography was observed. In general, subthalamic high-gamma activity varied along the ventral?dorsal trajectory of the electrodes, with greater high-gamma power recorded in the dorsal locations of the STN. Interestingly, the majority of significant articulator-discriminative activity in the STN occurred before that in sensorimotor cortex. These results demonstrate that articulator-specific speech information is contained within high-gamma activity of the STN, but with different spatial and temporal organization compared with similar information encoded in the sensorimotor cortex.Fil: Chrabaszcz, Anna. University of Pittsburgh; Estados UnidosFil: Neumann, Wolf Julian. Universität zu Berlin; AlemaniaFil: Stretcu, Otilia. University of Pittsburgh; Estados UnidosFil: Lipski, Witold J.. University of Pittsburgh; Estados UnidosFil: Dastolfo Hromack, Christina A.. University of Pittsburgh; Estados UnidosFil: Bush, Alan. University of Pittsburgh; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Física de Buenos Aires. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Física de Buenos Aires; ArgentinaFil: Wang, Dengyu. Tsinghua University; China. University of Pittsburgh; Estados UnidosFil: Crammond, Donald J.. University of Pittsburgh; Estados UnidosFil: Shaiman, Susan. University of Pittsburgh; Estados UnidosFil: Dickey, Michael W.. University of Pittsburgh; Estados UnidosFil: Holt, Lori L.. University of Pittsburgh; Estados UnidosFil: Turner, Robert S.. University of Pittsburgh; Estados UnidosFil: Fiez, Julie A.. University of Pittsburgh; Estados UnidosFil: Richardson, R. Mark. University of Pittsburgh; Estados Unido