The Neural and Behavioral Correlates of Auditory Streaming

Perceptual representations of auditory stimuli—which are called auditory streams or objects—are derived from the auditory system\u27s ability to segregate and group stimuli based upon spectral, temporal, and spatial features. However, it remains unclear how our auditory system encodes these auditory streams at the level of the single neuron. In order to address this question directly, we first validated an animal model of auditory streaming. Specifically, we trained rhesus macaques to report their streaming percept using methodologies and controls similar to those presented in previous human studies. We found that the monkeys\u27 behavioral reports were qualitatively consistent with those of human listeners. Next, we recorded from neurons in the primary auditory cortex while monkeys simultaneously reported their streaming percepts. We found that A1 neurons had frequency-tuned responses that habituated, independent of frequency content, as the auditory sequence unfolded over time; and we report for the first time that firing rate of A1 neurons was modulated by the monkeys’ choices. This modulation increased with listening time and was independent of the frequency difference between consecutive tone bursts. Overall, our results suggest that A1 activity contributes to the sensory evidence underlying the segregation and grouping of acoustic stimuli into distinct auditory streams. However, because we observe choice-related activity based upon firing rate alone, our data are at partially at odds with Micheyl et al.’s (2005) prominent hypothesis, which argued that frequency-dependent habituation may be a coding mechanism for the streaming percept

Impact of Race and Insurance on Door-to-Appendectomy Time among Pediatric Patients

Racial and ethnic disparities in the rate of appendiceal rupture have been widely reported among the pediatric population. The main reasons for this remain largely unknown given that previous explanations pointing to signs of poor health care access have recently been shown to account for only a small percentage of the difference in perforation rates between white and minority children. Because the risk of perforation increases with time, racial disparities in time delay from emergency department presentation to OR appendectomy may help account for the higher appendiceal perforation rates observed among minority children. This is the first study dedicated to analyzing racial differences in door-to-appendectomy time. Insurance status and language barriers were also considered as variables of interest. Retrospective, observational study using admission and treatment data of 607 consecutive children less than or equal to 18 years of age with surgical confirmation of appendicitis. Patients were admitted from February 2, 2013 (start of electronic medical record use) to April 27, 2017. A significant association was found between race and perforation rate (p0.05 for all). Door-to-appendectomy times were also not significantly longer for Medicaid/uninsured patients (613 minutes) compared to private insurance patients (597 minutes) (p=0.60), nor for patients with language barriers (545 minutes) compared to patients without (612 minutes) (p=0.23). While there was a higher appendiceal perforation rate among minority children, it was not due to differences in door-to-appendectomy time. Insurance status and language barriers also did not lead to differential treatment among pediatric patients

The Contribution of Primary Auditory Cortex to Auditory Categorization in Behaving Monkeys

The specific contribution of core auditory cortex to auditory perception –such as categorization– remains controversial. To identify a contribution of the primary auditory cortex (A1) to perception, we recorded A1 activity while monkeys reported whether a temporal sequence of tone bursts was heard as having a “small” or “large” frequency difference. We found that A1 had frequency-tuned responses that habituated, independent of frequency content, as this auditory sequence unfolded over time. We also found that A1 firing rate was modulated by the monkeys’ reports of “small” and “large” frequency differences; this modulation correlated with their behavioral performance. These findings are consistent with the hypothesis that A1 contributes to the processes underlying auditory categorization

Modulation of Cross-Frequency Coupling by Novel and Repeated Stimuli in the Primate Ventrolateral Prefrontal Cortex

Adaptive behavior depends on an animal’s ability to ignore uninformative stimuli, such as repeated presentations of the same stimulus, and, instead, detect informative, novel stimuli in its environment. The primate prefrontal cortex (PFC) is known to play a central role in this ability. However, the neural mechanisms underlying the ability to differentiate between repeated and novel stimuli are not clear. We hypothesized that the coupling between different frequency bands of the local field potential (LFP) underlies the PFC’s role in differentiating between repeated and novel stimuli. Specifically, we hypothesized that whereas the presentation of a novel-stimulus induces strong cross-frequency coupling, repeated presentations of the same stimulus attenuates this coupling. To test this hypothesis, we recorded LFPs from the ventrolateral PFC (vPFC) of rhesus monkeys while they listened to a novel vocalization and repeated presentations of the same vocalization. We found that the cross-frequency coupling between the gamma-band amplitude and theta-band phase of the LFP was modulated by repeated presentations of a stimulus. During the first (novel) presentation of a stimulus, gamma-band activity was modulated by the theta-band phase. However, with repeated presentations of the same stimulus, this cross-frequency coupling was attenuated. These results suggest that cross-frequency coupling may play a role in the neural computations that underlie the differentiation between novel and repeated stimuli in the vPFC

Prognostic Factors and Survival in Pediatric and Adolescent Liposarcoma

Purpose. Liposarcoma is extremely rare in the pediatric population. To identify prognostic factors and determine treatment outcomes, we reviewed our institutional experience with pediatric liposarcoma. Methods. We retrospectively reviewed all pediatric patients (age < 22 years) with confirmed liposarcoma treated at Memorial Sloan-Kettering Cancer Center. Histologic subtype, tumor location, margin status, recurrence, and adjuvant therapy were analyzed and correlated with overall survival. Results. Thirtyfour patients (56% male) with a median age of 18.1 years were identified. Twenty-two (65%) had peripheral tumors and 12 (35%) had centrally located tumors. Histologically, 29 (85%) tumors were low grade, and 5 (15%) were high grade pleomorphic. Eleven (32%) had recurrent disease, 9 patients with central tumors and 2 patients with peripheral lesions. Eight deaths occurred, all in patients with central disease. Five-year overall survival was 78%, with a median follow-up time of 5.4 years (range, 0.3-30.3 years). Tumor grade (P = .003), histologic subtype (P = .01), and primary location (P < .001) all correlated with survival, as did stage (P < .001) and margin status (P = .001). Conclusions. Central location of the primary tumor, high tumor grade, and positive surgical margins are strongly correlated with poor survival in pediatric patients with liposarcoma

Shifting patterns of genomic variation in the somatic evolution of papillary thyroid carcinoma

Shows Single Nucleotide Substitutions in the MAPK Pathway. (XLSX 43 kb

Stream segregation in the anesthetized auditory cortex

Auditory stream segregation describes the way that sounds are perceptually segregated into groups or streams on the basis of perceptual attributes such as pitch or spectral content. For sequences of pure tones, segregation depends on the tones' proximity in frequency and time. In the auditory cortex (and elsewhere) responses to sequences of tones are dependent on stimulus conditions in a similar way to the perception of these stimuli. However, although highly dependent on stimulus conditions, perception is also clearly influenced by factors unrelated to the stimulus, such as attention. Exactly how ‘bottom-up’ sensory processes and non-sensory ‘top-down’ influences interact is still not clear. Here, we recorded responses to alternating tones (ABAB …) of varying frequency difference (FD) and rate of presentation (PR) in the auditory cortex of anesthetized guinea-pigs. These data complement previous studies, in that top-down processing resulting from conscious perception should be absent or at least considerably attenuated. Under anesthesia, the responses of cortical neurons to the tone sequences adapted rapidly, in a manner sensitive to both the FD and PR of the sequences. While the responses to tones at frequencies more distant from neuron best frequencies (BFs) decreased as the FD increased, the responses to tones near to BF increased, consistent with a release from adaptation, or forward suppression. Increases in PR resulted in reductions in responses to all tones, but the reduction was greater for tones further from BF. Although asymptotically adapted responses to tones showed behavior that was qualitatively consistent with perceptual stream segregation, responses reached asymptote within 2 s, and responses to all tones were very weak at high PRs (>12 tones per second). A signal-detection model, driven by the cortical population response, made decisions that were dependent on both FD and PR in ways consistent with perceptual stream segregation. This included showing a range of conditions over which decisions could be made either in favor of perceptual integration or segregation, depending on the model ‘decision criterion’. However, the rate of ‘build-up’ was more rapid than seen perceptually, and at high PR responses to tones were sometimes so weak as to be undetectable by the model. Under anesthesia, adaptation occurs rapidly, and at high PRs tones are generally poorly represented, which compromises the interpretation of the experiment. However, within these limitations, these results complement experiments in awake animals and humans. They generally support the hypothesis that ‘bottom-up’ sensory processing plays a major role in perceptual organization, and that processes underlying stream segregation are active in the absence of attention