Neuromagnetic Evidence for Early Auditory Restoration of Fundamental Pitch

Background: Understanding the time course of how listeners reconstruct a missing fundamental component in an auditory stimulus remains elusive. We report MEG evidence that the missing fundamental component of a complex auditory stimulus is recovered in auditory cortex within 100 ms post stimulus onset. Methodology: Two outside tones of four-tone complex stimuli were held constant (1200 Hz and 2400 Hz), while two inside tones were systematically modulated (between 1300 Hz and 2300 Hz), such that the restored fundamental (also knows as ‘‘virtual pitch’’) changed from 100 Hz to 600 Hz. Constructing the auditory stimuli in this manner controls for a number of spectral properties known to modulate the neuromagnetic signal. The tone complex stimuli only diverged on the value of the missing fundamental component. Principal Findings: We compared the M100 latencies of these tone complexes to the M100 latencies elicited by their respective pure tone (spectral pitch) counterparts. The M100 latencies for the tone complexes matched their pure sinusoid counterparts, while also replicating the M100 temporal latency response curve found in previous studies. Conclusions: Our findings suggest that listeners are reconstructing the inferred pitch by roughly 100 ms after stimulus onset and are consistent with previous electrophysiological research suggesting that the inferential pitch is perceived i

Freezing of Enkephalinergic Functions by Multiple Noxious Foci: A Source of Pain Sensitization?

BACKGROUND:The functional significance of proenkephalin systems in processing pain remains an open question and indeed is puzzling. For example, a noxious mechanical stimulus does not alter the release of Met-enkephalin-like material (MELM) from segments of the spinal cord related to the stimulated area of the body, but does increase its release from other segments. METHODOLOGY/PRINCIPAL FINDINGS:Here we show that, in the rat, a noxious mechanical stimulus applied to either the right or the left hind paw elicits a marked increase of MELM release during perifusion of either the whole spinal cord or the cervico-trigeminal area. However, these stimulatory effects were not additive and indeed, disappeared completely when the right and left paws were stimulated simultaneously. CONCLUSION/SIGNIFICANCE:We have concluded that in addition to the concept of a diffuse control of the transmission of nociceptive signals through the dorsal horn, there is a diffuse control of the modulation of this transmission. The "freezing" of Met-enkephalinergic functions represents a potential source of central sensitization in the spinal cord, notably in clinical situations involving multiple painful foci, e.g. cancer with metastases, poly-traumatism or rheumatoid arthritis

No frequency shift in the “D” notes of Carolina chickadee calls in response to traffic noise

Loud, low-frequency traffic noise can mask songbird vocalizations, and populations of some urban songbird species have shifted the frequency of their vocalizations upward in response. However, the spectral structure of certain vocalization elements may make them resistant to masking, suggesting that species that use these notes could be more successful in areas with high levels of traffic noise. To test this idea, we recorded Carolina chickadees (Poecile carolinensis), whose calls feature “D” notes with an overtone spectral structure, along a traffic noise gradient in Durham and Orange Counties, North Carolina, USA. Frequency parameters of “D” notes did not change with noise level suggesting the possibility that these notes can be communicated effectively in noise, but further investigation is needed to test this hypothesis directly. In addition, we performed a playback experiment demonstrating how the use of spectrograms to measure note frequencies is unreliable, especially when recordings are made in noisy areas. We used an alternative method based on the predictable frequency structure of “D” notes. Our experiment is one of few that address the effects of urban noise on calls produced by both sexes as opposed to song produced only by males during the breeding season. Understanding how vocalizationswith different spectral structures may be affected differentially by traffic noise will increase our ability to predict how the expansion of noisy areas may impact songbird community composition in the future