Units of processing in perceptual normalization for speaking rate

Because speaking rates are highly variable, listeners must use cues like phoneme or sentence duration to scale or normalize speech across different contexts. Scaling speech perception in this way allows listeners to distinguish between temporal contrasts, like voiced and voiceless stops, even at different speech speeds. It has long been assumed that this normalization or adjustment of speaking rate can occur over individual phonemes. However, phonemes are often undefined in running speech, so it is not clear that listeners can rely on them for normalization. To evaluate this, we isolate two potential processing units for speaking rate normalization---the phoneme and the syllable---by manipulating phoneme duration in order to cue speaking rate, while also holding syllable duration constant. In doing so, we show that changing the duration of phonemes both with unique acoustic signatures (/k\textscripta/) and overlapping acoustic signatures (/w\textsci/) results in a speaking rate normalization effect. These results suggest that even absent clear acoustic boundaries within syllables, listeners can normalize for rate differences on the basis of individual phonemes.

Neural Model of Coding Stimulus Orientation and Adaptation

The coding of line orientation in the visual system has been investigated extensively. During the prolonged viewing of a stimulus, the perceived orientation continuously changes (normalization effect). Also, the orientation of the adapting stimulus and the background stimuli influence the perceived orientation of the subsequently displayed stimulus: tilt after-effect (TAE) or tilt illusion (TI). The neural mechanisms of these effects are not fully understood. The proposed model includes many local analyzers, each consisting of two sets of neurons. The first set has two independent cardinal detectors (CDs), whose responses depend on stimulus orientation. The second set has many orientation detectors (OD) tuned to different orientations of the stimulus. The ODs sum up the responses of the two CDs with respective weightings and output a preferred orientation depending on the ratio of CD responses. It is suggested that during prolonged viewing, the responses of the CDs decrease: the greater the excitation of the detector, the more rapid the decrease in its response. Thereby, the ratio of CD responses changes during the adaptation, causing the normalization effect and the TAE. The CDs of the different local analyzers laterally inhibit each other and cause the TI. We show that the properties of this model are consistent with both psychophysical and neurophysiological findings related to the properties of orientation perception, and we investigate how these mechanisms can affect the orientation's sensitivity.

X-RAY IRRADIATION AFFECTS MORPHOLOGY, PROLIFERATION AND MIGRATION RATE OF HEALTHY AND CANCER CELLS

Cytoskeleton plays a central role in many cellular processes, such as migration, adhesion and proliferation. Alterations of its structural properties are commonly associated with different diseases (malignancy, cardiac hypertrophy, etc.). In this work, we studied the effects of X-radiations on cytoskeleton architecture of two cell lines: BALBc/3T3 and Simian virus 40-transformed BALBc/3T3 (SVT2) cells. In agreement with the current literature, we observed reduced adhesion and increased motility of SVT2 cells respect to non-transformed BALBc/3T3. In addition, we showed that two different doses of X-rays (1 and 2 Gy) increased cell-dish adhesiveness and reduced cell proliferation and cell motility of transformed cells, whereas minor effects were measured on the normal counterpart. These results suggested that low doses or fractioning of X-rays may have a normalization effect on the investigated parameters for the transformed cell phenotype.