Learning to discriminate frequency modulation rate can benefit and worsen pitch acuity.

Participants were trained to discriminate frequency modulation rates (FM-rate training) or Gabor patch orientations (visual training) in a same-different task for two different training lengths. Test discriminations involved trains of FM sweeps with identical modulation rates, but different frequencies. FM-rate training enhanced test accuracy (relative to visual) when sweep trains contained frequencies similar to training. For extended FM-rate training, the opposite was true for trains shifted one octave higher. In contrast to previous work, generalization of learning to the untrained dimension (pitch) was not well accounted for by conceptual learning. Mechanisms of stimulus learning may better explain the current cross-dimensional generalization.

Temporal dynamics in auditory perceptual learning: impact of sequencing and incidental learning.

Training can improve perceptual sensitivities. We examined whether the temporal dynamics and the incidental versus intentional nature of training are important. Within the context of a birdsong rate discrimination task, we examined whether the sequencing of pretesting exposure to the stimuli mattered. Easy-to-hard (progressive) sequencing of stimuli during preexposure led to a more accurate performance with the critical difficult contrast and greater generalization to new contrasts in the task, compared with equally variable training in either a random or an antiprogressive order. This greater accuracy was also evident when participants experienced the progressively sequenced stimuli in a different incidental learning task that did not involve direct auditory training. The results clearly show the importance of temporal dynamics (sequencing) in learning and show that the progressive training advantages cannot be fully explained by direct associations between stimulus features and the corresponding responses. The current findings are consistent with a hierarchical account of perceptual learning, among other possibilities, but not with explanations that focus on stimulus variability.

Evoked-potential changes following discrimination learning involving complex sounds.

OBJECTIVE: Perceptual sensitivities are malleable via learning, even in adults. We trained adults to discriminate complex sounds (periodic, frequency-modulated sweep trains) using two different training procedures, and used psychoacoustic tests and evoked potential measures (the N1-P2 complex) to assess changes in both perceptual and neural sensitivities. METHODS: Training took place either on a single day, or daily across eight days, and involved discrimination of pairs of stimuli using a single-interval, forced-choice task. In some participants, training started with dissimilar pairs that became progressively more similar across sessions, whereas in others training was constant, involving only one, highly similar, stimulus pair. RESULTS: Participants were better able to discriminate the complex sounds after training, particularly after progressive training, and the evoked potentials elicited by some of the sounds increased in amplitude following training. Significant amplitude changes were restricted to the P2 peak. CONCLUSIONS: Our findings indicate that changes in perceptual sensitivities parallel enhanced neural processing. SIGNIFICANCE: These results are consistent with the proposal that changes in perceptual abilities arise from the brain's capacity to adaptively modify cortical representations of sensory stimuli, and that different training regimens can lead to differences in cortical sensitivities, even after relatively short periods of training.

Multidimensional processing of dynamic sounds: more than meets the ear.

Strong cross-modal interactions exist between visual and auditory processing. The relative contributions of perceptual versus decision-related processes to such interactions are only beginning to be understood. We used methodological and statistical approaches to control for potential decision-related contributions such as response interference, decisional criterion shift, and strategy selection. Participants were presented with rising-, falling-, and constant-amplitude sounds and were asked to detect change (increase or decrease) in sound amplitude while ignoring an irrelevant visual cue of a disk that grew, shrank, or stayed constant in size. Across two experiments, testing context was manipulated by varying the grouping of visual cues during testing, and cross-modal congruency showed independent perceptual and decision-related effects. Whereas a change in testing context greatly affected criterion shifts, cross-modal effects on perceptual sensitivity remained relatively consistent. In general, participants were more sensitive to increases in sound amplitude and less sensitive to sounds paired with dynamic visual cues. As compared with incongruent visual cues, congruent cues enhanced detection of amplitude decreases, but not increases. These findings suggest that the relative contributions of perceptual and decisional processing and the impacts of these processes on cross-modal interactions can vary significantly depending on asymmetries in within-modal processing, as well as consistencies in cross-modal dynamics.

Emotional modulation of the late positive potential (LPP) generalizes to Chinese individuals.

Late positive potential (LPP) is an event-related potential (ERP) component involved in emotional processing that has been consistently observed in Caucasians. Previous studies have demonstrated that emotionally arousing pictures typically elicit larger LPPs than neutral pictures. In the present study, we examined whether the emotional content effect on LPPs generalizes to Chinese individuals. Brain potentials were recorded from participants viewing both emotional and neutral pictures from the international affective picture system (IAPS). Our results showed greater LPPs for emotional than for neutral pictures. The effects of both pleasant and unpleasant pictures appeared relatively early, and lasted for up to 6s. In addition, subjective ratings for picture arousal correlated strongly with corresponding LPP amplitudes. These results replicate previous findings in Caucasians, and suggest that the emotion processes underlying the LPP are more universal than cultural-specific in nature.

The effect of prolonged ED stay on outcome in patients with necrotizing fasciitis.

OBJECTIVE: Overcrowding in hospitals, especially in EDs, is a serious problem in the United States, Europe, and Taiwan. However, the association between prolonged ED boarding stay and mortality in patients with necrotizing fasciitis remains underinvestigated. METHODS: This was a retrospective study. A total of 195 patients were enrolled and analyzed. The sample was divided into 2 groups: nonmortality and mortality. A stepwise logistic regression model was developed to investigate 3 factors of clinical relevance predicting patient mortality. RESULT: The results of the stepwise logistic regression analysis revealed that hypotension (odds ratio [OR], 32.9; 95% confidence interval [CI], 6.9-156.0) and prolonged ED boarding stay (OR, 3.4; 95% CI 1.3-8.6) were both associated with higher mortality. Early operation (OR: 0.16; 95% CI: 0.06-0.45) was associated with lower mortality. CONCLUSION: Prolonged ED boarding stay was associated with increased mortality in patients with necrotizing fasciitis. Early operation (within 24 hours of ED arrival) was associated with decreased mortality.

The easy-to-hard effect in human (Homo sapiens) and rat (Rattus norvegicus) auditory identification.

The authors examined whether progressively training humans and rats to perform a difficult auditory identification task led to larger improvements than extensive training with highly similar sounds (the easy-to-hard effect). Practice improved humans' ability to distinguish sounds regardless of the training regimen. However, progressively trained subjects were more accurate and showed more generalization, despite significantly less training with the stimuli that were the most difficult to distinguish. Rats showed less capacity to improve with practice but still benefited from progressive training. These findings indicate that transitioning from an easier to a more difficult task during training can facilitate, and in some cases may be essential for, auditory perceptual learning. The results are not predicted by an explanation that assumes interaction of generalized excitation and inhibition but are consistent with a hierarchical account of perceptual learning in which the representational precision required to distinguish stimuli determines the mechanisms engaged during learning.