Linear mixed-effects models (LMMs) are increasingly being used for data analysis in cognitive neuroscience and experimental psychology, where within-participant designs are common. The current article provides an introductory review of the use of LMMs for within-participant data analysis and describes a free, simple, graphical user interface (LMMgui). LMMgui uses the package lme4 (Bates et al., 2014a,b) in the statistical environment R (R Core Team).

In humans, horizontal sound localization of low-frequency sounds is mainly based on interaural time differences (ITDs). Traditionally, it was assumed that ITDs are converted into a topographic (or rate-place) code, supported by an array of neurons with parametric tuning to ITDs within the behaviorally relevant range. Although this topographic model has been confirmed in owls, its applicability to mammals has been challenged by recent physiological results suggesting that, at least in small-headed species, ITDs are represented by a nontopographic population rate code, which involves only two opponent (left and right) channels, broadly tuned to ITDs from the two auditory hemifields. The current study investigates which of these two models of ITD processing is more likely to apply to humans. For that, evoked responses to abrupt changes in the ITDs of otherwise continuous sounds were measured with electroencephalography. The ITD change was either away from ("outward" change) or toward the midline ("inward" change). According to the opponent-channel model, the response to an outward ITD change should be larger than the response to the corresponding inward change, whereas the topographic model would predict similar response sizes for both conditions. The measured response sizes were highly consistent with the predictions of the opponent-channel model and contravened the predictions of the topographic model, suggesting that, in humans, ITDs are coded nontopographically. The hemispheric distributions of the ITD change responses suggest that the majority of ITD-sensitive neurons in each hemisphere are tuned to ITDs from the contralateral hemifield.

In highly proficient, early bilinguals, behavioural studies of the cost of switching language or task suggest qualitative differences between language control and domain-general cognitive control. By contrast, several neuroimaging studies have shown an overlap of the brain areas involved in language control and domain-general cognitive control. The current study measured both behavioural responses and eventrelated potentials (ERPs) from bilinguals who performed picture naming in single-or mixed-language contexts, as well as an alphanumeric categorisation task in single-or mixed-task context. Analysis of switch costs during the mixed-context conditions showed qualitative differences between language control and domain-general cognitive control. A 2 Â 2 ANOVA of the ERPs, with domain (linguistic, alphanumeric) and context (single, mixed) as within-participant factors, revealed a significant interaction, which also suggests a partly independent language-control mechanism. Source estimations revealed the neural basis of this mechanism to be in bilateral frontal-temporal areas.

Binaural sluggishness refers to the binaural system's inability to follow fast changes in the interaural configuration of the incoming sound stream. Several studies have measured binaural sluggishness by measuring signal detection in conditions of binaural unmasking when the interaural configuration of the masker is changed over time. However, it has been shown that, in conditions of binaural unmasking, binaural sluggishness also affects the perception of temporal changes in the properties of the signal (i.e., its frequency or level) and not just in the interaural configuration of the masker. By measuring the temporal modulation transfer function for sinusoidally modulated noise presented in conditions of binaural unmasking, the first experiment of the current study showed that, due to binaural sluggishness, the internal representation of binaurally unmasked sounds conveys little or no information about envelope fluctuations with rates within the pitch range (i.e., above 30 Hz). The second experiment measured the masked detection threshold for musical interval recognition in binaurally unmasked harmonic tones and showed that, in conditions of binaural unmasking, pitch wanes when the harmonics become unresolved by the cochlear filters. These results suggest that binaural sluggishness precludes temporal pitch processing based on envelope cues in binaurally unmasked sounds.