Olfactory habituation to food and nonfood odours.

Olfactory perception can be modulated by the repeated exposure to odours. Olfactory habituation is a reduced behavioural response to repetitive stimulation. Edibility is considered an important top-down feature that can affect olfactory perception, but whether it could modulate olfactory habituation when food or nonfood odours are repeatedly smelled remains unclear. Indeed, due to their ecological salience, food odours attract attention automatically which might slow down habituation. This registered report aimed to determine whether olfactory habituation shows a different pattern when participants are presented with food or nonfood odours. In a within-subject design, 50 participants were tested under satiated and fasted states in separated experimental sessions. In each session, participants were exposed to the same food and nonfood odour in different blocks of 20 trials each. Participants rated the perceived odour intensity and pleasantness after each trial. We used an intermittent odour presentation to reduce olfactory fatigue while capitalising on the effect of cognitive states on habituation. Linear mixed-effects models showed that the perceived odour intensity decreased over time only for nonfood odours. Conversely, the perceived odour pleasantness decreased significantly more across trials for food odours. These effects were retrieved regardless of the participant's hunger state. Our results are in line with the olfactory-specific satiety theory which posits a specific decrease in the perceived pleasantness of food odours, without changes in the perceived odour intensity. In short, our findings indicate that perceived odour edibility modulates olfactory habituation, extending the previous literature on the impact of top-down factors on olfactory perception.

Perceptual association enhances intersensory temporal precision.

The brain is able to extract associative regularities between stimuli and readjust the perceived timing of correlated sensory signals. In order to elucidate whether these two mechanisms interact with each other or not, we exposed participants to two different visual stimuli (a circle and a triangle) that appeared continuously and unpredictably, for 5min. While the circle always preceded the tone for 700ms, the triangle did not. Yet, the triangle could appear, by chance, before and after the tone, and between the circle and the tone. In two different test blocks, conducted before and after the 5-min exposure phase, participants performed simultaneity judgments regarding one of the visual stimuli (the circle or the triangle) and the exposed tone presented at different stimulus onset asynchronies. The results revealed that the precision at judging the temporal relation between the 'associated figure' (the circle) and the tone increased significantly after the 5-min exposure. This effect was not observed for the non-associated figure (the triangle) and occurred even when participants reported to be unaware of any association between the stimuli presented. This pattern of results indicates that the perceptual association between sensory signals can influence their subjective temporal processing.

Early detection of subtle motor dysfunction in cognitively normal subjects with amyloid-ß positivity.

Since the current neuropsychological assessments are not sensitive to subtle deficits that may be present in cognitively normal subjects with amyloid-ß positivity, more accurate and efficient measures are needed. Our aim was to investigate the presence of subtle motor deficits in this population and its relationship with cerebrospinal fluid (CSF) amyloid-ß levels. We adapted the Finger Tapping Task to measure tapping speed and intrasubject variability. Seventy-two right-handed participants completed the study. Subjects were divided into three groups according to their CSF biomarker profile: 37 control participants (negative CSF AD biomarkers, CTR), 20 cognitively normal subjects with amyloid-ß positivity (abnormal levels of CSF Aß42, Aß+) and 15 AD patients. All subjects underwent lumbar puncture for the CSF analysis, apolipoprotein E genotyping and completed the Finger Tapping Task, a neuropsychological battery and cardiovascular risk factor and physical activity assessments. An overall difference between groups was found both in tapping speed [F(2,66) = 19.37, p < .01] and in intrasubject variability [F(2,66) = 11.40, p < .01]. More specifically, the Aß+ group showed lower speed [F(1,52) = 5.33, p < .05] and greater intrasubject variability [F(1,52) = 8.48, p < .01] than the CTR group, and higher speed than the AD group [F(1,30) = 13.61, p < .01]. Speed (ß = .263, p < .05) and intrasubject variability (ß = -.558, p < .01) were significantly associated with CSF amyloid-ß levels. The present findings suggest that subtle motor difficulties can be detected in cognitively healthy subjects with amyloid-ß positivity and be related to CSF Aß42 levels. An accurate assessment of motor functions could help on identifying individuals at the earliest stage of the Alzheimer's continuum.

Seeing music: The perception of melodic 'ups and downs' modulates the spatial processing of visual stimuli.

Musical melodies have "peaks" and "valleys". Although the vertical component of pitch and music is well-known, the mechanisms underlying its mental representation still remain elusive. We show evidence regarding the importance of previous experience with melodies for crossmodal interactions to emerge. The impact of these crossmodal interactions on other perceptual and attentional processes was also studied. Melodies including two tones with different frequency (e.g., E4 and D3) were repeatedly presented during the study. These melodies could either generate strong predictions (e.g., E4-D3-E4-D3-E4-[D3]) or not (e.g., E4-D3-E4-E4-D3-[?]). After the presentation of each melody, the participants had to judge the colour of a visual stimulus that appeared in a position that was, according to the traditional vertical connotations of pitch, either congruent (e.g., high-low-high-low-[up]), incongruent (high-low-high-low-[down]) or unpredicted with respect to the melody. Behavioural and electroencephalographic responses to the visual stimuli were obtained. Congruent visual stimuli elicited faster responses at the end of the experiment than at the beginning. Additionally, incongruent visual stimuli that broke the spatial prediction generated by the melody elicited larger P3b amplitudes (reflecting 'surprise' responses). Our results suggest that the passive (but repeated) exposure to melodies elicits spatial predictions that modulate the processing of other sensory events.

Does Language Influence the Vertical Representation of Auditory Pitch and Loudness?

Higher frequency and louder sounds are associated with higher positions whereas lower frequency and quieter sounds are associated with lower locations. In English, "high" and "low" are used to label pitch, loudness, and spatial verticality. By contrast, different words are preferentially used, in Catalan and Spanish, for pitch (high: "agut/agudo"; low: "greu/grave") and for loudness/verticality (high: "alt/alto"; low: "baix/bajo"). Thus, English and Catalan/Spanish differ in the spatial connotations for pitch. To analyze the influence of language on these crossmodal associations, a task was conducted in which English and Spanish/Catalan speakers had to judge whether a tone was higher or lower (in pitch or loudness) than a reference tone. The response buttons were located at crossmodally congruent or incongruent positions with respect to the probe tone. Crossmodal correspondences were evidenced in both language groups. However, English speakers showed greater effects for pitch, suggesting an influence of linguistic background.

Subtle visuomotor difficulties in preclinical Alzheimer's disease.

BACKGROUND: Individuals with preclinical Alzheimer's disease (Pre-AD) present nonimpaired cognition, as measured by standard neuropsychological tests. However, detecting subtle difficulties in cognitive functions may be necessary for an early diagnosis and intervention. OBJECTIVES: A new computer-based visuomotor coordination task (VMC) was developed to investigate the possible presence of early visuomotor difficulties in Pre-AD individuals. Associations between VMC task performance and AD biomarkers were studied. The influence of ApoE status on participants' performance was addressed, as well as the relationship between performance and subjective cognitive decline (SCD). METHODS: Sixty-six cognitively normal (CN) elders (19 Pre-AD and 47 control participants [CTR]) and 15 patients with AD performed the VMC task, which consisted in executing visually guided goal-directed movements that required the coordination of the visual and motor systems. All participants underwent ApoE analysis and lumbar puncture. CN participants also completed an extensive standard neuropsychological battery. RESULTS: Despite presenting normal cognition in standard tests, Pre-AD participants exhibited higher response times (RTs) to complete the VMC task than CTR (p < .01). Besides, patients with AD showed higher RTs than CTR (p < .001) and Pre-AD (p < .05), and more errors than CTR (p < .005). RTs in ApoE4 carriers were higher than that observed in ApoE4 noncarriers (p < .01). In CN individuals, RTs were related to amyloid ß-protein 42 (AB42) biomarker (p < .01) and informant-rated SCD (p < .01). CONCLUSIONS: The VMC task is able to discriminate Pre-AD from CTR individuals. Moreover, VMC results are associated with AB42 levels in CN individuals, suggesting that visuomotor dysfunction may be a sensitive marker of Pre-AD.

How big is this sound? Crossmodal association between pitch and size in infants.

We examined 4- and 6-month-old infants' sensitivity to the perceptual association between pitch and object size. Crossmodal correspondence effects were observed in 6-month-old infants but not in younger infants, suggesting that experience and/or further maturation is needed to fully develop this crossmodal association.

Realigning thunder and lightning: temporal adaptation to spatiotemporally distant events.

The brain is able to realign asynchronous signals that approximately coincide in both space and time. Given that many experience-based links between visual and auditory stimuli are established in the absence of spatiotemporal proximity, we investigated whether or not temporal realignment arises in these conditions. Participants received a 3-min exposure to visual and auditory stimuli that were separated by 706 ms and appeared either from the same (Experiment 1) or from different spatial positions (Experiment 2). A simultaneity judgment task (SJ) was administered right afterwards. Temporal realignment between vision and audition was observed, in both Experiment 1 and 2, when comparing the participants' SJs after this exposure phase with those obtained after a baseline exposure to audiovisual synchrony. However, this effect was present only when the visual stimuli preceded the auditory stimuli during the exposure to asynchrony. A similar pattern of results (temporal realignment after exposure to visual-leading asynchrony but not after exposure to auditory-leading asynchrony) was obtained using temporal order judgments (TOJs) instead of SJs (Experiment 3). Taken together, these results suggest that temporal recalibration still occurs for visual and auditory stimuli that fall clearly outside the so-called temporal window for multisensory integration and appear from different spatial positions. This temporal realignment may be modulated by long-term experience with the kind of asynchrony (vision-leading) that we most frequently encounter in the outside world (e.g., while perceiving distant events).