Neural correlates of responses to emotionally valenced olfactory, visual, and auditory stimuli were examined using positron emission tomography. Twelve volunteers were scanned using the water bolus method. For each sensory modality, regional cerebral blood flow (rCBF) during presentation of both pleasant and unpleasant stimuli was compared with that measured during presentation of neutral stimuli. During the emotionally valenced conditions, subjects performed forced-choice pleasant and unpleasant judgments. During the neutral conditions, subjects were asked to select at random one of a two key-press buttons. All stimulations were synchronized with inspiration, using an airflow olfactometer, to present the same number of stimuli for each sensory modality. A no-stimulation control condition was also performed in which no stimulus was presented. For all three sensory modalities, emotionally valenced stimuli led to increased rCBF in the orbitofrontal cortex, the temporal pole, and the superior frontal gyrus, in the left hemisphere. Emotionally valenced olfactory and visual but not auditory stimuli produced additional rCBF increases in the hypothalamus and the subcallosal gyrus. Only emotionally valenced olfactory stimuli induced bilateral rCBF increases in the amygdala. These findings suggest that pleasant and unpleasant emotional judgments recruit the same core network in the left hemisphere, regardless of the sensory modality. This core network is activated in addition to a number of circuits that are specific to individual sensory modalities. Finally, the data suggest a superior potency of emotionally valenced olfactory over visual and auditory stimuli in activating the amygdala.Key words: emotion; hedonic judgment; odor processing; visual processing; auditory processing; PET Everyday, we make numerous judgments about the pleasantness or unpleasantness of external sensory stimuli. Exposure to such stimuli can induce subjective emotional experiences such as pleasure or fear and behavioral responses aimed at engaging or avoiding continued exposure. Neurobehavioral studies in animals have historically implicated structures related to the limbic system in these emotional processes, with a particular emphasis on the amygdala and hypothalamus (LeDoux, 1987(LeDoux, , 1995Davis, 1992;Rolls, 1999). Electrophysiological and lesion studies also indicate that the orbitofrontal cortex (OFC) makes a significant contribution to these processes in animals (Zald and Kim, 1996b;Rolls, 1999).Several recent neuroimaging studies have attempted to delineate the cortical and subcortical regions involved in processing emotionally valenced stimuli in humans. Such studies have examined responses to pleasant and/or unpleasant visual (Cahill et al

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The aim of this study was to provide evidence that memory and perceptual processing are underpinned by the same mechanisms. Specifically, the authors conducted 3 experiments that emphasized the sensory aspect of memory traces. They examined their predictions with a short-term priming paradigm based on 2 distinct phases: a learning phase consisting of the association between a geometrical shape and a white noise and a priming phase examining the priming effect of the geometrical shape, seen in the learning phase, on the processing of target tones. In the 3 experiments, the authors found that only the prime associated with the sound in the learning phase had an effect on the target processing. The perceptual nature of the auditory component reactivated by the prime was shown in Experiments 1 and 2 via manipulation of the white noise duration in the learning phase and the stimulus onset asynchrony in the priming phase. Moreover, Experiment 3 highlighted the importance of the simultaneous association of sensory components in the learning phase, which makes it possible to integrate these components in a memory trace.

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The aim of the present study was to show the perceptual nature of conceptual knowledge by using a priming paradigm that excluded an interpretation exclusively in terms of amodal representation. This paradigm was divided into two phases. The first phase consisted in learning a systematic association between a geometrical shape and a white noise. The second phase consisted of a short-term priming paradigm in which a primed shape (either associated or not with a sound in the first phase) preceded a picture of an object, which the participants had to categorize as representing a large or a small object. The objects were chosen in such a way that their principal function either was associated with the production of noise ("noisy" target) or was not typically associated the production of noise ("silent" target). The stimulus onset asynchrony (SOA) between the prime and the target was 100 ms or 500 ms. The results revealed an interference effect with a 100-ms SOA and a facilitatory effect with a 500-ms SOA for the noisy targets only. We interpreted the interference effect obtained at the 100-ms SOA as the result of an overlap between the components reactivated by the sound prime and those activated by the processing of the noisy target. At an SOA of 500 ms, there was no temporal overlap. The observed facilitatory effect was explained by the preactivation of auditory areas by the sound prime, thus facilitating the categorization of the noisy targets only.

Two experiments studied the necessary conditions for the occurrence of repetition priming and word frequency effect on priming in a lexical decision task. To examine the role of prime processing duration, the prime was presented either for 50 ms or for 700 ms, and an interfering task was introduced between the prime and the target in order to restrict the time during which the prime was effectively processed and to limit it to exactly 50 ms or 700 ms. The interstimulus interval (ISI) between the prime and the target was 1500 ms or 3000 ms in Expt 1, and 600 ms in Expt 2. With primes presented for 50 ms, repetition priming effects were not dependent on target frequency, decreased with an increase of the ISI, and were no longer significant with an ISI of 3000 ms. With primes presented for 700 ms, repetition priming was systematically larger for low-frequency words than for high-frequency words, and remained reliable even with an ISI of 3000 ms. Thus, a minimum of prime duration was required both for maintaining repetition priming effects over more than some hundreds of milliseconds and for the occurrence of frequency effect on repetition priming. Theoretical interpretations of these results are discussed.

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Summary Slow wave sleep (SWS) is known to favour episodic memory consolidation. Given that ageing is associated with a reduction in SWS and episodic memory impairment, our aim was to investigate whether memory continues to benefit from sleep in older adults. Episodic memory consolidation was tested in 20 young (22.1 ± 1.7 years) and 20 older volunteers (68.9 ± 5.3 years) who performed a visuospatial two‐dimensional object‐location task. Retention capacities were evaluated after 12 h of wakefulness or 12 h of sleep. Performances before and after the interval allowed us to calculate a forgetting rate. Sleep architecture was measured by polysomnography (older adults = 410 min; young adults: 467 min). Our results showed that the beneficial effect of sleep on memory consolidation was reduced in older adults compared to young adults. In older adults, sleep did not enhance memory consolidation significantly compared to wakefulness. Sleep prevented young adults from forgetting (−0.10% ± 2.1), while the forgetting rate in older adults was still important after a period of sleep (16.60% ± 4.2; P = 0.05). The sleep architecture of older adults was characterized by a decrease in sleep efficiency (−12%; P < 0.05), in total cycle time (−137 min; P < 0.05), in percentage of total cycle time (−21%; P < 0.05) and in rapid eye movement time (−41 min; P < 0.05) compared to young adults. However, no difference in slow wave sleep was observed (−1%; not significant) and no correlation was found with performance. Age‐related changes in sleep parameters may have a negative impact on memory consolidation in older adults.