Emotional responses to pleasant and unpleasant olfactory, visual, and auditory stimuli: a positron emission tomography study.

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.

[Emotional processes in schizophrenia: investigation of the evaluative component]. / Processus émotionnel dans la schizophrénie: étude de la composante d'évaluation.

Schizophrenia is a disease that constitutes a particularly relevant way to investigate emotional processing. Indeed, major clinical signs of emotional disturbance (eg, anhedonia) suggest that some emotional mechanisms are defective in patients with schizophrenia. Evaluation can be considered as a fundamental component of the emotional system (28) and the first aim of the present study was to test the polarity hypothesis according to which different mechanisms are involved in the evaluation of positive vs negative emotional events. The second aim was to disentangle a -paradox emerging from the schizophrenia literature. On one hand, the tendency that schizophrenic patients have to under-evaluate the level of unpleasantness of negative stimuli suggests a deficit in the evaluation of negative events. For instance, it was proposed that patients with schizophrenia show a major deficit in the recognition of negative emotions, but a preserved recognition of positive emotions. On the other hand, the fact that anhedonia constitutes a critical cli-nical feature of schizophrenia suggests a deficit in the eva-luation of positive events. For instance, Crespo-Facorro et al. showed that patients with schizophrenia had a tendency to under-evaluate the level of pleasantness of positive stimuli but correctly evaluated the level of unpleasantness of negative stimuli. Given the importance of the social component in the analysis of deficits in patients with schizophrenia, we hypothesized that the variation of this component in stimuli used in the literature could explain the apparently inconsistent results described above. For example, the Bell et al. study used social stimuli whereas the Crespo-Facorro et al. study used non-social stimuli. Therefore, in our study, we have decided to manipulate the social component of stimuli. Another research issue of the present experiment was to study the explicit and/or implicit mode of processing of eva-luation in schizophrenic patients. In general, the experimental logic was to expect interaction effects between the factors polarity (negative vs positive) and participants (schizophrenic patients vs controls). Moreover, given the potential importance of the social component, a three-way interaction of the factors polarity, participants, and social component was expected. Finally, the experimental paradigm allowed us to search for dissociations in the context of both explicit and implicit evaluation. Stimuli used were negative and positive emotional pictures from the International Affective Picture System. Stimuli were chosen so that the mean valence -ratings of negative and positive pictures were at the same distance from neutrality. The factor arousal was controlled so that negative and positive pictures had equivalent mean arousal ratings. The social component factor was operatio-nalized by selecting pictures that either depicted or not a social scene. A fundamental criterion was that all social pictures were depicting at least one human being (eg, a wedding or a funeral), whereas non-social pictures never depicted any human being (eg, animals and landscapes). An upper and a lower border, that were either identical or different, were added to each picture. In a first experiment (the "implicit-task experiment"), patients with schizophrenia and matched controls were requested to decide whether the two borders surrounding the pictures were identical or different. Asking participants to process the borders was an experimental ruse to test if emotional processing takes place even when it is not task-relevant, and therefore if it is implicit. In a second experiment (the "explicit-task experiment"), the same participants were requested to evaluate whether the pictures were pleasant or unpleasant. Analyses of variance (ANOVA) were computed on response time and number of correct responses for both tasks. An important result was the observation of the expected three-way interaction effect of the factors polarity, participants, and social component on response time in the explicit task F(1, 19)=4.8, p<0.05. Critically, we observed that, for non-social stimuli, the interaction effect of the factors participants and polarity on response time was significant in the explicit task, F(1, 8)=4.9, p<0.05. These results are consistent with the polarity hypothesis and suggest a deficit in the processing of non-social positive stimuli in patients with schizophrenia. The expected three-way interaction effect was also observed on the number of correct responses in the explicit task F(1, 19)=5, p<0.04. For this task, we critically observed that, for social stimuli, the interaction effect of the factors participants and polarity on the number of correct responses was significant F(1, 19)=8.4, p<0.04. These results are also consistent with the polarity hypothesis and suggest a deficit in the processing of social negative stimuli in patients with schizophrenia. Moreover, let us notice that a comparison of the performances of the two groups revealed that patients made significantly more errors than controls for the evaluation of non-social positive stimuli, F(1, 19)=10,5, p<0.001, but not for the evaluation of non-social negative stimuli, F<1. In the implicit-task experiment, the analysis revealed that patients had a tendency to make more errors in the judgment of borders configuration for negative than for positive stimuli, whereas control participants showed the opposite tendency F(1, 19)=5.7, p<0.03, for the interaction of the factors polarity and participants. This result is consistent with the idea that distinct cognitive mechanisms are involved in the evaluation of positive vs negative emotional events even in the context of implicit processing. In conclusion, results obtained support the hypothesis according to which different cognitive mechanisms are involved in the evaluation of positive vs negative emotional events. Moreover, results suggest that patients with schizophrenia show a deficit in hedonic judgment of social negative and non-social positive stimuli. The later result indicates that the paradox described above becomes clearer whenever the social component of emotional stimuli happens to be taken into account. Results suggest that the polarity and the social component of events evaluated by patients with schizophrenia are critical parameters that should be considered in forthcoming studies that investigate affect disorders in schizophrenia.

Dichhaptic recognition of textures in normal adults.

Dichhaptic procedures usually use nonsense shapes or letters as stimuli. The present study was designed to investigate hand asymmetry in a texture recognition task, in male right-handed adults. An overall left hand (right hemisphere) advantage was observed. However, when examining the order-of-report effect, the asymmetry appeared for the first report only. These results are discussed in terms of inter-hemispheric cooperation that can emerge for the second report.

Tactual extinction without anomia: evidence of attentional factors in a patient with a partial callosal disconnection.

Tactual extinction was examined in a 43-yr-old left-handed male patient (MM) with a hematoma in the trunk of the corpus callosum sparing the genu and the ventral part of the splenium as well as the cerebral hemispheres. Experiments I and II showed no deficit in tactual perception nor in the inter-hemispheric transfer of tactual information. In Experiment III, MM palpated stimuli differing in their association value, and responded vocally or manually. There was no difference in performance between the hands in unimanual control conditions, but in a dichhaptic condition an overall right-hand advantage was observed, depending on the kind of stimulus and on the mode of response: such results were not observed in control subjects. Results showed that MM's left-hand performance reached right-hand levels after specific modifications in the allocation of attention between the hands or the load of information in haptic memory (Experiment IV). Experiment V revealed a major deficit in the matching of left- and right-hand information only for the dichhaptic procedure. The results are discussed with a view of cerebral mechanisms as dynamic rather than structurally determined: it is suggested that extinction phenomena are sensitive to cognitive strategies and attentional factors and that the corpus callosum plays a critical role in the lateral control of attention to tactual as well as to auditory and visual information.

Procedural learning in Parkinson's disease: intact and impaired cognitive components.

Two experiments were carried out to study procedural learning in Parkinson's disease (PD) patients. In Experiment 1, ten patients and their normal controls participated in a classical mirror reading task and in an inverted reading task where word-stimuli made of non inverted letters had to be processed from right to left (e.g., ygoloruen). In both tasks, reading times for new stimuli were compared to reading times for stimuli that repeated over blocks. Although PD patients and their controls exhibited learning for repeated words in both tasks, PD patients did not respond faster with practice for new words in the inverted reading task. In Experiment 2, PD patients and their controls were presented with an original dot counting task in which participants were asked to process a horizontal series of black and white dots from right to left and to indicate whether a dot that had been designated by a number at the beginning of each trial was black or white. Results showed that PD patients, in contrast to controls, did not exhibit learning in this task. Results are discussed in terms of the cognitive components involved in these tasks. It is suggested that PD patients are impaired in the acquisition of a right-to-left visual scanning skill that could be studied directly in Experiment 2.

Midazolam effects on implicit and explicit memory processes in healthy subjects.

RATIONALE: Studying midazolam-induced amnesia offers an interesting approach to the organization of normal memory processes, since memory performance can be studied in the same subject in "on" and "off" drug conditions. OBJECTIVE: The present study investigated the effect of midazolam on skill learning. The task and the experimental design we used also allowed us to assess the effect of midazolam on priming and explicit memory. METHODS: Eighteen patients who underwent minor ear surgery and who were anaesthetized with intravenous midazolam, and 18 matched control subjects participated in a mirror reading task on 2 separate days. Patients were tested under midazolam on day 1 and without any medication on day 2. The mirror reading task was made of French words, some of which repeated across trial blocks, others being new. RESULTS: Patients under midazolam read new mirror written words faster with practice, which attested for intact skill learning. Moreover, they read repeated words faster than new words with practice, which was interpreted as reflecting intact priming abilities. These spared implicit memory capacities were observed along with severe explicit memory impairments. Learning for both new and repeated mirror written words on day 2 was similar in patients and in controls, which was interpreted as suggesting that the implicit learning that occurred on day 1 under midazolam was normal. CONCLUSIONS: The quality of skill learning, both in terms of speed of and lasting effect, was normal under midazolam in the task we used. In the context of the present task, midazolam offers an interesting, reversible model of amnesia.

Categorical and coordinate spatial relations: fMRI evidence for hemispheric specialization.

Functional magnetic resonance imaging (fMRI) was applied to determine the involvement of the angular gyri in the processing of categorical and coordinate spatial relations. In a categorical task, subjects were asked to judge whether a dot was presented above or below a horizontal line. In a coordinate task, they were asked to judge whether or not the distance between the dot and the bar was within a reference distance. Results showed stronger activation of the left than of the right angular gyrus in the categorical task, and stronger activation, initially, of the right than of the left angular gyrus in the coordinate task. In addition, in the latter task, the involvement of the right angular gyrus decreased with practice while that of the left angular gyrus increased. These results are interpreted in terms of the development of new categorical representations with practice in the coordinate task.

Transposon mutagenesis in Staphylococcus epidermidis using the Enterococcus faecalis transposon Tn917.

We transformed a clinical Staphylococcus epidermidis isolate with the Enterococcus faecalis transposon Tn917-carrying plasmid pTV1. Loss of plasmid replication was observed at 47 degrees C. Tn917 transposes efficiently and apparently randomly. The transposition frequency could be stimulated by erythromycin. Transposon mutagenesis in S. epidermidis provides a means for genetic study of the various virulence factors of this pathogen.

Categorical versus coordinate spatial relations: computational analyses and computer simulations.

Results of 4 sets of neural network simulations support the distinction between categorical and coordinate spatial relations representations: (a) Networks that were split so that different hidden units contributed to each type of judgment performed better than unsplit networks; the reverse was observed when they made 2 coordinate judgments. (b) Both computations were more difficult when finer discriminations were required; this result mirrored findings with human Ss. (c) Networks with large, overlapping "receptive fields" performed the coordinate task better than did networks with small, less overlapping receptive fields, but vice versa for the categorical task; this suggests a possible basis for observed cerebral lateralization of the 2 kinds of processing. (d) The previously observed effect of stimulus contrast on this hemispheric asymmetry could reflect contributions of more neuronal input in high-contrast conditions.

Evidence for two types of spatial representations: hemispheric specialization for categorical and coordinate relations.

Analyses of human object recognition abilities led to the hypothesis that 2 kinds of spatial relation representations are used in human vision. Evidence for the distinction between abstract categorical spatial relation representations and specific coordinate spatial relation representations was provided in 4 experiments. These results indicate that Ss make categorical judgments--on/off, left/right, and above/below--faster when stimuli are initially presented to the left cerebral hemisphere, whereas they make evaluations of distance--in relation to 2 mm, 3 mm, or 1 in. (2.54 cm)--faster when stimuli are initially presented to the right cerebral hemisphere. In addition, there was evidence that categorical representations developed with practice.

On computational evidence for different types of spatial relations encoding: reply to Cook et al. (1995).

Computational models in psychology play an increasingly important role in characterizing theoretical distinctions, understanding empirical results, and formulating new predictions. However, the proper use of models is subject to debate and interpretation, as Cook, Früh, and Landis (1995) have demonstrated in a critique of neural network simulations reported by Kosslyn, Chabris, Marsolek, and Koenig (1992). These simulation results supported a distinction between two types of spatial relations encoding. Cook et al. argue that Kosslyn et al.'s models did not process "spatial" representations and that input-output correlations rather than properties of spatial relations encoding processes explain the performance of the models. This article provides conceptual and analytic rebuttals of those criticisms.

Mental imagery and dyslexia: a deficit in processing multipart visual objects?

Dyslexic and normal control subjects memorized simple line patterns inside a grid and subsequently judged whether an "X" would have fallen on the pattern had it been present in an empty grid. The patterns were letters and novel shapes. The grids were presented to the left visual field, to the right visual field, or in central vision. Dyslexic subjects had difficulty generating images of multipart patterns, but this deficit was limited to letters. The findings suggest that dyslexics may have selective difficulty integrating visual information stored in long-term memory.

Phonological representations in postlingual deaf subjects using a multichannel cochlear implant.

Our research is a first attempt to study phonological representations in postlingually deaf subjects using a multichannel cochlear implant. Before deafness, these subjects had developed normal language. The present study investigated how phonological representations are assessed through cochlear implant inputs by comparing priming within the auditory modality, and priming in a visual-auditory, cross-modal, condition. Two postlingually deafened adults participated in two lexical decision experiments where word primes were phonologically paired with a word target (e.g. vedette/dette), or a pseudoword target (e.g. banane/nane). The same word primes were also paired with non phonologically related target words (e.g. vedette/chat) and pseudowords (e.g. banane/repe). In addition, the same targets were used in phonologically-related pairs and in phonologically-unrelated ones. Results showed different priming effects for each patient. In one patient, priming was observed for word targets in the unimodal condition only. In the other patient, priming was observed for word targets and interference was observed for pseudoword targets in the cross-modal condition, whereas no effect was observed in the unimodal condition. In addition, this last patient made more errors for pseudowords than for words in the cross-modal condition. These results were interpreted as suggesting that lexical phonological representations participated to priming effects. Moreover, our results suggest that phonological word forms can be activated by visual primes via cochlear implants.

[Preservation of procedural memory in 18 patients operated for aneurysm of the anterior communicating artery]. / Préservation de la mémoire procédurale chez dix-huit patients opérés d'un anévrisme de l'artère communicante antérieure.

Organic amnesia is typically associated with lesions in either the diencephalic or medial temporal regions of the brain. However, amnesia can result from other kinds of lesions, in particular those resulting from an aneurysm of the anterior communicating artery (ACoA). In the present study, 7 patients who became amnesic following a ruptured and operated ACoA aneurysm were comparated neuropsychologically with 11 patients with ruptures but no cognitive complaints and 18 normal control subjects. They were submitted to explicit and implicit memory tests and to tests claimed to be sensitive to frontal lobe dysfunction. The performance of the 11 ACoa patients without cognitive complaints revealed evidence for a functional frontal dysfunction (test of Stroop) and a partial deficit of explicit memory (free recall and long-term recall). The performance of the 7 ACoa amnesics revealed evidence for a functional frontal dysfunction and a deficit of explicit memory (safe in recognition). Anosognosia was also observed. The performance of all patients revealed the preservation of implicit memory in procedural tasks (serial reaction time and mirror reading) as diencephalic and temporal amnesia. The functionnal nature of the syndrome is discussed.

Separable mechanisms in face processing: evidence from hemispheric specialization.

This article addresses three issues in face processing: First, is face processing primarily accomplished by the right hemisphere, or do both left- and right-hemisphere mechanisms play important roles? Second, are the mechanisms the same as those involved in general visual processing, or are they dedicated to face processing? Third, how can the mechanisms be characterized more precisely in terms of processes such as visual parsing? We explored these issues using the divided visual field methodology in four experiments. Experiments 1 and 2 provided evidence that both left- and right-hemisphere mechanisms are involved in face processing. In Experiment 1, a right-hemisphere advantage was found for both Same and Different trials when Same faces were identical and Different faces differed on all three internal facial features. Experiment 2 replicated the right-hemisphere advantage for Same trials but showed a left-hemisphere advantage for Different trials when one of three facial features differed between the target and the probe faces. Experiment 3 showed that the right-hemisphere advantage obtained with upright faces in Experiment 2 disappeared when the faces were inverted. This result suggests that there are right-hemisphere mechanisms specialized for processing upright faces, although it could not be determined whether these mechanisms are completely face-specific. Experiment 3 also provided evidence that the left-hemisphere mechanisms utilized in face processing tasks are general-purpose visual mechanisms not restricted to particular classes of visual stimuli. In Experiment 4, a left-hemisphere advantage was obtained when the task was to find one facial feature that was the same between the target and the probe faces. We suggest that left-hemisphere advantages shown in face processing are due to the parsing and analysis of the local elements of a face.

The development of spatial relation representations: evidence from studies of cerebral lateralization.

Twenty-four-5-year-olds and 24 7-year-olds completed two divided-visual-field tasks; one task required subjects to categorize a dot as above or below a line, whereas the other required subjects to determine whether the dot was within 3 mm of the line. There was a relative left-hemisphere advantage for the above/below task and a relative right-hemisphere advantage for the distance task. The results indicate that distinct processing subsystems compute different kinds of visuo-spatial relations as early as 5 years of age.

Evidence for separate perceptive and semantic memories for odours: a priming experiment.

Sixty-four subjects participated in an olfactory priming experiment comprising separate study and test phases. Priming was measured within the olfactory modality (intramodal condition) and from the visual modality to the olfactory modality (intermodal condition). In the study phase of the intramodal condition, subjects were exposed twice to a series of odours: once performing a semantic orientation task (deciding which of seven categories odour stimuli belonged to) and once performing a perceptual orientation task (judging the intensity, the hedonicity and the familiarity of odour stimuli). Half of the odour stimuli corresponded to edible products, the other half did not. The study phase of the intermodal condition was similar, with the exception that the names of the odours (instead of the odours themselves) were presented. In the test phase, subjects were presented with primed and non-primed odour targets and had to decide as fast as possible whether the target corresponded to an edible product or not. Response times and types were recorded by a computer. The analysis of response times revealed a priming effect in the intramodal condition only. Results are discussed in terms of separate perceptual and semantic subsystems that store odour representations.

Functional anatomy of perceptual and semantic processing for odors.

The functional anatomy of perceptual and semantic processings for odors was studied using positron emission tomography (PET). The first experiment was a pretest in which 71 normal subjects were asked to rate 185 odorants in terms of intensity, familiarity, hedonicity, and comestibility and to name the odorants. This pretest was necessary to select the most appropriate stimuli for the different cognitive tasks of the second experiment. The second one was a PET experiment in which 15 normal subjects were scanned using the water bolus method to measure regional cerebral blood flow (rCBF) during the performance in three conditions. In the first (perceptual) condition, subjects were asked to judge whether an odor was familiar or not. In the second (semantic) condition, subjects had to decide whether an odor corresponded to a comestible item or not. In the third (detection) condition, subjects had to judge whether the perceived stimulus was made of an odor or was just air. It was hypothetized that the three tasks were hierarchically organized from a superficial detection level to a deep semantic level. Odorants were presented with an air-flow olfactometer, which allowed the stimulations to be synchronized with breathing. Subtraction of activation images obtained between familiarity and control judgments revealed that familiarity judgments were mainly associated with the activity of the right orbito-frontal area, the subcallosal gyrus, the left inferior frontal gyrus, the left superior frontal gyrus, and the anterior cingulate (Brodmann's areas 11, 25, 47, 9, and 32, respectively). The comestibility minus familiarity comparison showed that comestibility judgments selectively activated the primary visual areas. In contrast, a decrease in rCBF was observed in these same visual areas for familiarity judgments and in the orbito-frontal area for comestibility judgments. These results suggest that orbito-frontal and visual regions interact in odor processing in a complementary way, depending on the task requirements.