PubMed Health⌕ Search

Biomedical subjects

Perrine Ruby

Publications and source records attributed to Perrine Ruby.

10 recordsLinked to original sources
PubMed2006

Implicit oculomotor sequence learning in humans: Time course of offline processing.

Studies of manual and digital sequence learning indicate that motor memories continue to be processed after training has ended, following a succession of identifiable steps. However, it is not known whether this offline memory processing constitutes a basic feature of motor learning and generalizes to the implicit learning of a sequence of eye movements. To assess this hypothesis, we have created the serial oculomotor reaction time task (SORT). Participants were trained to the SORT then tested after either 30 min, 5 h or 24 h. During training, ocular reaction times decreased monotonically over practice of a repeated sequence, then increased when a different sequence was displayed, demonstrating oculomotor learning of the trained sequence. When tested 30 min after training, a significant gain in oculomotor performance was observed irrespective of the sequence learning. This gain was no longer present after 5 h. Remarkably, a gain in performance specific to the learned sequence emerged only 24 h after training. After testing, a generation task confirmed that most subjects learned implicitly the regularities of the sequence. Our results show that, as for manual or digital sequences, oculomotor sequences can be implicitly learned. The offline processing of oculomotor memories follows distinct stages in a way similar to those observed after manual or digital sequence learning.

Adult↗
PubMed2005

Neural mechanisms involved in the detection of our first name: a combined ERPs and PET study.

In everyday social interactions, hearing our own first name captures our attention and gives rise to a sense of self-awareness, since it is one of the most socially self related stimulus. In the present study, we combined ERPs and PET scan methods to explore the cerebral mechanisms underlying the detection of our own name. While categorical analyses of PET data failed to reveal significant results, we found that the amplitude of the P3 component, elicited when hearing one's own name, correlates with regional cerebral blood changes in right superior temporal sulcus, precuneus and medial prefrontal cortex. Additionally, the latter was more correlated to the P3 obtained for the subject's name compared to that obtained for other first names. These results suggest that the medial prefrontal cortex plays the most prominent role in self-processing.

Adult↗
PubMed2005

Human cognition during REM sleep and the activity profile within frontal and parietal cortices: a reappraisal of functional neuroimaging data.

In this chapter, we aimed at further characterizing the functional neuroanatomy of the human rapid eye movement (REM) sleep at the population level. We carried out a meta-analysis of a large dataset of positron emission tomography (PET) scans acquired during wakefulness, slow wave sleep and REM sleep, and focused especially on the brain areas in which the activity diminishes during REM sleep. Results show that quiescent regions are confined to the inferior and middle frontal cortex and to the inferior parietal lobule. Providing a plausible explanation for some of the features of dream reports, these findings may help in refining the concepts, which try to account for human cognition during REM sleep. In particular, we discuss the significance of these results to explain the alteration in executive processes, episodic memory retrieval and self representation during REM sleep dreaming as well as the incorporation of external stimuli into the dream narrative.

Cognition↗
PubMed2005

Two aspects of impaired consciousness in Alzheimer's disease.

Alzheimer's disease (AD) is a degenerative dementia characterized by different aspects of impaired consciousness. For example, there is a deficit of controlled processes that require conscious processing of information. Such an impairment is indexed by decreased performances at controlled cognitive tasks, and it is related to reduced brain metabolic activity in a network of frontal, posterior associative, and limbic regions. Another aspect of impaired consciousness is that AD patients show variable levels of anosognosia concerning their cognitive deficits. A discrepancy score between patient's and caregiver's assessment of cognitive functions is one of the most frequently used measures of anosognosia. A high discrepancy score has been related to impaired activity in the superior frontal sulcus and the parietal cortex in AD. Anosognosia for cognitive deficits in AD could be partly explained by impaired metabolism in parts of networks subserving self-referential processes (e.g., the superior frontal sulcus) and perspective-taking (e.g., the temporoparietal junction). We hypothesize that these patients are impaired in the ability to see themselves with a third-person perspective (i.e., being able to see themselves as other people see them).

Agnosia↗
PubMed2003

A relation between rest and the self in the brain?

Neuroimaging techniques such as positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) are widely used to identify the cerebral correlates of cognitive tasks. The resting state presents the advantage to serve as a reference in all experiments but is also an ill-defined mental state because it may vary both from one subject to another and within the same subject. The most challenging question concerns the areas whose activity (revealed by PET or fMRI imaging) is greater in rest state than in an active condition. The present work reports the result of a meta-analysis including five previously published studies. The five different tasks involved are the following: attribution of intention, judgement of stimulus pleasantness, discrimination of spatial attributes, judgement of other peoples' belief and perception of gaze. For each study, the general linear model was used to assess statistical difference and a contrast resting state minus other conditions was calculated. The intersection of the five contrasts was used to search for the variation jointly observed across the different experiments. This lead to a reduced number of clusters: one cluster in the lower/anterior part of the cingulate gyrus and four clusters located in the medial/superior frontal gyrus, along the superior frontal sulcus. We discuss the location of these areas with respect to the location of activations induced by different tasks: externally focused attention, memory, general reasoning, theory of mind and self-referential tasks. We observed that medial prefrontal cortex exhibits a lower activity when the subject's attention is focused towards the external world than when the subject has to additionally refer to some internal states. By contrast, this activity is greater during resting state than during both externally directed and internally directed attention. Thus, we hypothesize that during rest, the subject is in a state where he refers only to his own self.

Brain↗
PubMed2003

What you believe versus what you think they believe: a neuroimaging study of conceptual perspective-taking.

Social communication requires shared representations as well as a cognitive flexibility for successful interactions between self and other. What neural mechanisms underlie the ability to distinguish between our own perspective vs. the perspective of others at a conceptual level? In this PET study subjects who were medical students were asked according to the experimental conditions to respond to a list of health-related questions, taking either their own perspective or the perspective of a 'lay person'. Third-person perspective as compared to first-person perspective was associated with activation in the medial part of the superior frontal gyrus, in the left superior temporal sulcus, in the left temporal pole and in the right inferior parietal lobe. The reverse comparison revealed a specific activation in the postcentral gyrus for the first-person conceptual perspective. This study provides congruent results at the conceptual level with previous studies investigating the neural correlates of self/other distinction at the motor level, and opens a new area of research in which conceptual cognition can be viewed in the continuity of motor cognition.

Adult↗
PubMed2002

Distinct areas in parietal cortex involved in long-term and short-term action planning: a PET investigation.

The sequential organization of events within a script, can be considered as a means to explore the cognitive mechanisms involved in action planning. Scripts are composed of goal-oriented sequences of events that typically occur in a specific and systematic order. The purpose of this study was to investigate the effect of temporal variation between script events (short-term versus long-term) on neural activity in normal volunteers. Subjects were required to judge whether the chronological order of three events was correct or not, while regional cerebral blood flow was measured using positron emission tomography. The modality of script presentation (graphic versus lexical) was manipulated. In the left hemisphere, the supramarginal gyrus, the middle frontal gyrus, the inferior temporal gyrus, and the middle occipital gyrus were more activated in the short-term script conditions, while the angular gyrus, the medial superior frontal gyrus, the precuneus bilaterally, the anterior cingulate gyrus and the inferior and middle temporal gyrus on the left were more involved during long-term scripts processing. The occipito-temporal junction (MT/V5) was significantly more activated in the graphic conditions as compared to the lexical ones, and in the short-term scripts conditions as compared to the long-term ones although all stimuli were static. Our results support the notion that two distinct frontal-parietal networks are engaged in short-term and long-term script processing. In addition, our study demonstrates two kinds of dissociations in the parietal lobe. A macro-dissociation between the anterior and the posterior portion of the inferior parietal lobe was found which accounts for processing short-term and long-term scripts respectively, as well as a micro-dissociation in each of these regions which is associated with distinct processing depending on the presentation modalities. These results may help to better understand apraxia at the neurophysiological level.

Adult↗
PubMedDate not supplied

How would you feel versus how do you think she would feel? A neuroimaging study of perspective-taking with social emotions.

Perspective-taking is a complex cognitive process involved in social cognition. This positron emission tomography (PET) study investigated by means of a factorial design the interaction between the emotional and the perspective factors. Participants were asked to adopt either their own (first person) perspective or the (third person) perspective of their mothers in response to situations involving social emotions or to neutral situations. The main effect of third-person versus first-person perspective resulted in hemodynamic increase in the medial part of the superior frontal gyrus, the left superior temporal sulcus, the left temporal pole, the posterior cingulate gyrus, and the right inferior parietal lobe. A cluster in the postcentral gyrus was detected in the reverse comparison. The amygdala was selectively activated when subjects were processing social emotions, both related to self and other. Interaction effects were identified in the left temporal pole and in the right postcentral gyrus. These results support our prediction that the frontopolar, the somatosensory cortex, and the right inferior parietal lobe are crucial in the process of self/other distinction. In addition, this study provides important building blocks in our understanding of social emotion processing and human empathy.

Adult↗