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Biomedical subjects

I Gauthier

Publications and source records attributed to I Gauthier.

At least 19 recordsLinked to original sources
PubMed2006

Impact of hemoglobin levels on outcomes of adjuvant chemotherapy in resected non-small cell lung cancer: the JBR.10 trial experience.

BACKGROUND: Cisplatin-induced anemia may correlate with adverse events, poor quality of life (QoL), decreased adjuvant chemotherapy (ACT) dose intensity, shorter relapse-free survival (RFS) or overall survival (OS). METHODS: The JBR.10 trial demonstrated significantly longer survival with adjuvant cisplatin and vinorelbine (n=242) compared to observation (n=240) in patients with resected NSCLC [Winton T, Livingston R, Johnson D, Rigas J, Johnston M, Butts C, et al. Vinorelbine plus cisplatin vs. observation in resected non-small-cell lung cancer. N Engl J Med 2005;352(25):2640-2]. This exploratory analysis evaluates the predictive value of baseline (in all patients) and during-treatment (in ACT arm only) hemoglobin (Hb) levels on OS and RFS when adjusted for prognostic factors. Baseline (in all patients) and during treatment (in ACT arm only) Hb levels were also correlated with adverse events, QoL, morbidity and ACT dose intensity. RESULTS: Baseline Hb did not predict RFS or OS. However, there was a trend to shorter OS (p=0.1) when baseline Hb was <120g/L. Lower baseline Hb predicted increased hospitalization (p=0.04) and worse QoL (SOB item, p=0.03) but had no impact on adverse events or dose intensity. There was a trend to longer RFS (p=0.08) in patients with lower nadir during-treatment Hb and to longer OS (p=0.06) and RFS (p=0.08) in patients with maximum during-treatment Hb drop >30% that was not maintained when ACT dose intensity was included in the model. Maximum during-treatment Hb drop >30% correlated with increased lethargy (p=0.003) and worse QoL (fatigue item, p=0.07). CONCLUSIONS: Lower baseline and during-treatment Hb levels seem associated with poorer QoL, fatigue and increased hospitalization. There is a trend for shorter OS in patients with lower baseline Hb levels.

Anemia↗
PubMed2006

A phase I, first in man study of OSI-7836 in patients with advanced refractory solid tumors: IND.147, a study of the Investigational New Drug Program of the National Cancer Institute of Canada Clinical Trials Group.

PURPOSE: To determine the maximum tolerated dose (MTD), recommended phase II dose (RP2D), safety, tolerability, toxicity profile, dose-limiting toxicities (DLTs), anti-tumor activity and pharmacokinetics of OSI-7836 given IV on day 1 and day 8 every 3 weeks in patients with advanced incurable cancer. METHODS: Twenty-seven previously treated patients with advanced or metastatic solid tumors were enrolled in this phase I study conducted by the National Cancer Institute of Canada Clinical Trial Group (NCIC CTG). OSI-7836 was administered IV on day 1 and day 8 every 3 weeks. The dose was initially escalated from 100 to 600 mg/m2 and finally de-escalated to 200 mg/m2 in seven cohorts of patients. Patients were evaluated every other cycle of treatment for radiological response. Pharmacokinetics were performed on day 1 and day 8 of cycle 1 for all patients. RESULTS: Twenty-six patients were evaluable for toxicity. All patients experienced reversible Grade 3 lymphopenia beginning at cycle 1. The maximal delivered dose was 600 mg/m2. MTD was reached at 400 mg/m2. DLTs included fever, fatigue, rash, herpes simplex infection, nausea and vomiting. The RP2D was 200 mg/m2. No objective responses were seen in 21 evaluable patients. Pharmacokinetics were dose proportional, with a mean half-life of 46.0 min and a clearance of 34 l/(h.m2). CONCLUSION: OSI-7836 given at 200 mg/m2 on day 1 and day 8 every 3 weekly is associated with manageable toxicity and is recommended for further study. While no objective responses were seen, the significant treatment related lymphopenia suggests that hematologic malignancies may warrant further investigation.

Adult↗
PubMed2002

Expertise training with novel objects leads to left-lateralized facelike electrophysiological responses.

Scalp event-related potentials (ERPs) in humans indicate that face and object processing differ approximately 170 ms following stimulus presentation, at the point of the N170 occipitotemporal component. The N170 is delayed and enhanced to inverted faces but not to inverted objects. We tested whether this inversion effect reflects early mechanisms exclusive to faces or whether it generalizes to other stimuli as a function of visual expertise. ERPs to upright and inverted faces and novel objects (Greebles) were recorded in 10 participants before and after 2 weeks of expertise training with Greebles. The N170 component was observed for both faces and Greebles. The results are consistent with previous reports in that the N170 was delayed and enhanced for inverted faces at recording sites in both hemispheres. For Greebles, the same effect of inversion was observed only for experts, primarily in the left hemisphere. These results suggest that the mechanisms underlying the electrophysiological face-inversion effect extend to visually homogeneous nonface object categories, at least in the left hemisphere, but only when such mechanisms are recruited by expertise.

Adult↗
PubMed2001

The development of face expertise.

Recent neuroimaging studies in adults indicate that visual areas selective for recognition of faces can be recruited through expertise for nonface objects. This reflects a new emphasis on experience in theories of visual specialization. In addition, novel work infers differences between categories of nonface objects, allowing a re-interpretation of differences seen between recognition of faces and objects. Whether there are experience-independent precursors of face expertise remains unclear; indeed, parallels between literature for infants and adults suggest that methodological issues need to be addressed before strong conclusions can be drawn regarding the origins of face recognition.

Adult↗
PubMed2000

Visual priming: the ups and downs of familiarity.

A dynamic picture of the neural processes underlying the 'priming' effects on the visual system of repeated object presentation has been obtained by combining functional magnetic resonance imaging with a gradual 'unmasking' procedure that slows down the process of visual recognition.

Brain↗
PubMed2000

The N170 occipito-temporal component is delayed and enhanced to inverted faces but not to inverted objects: an electrophysiological account of face-specific processes in the human brain.

Behavioral studies have shown that picture-plane inversion impacts face and object recognition differently, thereby suggesting face-specific processing mechanisms in the human brain. Here we used event-related potentials to investigate the time course of this behavioral inversion effect in both faces and novel objects. ERPs were recorded for 14 subjects presented with upright and inverted visual categories, including human faces and novel objects (Greebles). A N170 was obtained for all categories of stimuli, including Greebles. However, only inverted faces delayed and enhanced N170 (bilaterally). These observations indicate that the N170 is not specific to faces, as has been previously claimed. In addition, the amplitude difference between faces and objects does not reflect face-specific mechanisms since it can be smaller than between non-face object categories. There do exist some early differences in the time-course of categorization for faces and non-faces across inversion. This may be attributed either to stimulus category per se (e.g. face-specific mechanisms) or to differences in the level of expertise between these categories.

Adult↗
PubMed2000

Abnormal ventral temporal cortical activity during face discrimination among individuals with autism and Asperger syndrome.

BACKGROUND: Recognition of individual faces is an integral part of both interpersonal interactions and successful functioning within a social group. Therefore, it is of considerable interest that individuals with autism and related conditions have selective deficits in face recognition (sparing nonface object recognition). METHOD: We used functional magnetic resonance imaging (fMRI) to study face and subordinate-level object perception in 14 high-functioning individuals with autism or Asperger syndrome (the autism group), in comparison with 2 groups of matched normal controls (normal control group ] [NC1] and normal control group 2 [NC2]) (n = 14 for each). Regions of interest (ROIs) were defined in NC1 and then applied in comparisons between NC2 and the autism group. Regions of interest were also defined in NC2 and then applied to comparisons between NC1 and the autism group as a replication study. RESULTS: In the first set of comparisons, we found significant task x group interactions for the size of activation in the right fusiform gyrus (FG) and right inferior temporal gyri (ITG). Post hoc analyses showed that during face (but not object) discrimination, the autism group had significantly greater activation than controls in the right ITG and less activation of the right FG. The replication study showed again that the autism group used the ITG significantly more for processing faces than the control groups, but for these analyses, the effect was now on the left side. Greater ITG activation was the pattern found in both control groups during object processing. CONCLUSIONS: Individuals with autism spectrum disorders demonstrate a pattern of brain activity during face discrimination that is consistent with feature-based strategies that are more typical of nonface object perception.

Adult↗
PubMed2000

Expertise for cars and birds recruits brain areas involved in face recognition.

Expertise with unfamiliar objects ('greebles') recruits face-selective areas in the fusiform gyrus (FFA) and occipital lobe (OFA). Here we extend this finding to other homogeneous categories. Bird and car experts were tested with functional magnetic resonance imaging during tasks with faces, familiar objects, cars and birds. Homogeneous categories activated the FFA more than familiar objects. Moreover, the right FFA and OFA showed significant expertise effects. An independent behavioral test of expertise predicted relative activation in the right FFA for birds versus cars within each group. The results suggest that level of categorization and expertise, rather than superficial properties of objects, determine the specialization of the FFA.

Adult↗
PubMed2000

The fusiform "face area" is part of a network that processes faces at the individual level.

According to modular models of cortical organization, many areas of the extrastriate cortex are dedicated to object categories. These models often assume an early processing stage for the detection of category membership. Can functional imaging isolate areas responsible for detection of members of a category, such as faces or letters? We consider whether responses in three different areas (two selective for faces and one selective for letters) support category detection. Activity in these areas habituates to the repeated presentation of one exemplar more than to the presentation of different exemplars of the same category, but only for the category for which the area is selective. Thus, these areas appear to play computational roles more complex than detection, processing stimuli at the individual level. Drawing from prior work, we suggest that face-selective areas may be involved in the perception of faces at the individual level, whereas letter-selective regions may be tuning themselves to font information in order to recognize letters more efficiently.

Adult↗
PubMed1999

Activation of the middle fusiform 'face area' increases with expertise in recognizing novel objects.

Part of the ventral temporal lobe is thought to be critical for face perception, but what determines this specialization remains unknown. We present evidence that expertise recruits the fusiform gyrus 'face area'. Functional magnetic resonance imaging (fMRI) was used to measure changes associated with increasing expertise in brain areas selected for their face preference. Acquisition of expertise with novel objects (greebles) led to increased activation in the right hemisphere face areas for matching of upright greebles as compared to matching inverted greebles. The same areas were also more activated in experts than in novices during passive viewing of greebles. Expertise seems to be one factor that leads to specialization in the face area.

Adult↗
PubMed1999

Can face recognition really be dissociated from object recognition?

We argue that the current literature on prosopagnosia fails to demonstrate unequivocal evidence for a disproportionate impairment for faces as compared to nonface objects. Two prosopagnosic subjects were tested for the discrimination of objects from several categories (face as well as nonface) at different levels of categorization (basic, subordinate, and exemplar levels). Several dependent measures were obtained including accuracy, signal detection measures, and response times. The results from Experiments 1 to 4 demonstrate that, in simultaneous-matching tasks, response times may reveal impairments with nonface objects in subjects whose error rates only indicate a face deficit. The results from Experiments 5 and 6 show that, given limited stimulus presentation times for face and nonface objects, the same subjects may demonstrate a deficit for both stimulus categories in sensitivity. In Experiments 7, 8 and 9, a match-to-sample task that places greater demands on memory led to comparable recognition sensitivity with both face and nonface objects. Regardless of object category, the prosopagnosic subjects were more affected by manipulations of the level of categorization than normal controls. This result raises questions regarding neuropsychological evidence for the modularity of face recognition, as well as its theoretical and methodological foundations.

Adolescent↗
PubMed1998

Do viewpoint-dependent mechanisms generalize across members of a class?

Evidence for viewpoint-specific image-based object representations have been collected almost entirely using exemplar-specific recognition tasks. Recent results, however, implicate image-based processes in more categorical tasks, for instance when objects contain qualitatively different 3D parts. Although such discriminations approximate class-level recognition. they do not establish whether image-based representations can support generalization across members of an object class. This issue is critical to any theory of recognition, in that one hallmark of human visual competence is the ability to recognize unfamiliar instances of a familiar class. The present study addresses this questions by testing whether viewpoint-specific representations for some members of a class facilitate the recognition of other members of that class. Experiment 1 demonstrates that familiarity with several members of a class of novel 3D objects generalizes in a viewpoint-dependent manner to cohort objects from the same class. Experiment 2 demonstrates that this generalization is based on the degree of familiarity and the degree of geometrical distinctiveness for particular viewpoints. Experiment 3 demonstrates that this generalization is restricted to visually-similar objects rather than all objects learned in a given context. These results support the hypothesis that image-based representations are viewpoint dependent, but that these representations generalize across members of perceptually-defined classes. More generally, these results provide evidence for a new approach to image-based recognition in which object classes are represented as cluster of visually-similar viewpoint-specific representations.

Adult↗
PubMed1998

Training 'greeble' experts: a framework for studying expert object recognition processes.

Twelve participants were trained to be experts at identifying a set of 'Greebles', novel objects that, like faces, all share a common spatial configuration. Tests comparing expert with novice performance revealed: (1) a surprising mix of generalizability and specificity in expert object recognition processes; and (2) that expertise is a multi-faceted phenomenon, neither adequately described by a single term nor adequately assessed by a single task. Greeble recognition by a simple neural-network model is also evaluated, and the model is found to account surprisingly well for both generalization and individuation using a single set of processes and representations.

Computer Simulation↗
PubMed1998

Chromium picolinate toxicity.

OBJECTIVE: To describe a case of toxicity secondary to chronic ingestion of 6-12 times the recommended daily allowance of over-the-counter (OTC) chromium picolinate. CASE SUMMARY: A 33-year-old white woman presented with weight loss, anemia, thrombocytopenia, hemolysis, liver dysfunction (aminotransferase enzymes 15-20 times normal, total bilirubin 3 times normal), and renal failure (serum creatinine 5.3 mg/dL; blood urea nitrogen 152 mg/dL). She had ingested chromium picolinate 1200-2400 microg/d for the previous 4-5 months to enhance weight loss. The patient had chromium plasma concentrations 2-3 times normal. Thrombotic thrombocytopenic purpura and hemolytic uremic syndrome were ruled out by clinical findings, peripheral blood smears, and a bone marrow biopsy. The patient was managed with supportive measures and received blood product transfusions and hemodialysis. Hemolysis stabilized and liver function improved over 6 days. Liver function returned to normal prior to discharge. Renal function began to return on day 12 and her serum creatinine on discharge was 1.3 mg/dL. One year later, all laboratory values were within normal limits. DISCUSSION: Trivalent chromium is an essential trace element that is considered safe when ingested in normal quantities. Trivalent chromium compounds are used by patients to enhance weight loss, increase lean body mass, and/or improve glycemic control. Information regarding the toxicity of chromium picolinate is limited. CONCLUSIONS: Chromium supplements may cause serious renal impairment when ingested in excess. Medication histories should include attention to the use of OTC nutritional supplements often regarded as harmless by the public and lay media.

Acute Kidney Injury↗
PubMed1998

Drug-food interactions in hospitalised patients. Methods of prevention.

Drug-food interactions in hospitalised patients may result in decreased drug efficacy or increased drug toxicity. The increasing complexity of drug therapy regimens has increased the potential for drug-food interactions to occur, reinforcing the need to develop methods to prevent clinically significant drug-food interactions. Before selecting the optimal method, in terms of feasibility of implementation and successful outcome, drugs with the potential for clinically significant interactions with food must be identified. From an analysis of the literature, 6 methods to prevent drug-food interactions have been suggested as useful tools. Each method has its own advantages and disadvantages. Most have been developed in response to guidelines from the most well recognised agency for quality review in the US, the Joint Commission on Accreditation of Healthcare Organisations (JCAHO). Based on those recommendations, an ideal programme to prevent drug-food interactions would be a combined patient counselling and label system to select the most appropriate drug administration times and increase nurse and patient awareness of the potential for drug-food interactions. However, because of time constraints and limited resources, a label system or the provision of a drug-food interaction pamphlet to the patient before discharge would be a more practical method. Newsletters and educational in-services combined with patient counselling or a label system would be a valuable method to prevent drug-food interactions in hospitalised patients.

Drug Administration Schedule↗