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T Nyffeler

Publications and source records attributed to T Nyffeler.

5 recordsLinked to original sources
PubMed2005

[A new method of visual exploration analysis].

The term visual field corresponds to the angular field of view that is seen by the eyes when they are fixed on a point straight-ahead. In neurological patients--e.g. stroke, trauma, or tumour patients--visual field function can be restricted, depending on lesion site and size. In contrast, the term "functional visual field" describes the area of visual field responsiveness under more ordinary viewing conditions. The visual exploration, i.e. the capacity to explore and analyze our visual world, is dependent on the integrity of the visual system and the oculomotor system which has to move the fovea from one object of interest to the next. In this paper, we present a new method to assess the functional visual field, conceptualized as the area that a patient actively scans with eye movements to detect predefined targets placed on everyday scenes. This method allows us to compare three levels of visual field function: (a) the spatial distribution of successful search (hits, i.e. which targets did the patient find?), (b) the spatial distribution of fixations (i.e. where did the patient preferentially search for targets?), and (c) the retinotopic level (i.e. the visual field assessed by perimetry). By integrating these three levels, one can evaluate functional outcomes of visual field disorders. Of particular importance is the question of how a patient compensates for a visual field loss with appropriate eye movements. A further clinical application of this method is the comparison of pre- with post-treatment data. Patients with visual field disorders usually undergo specific exploration trainings, aimed at enhancing the number and amplitude of saccades towards the region of the visual field deficit. The first experiences and clinical application with this method are presented here.

Eye Movements↗
PubMed2005

The role of the human dorsolateral prefrontal cortex in ocular motor behavior.

The dorsolateral prefrontal cortex (DLPFC) is involved in the preparation of saccadic eye movements. Lesion studies and functional magnetic resonance imaging (fMRI) studies suggest that the human DLPFC is located in area 46 of Brodmann. The DLPFC has direct connections with the main cortical ocular motor areas, that is with the frontal eye field (FEF) and the supplementary eye field (SEF) in the frontal lobe; with several (associative, attentional, and motor) areas in the posterior parietal cortex (PPC), including the parietal eye field (PEF); with the cingulate eye field in the anterior cingulate cortex; and directly downstream with the superior colliculus in the brainstem. Lesion and fMRI studies using the antisaccade paradigm have shown that the DLPFC is involved in the inhibition of unwanted reflexive saccades (triggered toward the target by the PEF), whereas the triggering of correct intentional antisaccades (made in the direction opposite to the target) may depend mainly upon the FEF. The DLPFC also controls short-term spatial working memory involved in memory-guided saccades, as shown by lesion and transcranial magnetic stimulation (TMS) studies. By contrast, medium-term spatial memory (after 25 s) may be controlled by the medial temporal cortex (MTC). Recently, TMS studies have suggested that the transmission of memorized information from the integrative parietal areas (PPC) to the MTC is performed via both an indirect pathway comprising the DLPFC (i.e., transmission in series) and a direct pathway bypassing the DLPFC (i.e., transmission in parallel). Furthermore, the DLPFC is involved in the preparation of predictive saccades (i.e., saccades made before the appearance of an expected target) and saccade sequences, and, therefore, also controls some aspects of temporal working memory. Lastly, the involvement of the DLPFC has recently been reported in tasks comprising a target selection or a directional decision to make for the forthcoming saccade. These different functions suggest that the DLPFC plays a major role in the decisional processes governing ocular motor behavior.

Animals↗
PubMed2001

Kleptomania in a patient with a right frontolimbic lesion.

OBJECTIVE: The authors report the case of a patient in whom kleptomania developed in the course of a right frontolimbic behavior syndrome after undergoing surgery. BACKGROUND: Kleptomania is a behavior abnormality that is classified as an impulse-control disorder; however, little is known about its organic correlates. METHOD: History included neurologic data, neuropsychological data, electroencephalographic data, and magnetic resonance images. RESULTS: Observation of kleptomania associated with a large sellar craniopharyngioma with right-sided extension suggests that the site of a lesion may be crucial for the development of an impulse-control disorder. CONCLUSIONS: The authors discuss kleptomania in the context of functional deficits associated with damage to orbitofrontal-subcortical circuits, and they suggest that kleptomania is a neuropsychiatric symptom that can be conceptualized as being an uncommon compulsive display of impulse dyscontrol.

Adult↗