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Biomedical subjects

A Sapir

Publications and source records attributed to A Sapir.

5 recordsLinked to original sources
PubMed2001

Attentional asymmetry in schizophrenia: disengagement and inhibition of return deficits.

This research examined 2 components of visual orienting in medicated schizophrenia patients: the validity effect and the inhibition of return (IOR). In the 1st experiment, patients showed the expected asymmetry in orienting attention, that is, larger validity effect in the right visual field than in the left. However, this asymmetry was due to a deficit in facilitatory processes rather than a disengagement deficit. In addition, patients showed a deficit in IOR. In the 2nd experiment, a 2nd central cue for summoning attention, explicitly, back to the center was used. In this experiment, normal IOR in schizophrenia patients was found. Because it was shown that schizophrenia patients do not have a disengagement deficit, IOR possibly could not be observed because of the increased facilitation in that location. It was proposed that the abnormality in visual attention in schizophrenia is due to a deficit in inhibitory processes.

Adult↗
PubMed2000

Component processes in task switching.

Participants switched between two randomly ordered, two-choice reaction-time (RT) tasks, where an instructional cue preceded the target stimulus and indicated which task to execute. Task-switching cost dissipated passively while the participants waited for the instructional cue in order to know which task to execute (during the Response-Cue Interval). Switching cost was sharply reduced, but not abolished, when the participants actively prepared for the task switch in response to the instructional cue (during the Cue-Target Interval). The preparation for a task switch has shown not to be a by-product of general preparation by phasic alertness or predicting target onset. It is suggested that task-switching cost has at least three components reflecting (1) the passive dissipation of the previous task set, (2) the preparation of the new task set, and (3) a residual component.

Cognition↗
PubMed1999

Sprouty is a general inhibitor of receptor tyrosine kinase signaling.

Sprouty was originally identified as an inhibitor of Drosophila FGF receptor signaling during tracheal development. By following the capacity of ectopic Sprouty to abolish the pattern of activated MAP kinase in embryos, we show that Sprouty can inhibit other receptor tyrosine kinase (RTK) signaling pathways, namely the Heartless FGF receptor and the EGF receptor. Similarly, in wing imaginal discs, ectopic Sprouty abolishes activated MAP kinase induced by the EGF receptor pathway. Sprouty expression is induced by the EGFR pathway in some, but not all, tissues in which EGFR is activated, most notably in follicle cells of the ovary, the wing imaginal disc and the eye disc. In the ovary, induction of sprouty expression follows the pattern of EGFR activation in the follicle cells. Generation of homozygous sprouty mutant follicle-cell clones demonstrates an essential role for Sprouty in restricting EGFR activation throughout oogenesis. At the stage when dorso-ventral polarity of the follicle cells is established, Sprouty limits the ventral expansion of the activating Gurken signal. Later, when dorsal appendage fates are determined, reduction of signaling by Sprouty facilitates the induction of inter-appendage cell fates. The capacity of Sprouty to reduce or eliminate accumulation of activated MAP kinase indicates that in vivo it intersects with the pathway upstream to MAP kinase. The ability of ectopic Sprouty to rescue lethality caused by activated Raf suggests that it may impinge upon the pathway by interacting with Raf or downstream to it.

Animals↗
PubMed1998

Sequential activation of the EGF receptor pathway during Drosophila oogenesis establishes the dorsoventral axis.

Previous work has demonstrated a role for the Drosophila EGF receptor (Torpedo/DER) and its ligand, Gurken, in the determination of anterioposterior and dorsoventral axes of the follicle cells and oocyte. The roles of DER in establishing the polarity of the follicle cells were examined further, by following the expression of DER-target genes. One class of genes (e.g. kekon) is induced by the DER pathway at all stages. Broad expression of kekon at the stage in which the follicle cells migrate posteriorly over the oocyte, demonstrates the capacity of the pathway to pattern all follicle cells except the ventral-most rows. This may provide the spatial coordinates for the ventral-most follicle cell fates. A second group of target genes (e.g. rhomboid (rho)) is induced only at later stages of oogenesis, and may require additional inputs by signals emanating from the anterior, stretch follicle cells. The function of Rho was analyzed by ectopic expression in the stretch follicle cells, and shown to induce a non-autonomous dorsalizing activity that is independent of Gurken. Rho thus appears to be involved in processing a DER ligand in the follicle cells, to pattern the egg chamber and allow persistent activation of the DER pathway during formation of the dorsal appendages.

Animals↗