The concept of "stimulus-secretion coupling" suggested by Douglas and co-workers to explain the events related to monamine discharge by the adrenal medulla (5, 7) may be applied to other endocrine tissues, such as adrenal cortex (36), pancreatic islets (4), and magnocellular hypothalamic neurons (6), which exhibit a similar iondependent process of hormone elaboration. In addition, they share another feature, that of joining neighbor cells via membrane junctions (12,26, and Fletcher, unpublished observation). Given this, and the reports that hormone secretion by the pars distalis also involves a secretagogue-induced decrease in membrane bioelectric potential accompanied by a rise in cellular [Ca ++] (27,34,41), it was appropriate to test the possibility that cells of the anterior pituitary gland are united by junctions. MATERIALS AND METHODS Electron MicroscopyPieces o.f rat anterior pituitary were processed for electron microscopy using isosmotic solutions (cf. reference 12). Tissues were immersed for 4 6 h in Karnovsky's dialdehyde fixative (19) buffered to pH 7.4 with 0.1 M sodium cacodylate containing 0.05% calcium chloride, then rinsed in buffer containing 4% sucrose. After this, they were postfixed in 2% osmium tetroxide containing 3% sucrose and either dehydrated in a graded series of ethanol or placed for I--4 h in a solution of 0.5% uranyl acetate and 5% sucrose, after which they were dehydrated. Cultured cells were fixed in situ using the dialdehyde described at half strength. They were then briefly rinsed in buffer as described above, postfixed in similarly buffered 1% osmium tetroxide and dehydrated.Tissues and cultures of cells both were imbedded in Epon 812 (Shell Chemical Co., New York).For some protocols, tissues were exposed to electrondense extracellular tracers either before or during fixation. Lanthanum was used as described by Revel and Karnovsky (31), potassium pyroantimonate (20) as a 1 2% solution, and ruthenium red according to Luft's method (23). In each case, Ca ++ was eliminated from buffer. Treatment of cultures with any of these tracers, especially lanthanum, before fixation caused cells to lift free of the substrate; thus, tracers were used only after dialdehyde fixation was begun.Tissues to be used for freeze-fracture were fixed in dialdehyde for 4-6 h, then passed through progressively increasing concentrations of glycerol buffered to pH 7.4 with 0.1 M sodium cacodylate containing 0.1% calcium chloride, and allowed to stay in the final concentration (20%) of glycerol for 4 6 h. Fracturing at -115~ was done in a Balzers 360-m device (Balzers High Vacuum Corp., Santa Ana, Calif.) at less than 6 x 10 -7 torr. Replicas were cast with platinum-carbon and stabilized with carbon. Preparation of Cell CulturesAnterior pituitary glands were removed from decapitated rats, rinsed in complete culture medium (Dulbeccos) plus 10% fetal-calf serum and 100gg/ml Gentamicin (Schering Diagnostics, Port Reading, N.J.), and diced into small pieces. The "clean" bits of gland were placed in a sterile ce...
Mind-wandering (MW) often involves a decoupling between attention and external information (Schooler et al., 2011). The present study examined whether eye movements during MW decouple from image content in a scene perception task. Participants studied real-world scenes and occasionally answered thought probes assessing their attentional states (on-task, intentional MW, and unintentional MW). We built salience maps (Graph-Based Visual salience; Harel, Koch, & Perona, 2007) and meaning maps (Henderson & Hayes, 2017) to represent how low- and high-level image features were distributed across the scene. Meaning values at viewed locations showed that participants prioritized meaningful regions over less meaningful ones even during MW. But a subsequent analysis incorporating unexamined locations showed that participants tended to overlook meaningful regions during MW compared to when being on-task. Results for image salience were similar to the results for meaningfulness, as meaning and salience were highly correlated (r = 0.84). When directly compared to each other, meaning maps outperformed salience maps in predicting fixations regardless of participants’ attentional state. In addition, there were no significant differences between intentional and unintentional MW in all analyses. In sum: (1) MW affected visual attention differently at the fixation level and the trial level: individual fixations preferred meaningful regions even during MW, but overall, attention was insufficient to cover meaningful regions in the scene. (2) Relatedly, meaning maps were less precise at predicting fixation allocation during MW compared to when being on-task. (3) Even during MW, eye movements appeared to be driven more by meaning than by salience.
People naturally move both their head and eyes to attend to information. Yet, little is known about how the head and eyes coordinate in attentional selection due to the relative sparsity of past work that has simultaneously measured head and gaze behaviour. In the present study, participants were asked to view fully immersive 360-degree scenes using a virtual reality headset with built-in eye tracking. Participants viewed these scenes through a small moving window that was yoked either to their head or gaze movements. We found that limiting peripheral information via the head- or gaze-contingent windows affected head and gaze movements differently. Compared with free viewing, gaze-contingent viewing was more disruptive than head-contingent viewing, indicating that gaze-based selection is more reliant on peripheral information than head-based selection. These data dovetail with the nested effectors hypothesis, which proposes that people prefer to use their head for exploration into non-visible space while using their eyes to exploit visible or semi-visible areas of space. This suggests that real-world orienting may be more head-based than previously thought. Our work also highlights the utility, ecological validity, and future potential of unconstrained head and eye tracking in virtual reality.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.