Auditory signal detection and decision processes in the nervous system.

Neuronal unit activity was recorded from auditory nuclei, the dorsal hippocampus, and the cerebellum in New Zealand White rabbits behaviorally detecting a threshold-level, constant intensity white noise stimulus. Results show that stimulus-evoked neuronal unit activity was present and identical on both detection and nondetection trials in auditory nuclei but was dichotomous in the hippocampus and in the cerebellum, the latter 2 systems predicting the occurrence of behavioral detection. It is concluded that the behavioral absolute threshold is not determined by differential activation of neurons in the primary auditory relay nuclei. (21 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of red-green, blue-yellow and achromatic losses in glaucoma

Achromatic losses in glaucoma would be expected to be greater than, or equal to, red-green chromatic losses if the following assumptions are made: (1) the function of the remaining axons is either unchanged or non-selectively reduced; (2) red-green chromatic information is signaled by the midget ganglion cell system; and (3) the function of the magnocellular system is reduced at least as much as that of the midget ganglion cells. This prediction was tested by measuring red-green (along with blue-yellow) mixture thresholds for 1 deg, 0.2 sec test spots presented on a color monitor on a white background of 50 cd/m2. Ellipses were fitted to plots of green contrast as a function of red contrast (or yellow as a function of blue), and major and minor axes of these ellipses were taken as measures of chromatic and achromatic thresholds, respectively. The study population consisted of 29 eyes in 29 patients with early glaucoma; control data were derived from a data bank of 83 normal eyes. Red-green losses were significantly (P < 0.05) greater than achromatic losses in 6 out of the 11 eyes which showed significant losses of either chromatic or achromatic sensitivity (or both). It is concluded that, for these eyes, at least one of the above three assumptions is incorrect.     

Auditory processing speed and signal detection in schizophrenia.

Examined 2 differing explanations of schizophrenic processing deficit, J. Chapman and A. McGhie's (1962) and A. J. Yates's (see PA, Vol 41:10769). 32 18-46 yr old schizophrenics, classified on the acute-chronic and paranoid-nonparanoid dimensions, and 8 17-45 yr old neurotics were tested on 2 dichotic listening tasks. One task gave reaction time measures of processing speed at 3 rates of stimulus presentation; the other assessed stimulus detection and channel selectivity using theory of signal detection methods. Results support Yates and indicate that schizophrenics can attend successfully to 1 of 2 competing channels. Neither reduced sensory sensitivity nor response bias appeared to affect the performance of any group of Ss. Slowness of processing was a deficit characteristic of chronic, particularly nonparanoid, schizophrenics, although the factors responsible for this slowness remain a matter for empirical investigation. (25 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Postreceptoral chromatic detection mechanisms revealed by noise masking in three-dimensional cone contrast space

We used a noise masking technique to test the hypothesis that detection is subserved by only two chromatic postreceptoral mechanisms (red-green and blue-yellow) and one achromatic (luminance) mechanism. The task was to detect a 1-c/deg Gaussian enveloped grating presented in a mask of static, spatially low-passed binary or Gaussian distributed noise. In the main experiment, the direction of the test stimulus (termed the signal) was constant in cone contrast space, and the direction of the noise was sampled in equally spaced directions within a plane (the noise plane) in the space. The signal was chosen to coincide with one of the three cardinal directions of three postulated mechanisms. The noise plane was selected to span two of the cardinal directions, including that chosen as the signal direction. As the noise direction was sampled around the noise plane, the signal detection threshold was found to vary in accordance with a linear cosine model, which predicted noise directions yielding maximum and minimum masking of the signal. In the direction of minimum masking (termed a null direction), the noise was found to have no masking effect on the signal. Moreover, the null was not orthogonal to the signal direction but lay instead in one of the cardinal directions. Our findings suggest that detection is mediated by only three mechanisms. In a further experiment we found little or no cross masking between each pair of cardinal directions up to the limit of our noise mask contrasts. This further supports the presence of no more than three independent postreceptoral mechanisms.     

深锥浓密机底流浓度模型及动态压密机理分析

泥层高度和底流浓度是深锥浓密机最为重要的两个参数,因此有必要研究底流浓度随泥层高度的变化规律.采用自制小型深锥浓密机,对尾矿非连续/连续动态压密过程进行了物理实验;借助于有效孔隙比与泥层压强间遵循的Power函数关系,结合对尾矿颗粒的受力分析,推导出了底流浓度与泥层高度的数学模型,揭示了浓密机底流浓度与泥层高度的内在关系,并从尾矿颗粒空间结构的角度解释了该模型的变化规律;结合矿山生产对于底流浓度的要求,应用该数学模型,为其推荐了泥层高度的合理范围,验证了底流浓度数学模型的可靠性.该模型为深锥浓密机的设计和运行提供了理论依据.     

Personality assessment as a signal detection task.

Conducted a series of studies with 2 experienced clinicians, 12 undergraduate psychology students who had taken a course in testing, and 8 clinical psychology graduate students to test 3 assumptions that would contribute to making the signal detection model applicable to interpreting MMPI profiles. It was hypothesized that a judge's discriminal process is a sample from a normal distribution of all possible discriminal processes for the MMPI stimulus set; that the standard deviations of 2 distributions of binary MMPI decisions are equal; and that the discriminative capacities of judges remain fixed from one decision session to the next, regardless of instructions. All assumptions were satisfactorily supported. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Process dissociation and mixture signal detection theory.

The process dissociation procedure was developed in an attempt to separate different processes involved in memory tasks. The procedure naturally lends itself to a formulation within a class of mixture signal detection models. The dual process model is shown to be a special case. The mixture signal detection model is applied to data from a widely analyzed study. The results suggest that a process other than recollection may be involved in the process dissociation procedure. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A dynamic stimulus-driven model of signal detection.

Signal detection theory forms the core of many current models of cognition, including memory, choice, and categorization. However, the classic signal detection model presumes the a priori existence of fixed stimulus representations—usually Gaussian distributions—even when the observer has no experience with the task. Furthermore, the classic signal detection model requires the observer to place a response criterion along the axis of stimulus strength, and without theoretical elaboration, this criterion is fixed and independent of the observer's experience. We present a dynamic, adaptive model that addresses these 2 long-standing issues. Our model describes how the stimulus representation can develop from a rough subjective prior and thereby explains changes in signal detection performance over time. The model structure also provides a basis for the signal detection decision that does not require the placement of a criterion along the axis of stimulus strength. We present simulations of the model to examine its behavior and several experiments that provide data to test the model. We also fit the model to recognition memory data and discuss the role that feedback plays in establishing stimulus representations. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Influences of hypothyroidism on the taste detection performance of rats: A signal detection analysis.

Determined the influences of hypothyroidism on behavioral measures of the taste function in male and female Long-Evans rats. Experimental rats' preferences for and ability to detect NaCl, HCl, sucrose, and quinine sulfate were examined before, during, and after 9 wks of maintenance on 0.1% propylthiouracil (PTU), an agent that produces marked hypothyroidism, with similar determinations made for control animals. Despite significant decreases in PTU-treated rats' serum triiodothyronine (T?) and thyroxin (T?), there were no changes in sensitivity or responsitivity to the target tastants. However, altered preferences for NaCl, HCl, and quinine sulfate were observed for PTU-treated rats; elevated consumption of HCl and quinine sulfate was present at the end of the study when serum T? and T? had returned to near-baseline levels. The data confirm observations that PTU-induced hypothyroidism alters rats' taste preference behavior. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biphasic alterations in cardiac beta-adrenoceptor signal transduction mechanism due to oxyradicals

To assess the effects of oxyradicals on cardiac beta-adrenoceptors, G-proteins and adenylyl cyclase, rat heart membranes were incubated with xanthine (X) plus xanthine oxidase (XO) for different intervals. The basal as well as forskolin-, NaF-, 5'-guanylylimidodiphosphate and isoproterenol-stimulated adenylyl cyclase activities showed an increase at 10 min and a decrease at 30 min of incubation with X plus XO. Treatment of membranes with H2O2 also produced biphasic changes in adenylyl cyclase activities. The density of beta1-adrenoceptors was decreased when cardiac membranes were treated with X plus XO for 10 and 30 min whereas the affinity of beta1-adrenoceptors was increased after 10 min and reduced after 30 min of incubation. The beta2-adrenoceptors were not modified at 10 min whereas incubation of cardiac membranes with X plus XO for 30 min increased the affinity and decreased the density. Cholera toxin-stimulated adenylyl cyclase activity, cholera toxin-catalyzed ADP-ribosylation and stimulatory guanine nucleotide binding protein immunoreactivity in cardiac membranes were increased at 10 min and decreased at 30 min of incubation with X plus XO. However, the pertussis toxin-stimulated adenylyl cyclase activity, pertussis toxin-catalyzed ADP ribosylation and inhibitory guanine nucleotide binding protein immunoreactivity were not affected on treatment of membranes with X plus XO. Addition of superoxide dismutase plus catalase in the incubation medium prevented the X plus XO-induced alterations in adenylyl cyclase activities, stimulatory guanine nucleotide binding protein-related ADP-ribosylation and changes in the characteristics of beta-adrenoceptors except the increased affinity of beta1-adrenoceptors at 10 min of incubation. These data suggest that alterations in the beta1-adrenoceptor-linked stimulatory guanine nucleotide binding protein-adenylyl cyclase pathway due to X plus XO are biphasic in nature and these changes may likely be due to the formation of H2O2.     

钢中非金属夹杂物异常光谱信号产生机理的研究

采用金属原位分析仪与扫描电镜相结合的方法对钢中非金属夹杂物的异常光谱行为进行了研究。研究表明,夹杂物与基体界面的优先放电呈“扩散”性,并未导致夹杂物异常光谱信号的立即出现,说明夹杂物边缘优先放电不是导致夹杂物异常光谱信号出现的直接原因。通过对夹杂物局部富集程度的计算表明,在相同体积区域内某元素分别以夹杂态和固溶态存在时,夹杂态相对于固溶态有很高的富集程度,结合原子发射光谱分析中影响谱线强度因素的讨论,提出夹杂物异常光谱信号是由于夹杂物局部富集产生。     

A signal detection analysis of memory for nonoccurrence in pigeons.

In a relatively unexplored memory procedure, pigeons indicated whether or not an event recently occurred. On positive trials, a sample stimulus was presented, followed by a delay, followed by a choice between the yes and no alternatives (with yes being the correct choice). On negative trials, the yes and no choice alternatives were presented without a preceding sample, and on these trials, no was the correct choice. Recent research on this topic seems to suggest that performance on negative trials is governed by a memory-free default response strategy, whereas performance on positive trials is governed by memory for the sample stimulus. However, a signal detection analysis leads to a different conclusion. In both cases, according to this account, performance was determined by the strength of a memory trace in relation to a decision criterion. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The mirror effect and mixture signal detection theory.

The mirror effect for word frequency refers to the finding that low-frequency words have higher hit rates and lower false alarm rates than high-frequency words. This result is typically interpreted in terms of conventional signal detection theory (SDT), in which case it indicates that the order of the underlying old item distributions mirrors the order of the new item distributions. However, when viewed in terms of a mixture version of SDT, the order of hits and false alarms does not necessarily imply the same order in the underlying distributions because of possible effects of mixing. A reversal in underlying distributions did not appear for fits of mixture SDT models to data from 4 experiments. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The molecular mechanism of costimulatory signal for T cell activation

The initiation of T cell responses against antigens requires two distinct signals. The first, the essential signal is the engagement of T cell receptor to antigen peptide in the context of MHC molecules on antigen presenting cells (APC). The presence of the second signal (costimulatory signal) determines whether responding T cells to be fully responsive or to be anergic (antigen specific nonresponsiveness). There are numbers of such costimulatory receptor/ligand pairs including B7/CD28: CTLA4, VCAM-1/VLA4, ICAM-1/LFA-1, HSA/unknown, and LFA-3/CD2. Among those ligand receptor pairs, B7/CD28 pathway is chosen and the molecular mechanism how T cell responses are regulated by B7/CD28 is discussed.     

Decision processes in discrimination: Fundamental misrepresentations of signal detection theory.

A new approach to studying decision making in discrimination tasks is described that does not depend on the technical assumptions of signal detection theory (e.g., normality of the encoding distributions). In 3 different experiments, results of these new distribution-free tests converge on a single, surprising conclusion: response biases had substantial effects on the encoding distributions but no effect on the decision rule, which was uniformly unbiased in equal and unequal base rate conditions and in symmetric and asymmetric payoff conditions. This seemingly paradoxical result is fundamentally inconsistent with the entire family of signal detection theory models, raising some important questions about the significance of many published results in the human performance literature. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Guilty knowledge technique: Application of signal detection measures.

Applied procedures for the computation of optimal cutoff points suggested by signal detection theory to an information detection situation with 60 undergraduates. The use of different payoff matrices relevant to a security screening situation and to a criminal court case produces different cutoff points to be used to classify the GSRs. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Pain assessment in self-injurious patients with borderline personality disorder using signal detection theory

Chronic dialysis access is plagued with the formation of stenoses and access thrombosis, with a thrombosis rate of 0.5 to 0.8 episodes per year. Surgical management of thrombosed accesses, including thrombectomy, patch angioplasty, and bypass, has been the traditional treatment for thrombosed grants. Percutaneous catheter-directed thrombolysis of thrombosed accesses, coupled with angioplasty of underlying stenoses, offers comparable results to surgical revascularization. The technical success of thrombolysis is between 75% and 92%, similar to surgical results, with the advantage of sparing vein as potential conduit for future access sites. Surgical therapy may successfully reestablish access function for those stenoses that fail angioplasty. Long-term patencies after a single revascularization procedure are poor (median patency, < 90 days) for both catheter-directed and surgical procedures, and repeat maintenance procedures are necessary. Access surveillance using various means with timely fistulography coupled with angioplasty of stenoses has been shown to decrease the rate of access thromboses by a factor of 3 and to increase patency of grafts. A combined approach with catheter-directed therapies and surgical interventions leads to maximal longevity of each access site.