SEARCH · PubMed Health
Results for “Signal Detection, Psychological”
Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Neural coding with graded membrane potential changes and spikes.
The neural encoding of sensory stimuli is usually investigated for spike responses, although many neurons are known to convey information by graded membrane potential changes. We compare by model simulations how well different dynamical stimuli can be discriminated on the basis of spiking or graded responses. Although a continuously varying membrane potential contains more information than binary spike trains, we find situations where different stimuli can be better discriminated on the basis of spike responses than on the basis of graded responses. Spikes can be superior to graded membrane potential fluctuations if spikes sharpen the temporal structure of neuronal responses by amplifying fast transients of the membrane potential. Such fast membrane potential changes can be induced deterministically by the stimulus or can be due to membrane potential noise that is influenced in its statistical properties by the stimulus. The graded response mode is superior for discrimination between stimuli on a fine time scale.
Detecting changes between real-world objects using spatiochromatic filters.
A behavioral and computational treatment of change detection is reported. The behavioral task was to judge whether a single object substitution change occurred between two "flickering" 9-object scenes. Detection performance was found to vary with the similarity of the changing objects; object changes violating orientation and category yielded the fastest and most accurate detection responses. To account for these data, the BOLAR model was developed, which uses color, orientation, and scale selective filters to compute the visual dissimilarity between the pre- and postchange objects from the behavioral study. Relating the magnitude of the BOLAR difference signals to change detection performance revealed that object pairs estimated as visually least similar were the same object pairs most easily detected by observers. The BOLAR model advances change detection theory by (1) demonstrating that the visual similarity between the change patterns can account for much of the variability in change detection behavior, and (2) providing a computational technique for quantifying these visual similarity relationships for real-world objects.
Perceptual binding of sensory events: the inclusive characteristics model.
A conceptual model of a perceptual system is proposed, in which each neural level forms characteristics inclusive of the data held in the underlying level. As a result, the stimulus field can be expressed as a hierarchically ordered set of overlying sensory characteristics: from sensory features to higher inclusive characteristics binding sensory data to form whole images and scenes. Specific patterns of electrical activity reflecting inclusive characteristics are transmitted via reverse projections from the upper neural levels to the lower. This forms a downward excitation transmission cascade, stimulating those neural structures whose signals correspond to the higher inclusive characteristics of the given perceptual act. It is demonstrated that these mechanisms are in good agreement with experimental data obtained from psychological and neurophysiological studies and may support the binding of sensory events at all perceptual levels.
Differential patterns of performance impairment result from changed reinforcer efficacy or distracting stimulation in a two-choice rodent spatial signal detection task.
Measures of the discriminabililty of stimuli in signal detection tasks can be influenced by alterations of motivational state. In the present study, rats performed an operant signal detection procedure that required the completion of a fixed number of responses before a stimulus was presented at one of two front cue lamps to separately measure the motivation to respond from the ability to respond accurately. One manipulation, presession water access, affected the speed and frequency that trials were initiated, but did not affect response accuracy. In contrast, a flashing houselight during the session, and i.p. ((5R,10S)-(+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d,] cyclohepten-5,10-imine (dizocilpine or MK-801), a glutamate N-methyl-D-aspartate receptor antagonist, impaired response accuracy in a stimulus duration-dependent manner. These results suggest that it is possible to procedurally isolate the motivation to respond to stimuli from accuracy of detection, and thereby protect attending from side effects of drugs that influence the motivation to respond.
Spreadsheet signal detection.
A number of studies in perception, attention, and memory employ signal detection theory (SDT) to assess the accuracy of an observer's detection or discrimination performance. Some of the problems that students have with understanding and using SDT are associated with the calculations needed to obtain SDT parameters and predictions. All of these calculations, plus the simulation of SDT processes, can be performed using a spreadsheet application program, such as Excel or Quattro Pro. This paper offers a short tutorial on how to use a spreadsheet program to increase your students' knowledge and understanding of SDT.
Within-category feature correlations and Bayesian adjustment strategies.
To the extent that categories inform judgments about items, the accuracy with which categories capture the statistical structure of experience should affect judgment accuracy. The authors argue that representations of feature correlations can serve as Bayesian priors, increasing the accuracy of stimulus estimates by decreasing variability. Participants viewed a series of objects that varied on two dimensions that were either uncorrelated or correlated. They estimated each item by manipulating a response object to make it match the presented stimulus. Subsequent classification and feature-inference tasks indicated that the correlation was detected. The pattern of variability in recollections of stimuli suggested that the feature correlation informed estimates as predicted by a Bayesian model of category effects on memory.
Amygdala activation during masked presentation of emotional faces predicts conscious detection of threat-related faces.
It has been argued that critical functions of the human amygdala are to modulate the moment-to-moment vigilance level and to enhance the processing and the consolidation of memories of emotionally arousing material. In this functional magnetic resonance study, pictures of human faces bearing fearful, angry, and happy expressions were presented to nine healthy volunteers using a backward masking procedure based on neutral facial expression. Activation of the left and right amygdala in response to the masked fearful faces (compared to neutral faces) was significantly correlated with the number of fearful faces detected. In addition, right but not left amygdala activation in response to the masked angry faces was significantly related to the number of angry faces detected. The present findings underscore the role of the amygdala in the detection and consolidation of memory for marginally perceptible threatening facial expression.
The development of change detection.
Changes to a scene often go unnoticed if the objects of the change are unattended, making change detection an index of where attention is focused during scene perception. We measured change detection in school-age children and young adults by repeatedly alternating two versions of an image. To provide an age-fair assessment we used a bimanual choice rather than open-ended verbal responses. The difference in detection speed and accuracy between 50-ms versus 250-ms blank screens between views indexed change detection in short-term visual memory independent of sensory and response processes. Younger children were significantly less efficient than older participants, especially when an object changed color or had a part deleted. Changes in object orientation were detected more readily. These results point to important differences in the perceptual reality of younger and older children.
An application of signal detection theory with finite mixture distributions to source discrimination.
A mixture extension of signal detection theory is applied to source discrimination. The basic idea of the approach is that only a portion of the sources (say A or B) of items to be discriminated is encoded or attended to during the study period. As a result, in addition to 2 underlying probability distributions associated with the 2 sources, there is a 3rd distribution that represents items for which sources were not attended to. Thus, over trials, the observed response results from a mixture of an attended (A or B) distribution and a nonattended distribution. The situation differs in an interesting way from detection in that, for detection, there is mixing only on signal trials and not on noise trials, whereas for discrimination, there is mixing on both A and B trials. Predictions of the mixture model are examined for data from several recent studies and in a new experiment.
The effects of caffeine and expectancy on attention and memory.
The present study contrasted caffeine's effects on individuals who expect caffeine to stimulate them and those who do not. Secondly, whether a message that caffeine rather than placebo was administered would also affect these two groups of subjects differently was investigated. The study was conducted single-blind in a 2x2x2 mixed design. The between subjects factor was whether they expected caffeine to stimulate them (E+) or not (E-) according to their self reports obtained before the experiment began. The within subjects factors were message (told caffeine vs told placebo) and beverage type (given caffeine vs placebo). Sixteen subjects in each group (n=32) performed on signal detection, memory scanning and delayed free recall tasks following ingestion of either caffeinated or decaffeinated coffee on two sessions each, a total of four experimental sessions. On each session, subjects were given a message regarding their drink (told caffeine vs told placebo). However, on two sessions there was a mismatch between the message and drink given. For signal detection, performance under caffeine was better than placebo in the E+ but not the E- group. However, subjects in the E+ group did not benefit more than the E- group in either message condition. On memory scanning, detections and false alarms did not differ for either beverage, nor was there a differential finding in the E+ and E- groups. However, reaction time under caffeine condition was shorter. No effects of message were found. Caffeine and message also did not have any effect on performance on the delayed free recall task. The hypothesis that caffeine and message would affect E+ and E- subjects differentially was partly supported.
Processing of facial expressions of negative emotion in alexithymia: the influence of temporal constraint.
Alexithymia, a characteristic involving a limited affective vocabulary appears to involve three components: difficulty identifying feelings, difficulty describing feelings, and externally oriented thinking. There is evidence that alexithymic characteristics are associated with differences in emotion information-processing. We examined the role of temporal factors in alexithymic emotion-processing deficits, taking into account the confound between alexithymic characteristics and positive and negative affectivity. One hundred forty-six participants completed the 20-item Toronto Alexithymia Scale and the Positive and Negative Affect Schedule. In a signal-detection paradigm, participants judged facial expressions depicting neutral or negative emotions under slow and rapid presentation conditions. The alexithymia component of difficulty in describing feelings was inversely related to the ability to detect expressions of negative emotion in the speeded condition. This relationship was independent of positive and negative affectivity. Alexithymic components positive and negative affectivity were unrelated to response bias. The results emphasize the influence of difficulty describing feelings within the alexithymia construct and its difference from positive and negative affectivity. They suggest that an alexithymic deficit in describing feelings is associated with a deficit in processing negative emotions that is most apparent when processing capacity is challenged. Theoretical and methodological implications are discussed.
Attentional prioritization to contextually new objects.
Using a hybrid paradigm of a contextual cuing task and a probe detection task, we tested whether or not contextually new objects can be prioritized in visual search. After several hundred visual search practice trials with repeated and nonrepeated layouts, an additional distractor that was contextually new was presented in the repeated layouts. The results showed that detection of probe dots appearing at the location of a search target was faster in the repeated than in the nonrepeated layouts. More importantly, detection of probe dots at the new object locations was as fast as that of probe dots at the target locations in repeated layouts, suggesting that the attentional system implicitly prioritizes the processing of a location where a change in contextual information has occurred.
A comparison of the multimemory and detection theories of know and remember recognition judgments.
Know and remember recognition judgments were made in 2 experiments. In Experiment 1 either 3 (new, know, remember) or 4 (new, guess, know, remember) judgment alternatives were used. Also, the recognition test was either immediate, delayed 2 days, or delayed 1 week. In Experiment 2 the proportion of test items that were studied items was either .20, .50, or .80. Predictions were made from 2 multimemory theories regarding how proportions of know and remember judgments would change with these manipulations. Predictions were also made from 2 detection theories regarding the values of memory sensitivity and judgment criteria. The results supported the revised detection theory, which assumes unequal variances for studied and unstudied items, more than the multimemory theories. Furthermore, general processing tree versions of the 2 multimemory models were created including guessing processes. These extended models were shown to be inadequate in accounting for the data from the 2 experiments.
Introduction of a retention interval in a sustained attention task in rats: effects of a visual distracter and increasing the inter-trial interval.
The impact of manipulating explicit attentional demands on working memory has not been well studied in rodents. The present experiment was designed to test the effects of incorporating a retention interval in a two-lever sustained attention task that requires discrimination of visual signals and non-signals and that has previously been shown to yield valid measures of attention in the rat. Upon establishing baseline performance, additional manipulations, including presentation of a visual distracter and increasing the length and variability of the inter-trial interval were conducted. During baseline conditions, accurate detection of signals, but not non-signals, decreased as the retention interval was increased. Presentation of a flashing houselight throughout the session eliminated delay-dependent detection of signals. Increasing the inter-trial interval improved detection of signals and decreased detection of non-signals at the longest retention interval. Finally, increasing the variability of the inter-trial interval did not have significant effects on performance above and beyond the effects of increasing the inter-trial interval. The present experiment demonstrates that manipulation of explicit attentional demands can alter working memory performance in the rat. This task may be employed to understand the neuropharmacological and neuroanatomical substrates mediating memory while attentional load is systematically varied.
The effect of object and event orientation on perception of biological motion.
Detection and recognition of point-light walking is reduced when the display is inverted, or turned upside down. This indicates that past experience influences biological motion perception. The effect could be the result of either presenting the human form in a novel orientation or presenting the event of walking in a novel orientation, as the two are confounded in the case of walking on feet. This study teased apart the effects of object and event orientation by examining detection accuracy for upright and inverted displays of a point-light figure walking on his hands. Detection of this walker was greater in the upright display, which had a familiar event orientation and an unfamiliar object orientation, than in the inverted display, which had a familiar object orientation and an unfamiliar event orientation. This finding supports accounts of event perception and recognition that are based on spatiotemporal patterns of motion associated with the dynamics of an event.
Altered performance of schizophrenia patients in an auditory detection and discrimination task: exploring the 'self-monitoring' model of hallucination.
It has been suggested that perceptual hallucination results from a bias in attributing a self-generated event to an external source. The 'self-monitoring' model proposes that the impairment arises from a defective corollary discharge in perceptual decisions. However, psychophysical studies in schizophrenia patients have not found consistent support for the model. We re-explored this issue by including subjects with mood disorders as patient controls and employed signals of variable intensities in an auditory detection and discrimination task. Using signal detection theory, we found decreased sensitivity in auditory detection and discrimination in schizophrenia patients, as compared to control subjects. Moreover, the psychometric functions of schizophrenics had a shallower slope than those of the controls. According to the uncertainty theory of signal detection, this suggested that schizophrenia patients monitored a smaller number of perceptual channels. On the other hand, hallucinating and non-hallucinating schizophrenia patients did not differ from each other, nor did they as a group differ from control subjects in terms of response bias. Overall, our results do not support the idea that hallucination results from an altered bias in the online processing of perceptual signals.
Failures of retrieval and comparison constrain change detection in natural scenes.
In a change detection paradigm, a target object in a natural scene either rotated in depth, was replaced by another object token, or remained the same. Change detection performance was reliably higher when a target postcue allowed participants to restrict retrieval and comparison processes to the target object (Experiment 1). Change detection performance remained excellent when the target object was not attended at change (Experiment 2) and when a concurrent verbal working memory load minimized the possibility of verbal encoding (Experiment 3). Together, these data demonstrate that visual representations accumulate in memory from attended objects as the eyes and attention are oriented within a scene and that change blindness derives, at least in part, from retrieval and comparison failure.