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PubMed1985

Alcohol effects on signal detection performance.

The acute effects of alcohol (0.7 g/kg) on visual signal detection performance and critical flicker fusion frequency (CFF) of normal volunteers were investigated using a signal detection theory analysis. When signal probability was low, alcohol affected the stimulus sensitivity and the reaction times of hits. Under a high signal probability these indices were not affected, whereas the response bias did not change after the administration of alcohol under both signal probabilities. CFF values were not altered by alcohol. A correlation was found between the magnitude of the alcohol effect and the performance level under placebo. Changing the signal probability caused significant differences between the sensitivity measures, the response bias measures and the reaction times of hits. It is concluded that alcohol affects signal detection performance under conditions of low signal probability. Individuals with a relatively low performance level are more susceptible to the effects of alcohol.

Adult↗
PubMed2003

Application of quantitative signal detection in the Dutch spontaneous reporting system for adverse drug reactions.

The primary aim of spontaneous reporting systems (SRSs) is the timely detection of unknown adverse drug reactions (ADRs), or signal detection. Generally this is carried out by a systematic manual review of every report sent to an SRS. Statistical analysis of the data sets of an SRS, or quantitative signal detection, can provide additional information concerning a possible relationship between a drug and an ADR. We describe the role of quantitative signal detection and the way it is applied at the Netherlands Pharmacovigilance Centre Lareb. Results of the statistical analysis are implemented in the traditional case-by-case analysis. In addition, for data-mining purposes, a list of associations of ADRs and suspected drugs that are disproportionally present in the database is periodically generated. Finally, quantitative signal generation can be used to study more complex relationships, such as drug-drug interactions and syndromes. The results of quantitative signal detection should be considered as an additional source of information, complementary to the traditional analysis. Techniques for the detection of drug interactions and syndromes offer a new challenge for pharmacovigilance in the near future.

Adverse Drug Reaction Reporting Systems↗
PubMed1979

Salt taste detection: an R-index approach to signal-detection measurements.

The R-index approach to the signal-detection P(A) index of sensitivity was used to measure taste sensitivity to NaCl solutions. The R-index is the predicted probability of the correct choice of a signal, for a given signal-noise pair. For flow-wise and sipwise presentation, R-indices did not fluctuate significantly, provided subjects could not see the stimuli yet to be presented, indicating a lack of systematic sensitivity drift. The simultaneous measurement of more than one signal strength with reference to a common noise stimulus was seen to be a viable and sensitive procedure. Comparison of flow-wise and sipwise presentation of stimuli using R-indices, indicated that the former elicited greater subject sensitivity to NaCl taste.

Adolescent↗
PubMed2001

Signal detection in amplitude-modulated maskers. I. Behavioural auditory thresholds in a songbird.

Vertebrates have evolved mechanisms to exploit amplitude modulations in background noise for improving signal detection. However, the mechanisms underlying this masking release are not yet well understood. Here we present evidence for masking release observed in European starlings (Sturnus vulgaris, Aves) that were trained in a Go/NoGo paradigm to report the detection of a short tone (20 ms) in 100% sinusoidally amplitude-modulated noise maskers (400 ms duration). Maskers centred at the tone frequency were composed of one, three, or five spectrally adjacent noise bands each of auditory filter bandwidth. Envelopes of the masking noise bands were either in-phase (i.e. coherent) or successively phase shifted by 90 degrees (i.e. incoherent). A release from masking of up to 28 dB was observed for detection of signals presented in dips of the envelope of coherent maskers compared with those presented in peaks of coherent maskers and in incoherent maskers. For maskers limited to one auditory filter (i.e. limited to the analysis channel tuned to the test signal) this masking release was about 10 dB less than that observed for maskers allowing a comparison across three or five auditory filters. This indicates that both within-channel cues and across-channel cues are important for signal detection. These behavioural data provide the reference for the study of responses of auditory forebrain neurons in the same species reported in a companion paper [Nieder & Klump (2001) Eur. J. Neurosci., 13, 1033-1044].

Animals↗
PubMed1986

Diazepam-induced changes in signal detection performance. A comparison with the effects on the Critical Flicker-Fusion Frequency and the Digit Symbol Substitution Test.

The effects of 10 mg diazepam on signal detection theory measures (stimulus sensitivity, response bias) and reaction times were studied in a 1-hour visual signal detection task with high and low signal probability, and on performance in two short-duration tasks: Critical Flicker-Fusion Frequency (CFF) and the Digit Symbol Substitution Test (DSST). 12 healthy volunteers participated in this placebo-controlled, double-blind cross-over study. Diazepam affected the stimulus sensitivity and the reaction times of hits in the signal detection task. DSST performance was also impaired while CFF did not change after diazepam treatment. No relationship between serum diazepam concentration and change in task performance was found. It is concluded that diazepam affects signal detection performance, independent of signal probability. A short-duration task like the DSST is as sensitive to the effects of diazepam as the (long-duration) signal detection task.

Adolescent↗
PubMed2003

Using the PLUM procedure of SPSS to fit unequal variance and generalized signal detection models.

The recent addition of aprocedure in SPSS for the analysis of ordinal regression models offers a simple means for researchers to fit the unequal variance normal signal detection model and other extended signal detection models. The present article shows how to implement the analysis and how to interpret the SPSS output. Examples of fitting the unequal variance normal model and other generalized signal detection models are given. The approach offers a convenient means for applying signal detection theory to a variety of research.

Algorithms↗
PubMed2005

Detecting effects of donepezil on visual selective attention using signal detection parameters in Alzheimer's disease.

BACKGROUND: Attentional function is impaired in Alzheimer's disease (AD). Moreover, attention is mediated by acetylcholine. But, despite the widespread use of acetylcholinesterase inhibitors (AChE-I) to augment available acetylcholine in AD, measures of attentional function have not been used to assess the drug response. OBJECTIVES: We hypothesized that as cholinergic augmentation impacts directly on the attentional system, higher-order measures of visual selective attention would be sensitive to effects of treatment using an AChE-I (donepezil hydrochloride). We also sought to determine whether these attentional measures were more sensitive to treatment than other measures of cognitive function. METHODS: Seventeen patients with AD (8 untreated, 9 treated with donepezil) were contrasted on performance of a selective cancellation task. Two signal detection parameters were used as outcome measures: decision strategy (beta, beta) and discriminability (d-prime, d'). Standard screening and cognitive domain measures of vigilance, language, memory, and executive function were also contrasted. RESULTS: Treated patients judged stimuli more conservatively (p = 0.29) by correctly endorsing targets and rejecting false alarms. They also discriminated targets from distractors more easily (p = 0.58). The screening and neuropsychological measures failed to differentiate the groups. CONCLUSIONS: Higher-order attentional measures captured the effects of donepezil treatment in small groups of patients with AD. The results suggest that cholinergic availability may directly affect the attentional system, and that these selective attention measures are sensitive markers to detect treatment response.

Aged↗
PubMed1978

Critical-band effects in two-channel auditory signal detection.

Two-channel auditory signal detection was investigated with 50-msec sinusoidal signals masked by binaurally uncorrelated noise. In the two-channel tasks, the signals in each earphone channel were presented with an independent probability during the single observation interval and the observers were required to detect the inputs in a single earphone (selective-attention condition) or in both earphones (divided-attention condition). When the signals in each earphone were within the same critical band (the assumed singled processing unit in frequency domain), there was a decrement in detection performance in both the selective- and divided-attention (i.e. dichotic) conditions compared with the monaural condition. However, when signals were separated in frequency by several critical bands, a decrement in dichotic performance, as compared with monaural performance, occurred only in the divided-attention condition. These findings are discussed in terms of their implications regarding models of multichannel signal processing and the definition of input channels in terms of earphones.

Attention↗
PubMed2007

Dual-process theory and signal-detection theory of recognition memory.

Two influential models of recognition memory, the unequal-variance signal-detection model and a dual-process threshold/detection model, accurately describe the receiver operating characteristic, but only the latter model can provide estimates of recollection and familiarity. Such estimates often accord with those provided by the remember-know procedure, and both methods are now widely used in the neuroscience literature to identify the brain correlates of recollection and familiarity. However, in recent years, a substantial literature has accumulated directly contrasting the signal-detection model against the threshold/detection model, and that literature is almost unanimous in its endorsement of signal-detection theory. A dual-process version of signal-detection theory implies that individual recognition decisions are not process pure, and it suggests new ways to investigate the brain correlates of recognition memory.

Humans↗
PubMed1990

Visual attention modulates signal detectability.

The mechanism by which visual-spatial attention affects the detection of faint signals has been the subject of considerable debate. It is well known that spatial cuing speeds signal detection. This may imply that attentional cuing modulates the processing of sensory information during detection or, alternatively, that cuing acts to create decision bias favoring input at the cued location. These possibilities were evaluated in 3 spatial cuing experiments. Peripheral cues were used in Experiment 1 and central cues were used in Experiments 2 and 3. Cuing similarly enhanced measured sensitivity, P(A) and d', for simple luminance detection in all 3 experiments. Under some conditions it also induced shifts in decision criteria (beta). These findings indicate that visual-spatial attention facilitates the processing of sensory input during detection either by increasing sensory gain for inputs at cued locations or by prioritizing the processing of cued inputs.

Adult↗
PubMedDate not supplied

Investigation of basic imaging properties in digital radiography. 9. Effect of displayed grey levels on signal detection.

Results of an 18-alternative forced-choice experiment have shown that observers were capable of detecting a signal with a contrast of 1 in terms of 10-bit data which were displayed on a CRT monitor with an 8-bit video generator and a window width setting of 1024. We investigated the conditions under which 10-bit signal data can be detected when displayed using an 8-bit video generator. Results show that the 10-bit digital quantum noise, which was approximately Gaussian distributed, can act as a carrier of the signal data, thus allowing a signal having a contrast of a fraction of a displayed grey level to be detected. We demonstrate the relationship between the rms value of the digital noise (obtainable with a clinical digital subtraction angiography system under various exposure levels), the number of bits available in the display video generator, and the "transmitted" signal contrast displayed on the CRT monitor.

Biometry↗
PubMed1971

Evoked potential correlates of auditory signal detection.

A long-latency comnponent of the averaged evoked potential recorded from the human scalp varied in close relationship with subjects' perceptual reports in an auditory signal detection task. Detected signals evoked potentials several times larger than did undetected signals, falsely reported signals, or correctly reported nonsignals. The threshold signal intensity at which detection perfornmance exceeded chance levels was identical with concurrently obtained electro-physiological measures of threshold.

Auditory Perception↗
PubMed2000

Visual signal detection in structured backgrounds. IV. Figures of merit for model performance in multiple-alternative forced-choice detection tasks with correlated responses.

Many investigators are currently developing models to predict human performance in detecting a signal embedded in complex backgrounds. A common figure of merit for model performance is d', an index of detectability that can be mathematically related to the proportion correct (Pc) when the responses of the model are Gaussian distributed and statistically independent. However, in many multiple-alternative forced-choice (MAFC) detection tasks, the target appears in one of M different locations within an image. If the image contains slow spatially varying luminance changes (low-pass noise), the pixel luminance values at the possible signal locations are correlated and therefore the model/human responses to the different locations might also be correlated. We investigate the effect of response correlations on model performance and compare different figures of merit for these conditions. Our results show that use of the standard d' index of detectability assuming statistical independence can lead to erroneous underestimates of Pc and misleading comparisons of models. We introduce a novel figure of merit d'(r) that takes into account response correlations and can be used to accurately estimate Pc. Furthermore, we show that d'(r) can be readily related to the standard index of detectability d' by d'(r) = d'/square root of (1 - r), where r is the correlation between the responses in any MAFC detection task. We illustrate the use of the theory by computing figures of merit for two linear models detecting a signal in one of four locations within medical image backgrounds.

Choice Behavior↗
PubMed1987

Signal detection analyses of delays in neonates' vocalizations.

Signal detection analyses were applied to momentary delays in the regular peeping of newborn chicks that occur in response to acoustic stimuli. Pulsing 1000-Hz tones at various intensities were repeatedly presented to chicks at 0 and 4 days posthatch. Durations of delays on both stimulus and control (mock) trials were collected in histograms. These histograms were then used to draw receiver operating characteristics (ROC curves) given variable definitions of what constitutes a "yes" response. Areas under these ROC curves were used to evaluate various ways of measuring the delay, as well as the effects of habituation, intensity, and age. Time to the second poststimulus peep was identified as a sensitive indicator of responsiveness. Habituation decreased responsiveness by about 5% per trial over the first three trials. Each dB of intensity increased responsiveness by about 1%. Maturation increased responsiveness by about 21 dB over 4 days. These ROC curves show that momentary delays in the vocalizations of newborn chickens are appropriate measures of auditory signal detection. Similar analyses could be useful in other psychophysical studies that depend on the changing rate of repetitive responses.

Acoustic Stimulation↗
PubMed2001

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.

Animals↗
PubMed1975

Differential reinforcement and signal detection.

Reinforcement was introduced for responses normally treated as errors in signal-detection procedures. The first experiment used a standard two-response discrete-trial procedure with no reinforcement for errors. Results showed that rats altered their response biases but maintained constant sensitivity to visual signals when reinforcement probabilities varied, and that their sensitivity depended on the physical difference between signals, in accordance with the predictions of signal-detection theory. Experiment II, with rats, and Experiment III, with pigeons, demonstrated that sensitivity decreased in this procedure when reinforcement was scheduled for errors with the signals held constant, despite independence of overall number of reinforcers and sensitivity. Experiment IV, with rats, replicated the decrease in sensitivity in a continuous procedure employing only one response. The decrements in sensitivity were similar across Experiments II, III, and IV, and accorded well with earlier research. Thus, contrary to a fundamental assumption of signal-detection theory, estimates of sensitivity are not always invariant with respect to the outcomes of responding, but depend on relative reinforcement of correct responses.

Animals↗
PubMed1975

The effect of signal probability, food intake, sex, and smoking on gustation, as measured by the theory of signal detection.

The possibility of applying Signal Detection Theory (SDT) to gustation was investigated by testing the effect of three variables--smoking, signal probability, and food intake (confounded with time of day)--on the taste sensitivity to sucrose of 24 male and 24 female Ss. No main effects or interactions were significant. The study indicated a "warm-up" effect, while adaptation was questionable. An analysis of false alarm (FA) reports was undertaken and discussed. Correlations were obtained between numerous variables and sensitivity. None of the correlations was statistically significant. It was concluded that although SDT is theoretically applicable to the gustatory modality, it is not practical for large-scale research.

Differential Threshold↗
PubMed1995

Temporal-signal detection and individual differences in timing.

Signal-detection procedures were used in three experiments to examine sensitivity and bias in time judgments and to evaluate individual differences in timing. The task required subjects to judge whether visual stimuli were presented for a certain target duration (the 'signal') or for a slightly longer duration. In experiment 1, subjects performed versions of the task involving both short (2 s) and long (12 s) target stimuli. Analyses of sensitivity and bias measures (d' and beta) provided evidence for consistency in timing performance within individuals. In experiment 2, subjects were tested on a detection task with 5, 10, or 15 s targets, followed by a temporal-reproduction task involving stimulus durations ranging from 3 to 17 s. Subjects with high temporal sensitivity showed less error in their reproductions than subjects with low temporal sensitivity. In experiment 3, subjects were pretested on a detection task with a 12 s target and then performed a temporal-production task where they attempted to generate a series of 12 s intervals under either control or informational feedback conditions. Feedback improved accuracy and reduced variability in temporal productions. However, the low-temporal-sensitivity subjects were more variable in their responses under both conditions than were the high-sensitivity subjects. The results point to the utility of a temporal-signal-detection task both as a means for studying individual differences in timing and as a pretesting technique for assigning subjects to high-sensitivity and low-sensitivity groups to reduce error in time-judgment data.

Analysis of Variance↗