Psychophysically principled models of visual simple reaction time.

Visual psychophysics has shown that the perceptual representation of a stimulus has complex time-varying properties that depend on the response characteristics of the channel on which it is encoded. A fundamental expression of these properties is the distinction between sustained and transient processing channels. A theoretical and mathematical framework is introduced that allows such properties to be incorporated into fully stochastic models of simple reaction time (RT). These models, the multichannel leaky stochastic integrators, combine a linear filter model of stimulus encoding with an accumulative decision process and yield a stimulus representation described by a time-inhomogeneous Ornstein-Uhlenbeck diffusion process. Methods for obtaining RT distributions for these models are described, together with comparative fits to luminance-increment data obtained under conditions of channel pooling and channel independence. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Levels of representation in visual word recognition: a dissociation between morphological and semantic processing

A robust semantic priming effect typically occurs in visual word recognition if the prime is read before a response to the target. However, this effect is dramatically reduced if a letter search is performed on the prime prior to responding to the target. Three lexical decision experiments document the new observation that morphological priming is preserved following letter search on the prime. This dissociation between morphological and semantic priming following letter search can be understood in the context of an interactive activation framework. In addition, the implications of these results for connectionist and compound cue accounts of word recognition, as well as the issue of automaticity in word recognition, are discussed.     

Repetition priming reveals sustained facilitation and transient inhibition in reaction time.

Reaction time (RT) in a detection or a location discrimination task increases when a target is repeatedly presented at the same location (inhibition), whereas RT decreases in feature (color or orientation) discrimination tasks (facilitation; Y. Tanaka & S. Shimojo, 1996a). Here, the time course of inhibition and facilitation was examined, using a repetition priming paradigm. Results indicate that inhibition occurred only in the immediately successive trial, whereas facilitation accumulated over several trials with location repetition. Moreover, inhibition and facilitation occurred in a task-relevant manner: Detection–location discrimination tasks produced transient RT increase, whereas feature discrimination tasks produced cumulative RT decrease. These results suggest a functional dissociation between spatial orienting and feature analysis, as well as top-down modulations by tasks leading to different types of visual memory. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The simple reaction time to changes in direction of visual motion

Recently Dzhafarov et al. presented a model explaining data on simple reaction time (RT) to unidimensional velocity changes. The authors suggested that having a motion with an initial velocity V0, the velocity change detection system is reinitialized by means of a "subtractive normalization" process. Therefore, any abrupt change from V0 to V1 is detected as if it were the onset of motion with a speed equal to /V1-V0/. They derived that the RT is a function of /V1-V0/(-2/3). We tested this model for the case of two-dimensional velocity changes. Our subjects observed a random dot pattern that moved horizontally, then changed the direction of motion by an angle alpha in the range between 6 degrees and 180 degrees without changing the speed V. Speeds of 4 and 12 deg/s were used. The subjects reacted as quickly as possible to the direction change. The RTs asymptotically decreased with increasing alpha; with 12 deg/s speed the RTs were shorter than those obtained with 4 deg/s. It was shown that the data can be well described as a function of /V1-V0/(-2/3)=(2Vsin(alpha/2))(-2/3). An extension of the "subtractive normalization" hypothesis for the case of two-dimensional velocity changes is proposed. It is based on the assumption that the velocity vector V1 after the change is decomposed into two orthogonal components. Alternative explanations based on the use of position or orientation cues are shown to contradict the data.     

Immunomodulatory effects of linomide in animals immunized with immunopathogenic retinal antigens: dissociation between different immune functions

Linomide (LS-2616, quinoline-3-carboxamide) has been reported to exert a diverse range of effects on the immune system. On one hand, this drug was found to stimulate the immune system and to enhance activities such as DTH or allograft rejection. On the other hand, linomide was shown to inhibit the induction of experimental autoimmune encephalomyelitis and myasthenia gravis, as well as the development of diabetes in non-obese diabetic (NOD) mice. Here we report the effects of linomide in animals immunized with uveitogenic retinal antigens. Treatment with linomide completely inhibited the development of experimental autoimmune uveoretinitis (EAU) in mice immunized with interphotoreceptor retinoid-binding protein and markedly suppressed EAU in rats immunized with S-antigen (S-Ag). In addition, linomide-treated rats exhibited reduced antibody production and lymphocyte proliferative response to S-Ag. In contrast to these suppressive activities, linomide treatment did not affect the development of adoptively transferred EAU in rats and moderately enhanced the DTH reactions to S-Ag in immunized rats in which EAU and other immune responses to this antigen were suppressed.     

Cortical and subcortical visual evoked potential correlates of reaction time in monkeys.

Investigated the relationships between reaction time (RT) and evoked potentials in 3 monkeys ( Macaca nemestrina ) during the performance of a simultaneous brightness discrimination task. Evoked potentials from the lateral geniculate, medial and inferior pulvinar, midbrain reticular formation, hippocampus, and striate and prestriate cortex were recorded concurrently with RT in response to the discriminative stimuli. An early component of the geniculate response and a late positive wave in striate cortex were found to be related systematically to RT. These components were largest for short RTs and diminished progressively in amplitude as RT lengthened. The statistical significance of these relationships is supported by a detailed analysis of single trials. The increases in amplitude of evoked potentials associated with short RTs are attributed to increased arousal level and are discussed in terms of reticular formation modulation of central excitability levels. (15 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Types and tokens in visual processing: A double dissociation between the attentional blink and repetition blindness.

In rapid serial visual presentation tasks, correct identification of a target triggers a deficit for reporting a 2nd target appearing within 500 ms: an attentional blink (AB). A different phenomenon, termed repetition blindness (RB), refers to a deficit for the 2nd of 2 stimuli that are identical. What is the relationship between these 2 deficits? The present study obtained a double dissociation between AB and RB. AB and RB followed different time courses (Experiments 1 and 4A), increased target-distractor discriminability alleviated AB but not RB (Experiments 2 and 4A), and enhanced episodic distinctiveness of the two targets eliminated RB but not AB (Experiments 3 and 4B). The implications of the double dissociation between AB and RB for theories of visual processing are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Number and position of visual stimuli as determinants of reaction time in schizophrenia.

Notes that RT in normal Ss has been shown to be linearly related to stimulus complexity, defined as the log of the number of equally probable stimuli to which a response may be made. Data from an earlier study of 40 short- and long-term paranoid and nonparanoid male schizophrenics and 10 male hospital employees were reanalyzed and compared with P. Venable's (see record 1959-10789-001) study of schizophrenic deficit. Although experimental procedures were dissimilar, both studies found that increased complexity did not result in schizophrenics having steeper regression slopes than normal Ss. Consideration of the position of the critical stimulus, however, clearly indicated that long-term, nonparanoid schizophrenics narrow attention to central cues when confronted by an increase in complexity. (French summary) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Further evidence of dissociation between reactivity and visual evoked response following septal lesions in rats.

Used a more sensitive method than that of a previous study by J. Schwartzbaum, C. Kreinick, and M. Levine (see record 1972-30527-001) for behavioral reactivity to discrete series of photic stimuli, to allow closer examination of relationships between reactivity and averaged visual evoked responses (VERs) recorded at the cortex. 12 male Holtzman rats served as Ss. Septal lesions markedly impaired habituation of behavioral reactivity to flashes but facilitated development of the VER. The elaboration of VERs, particularly late components, is normally associated with habituation of behavioral reactivity to the stimuli. This lesion-induced dissociation was also confirmed through correlational analysis of the relationship between VERs and activity. It is concluded that septal lesions, in effect, attenuate the normal relationship between motoric activity and sensory-evoked response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Relation between latency and redundancy-associated deficit in schizophrenic reaction time performance.

Evaluated the independence of 2 well-established measures of information-processing difficulties in process schizophrenics, namely, reaction time measures of latency and redundancy-associated deficit. Training exercises were designed to improve the speed of reaction time performance in 16 male Ss (average age 32.5 yrs). These exercises were successful in reducing latency over the course of training and from pre- to posttraining assessments to levels falling around the range of performance expected of normals. Redundancy-associated deficit, however, did not change from pre- to postassessment, indicating that this index is not a simple reflection of latency and is not responsive to training procedures involving positive motivation. Intercorrelations of the 2 indexes also showed that these measures were independent, at least within the process end of the schizophrenic spectrum. Furthermore, the 2 measures correlated with different types of S factors. Latency measures correlated with measures of chronicity, and the redundancy-deficit measure was correlated with prognosis. Findings help to clarify the utility of reaction time indexes as markers of various aspects of schizophrenic pathology. (33 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Prothrombin time: one tube or two

This study compares the prothrombin times (PTs) and calculated international normalized ratios (INRs) from first and second evacuation blood tubes to determine the clinical importance of using a second tube specimen for protime coagulation studies. The National Committee for Clinical Laboratory Standards (NCCLS) currently recommends that all coagulation studies be done on a second or later drawn blood tube. For patients on long-term anticoagulation therapy, this often requires that first blood tubes be drawn and discarded at each prothrombin evaluation. In this prospective study, a first and second evacuation blood tube was drawn from 343 outpatients who had a physician-ordered prothrombin time test performed. There was no statistically significant difference in the paired PT or calculated INR from any of the first and second tubes. The average difference in the INR from tube 1 to tube 2 was 2% (standard deviation [SD] 1.1%). In this sample of outpatients, the use of a second tube for PT testing was not clinically justified.     

A random-walk model of accuracy and reaction time applied to three experiments on pigeon visual discrimination.

A random-walk model of visual discrimination is described and applied to reaction time (RT) distributions from three discrete-trial experiments with pigeons. Experiment 1 was a two-choice hue discrimination task with multiple hues. Choice percentages changed with hue discriminability; RTs were shortest for the least and most discriminable stimuli. Experiments 2 and 3 used go/no-go hue discriminations. Blocks of sessions differed in reward probability associated with a variable red stimulus in Experiment 2 and with a constant green stimulus in Experiment 3. Changes in hue had a large effect on response percentage and a small effect on RT; changes in reward shifted RT distributions on the time axis. The “random-walk, pigeon” model applied to these data is closely related to Ratcliff's diffusion model (Ratcliff, 1978; Ratcliff & Rouder, 1998). Simulations showed that stimulus discriminability affected the speed with which evidence accumulated toward a response threshold, in line with comparable effects in human subjects. Reward probability affected bias, modeled as the amount of evidence needed to reach one threshold rather than the other. The effects of reward probability are novel, and their isolation from stimulus effects within the decision process can guide development of a broader model of discrimination. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Life-span development of visual working memory: When is feature binding difficult?

We asked whether the ability to keep in working memory the binding between a visual object and its spatial location changes with development across the life span more than memory for item information. Paired arrays of colored squares were identical or differed in the color of one square, and in the latter case, the changed color was unique on that trial (item change) or was duplicated elsewhere in the array (color-location binding change). Children (8-10 and 11-12 years old) and older adults (65-85 years old) showed deficits relative to young adults. These were only partly simulated by dividing attention in young adults. The older adults had an additional deficiency, specifically in binding information, which was evident only when item- and binding-change trials were mixed together. In that situation, the older adults often overlooked the more subtle, binding-type changes. Some working memory processes related to binding undergo life-span development in an inverted-U shape, whereas other, bias- and salience-related processes that influence the use of binding information seem to develop monotonically. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Risperidone vs. haloperidol on reaction time, manual dexterity, and motor learning in treatment-resistant schizophrenia patients

BACKGROUND: The present study compared the effects of risperidone vs. haloperidol on reaction time, manual dexterity, and two types of motor learning in a sample of treatment-resistant schizophrenia patients. METHODS: Fifty-six DSM-III-R diagnosed schizophrenia inpatients participated in a randomized, double-blind comparison of risperidone vs. haloperidol. Measures of reaction time, manual dexterity, motor sequence learning, and gross motor learning were administered at baseline, after 4 weeks of fixed-dose medication, and after 4 weeks of flexible-dose medication. RESULTS: The results indicated that patients receiving risperidone showed greater improvement in reaction time and manual dexterity than patients receiving haloperidol. After covarying symptom changes and movement disorder ratings, the results remained significant. The two treatment groups did not differ on either measure of motor learning. CONCLUSIONS: The differences in performance in reaction time and manual dexterity may be due to a specific beneficial effect of risperidone, as opposed to a general reduction in extrapyramidal symptom liability, compared to haloperidol.     

Pharmacological dissociation between the reinforcing, sensitizing, and response-releasing functions of reward in honeybee classical conditioning.

Reserpine depletes biogenic amines from their stores in the honeybee (Apis mellifera camica) brain and leads to impaired appetitive conditioning using sucrose as a reinforcer. Compensatory injection of octopamine or dopamine directly into the brain restores these behavioral losses. Dopamine rescues the slowing-down effect on motor patterns, but not sensitization or conditioning. Octopamine leaves the motor patterns as well as sensitization unchanged but rescues conditioning. Specifically, octopamine rescues acquisition but not retrieval. Serotonin has no significant effect on sensitization but impairs conditioning. The authors conclude that octopamine is involved in selectively mediating the reinforcing but not the sensitizing or response-releasing function of the sucrose reward, whereas dopamine is selectively involved in the expression of the motor response. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

On the relations between discrimination reaction time, anxiety, and intelligence.

In a test of a theory concerning the effects of drive on performance involving conflicting habits, the current author, Grice, found the predicted difference on a complex discrimination reaction time task between two groups differing in "manifest anxiety." However, a covariance analysis indicated that this difference could be attributed to differences between the groups in intellectual ability. Freeman and Maher have criticized Grice's conclusion on the basis of speculations that the Discrimination Reaction Time Test (DRT) is "largely perceptual in character" and that perceptual factors in the Clerical Aptitude Index (employed as an intellectual measure) may have produced the obtained relation rather than general intellectual ability. Citing the excellent study by Fleishman and Hempel as evidence, they argue that intellectual components in DRT tend to disappear with practice and that perceptual speed and simple reaction time assume greater importance. The author comments on their criticisms. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A double dissociation between the rat hippocampus and medial caudoputamen in processing two forms of knowledge.

Rats with hippocampus, medial caudoputamen (CPU), lateral CPU, or control lesions were trained on declarative and procedural knowledge variants of a novel rodent sequential learning task. Medial CPU lesions impaired rats' ability to learn the procedure of running through a sequence of open maze arms but did not disrupt their capacity to explicitly generate (i.e., "declare") maze arm sequences. Hippocampus lesions produced the opposite set of results. Rats with lateral CPU lesions were not impaired on either version of the task. Transfer tests indicated that control rats predominantly used egocentric cues to solve the procedural task and allocentric spatial cues to solve the declarative task. These findings suggest a double dissociation between the medial CPU and hippocampus in processing egocentric-procedural and allocentric- declarative sequential information, respectively. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Guided search: An alternative to the feature integration model for visual search.

Subjects searched sets of items for targets defined by conjunctions of color and form, color and orientation, or color and size. Set size was varied and reaction times (RTs) were measured. For many unpracticed subjects, the slopes of the resulting RT?×?Set Size functions are too shallow to be consistent with A. Treisman's (see record 1988-00255-001) and A. Treisman and G. Gelade's (see record 1980-04680-001) feature integration model, which proposes serial, self-terminating search for conjunctions. Searches for triple conjunctions (Color?×?Size?×?Form) are easier than searches for standard conjunctions and can be independent of set size. A guided search model similar to J. E. Hoffman's (see record 1981-04707-001) two-stage model can account for these data. In the model, parallel processes use information about simple features to guide attention in the search for conjunctions. Triple conjunctions are found more efficiently than standard conjunctions because three parallel processes can guide attention more effectively than two. (PsycINFO Database Record (c) 2010 APA, all rights reserved)