Accuracy Of Visual Discrimination Research Articles

Value-driven modulation of visual perception by visual and auditory reward cues: The role of performance-contingent delivery of reward.

Perception is modulated by reward value, an effect elicited not only by stimuli that are predictive of performance-contingent delivery of reward (PC) but also by stimuli that were previously rewarded (PR). PC and PR cues may engage different mechanisms relying on goal-driven versus stimulus-driven prioritization of high value stimuli, respectively. However, these two modes of reward modulation have not been systematically compared against each other. This study employed a behavioral paradigm where participants' visual orientation discrimination was tested in the presence of task-irrelevant visual or auditory reward cues. In the first phase (PC), correct performance led to a high or low monetary reward dependent on the identity of visual or auditory cues. In the subsequent phase (PR), visual or auditory cues were not followed by reward delivery anymore. We hypothesized that PC cues have a stronger modulatory effect on visual discrimination and pupil responses compared to PR cues. We found an overall larger task-evoked pupil dilation in PC compared to PR phase. Whereas PC and PR cues both increased the accuracy of visual discrimination, value-driven acceleration of reaction times (RTs) and pupillary responses only occurred for PC cues. The modulation of pupil size by high reward PC cues was strongly correlated with the modulation of a combined measure of speed and accuracy. These results indicate that although value-driven modulation of perception can occur even when reward delivery is halted, stronger goal-driven control elicited by PC reward cues additionally results in a more efficient balance between accuracy and speed of perceptual choices.

Visual discrimination accuracy does not differ between nasal inhalation and exhalation when stimuli are voluntarily aligned to breathing phase

This study investigated the possible enhancement of visual discrimination accuracy by voluntarily adjusting the timing of stimulus presentation to a specific respiratory phase. Previous research has suggested that respiratory phases modulate perceptual and cognitive processing. For instance, a fearful face was identified faster when presented during nasal inhalation than during nasal exhalation, which could be related to changes in neural oscillatory activity synchronized with breathing in through one's nose. Based on such findings, the present study asked 40 young adults to perform an emotional discrimination task consisting of distinguishing fearful vs. neutral faces and a physical discrimination task consisting of distinguishing high- vs. low-contrast Gabor patches during nasal respiration. Participants presented themselves with the stimuli to be judged in a designated respiratory phase by pressing a button. It was hypothesized that fear discrimination accuracy would be higher during inhalation than exhalation if sensitivity to emotional stimuli increased during inhalation. Conversely, if overall visual sensitivity was enhanced during inhalation, the identical effect was expected for contrast discrimination. The results indicated that discrimination accuracy did not differ between inhalation and exhalation phases in either task. This result provided no evidence that the respiratory phase affected visual discrimination accuracy when people adjusted the timing of stimulus presentation to the onset of inhalation or exhalation.

Dedifferentiation of Functional Brain Activation Associated With Greater Visual Discrimination Accuracy in Middle-Aged and Older Adults.

Neural dedifferentiation refers to an age-related phenomenon whereby brain functions that are localized to specific, distinct, and differentiated brain areas in young adults become less so as people reach more advanced age. Older adults tend to exhibit greater spread of cortical activation on fMRI during cognitive processing compared to younger adults, with evidence that this occurs during visuoperceptual processing. Some age-related functional changes are considered compensatory, but whether dedifferentiation is compensatory is not clearly understood. The current study assessed dedifferentiation and visual discrimination performance during simultaneous match-to-sample tasks from the Visual Assessment Battery (VAB) among 40 healthy middle-aged and older adults using fMRI. Task-relevant regions of interest (ROIs) were created in the dorsal stream for discrimination of spatial location, the ventral stream for shape, and an area encompassing V5 for velocity. Dedifferentiation, or less specificity in functional activation, was associated with greater discrimination accuracy and more years of education. Secondary analyses showed that reduced functional activation in task-relevant ROIs was associated with faster discrimination speed. Age was unassociated with functional activation. Results suggest that dedifferentiation is compensatory. Lack of age effects suggest that other factors beyond age, such as cognitive or brain reserve, may better predict performance when considering cognitive skills that are relatively stable as adults age, such as visual discrimination.

Multi-band MEG signatures of BOLD connectivity reorganization during visuospatial attention

The functional architecture of the resting brain, as measured with the blood oxygenation level-dependent functional connectivity (BOLD-FC), is slightly modified during task performance. In previous work, we reported behaviorally relevant BOLD-FC modulations between visual and dorsal attention regions when subjects performed a visuospatial attention task as compared to central fixation (Spadone et al., 2015).Here we use magnetoencephalography (MEG) in the same group of subjects to identify the electrophysiological correlates of the BOLD-FC modulation found in our previous work. While BOLD-FC topography, separately at rest and during visual attention, corresponded to neuromagnetic Band-Limited Power (BLP) correlation in the alpha and beta bands (8–30 Hz), BOLD-FC modulations evoked by performing the visual attention task (Spadone et al. 2015) did not match any specific oscillatory band BLP modulation. Conversely, following the application of an orthogonal spatial decomposition that identifies common inter-subject co-variations, we found that attention–rest BOLD-FC modulations were recapitulated by multi-spectral BLP-FC components. Notably, individual variability of alpha connectivity between Frontal Eye Fields and visual occipital regions, jointly with decreased interaction in the Visual network, correlated with visual discrimination accuracy. In summary, task-rest BOLD connectivity modulations match multi-spectral MEG BLP connectivity.

Visual Discrimination Accuracy across Reaction Time in Rats

Visual Discrimination Accuracy across Reaction Time in Rats

Pre-cooling moderately enhances visual discrimination during exercise in the heat

ABSTRACTPre-cooling has been reported to attenuate the increase in core temperature, although, information regarding the effects of pre-cooling on cognitive function is limited. The present study investigated the effects of pre-cooling on visual discrimination during exercise in the heat. Eight male recreational runners completed 90 min of treadmill running at 65% 2max in the heat [32.4 ± 0.9°C and 46.8 ± 6.4% relative humidity (r.h.)] on two occasions in a randomised, counterbalanced crossover design. Participants underwent pre-cooling by means of water immersion (20.3 ± 0.3°C) for 60 min or remained seated for 60 min in a laboratory (20.2 ± 1.7°C and 60.2 ± 2.5% r.h.). Rectal temperature (Trec) and mean skin temperature (Tskin) were monitored throughout the protocol. At 30-min intervals participants performed a visual discrimination task. Following pre-cooling, Trec (P = 0.040; = 0.48) was moderately lower at 0 and 30 min and Tskin (P = 0.003; = 0.75) lower to a large extent at 0 min of exercise. Visual discrimination was moderately more accurate at 60 and 90 min of exercise following pre-cooling (P = 0.067; = 0.40). Pre-cooling resulted in small improvements in visual discrimination sensitivity (F1,7 = 2.188; P = 0.183; = 0.24), criterion (F1,7 = 1.298; P = 0.292; = 0.16) and bias (F1,7 = 2.202; P = 0.181; = 0.24). Pre-cooling moderately improves visual discrimination accuracy during exercise in the heat.

Interindividual variation in fornix microstructure and macrostructure is related to visual discrimination accuracy for scenes but not faces.

Transection of the nonhuman primate fornix has been shown to impair learning of configurations of spatial features and object-in-scene memory. Although damage to the human fornix also results in memory impairment, it is not known whether there is a preferential involvement of this white-matter tract in spatial learning, as implied by animal studies. Diffusion-weighted MR images were obtained from healthy participants who had completed versions of a task in which they made rapid same/different discriminations to two categories of highly visually similar stimuli: (1) virtual reality scene pairs; and (2) face pairs. Diffusion-MRI measures of white-matter microstructure [fractional anisotropy (FA) and mean diffusivity (MD)] and macrostructure (tissue volume fraction, f) were then extracted from the fornix of each participant, which had been reconstructed using a deterministic tractography protocol. Fornix MD and f measures correlated with scene, but not face, discrimination accuracy in both discrimination tasks. A complementary voxelwise analysis using tract-based spatial statistics suggested the crus of the fornix as a focus for this relationship. These findings extend previous reports of spatial learning impairments after fornix transection in nonhuman primates, critically highlighting the fornix as a source of interindividual variation in scene discrimination in humans.

Brain signatures of reward-dependent bias in visual attention

According to the Theory of Visual Attention (TVA), important visual features (features with a high valence) are processed more rapidly than unimportant ones. In the present study, we tested this assumption and assessed brain correlates of reward-dependent changes in visual processing by combining the formal framework of TVA with electrophysiology (EEG). We recorded EEG while participants completed a task in which accuracy of discriminating certain stimulus features was selectively associated with contingent monetary rewards. More specifically, the rewards for detecting Landolt ring gap locations on the diagonal and straight axes were varied across blocks, thereby abstracting valence from salience effects. We quantified performance using TVA-based fitting, and analyzed event-related potentials (ERP) and linear discriminant components to unveil brain mechanisms underlying behavioral changes related to reward. We found a higher processing rate for features associated with high reward relative to those associated with low reward. The behavioral effect was mirrored in multiple grand-average ERP modulations: The P1 was higher, and mid-latency central positivity was lower, when the to-be-discriminated feature's valence was high. A stronger medial frontal negativity (MFN) later in time was found for lower-rewarded features. The results suggest that sensory, attentional, and motivational processes contribute to the effects of reward on visual discrimination accuracy. On the single-trial level, we separated spatio-temporal components giving information about the dynamics of these processes. In accordance with TVA, we argue that a controlled setting of perceptual biases, such that important features are associated with stronger perceptual biases (β values), eases the encoding of features associated with high positive outcomes from early perceptual stages on. Meeting abstract presented at VSS 2014

Video-based training improves the accuracy of seizure diagnosis

Background and aimThe difficulties in differentiating epileptic seizures (ES) from psychogenic non-epileptic seizures (PNES) are well known. However, interventions to enhance diagnostic accuracy have not been well studied. We sought...

Estimating the growth of internal evidence guiding perceptual decisions

Perceptual decision-making is thought to involve a gradual accrual of noisy evidence. Temporal integration of the evidence reduces the relative contribution of dynamic internal noise to the decision variable, thereby boosting its signal-to-noise ratio. We aimed to estimate the internal evidence guiding perceptual decisions over time, using a novel combination of external noise and the response signal methods. Observers performed orientation discrimination of patterns presented in external noise. We varied the contrast of the patterns and the delay at which observers were forced to signal their decision. Each test stimulus (patterns and noise sample) was presented twice. Across two experiments we varied the availability of the visual stimulus for processing. Observer model analyses of discrimination accuracy and response consistency to two passes of the same stimulus, suggested that there was very little growth in the internal evidence. The improvement in accuracy over time characterised by the speed-accuracy trade-off function predominantly reflected a decreasing proportion of non-visual decisions, or pure guesses. There was no advantage to having the visual patterns visible for longer than 80 ms, indicating that only the visual information in a short window after display onset was used to drive the decisions. The remarkable constancy of the internal evidence over time suggests that temporal integration of the sensory information was very limited. Alternatively, more extended integration of the evidence from memory could have taken place, provided that the dominant source of internal noise limiting performance occurs between-trials, which cannot be reduced by prolonged evidence integration.

Synergistic interaction of dopamine D1 and glutamate N-methyl-d-aspartate receptors in the rat dorsal striatum controls attention

The balance between corticostriatal glutamate inputs and mesostriatal dopamine afferents converging onto the same postsynaptic spines of striatal medium spiny neurons in the dorsal striatum is believed to be crucial for regulating executive functions including attention.In the present study we examined the role of dopamine D(1) and glutamate N-methyl-d-aspartate (NMDA) receptors within the medial territory of the dorsal striatum (dm-STR) of the rat during performance of a selective attention task such as the 5-choice serial reaction time (5-CSRT) task, which incorporates a variety of measures including accuracy of visual discrimination (an index of attentional functioning), omissions, premature and perseverative responses (indices of inhibitory response control) and correct response latency (decision time). Infusion of 30 ng/side of the competitive NMDA receptor antagonist 3-(R)-2-carboxypiperazin-4-propyl-1-phosphonic acid (CPP) in the dm-STR decreased accuracy and increased the proportion of omission but had no effect on premature or perseverative responding or correct response latency. A lower dose of 10 ng/side CPP only affected omissions. Blockade of D(1) receptors in the dm-STR by SCH23390 (50 and 100 ng/side) had no effect on accuracy but at 100 ng/side SCH23390 decreased anticipatory responding and increased the proportion of omissions. Co-infusion of SCH23390 (50 ng/side) and CPP (10 ng/side), at individually ineffective doses, potently reduced the accuracy of visual discrimination. The effects were highly selective as no changes in response control, decision time and omissions were detected. The data suggest that the synergistic interaction of D(1) and NMDA receptors on the dendritic spines of GABA neurons within the dm-STR may represent a mechanism for the control of attention.

Attention deficit induced by blockade of N-methyl d-aspartate receptors in the prefrontal cortex is associated with enhanced glutamate release and cAMP response element binding protein phosphorylation: role of metabotropic glutamate receptors 2/3

The hypothesis that attention deficits induced by the hypofunction of N-methyl d-aspartate (NMDA) receptors in the prefrontal cortex (PFC) might be associated with increased glutamate release and changes in the phosphorylation of the cyclic adenosine monophosphate response element-binding protein on serine 133 (p-S133CREB) was investigated in this study. Infusion of 50 ng/side 3-(R)-2-carboxypiperazin-4-propyl-1-phosphonic acid ((R)-CPP), a competitive glutamate NMDA receptor antagonist, into the medial prefrontal cortex (mPFC) of rats performing the five-choice serial reaction time (5-CSRT) task, reduced accuracy of visual discrimination (measured by % correct responses) and enhanced impulsivity (measured by the number of premature responses) and compulsivity (measured by the number of perseverative responses). The mGluR2/3 receptor agonist, LY379268, injected s.c. at 0.1 mg/kg, reduced (R)-CPP-induced impairment in attentional functioning (accuracy) and impulsivity but not compulsive perseveration. In parallel studies using microdialysis technique and Western blot analysis we found that (R)-CPP (100 μM) infused in the medial prefrontal cortex increased glutamate efflux whereas injected in the medial prefrontal cortex at a dose causing impairments in attentional performance (50 ng/side) increased p-S133CREB in the frontal cortex (FC), decreased it in the caudate-putamen (CPu) and was without effect in the nucleus accumbens (NAC). LY379268 at the dose effective in reducing (R)-CPP-induced behavioral deficit reduced both the (R)-CPP-induced rise in glutamate efflux in the prefrontal cortex and the increase in p-S133CREB in the frontal cortex but was without effect on the decrease in p-S133CREB in the caudate-putamen. The data provide evidence that enhanced glutamate release and phosphorylation of cAMP response element binding protein (CREB) on serine 133 may be associated to attention deficit and loss of impulse control. Furthermore they suggest that mGluR2/3 agonists have a therapeutic potential for cognitive deficits.

Sertindole restores attentional performance and suppresses glutamate release induced by the NMDA receptor antagonist CPP

Blockade of N-methyl-d-aspartic acid (NMDA) receptors in the rat medial prefrontal cortex (mPFC) impairs performance in the five-choice serial reaction time task (5-CSRTT) and increases glutamate (GLU) release. Recent research suggests that excessive GLU release may be critical for attention deficits. We tested this hypothesis by investigating the effects of the atypical antipsychotics sertindole and clozapine on 3-(R)-2-carboxypiperazin-4-propyl-1-phosphonic acid (CPP)-induced performance deficits in the 5-CSRTT and on the CPP-induced GLU release in the mPFC. The 5-CSRTT, a test of divided and sustained visual attention providing indices of attentional functioning (accuracy of visual discrimination), response control (anticipatory and perseverative responses) and intracortical microdialysis in conscious rats were used to investigate the effects of sertindole and clozapine. Low doses of sertindole (0.02-0.32mg/kg) prevented CPP-induced accuracy deficits, anticipatory over-responding and the rise in GLU release. In contrast, doses ranging from 0.6 to 2.5mg/kg had no effect or even enhanced the effect of CPP on anticipatory responding. Similarly, 2.5mg/kg sertindole was unable to reverse CPP-induced rise in GLU release. Clozapine (2.5mg/kg) prevented accuracy deficits and the increase in anticipatory responding and abolished the rise in GLU release induced by CPP. These findings show that the ameliorating effects of sertindole and clozapine on NMDA receptor dependent attention deficit is associated with suppression in GLU release in the mPFC. This supports the proposal that suppression in GLU release might be a target for the development of novel drugs aimed at counteracting some aspects of cognitive deficits of schizophrenia.

Effects of aripiprazole, olanzapine, and haloperidol in a model of cognitive deficit of schizophrenia in rats: relationship with glutamate release in the medial prefrontal cortex

Disruption in cognition is characteristic of psychiatric illnesses such as schizophrenia. Studies of drugs that improve cognition might provide a better insight into the mechanisms underlying cognitive deficits. We compared the effects of the antipsychotic drugs aripiprazole, olanzapine, and haloperidol on performance deficit in a test of divided and sustained visual attention, the five-choice serial reaction time task (5-CSRTT), which provides information on attentional functioning (accuracy of visual discrimination), response control (measured by anticipatory and perseverative responses) and speed. The cognitive deficit was induced by infusion of the competitive NMDA receptor antagonist 3-(R)-2-carboxypiperazin-4-propyl-1-phosphonic acid (CPP) in the rat medial prefrontal cortex (mPFC). In vivo microdialysis was used to compare the effects of aripiprazole, olanzapine and haloperidol on CPP-induced glutamate (GLU) and serotonin (5-HT) release in the mPFC of conscious rats. Oral aripiprazole (1.0 and 3.0mg/kg) and olanzapine (0.3 and 1.0mg/kg), but not haloperidol (0.1mg/kg), abolished the CPP-induced accuracy deficit and GLU release. Haloperidol and aripiprazole, but not olanzapine, reduced perseverative over-responding, while anticipatory responding was best controlled by olanzapine. However, these effects were not associated with changes in GLU release. No association was found between the effects of these antipsychotics on CPP-induced attentional performance deficits in the 5-CSRTT and 5-HT efflux. The data confirm that excessive GLU release in the mPFC is associated with attentional deficits. Thus, suppression of GLU release may be a target for the development of novel antipsychotic drugs with greater effect on some aspects of cognitive deficits.

Temporal uncertainty degrades perceptual processing

When participants are required to react to a stimulus, reaction times (RTs) are usually reduced when temporal uncertainty about stimulus occurrence is minimized. Contrary to the common assumption attributing this RT benefit solely to the speeding of motor processes, recent evidence suggests that temporal uncertainty might rather influence premotoric processing levels. We employed a backward-masking procedure to further confine the locus of the temporal uncertainty effect. Participants performed a discrimination task and indicated whether a spatial gap within a square was on the right or the left side. In addition to the shorter RTs, visual discrimination accuracy was improved when temporal uncertainty was low. This result demonstrates that temporal uncertainty influences stimulus processing at a perceptual level.

Perceptual learning of line orientation modifies the effects of transcranial magnetic stimulation of visual cortex

Perceptual learning may be accompanied by physiological changes in early visual cortex. We used transcranial magnetic stimulation (TMS) to test the postulate that perceptual learning of a visual task initially performed at 60-65% accuracy strengthens visual processing in early visual cortex. Single pulse TMS was delivered to human occipital cortex at time delays of 70-154 ms after the onset of an odd-element, line orientation discrimination task. When TMS was delivered at a delay of 84 ms or later the accuracy of visual discrimination was transiently degraded in ten subjects. As visual performance in control trials without TMS improved with training, the absolute magnitude of TMS suppression of performance decreased in parallel. This result occurred both when TMS was delivered to broad areas of occipital cortex and when TMS was optimally delivered to early occipital cortex. No change in TMS suppression was observed when three new subjects were given feedback during an odd-element task that did not require substantial perceptual learning. Thus, perceptual learning improved visual performance and reduced TMS suppression of early visual cortex in parallel.

Secondary hypoxemia exacerbates the reduction of visual discrimination accuracy and neuronal cell density in the dorsal lateral geniculate nucleus resulting from fluid percussion injury.

The purpose of this study was to determine the impact of secondary hypoxemia on visual discrimination accuracy after parasagittal fluid percussion injury (FPI). Rats lived singly in test cages, where they were trained to repeatedly execute a flicker-frequency visual discrimination for food. After learning was complete, all rats were surgically prepared and then retested over the following 4-5 days to ensure recovery to presurgery levels of performance. Rats were then assigned to one of three groups [FPI + Hypoxia (IH), FPI + Normoxia (IN), or Sham Injury + Hypoxia (SH)] and were anesthetized with halothane delivered by compressed air. Immediately after injury or sham injury, rats in groups IH and SH were switched to a 13% O2 source to continue halothane anesthesia for 30 min before being returned to their test cages. Anesthesia for rats in group IN was maintained using compressed air for 30 min after injury. FPI significantly reduced visual discrimination accuracy and food intake, and increased incorrect choices. Thirty minutes of immediate posttraumatic hypoxemia significantly (1) exacerbated the FPI-induced reductions of visual discrimination accuracy and food intake, (2) further increased numbers of incorrect choices, and (3) delayed the progressive recovery of visual discrimination accuracy. Thionine stains of midbrain coronal sections revealed that, in addition to the loss of neurons seen in several thalamic nuclei following FPI, cell loss in the ipsilateral dorsal lateral geniculate nucleus (dLG) was significantly greater after FPI and hypoxemia than after FPI alone. In contrast, neuropathological changes were not evident following hypoxemia alone. These results show that, although hypoxemia alone was without effect, posttraumatic hypoxemia exacerbates FPI-induced reductions in visual discrimination accuracy and secondary hypoxemia interferes with control of the rat's choices by flicker frequency, perhaps in part as a result of neuronal loss and fiber degeneration in the dLG. These results additionally confirm the utility of this visual discrimination procedure as a sensitive, noninvasive means of assessing behavioral function after experimental traumatic brain injury.

Effects of dopaminergic drugs on working and reference memory in rats

Changes in dopaminergic function have been associated with alterations in motor and cognitive function in man and in animals. This study was designed to assess the effects of dopaminergic drugs on these aspects of conditioned behavior in animals. Male Long-Evans rats were trained to perform an appetitive operant task that allowed daily quantification of working memory (accuracy of spatial delayed nonmatching-to-position), reference memory (accuracy of visual discrimination) and motor function [choice lever-press latency and nosepoke interresponse time (IRT) during delay]. The indirect dopamine agonist d-amphetamine (0.3–1.0 mg/kg) reduced nonmatching accuracy without significantly affecting discrimination accuracy, response latency, or nosepoke IRT. The D 2/D 3 agonist quinpirole (0.01–0.056 mg/kg) also decreased nonmatching accuracy without changing discrimination accuracy, but increased choice response latency and nosepoke IRT as well. The D 1 agonist SKF 38393 (1.0–3.0 mg/kg) and the D 1 antagonist SCH 23390 (0.01–0.03 mg/kg) only affected nosepoke IRT, at doses below those causing response failure. The D 2 antagonist raclopride (0.056–0.177 mg/kg) exerted no significant effects at doses that did not suppress responding completely. The selective reduction of nonmatching accuracy by d-amphetamine and quinpirole indicates a mnemonic impairment specific to working memory (relative to reference memory). These results suggest further 1) that stimulation of D 2/D 3, but not D 1, receptors may account for the d-amphetamine-induced deficit in working memory; 2) that stimulation of D 2/D 3 receptors alone by quinpirole may also impair spatial working memory, but only in conjunction with motor slowing; and 3) that antagonism of either receptor type (by SCH 23390 or raclopride) does not significantly affect memory at doses causing motor slowing and response failure.

Body energy balance and food intake: a neuroendocrine regulatory mechanism.

Body energy balance and food intake: a neuroendocrine regulatory mechanism.

Acute and chronic single dose effects of LSD-25 on visual discrimination in rats

Rats subjected to either a frontal cortex lesion or to a sham operation were trained to discriminate between a lighted and unlit alley to escape shock. Following intubation with either placebo or LSD-25 (1.0 mg/kg), they were given discrimination trials 2 hr, 1 week, and 1 month later, but with an increased level of task difficulty. Single dose effects of LSD-25 were observed acutely in a transient impairment of visual discrimination accuracy, and more chronically in slower running time. Although no significant drug-lesion interactions were noted, the results were in the direction of a combinatory effect. The value of increasing the level of post-treatment task was confirmed.