Discrimination Task (discrimination + task)

Distribution by Scientific Domains


Selected Abstracts


Visual event-related potentials in children with phenylketonuria

ACTA PAEDIATRICA, Issue 1 2000
RM Henderson
Visual event-related potentials (ERPs) were examined in 16 children (aged 5,14 y) with phenylketonuria (PKU) and 16 age- and sex-matched controls. Lifetime median measures of phenylalanine (Phe) were 230-460 ,mol/l. The most recent Phe levels were 56,624 ,mol/l. ERPs were recorded whilst the children performed a discrimination task. All stimuli were square wave gratings degree, which appeared for 33 ms. A response to an infrequent grating that differed in orientation or spatial frequency was required. The older children with PKU had a delay in the first peak (P1) of the ERP, and age-related changes in the amplitude of P1. There was attenuation of the second peak across age groups in PKU. There was no evidence of reduced response accuracy or longer reaction times in children with PKU. Latencies of the cognitive P3 were not delayed in PKU. The delayed early peaks are consistent with previous studies that have shown delayed visual evoked potentials in PKU. The lack of differences in reaction time and P3 may be due to relatively good Phe control in children with PKU, or to the simplicity of the task. Suggestions are made for future ERP studies of PKU. [source]


Neonatal alcohol exposure impairs acquisition of eyeblink conditioned responses during discrimination learning and reversal in weanling rats

DEVELOPMENTAL PSYCHOBIOLOGY, Issue 3 2007
Kevin L. Brown
Abstract Discrimination and reversal of the classically conditioned eyeblink response depends on cerebellar,brainstem interactions with the hippocampus. Neonatal "binge" exposure to alcohol at doses of 5 g/kg/day or more has been shown to impair single-cue eyeblink conditioning in both weanling and adult rats. The present study exposed neonatal rats to acute alcohol intubations across different developmental periods (postnatal day [PND] 4-9 or PND7-9) and tested them from PND26-31 on discriminative classical eyeblink conditioning and reversal. A high dose of alcohol (5 g/kg/day) dramatically impaired conditioning relative to controls when exposure occurred over PND4-9, but produced mild or no impairments when delivered over PND7-9. These findings support previous claims that developmental exposure period plays a critical role in determining the deleterious effects of alcohol on the developing brain. A lower dose of alcohol (4 g/kg/day) delivered from PND4-9,lower than has previously been shown to affect single-cue eyeblink conditioning,also produced deficits on the discrimination task, suggesting that discrimination learning and acquisition of responding to CS+ during reversal may be especially sensitive behavioral indicators of alcohol-induced brain damage in this rat model. © 2007 Wiley Periodicals, Inc. Dev Psychobiol 49: 243,257, 2007. [source]


Evidence for reduced domain-specificity in auditory processing in autism

DEVELOPMENTAL SCIENCE, Issue 6 2007
Anna Järvinen-Pasley
Neurological and behavioral findings indicate that atypical auditory processing characterizes autism. The present study tested the hypothesis that auditory processing is less domain-specific in autism than in typical development. Participants with autism and controls completed a pitch sequence discrimination task in which same/different judgments of music and/or speech stimulus pairs were made. A signal detection analysis showed no difference in pitch sensitivity across conditions in the autism group, while controls exhibited significantly poorer performance in conditions incorporating speech. The results are largely consistent with perceptual theories of autism, which propose that a processing bias towards featural/low-level information characterizes the disorder, as well as supporting the notion that such individuals exhibit selective attention to a limited number of simultaneously presented cues. [source]


Computer-based training with ortho-phonological units in dyslexic children: new investigations

DYSLEXIA, Issue 3 2009
Jean Ecalle
Abstract This study aims to show that training using a computer game incorporating an audio-visual phoneme discrimination task with phonological units, presented simultaneously with orthographic units, might improve literacy skills. Two experiments were conducted, one in secondary schools with dyslexic children (Experiment 1) and the other in a speech-therapy clinic with individual case studies (Experiment 2). A classical pre-test, training, post-test design was used. The main findings indicated an improvement in reading scores after short intensive training (10,h) in Experiment 1 and progress in the reading and spelling scores obtained by the dyslexic children (training for 8,h) in Experiment 2. These results are discussed within the frameworks of both the speech-specific deficit theory of dyslexia and the connectionist models of reading development. Copyright © 2008 John Wiley & Sons, Ltd. [source]


Recollective experience in alcohol dependence: a laboratory study

ADDICTION, Issue 12 2008
Patrizia Thoma
ABSTRACT Aims Alcohol dependence has been linked to dysfunction of fronto-temporo-striatal circuits which mediate memory and executive function. The present study aimed to explore the specificity of recognition memory changes in alcohol dependence. Design, setting and participants Twenty hospitalized alcohol-dependent detoxified patients and 20 healthy control subjects completed a verbal list discrimination task. Measurements Hits and false alarm rates were analysed. Additionally, both the dual process signal detection model (DPSD) and the process dissociation procedure (PDP) were used to derive estimates of the contribution of recollection and familiarity processes to the recognition memory performance in patients and controls. Findings Alcohol-dependent patients showed intact hit rates, but increased false alarm rates and an impaired ability to remember the learning context. Both the DPSD model and PDP estimates yielded significantly reduced recollection estimates in the alcohol-dependent compared to control subjects. Whether or not familiarity was impaired, depended upon the sensitivity of the estimation procedure. Conclusion Taken together, the result pattern suggests a significant impairment in recollection and mild familiarity changes in recently detoxified, predominantly male, alcohol-dependent subjects. [source]


PRECLINICAL STUDY: Pavlovian drug discrimination with bupropion as a feature positive occasion setter: substitution by methamphetamine and nicotine, but not cocaine

ADDICTION BIOLOGY, Issue 2 2009
Jamie L. Wilkinson
ABSTRACT Bupropion can serve as a discriminative stimulus (SD) in an operant drug discrimination task, and a variety of stimulants substitute for the bupropion SD. There are no reports, however, of bupropion functioning as a Pavlovian occasion setter (i.e. feature positive modulator). The present experiment seeks to fill this gap in the literature by training bupropion in rats as a feature positive modulator that disambiguates when a light will be paired with sucrose. Specifically, on bupropion (10 mg/kg intraperitoneal) sessions, offset of 15-second cue lights were followed by brief delivery of liquid sucrose; saline sessions were similar except no sucrose was available. Rats readily acquired the discrimination with more conditioned responding to the light on bupropion sessions. Bupropion is approved for use as a smoking cessation aid, and more recently has drawn attention as a potential pharmacotherapy for cocaine and methamphetamine abuse. Accordingly, after discrimination training, we tested the ability of cocaine (1,10 mg/kg), methamphetamine (0.1 to 1 mg/kg) and nicotine (0.00625 to 0.2 mg/kg) to substitute for the bupropion feature. Nicotine (0.05 mg/kg) and methamphetamine (0.3 mg/kg) substituted fully for bupropion; cocaine did not substitute. These results extend previous research on shared stimulus properties between bupropion and other stimulants to a Pavlovian occasion setting function. Further, this is the first report of nicotine and methamphetamine substitution for bupropion. The overlap in stimulus properties might explain the effectiveness of bupropion as a smoking cessation aid and highlight the possible utility of bupropion for treatment of stimulant use disorder. [source]


Abnormal associative encoding in orbitofrontal neurons in cocaine-experienced rats during decision-making

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2006
Thomas A. Stalnaker
Abstract Recent evidence has linked exposure to addictive drugs to an inability to employ information about adverse consequences, or outcomes, to control behavior. For instance, addicts and drug-experienced animals fail to adapt their behavior to avoid adverse outcomes in gambling and reversal tasks or after changes in the value of expected rewards. These deficits are similar to those caused by damage to the orbitofrontal cortex, suggesting that addictive drugs may cause long-lasting changes in the representation of outcome associations in a circuit that includes the orbitofrontal cortex. Here we test this hypothesis by recording from orbitofrontal neurons in a discrimination task in rats previously exposed to cocaine (30 mg/kg i.p. for 14 days). We found that orbitofrontal neurons recorded in cocaine-experienced rats failed to signal the adverse outcome at the time a decision was made in the task. The loss of this signal was associated with abnormal changes in response latencies on aversive trials. Furthermore, upon reversal of the cue,outcome associations, orbitofrontal neurons in cocaine-treated rats with enduring reversal impairments failed to reverse their cue-selectivity, while orbitofrontal neurons in cocaine-treated rats with normal performance showed an increase in the plasticity of cue-selective firing after reversal. These results provide direct neurophysiological evidence that exposure to cocaine can cause behaviorally relevant changes in the processing of associative information in a circuit that includes the orbitofrontal cortex. [source]


Selective prefrontal serotonin depletion impairs acquisition of a detour-reaching task

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2006
S.C. Walker
Abstract We have recently shown that serotonin in the primate orbitofrontal cortex (OFC) contributes to the flexible control of behaviour. 5,7-dihydroxytryptamine-induced 5-HT depletions of OFC impair performance on a serial reversal discrimination task [Clarke et al. (2004)Science, 304, 878,880]. The deficit is characterized by perseverative responding to the previously rewarded stimulus, a deficit similar to that seen following lesions of the intrinsic neurones of the OFC [Dias et al. (1996)Nature, 380, 69,72]. The effect is neurochemically selective as dopaminergic lesions of the OFC, induced by 6-hydroxydopamine, have no effect [Clarke et al. (2006)Cerebral Cortex]. In order to test for the generality of the effect of serotonin on orbitofrontal processing and, in particular, its effects on flexible behaviour, the present study investigated the effects of serotonin depletions of OFC on performance of another task dependent upon an intact OFC, the detour-reaching task [Wallis et al. (2001)European Journal of Neuroscience, 13, 1797,1808]. Successful performance of this task requires inhibition of the animal's prepotent response tendency to reach directly along its line of sight to the reward. Compared with sham-operated controls, we found that lesioned monkeys made significantly more barrier reaches directly along their line of sight to the visible reward during task acquisition. This finding provides further support for the role of prefrontal serotonin in inhibitory control processes specifically in tasks sensitive to OFC dysfunction. [source]


Disruption of self-organized actions in monkeys with progressive MPTP-induced parkinsonism: II.

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2004
Effects of reward preference
Abstract The motor and cognitive symptoms of Parkinson's disease (PD) are well documented, but little is known about the functionality of motivational processes mediated by the limbic circuits of basal ganglia. The aim of this study was to test the ability of motivational processes to direct and to urge behaviour, in four vervet monkeys (Cercopithecus aethiops) progressively intoxicated with systemic 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) injections (0.3,0.4 mg/kg every 4,7 days). In the food preference task, the monkeys had to retrieve two types of directly visible food, simultaneously available in the wells of a reward board. At all stages of MPTP-induced parkinsonism, the monkeys continued to take their favourite food first. In the symbol discrimination task, the wells were covered with sliding plaques cued by symbols indicating the absence or presence of a reward, and the different types of food were blocked in separate sessions. Monkeys with mild or moderate parkinsonism made fewer attempts and took longer to retrieve non-preferred compared with preferred rewards. These results indicate that motivational processes are still able to direct (food preference task) and to urge (symbol discrimination task) behaviour in MPTP-lesioned monkeys. Such a functional preservation may be related to the relatively spared dopaminergic innervation of the limbic circuits that we found in our monkeys, in agreement with the literature on humans. Furthermore, the frequency of executive disorders (such as hesitations and freezing) appeared to be much lower with the preferred rewards. Thus, the preserved motivational processes may help to overcome executive dysfunction in the early stages of human PD. [source]


Cholinergic and noncholinergic septal neurons modulate strategy selection in spatial learning

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2001
Jonathan F. X. Cahill
Abstract Rats solving a simple spatial discrimination task in a plus maze initially employ a place-learning strategy, then switch to a motor response strategy. The hippocampus is required for the use of a place-learning strategy in this task. Rats with 192 IgG-saporin lesions of the medial septum/vertical limb of the diagonal band (MS/VDB), that selectively removed cholinergic neurons projecting to the hippocampus, were significantly facilitated in acquisition of the spatial discrimination, and switched from place to response strategies just as control rats did. Rats with ibotenic acid lesions of the MS/VDB, that produced cell loss in the MS/VDB but little damage to cholinergic neurons, were significantly impaired in acquiring the spatial discrimination and did not reliably employ either a place or response strategy at any point in training. This suggests that the MS/VDB modulates hippocampal involvement in place learning, but that cholinergic MS/VDB neurons are neither necessary nor sufficient for using a place strategy to solve a spatial discrimination. [source]


Antisense oligodeoxynucleotide-induced suppression of basal forebrain NMDA-NR1 subunits selectively impairs visual attentional performance in rats

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2001
Janita Turchi
Abstract It is generally agreed that basal forebrain neuronal circuits contribute to the mediation of the ability to detect, select and discriminate signals, to suppress the processing of irrelevant information, and to allocate processing resources to competing tasks. Rats were trained in a task designed to assess sustained attention, or in a cued discrimination task that did not tax attentional processes. Animals were equipped with guide cannula to infuse bilaterally antisense oligodeoxynucleotides (ODNs) against the N -methyl- d -aspartate (NMDA) NR1 subunits, or missense ODNs, into the substantia innominata of the basal forebrain. Infusions of antisense or missense ODNs did not affect cued visual discrimination performance. Infusions of antisense ODNs dose-dependently impaired sustained attention performance by selectively decreasing the animals' ability to detect signals while their ability to reject nonsignal trials remained unchanged. The detrimental attentional effects of antisense infusions were maximal 24 h after the third and final infusion, and performance returned to baseline 24 h later. Missense infusions did not affect attentional performance. Separate experiments demonstrated extensive suppression of NR1 subunit immunoreactivity in the substantia innominata. Furthermore, infusions of antisense did not produce neurotoxic effects in that region as demonstrated by the Fluoro-Jade method. The present data support the hypothesis that NMDA receptor (NMDAR) stimulation in the basal forebrain, largely via glutamatergic inputs originating in the prefrontal cortex, represents a necessary mechanism to activate the basal forebrain corticopetal system for mediation of attentional performance. [source]


Effects of Distraction Versus Spatial Discrimination on Laser-Evoked Potentials in Migraine

HEADACHE, Issue 3 2008
Marina De Tommaso MD
Objectives., To evaluate whether migraine patients exhibit less inhibition to painful stimuli when distracted from pain as compared to healthy subjects, testing the spatial discrimination of painful stimuli, the performance during the mental arithmetic task used to contrast the discrimination performance and the behavior of N1 and N2-P2 laser-evoked potentials (LEPs) amplitudes during spatial discrimination and during distraction. Methods., Eight migraine patients and 8 healthy controls were examined. During repetitive series of painful laser stimulation of the hand, they had to (1) perform a spatial discrimination task, contrasted by (2) a mental arithmetic task that served as distraction. Results., Patients made 50% to 100% more mistakes than controls in the spatial discrimination task (P < .001) as well as during mental arithmetic (P < .05). Whereas healthy subjects showed a marked decrease of the LEP vertex potential amplitudes during distraction compared to the discrimination task, no such attenuation of LEPs was seen in migraine patients (group × task interaction, P < .05). N1 amplitude exhibited a left-hemisphere dominance in both groups, significantly smaller amplitude in migraine patients, but no significant task modulation. Conclusion., Migraine patients exhibited reduced inhibition by attentional modulation of pain processing, accompanied by impaired spatial discrimination of painful stimuli. [source]


Neural bases of categorization of simple speech and nonspeech sounds

HUMAN BRAIN MAPPING, Issue 8 2006
Fatima T. Husain
Abstract Categorization is fundamental to our perception and understanding of the environment. However, little is known about the neural bases underlying the categorization of sounds. Using human functional magnetic resonance imaging (fMRI) we compared the brain responses to a category discrimination task with an auditory discrimination task using identical sets of sounds. Our stimuli differed along two dimensions: a speech,nonspeech dimension and a fast,slow temporal dynamics dimension. All stimuli activated regions in the primary and nonprimary auditory cortices in the temporal cortex and in the parietal and frontal cortices for the two tasks. When comparing the activation patterns for the category discrimination task to those for the auditory discrimination task, the results show that a core group of regions beyond the auditory cortices, including inferior and middle frontal gyri, dorsomedial frontal gyrus, and intraparietal sulcus, were preferentially activated for familiar speech categories and for novel nonspeech categories. These regions have been shown to play a role in working memory tasks by a number of studies. Additionally, the categorization of nonspeech sounds activated left middle frontal gyrus and right parietal cortex to a greater extent than did the categorization of speech sounds. Processing the temporal aspects of the stimuli had a greater impact on the left lateralization of the categorization network than did other factors, particularly in the inferior frontal gyrus, suggesting that there is no inherent left hemisphere advantage in the categorical processing of speech stimuli, or for the categorization task itself. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source]


Brain mechanisms of involuntary visuospatial attention: An event-related potential study

HUMAN BRAIN MAPPING, Issue 4 2005
Shimin Fu
Abstract The brain mechanisms mediating visuospatial attention were investigated by recording event-related potentials (ERPs) during a line-orientation discrimination task. Nonpredictive peripheral cues were used to direct participant's attention involuntarily to a spatial location. The earliest attentional modulation was observed in the P1 component (peak latency about 130 ms), with the valid trials eliciting larger P1 than invalid trials. Moreover, the attentional modulations on both the amplitude and latency of the P1 and N1 components had a different pattern as compared to previous studies with voluntary attention tasks. In contrast, the earliest visual ERP component, C1 (peak latency about 80 ms), was not modulated by attention. Low-resolution brain electromagnetic tomography (LORETA) showed that the earliest attentional modulation occurred in extrastriate cortex (middle occipital gyrus, BA 19) but not in the primary visual cortex. Later attention-related reactivations in the primary visual cortex were found at about 110 ms after stimulus onset. The results suggest that involuntary as well as voluntary attention modulates visual processing at the level of extrastriate cortex; however, at least some different processes are involved by involuntary attention compared to voluntary attention. In addition, the possible feedback from higher visual cortex to the primary visual cortex is faster and occurs earlier in involuntary relative to voluntary attention task. Hum Brain Mapp, 2005. © 2005 Wiley-Liss, Inc. [source]


Transposition of line-length discrimination in African penguins (Spheniscus demersus),

JAPANESE PSYCHOLOGICAL RESEARCH, Issue 3 2009
KAZUCHIKA MANABE
Abstract Four penguins (Spheniscus demersus) were trained to discriminate line length in a simultaneous discrimination task. After the birds' performances reached a discrimination criterion, the reinforcement ratio was decreased to .33. After the ratio of correct trials reached .90 in three successive sessions with a partial reinforcement procedure, probe-test sessions were introduced. In the probe-test trials, untrained lines were presented paired with the trained lines. The four probe-test trials were mixed into 45 discrimination trials. In the probe-test trials, the penguins that had been trained to peck shorter lines pecked the untrained shorter line rather than the longer line that was reinforced in the discrimination trials. In contrast, those birds that had been trained to peck the longer line pecked the untrained longer line, rather than the shorter line which was reinforced in the discrimination trials. All four birds demonstrated transposition in the line-length discrimination task. [source]


Executive cognitive functioning and aggression: Is it an issue of impulsivity?

AGGRESSIVE BEHAVIOR, Issue 1 2003
Peter N.S. Hoaken
Abstract A large body of research has documented a relation between the executive cognitive functions (ECFs) and interpersonal aggressive behavior. A predominant theory proposes that individuals with poor ECFs are more aggressive because they are unable to inhibit impulsive behaviors. However, evidence for this relationship is typically indirect. In this study, 46 healthy men and women completed measures of ECF, the Taylor Aggression Paradigm, and the Go/No-Go discrimination task, a behavioral measure of impulsivity. Also, impulsiveness of participant responses during the aggression task was directly assessed by measuring latency of responses to provocation ("set-time"). It was hypothesized that low-quartile,scoring ECF men and women would perform more aggressively and more impulsively than high-quartile peers. Consistent with expectations, results indicated that ECF was related to aggression and to impulsivity on the Go/No-Go task. However, low-ECF men and women did not have shorter set-times; in fact, on this task, low-ECF participants' behavioral decisions seemed slightly slower than those of high-ECF participants. In light of these results, the authors speculate that a social information-processing problem may mediate the ECF aggression relationship rather than altered impulsivity per se. Aggr. Behav. 29:15,30, 2003. © 2003 Wiley-Liss, Inc. [source]


Coregulation of Ethanol Discrimination by the Nucleus Accumbens and Amygdala

ALCOHOLISM, Issue 3 2003
Joyce Besheer
Background: Activation of GABAA receptors in the amygdala or nucleus accumbens produces discriminative stimulus effects that substitute fully for those of systemically administered ethanol. This study was conducted to determine if GABAA receptors in the amygdala and nucleus accumbens interactively modulate ethanol discrimination. Methods: Male Long-Evans rats were trained to discriminate between intraperitoneal injections of ethanol (1 g/kg) and saline on a 2-lever drug discrimination task. The rats were then surgically implanted with bilateral injection cannulae aimed at the nucleus accumbens and the amygdala. Results: Infusion of the GABAA agonist muscimol in the nucleus accumbens resulted in full substitution for systemically administered ethanol. Concurrent infusion of the GABAA antagonist bicuculline in the amygdala shifted the muscimol substitution curve in the nucleus accumbens 10-fold to the right. Conclusions: These results indicate that blockade of GABAA receptors in the amygdala significantly reduces the potency of the GABAA agonist in the nucleus accumbens. This suggests that the ethanol-like stimulus effects of GABAA receptor activation in the nucleus accumbens are modulated by GABAA receptor activity in the amygdala. These data support the hypothesis that the addictive stimulus properties of alcohol are mediated by GABAergic transmission in a neural circuit involving the amygdala and nucleus accumbens. [source]


Flexible modelling of neuron firing rates across different experimental conditions: an application to neural activity in the prefrontal cortex during a discrimination task

JOURNAL OF THE ROYAL STATISTICAL SOCIETY: SERIES C (APPLIED STATISTICS), Issue 4 2006
Carmen Cadarso-Suárez
Summary., In many electrophysiological experiments the main objectives include estimation of the firing rate of a single neuron, as well as a comparison of its temporal evolution across different experimental conditions. To accomplish these two goals, we propose a flexible approach based on the logistic generalized additive model including condition-by-time interactions. If an interaction of this type is detected in the model, we then establish that the use of the temporal odds ratio curves is very useful in discriminating between the conditions under which the firing probability is higher. Bootstrap techniques are used for testing for interactions and constructing pointwise confidence bands for the true odds ratio curves. Finally, we apply the new methodology to assessing relationships between neural response and decision-making in movement-selective neurons in the prefrontal cortex of behaving monkeys. [source]


Modulatory effects of 5Hz rTMS over the primary somatosensory cortex in focal dystonia,An fMRI-TMS study,

MOVEMENT DISORDERS, Issue 1 2010
Susanne A. Schneider MD
Abstract Dystonia is associated with impaired somatosensory ability. The electrophysiological method of repetitive transcranial magnetic stimulation (rTMS) can be used for noninvasive stimulation of the human cortex and can alter cortical excitability and associated behavior. Among others, rTMS can alter/improve somatosensory discrimation abilities, as shown in healthy controls. We applied 5Hz-rTMS over the left primary somatosensory cortex (S1) in 5 patients with right-sided writer's dystonia and 5 controls. We studied rTMS effects on tactile discrimination accuracy and concomitant rTMS-induced changes in hemodynamic activity measured by functional magnetic resonance imaging (fMRI). Before rTMS, patients performed worse on the discrimination task than controls even though fMRI showed greater task-related activation bilaterally in the basal ganglia (BG). In controls, rTMS led to improved discrimination; fMRI revealed this was associated with increased activity of the stimulated S1, bilateral premotor cortex and BG. In dystonia patients, rTMS had no effect on discrimination; fMRI showed similar cortical effects to controls except for no effects in BG. Improved discrimination after rTMS in controls is linked to enhanced activation of S1 and BG. Failure of rTMS to increase BG activation in dystonia may be associated with the lack of effect on sensory discrimination in this group and may reflect impaired processing in BG-S1 connections. Alternatively, the increased BG activation seen in the baseline state without rTMS may reflect a compensatory strategy that saturates a BG contribution to this task. © 2010 Movement Disorder Society [source]


Motor and nonmotor event-related potentials during a complex processing task

PSYCHOPHYSIOLOGY, Issue 6 2000
Charles H. Hillman
Identification of the necessary stimulus properties to elicit the stimulus preceding negativity (SPN) has been the impetus for numerous research studies. The current study was conducted to explore the possibility that the SPN is an index of cognitive resource allocation. An auditory warning stimulus (S1) indicated whether an easy or difficult discrimination would occur at S2. The SPN was collected before a nonmotor discrimination task (S2) that consisted of identifying the higher of two bars. To eliminate the influence of motor processing prior to S2, a button press on the side of the higher bar was held until perception of a response cue (S3). Additionally, P3, contingent negative variation (CNV), and behavioral measures were collected to assist in assessing the SPN. Results indicated that although the SPN exhibited increased negativity, no differences were observed based on task difficulty. However, task difficulty did affect P3 data for both the warning tone and the discrimination task, an effect not observed for the CNV. Overall, the data did not support that hypothesis that the SPN provides an index of cognitive demand. [source]


Visual acuity in the cathemeral strepsirrhine Eulemur macaco flavifrons

AMERICAN JOURNAL OF PRIMATOLOGY, Issue 4 2009
Carrie C. Veilleux
Abstract Studies of visual acuity in primates have shown that diurnal haplorhines have higher acuity (30,75 cycles per degree (c/deg)) than most other mammals. However, relatively little is known about visual acuity in non-haplorhine primates, and published estimates are only available for four strepsirrhine genera (Microcebus, Otolemur, Galago, and Lemur). We present here the first measurements of visual acuity in a cathemeral strepsirrhine species, the blue-eyed black lemur (Eulemur macaco flavifrons). Acuity in two subjects, a 3-year-old male and a 16-year-old female, was assessed behaviorally using a two-alternative forced choice discrimination task. Visual stimuli consisted of high contrast square wave gratings of seven spatial frequencies. Acuity threshold was determined using a 70% correct response criterion. Results indicate a maximum visual acuity of 5.1,c/deg for the female (1718 trials) and 3.8,c/deg for the male (846 trials). These values for E. macaco are slightly lower than those reported for diurnal Lemur catta, and are generally comparable to those reported for nocturnal Microcebus murinus and Otolemur crassicaudatus. To examine ecological sources of variation in primate visual acuity, we also calculated maximum theoretical acuity for Cheirogaleus medius (2.8,c/deg) and Tarsius syrichta (8.9,c/deg) using published data on retinal ganglion cell density and eye morphology. These data suggest that visual acuity in primates may be influenced by activity pattern, diet, and phylogenetic history. In particular, the relatively high acuity of T. syrichta and Galago senegalensis suggests that visual predation may be an important selective factor favoring high visual acuity in primates. Am. J. Primatol. 71:343,352, 2009. © 2009 Wiley-Liss, Inc. [source]


The influence of social factors and implicit racial bias on a generalized own-race effect

APPLIED COGNITIVE PSYCHOLOGY, Issue 4 2008
Pamela M. Walker
The current study sought to determine whether the experimentally reported ,own-race effect' is other-race specific, or whether it is a generalized effect. The perceptual processing of own- versus two groups of other-race faces was therefore explored in White and South Asian individuals. Participants completed a computer-based discrimination task of White, South Asian and Black face-morphs. Results showed a generalized own-race effect for White and South Asian participants discriminating own- versus other-race (White/South Asian and Black) faces, such that individuals demonstrated a perceptual discrimination advantage for own- versus other-race faces in general. These findings were linked to implicit racial bias and other-race individuating experience, demonstrating that social variables play an important role in the magnitude of the own-race effect. Copyright © 2007 John Wiley & Sons, Ltd. [source]


Brief exposure to a 50 Hz, 100 ,T magnetic field: Effects on reaction time, accuracy, and recognition memory

BIOELECTROMAGNETICS, Issue 3 2002
John Podd
Abstract The present study investigated both the direct and delayed effects of a 50 Hz, 100 ,T magnetic field on human performance. Eighty subjects completed a visual duration discrimination task, half being exposed to the field and the other half sham exposed. The delayed effects of this field were also examined in a recognition memory task that followed immediately upon completion of the discrimination task, Unlike our earlier studies, we were unable to find any effects of the field on reaction time and accuracy in the visual discrimination task. However, the field had a delayed effect on memory, producing a decrement in recognition accuracy. We conclude that after many years of experimentation, finding a set of magnetic field parameters and human performance measures that reliably yield magnetic field effects is proving elusive. Yet the large number of significant findings suggests that further research is warranted. Bioelectromagnetics 23:189,195, 2002. © 2002 Wiley-Liss, Inc. [source]


A Method for Simulating Signal Evolution Using Real Animals

ETHOLOGY, Issue 10 2000
Björn Forkman
We studied response biases to visual stimulation using a new experimental technique. The subjects (hens, Gallus gallus domesticus) were confronted with several rewarding and non-rewarding patterns on a computer screen. In contrast with standard discrimination tasks the rewarding patterns were not identical and varied in a dimension differentiating them from the non-rewarding patterns. The rewarding patterns changed in response to hens' biases in selection of patterns. The aim of the study was to examine the possibility of receivers being a driving force in signal evolution. In one of the experiments a clear-cut result was obtained. During the course of the experiment the rewarding patterns became gradually more different from the non-rewarding one, a result expected from theoretical studies of the effect of response bias in signal evolution. A second similar experiment was less conclusive, with ceiling and floor effects influencing the results. [source]


Direction of cross-modal information transfer affects human brain activation: a PET study

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2002
Ryuta Kawashima
Abstract The purpose of this study was to determine the functional organization of the human brain involved in cross-modal discrimination between tactile and visual information. Regional cerebral blood flow was measured by positron emission tomography in nine right-handed volunteers during four discrimination tasks; tactile,tactile (TT), tactile,visual (TV), visual,tactile (VT), and visual,visual (VV). The subjects were asked either to look at digital cylinders of different diameters or to grasp the digital cylinders with the thumb and index finger of the right hand using haptic interfaces. Compared with the motor control task in which the subjects looked at and grasped cylinders of the same diameter, the right lateral prefrontal cortex and the right inferior parietal lobule were activated in all the four discrimination tasks. In addition, the dorsal premotor cortex, the ventral premotor cortex, and the inferior temporal cortex of the right hemisphere were activated during VT but not during TV. Our results suggest that the human brain mechanisms underlying cross-modal discrimination have two different pathways depending on the temporal order in which stimuli are presented. [source]


Aging and the interaction of sensory cortical function and structure

HUMAN BRAIN MAPPING, Issue 1 2009
Ann M. Peiffer
Abstract Even the healthiest older adults experience changes in cognitive and sensory function. Studies show that older adults have reduced neural responses to sensory information. However, it is well known that sensory systems do not act in isolation but function cooperatively to either enhance or suppress neural responses to individual environmental stimuli. Very little research has been dedicated to understanding how aging affects the interactions between sensory systems, especially cross-modal deactivations or the ability of one sensory system (e.g., audition) to suppress the neural responses in another sensory system cortex (e.g., vision). Such cross-modal interactions have been implicated in attentional shifts between sensory modalities and could account for increased distractibility in older adults. To assess age-related changes in cross-modal deactivations, functional MRI studies were performed in 61 adults between 18 and 80 years old during simple auditory and visual discrimination tasks. Results within visual cortex confirmed previous findings of decreased responses to visual stimuli for older adults. Age-related changes in the visual cortical response to auditory stimuli were, however, much more complex and suggested an alteration with age in the functional interactions between the senses. Ventral visual cortical regions exhibited cross-modal deactivations in younger but not older adults, whereas more dorsal aspects of visual cortex were suppressed in older but not younger adults. These differences in deactivation also remained after adjusting for age-related reductions in brain volume of sensory cortex. Thus, functional differences in cortical activity between older and younger adults cannot solely be accounted for by differences in gray matter volume. Hum Brain Mapp 2009. © 2007 Wiley-Liss, Inc. [source]


Feature uncertainty activates anterior cingulate cortex,

HUMAN BRAIN MAPPING, Issue 1 2004
Szabolcs Kéri
Abstract In visual discrimination tasks, the relevant feature to discriminate is defined before stimulus presentation. In feature uncertainty tasks, a cue about the relevant feature is provided after stimulus offset. We used 15O-butanol positron emission tomography (PET) in order to investigate brain activation during a feature uncertainty task. There was greater activity during the feature uncertainty task, compared with stimulus detection and discrimination of orientation and spatial frequency, in the lateral and medial prefrontal cortex, the cuneus, superior temporal and inferior parietal cortex, cortical motor areas, and the cerebellum. The most robust and consistent activation was observed in the dorsal anterior cingulate cortex (Brodmann area 32; x = 0 y = 16, z = 40). The insula, located near the claustrum (x = ,38, y = 8, z = 4), was activated during the discrimination tasks compared with the feature uncertainty condition. These results suggest that the dorsal anterior cingulate cortex is important in feature uncertainty conditions, which include divided attention, expectancy under uncertainty, and cognitive monitoring. Hum. Brain Mapp. 21:26,33, 2004. © 2003 Wiley-Liss, Inc. [source]


Modeling Infant Speech Sound Discrimination Using Simple Associative Networks

INFANCY, Issue 1 2001
Graham Schafer
Infants' responses in speech sound discrimination tasks can be nonmonotonic over time. Stager and Werker (1997) reported such data in a bimodal habituation task. In this task, 8-month-old infants were capable of discriminations that involved minimal contrast pairs, whereas 14-month-old infants were not It was argued that the older infants' attenuated performance was linked to their processing of the stimuli for meaning. The authors suggested that these data are diagnostic of a qualitative shift in infant cognition. We describe an associative connectionist model showing a similar decrement in discrimination without any qualitative shift in processing. The model suggests that responses to phonemic contrasts may be a nonmonotonic function of experience with language. The implications of this idea are discussed. The model also provides a formal framework fer studying habituation-dishabituation behaviors in infancy. [source]


Emotional processing in psychopathic personality

AGGRESSIVE BEHAVIOR, Issue 5 2002
Ute Habel
Abstract Emotional-processing deficits may be one of the characteristic features of impaired affect in individuals with psychopathy. These include shallowness and profound lack of remorse or empathy. Performances on standardized emotion discrimination tasks and mood induction tasks were compared between 17 patients with antisocial personality disorder (DSM-IV) and 17 nonpsychopaths. Subjects with psychopathic personality demonstrated poorer performance on emotion-discrimination tasks compared with controls. However, higher scores on factor "emotional detachment" of the Psychopathy Checklist (PCL-R) were associated with better discrimination ability. Subjective ratings were comparable between groups during mood induction. Although the findings support the hypothesis of a significant association between impaired emotional processing and psychopathy, they also suggest a relationship between emotional discrimination and the core personality features of psychopathy. Aggr. Behav. 28:394,400, 2002. © 2002 Wiley-Liss, Inc. [source]


Extended testing across, not within, tasks raises diagnostic accuracy of smell testing in Parkinson's disease,

MOVEMENT DISORDERS, Issue 1 2009
Sanne Boesveldt MSc
Abstract The aim of this study was to determine whether extended olfactory testing within a single olfactory task and/or across olfactory tasks increases diagnostic accuracy of olfactory testing in Parkinson's disease (PD). Olfactory function was assessed using an extended version of the "Sniffin' Sticks", comprising 32-item odor identification and discrimination tasks, and a detection threshold task in 52 PD patients and 50 controls, all aged between 49 and 78 years. ROC curves based on sensitivity and specificity estimates were used to compare the diagnostic accuracy of extended and combined olfactory testing. There was no significant difference in diagnostic accuracy between the 16-item and the 32-item versions of the odor identification or discrimination test. The single olfactory test that was best in discriminating between PD patients and controls was a 16-item odor identification test. A combination of the 16-item identification test and the detection threshold task had a significantly higher area under the curve than the 16-item odor identification test alone. In conclusion, extended testing across, and not within, olfactory tasks increases diagnostic accuracy of olfactory testing in PD. A combination of an odor detection threshold task and a 16-item odor identification test had the highest sensitivity and specificity in distinguishing between PD patients and controls. © 2008 Movement Disorder Society [source]