Performance In Discrimination Tasks Research Articles

The effects of moderate prenatal alcohol exposure on performance in object and spatial discrimination tasks by adult male rats

Exposure to alcohol during pregnancy produces Fetal Alcohol Spectrum Disorders, which in its most severe form is characterized by physical dysmorphology and neurobehavioral alterations. Moderate prenatal alcohol exposure (mPAE) is known to produce deficits in discrimination of spatial locations in adulthood. However, the impact of mPAE on higher-order sensory representations, such as discrimination of perceptually similar stimuli, is currently unknown. In the present study, we tested the hypothesis that mPAE would disrupt performance on hippocampal-sensitive tasks that require discrimination between perceptually similar objects or discrimination between spatial locations in a radial arm maze. Here we report that male mPAE rats exhibited intact performance on three types of object discrimination tasks: one in which rats discriminated between distinct toy objects, a second in which discrimination was made between distinct and similar LEGO objects, and a mnemonic similarity task in which rats discriminated between randomly presented LEGO objects that varied in similarity with a learned object. Although adult male mPAE rats performed similarly to control rats on all three object discrimination tasks, they showed deficits when tested in a radial arm maze spatial discrimination task. Specifically, male mPAE rats expressed a significantly higher number of working memory errors (returns to previously visited arms) and were more likely to use non-spatial strategies during training. Together, the findings of the present study support the conclusion that mPAE produces specific deficits in the online processing of spatial information and executing spatial navigation strategies, but spares the ability to discriminate between perceptually similar stimuli.

Association among childhood adversity and susceptibility to interference during varying salience: two studies in healthy males

Childhood adversity, a prevalent experience, is related to a higher risk for externalizing and internalizing psychopathology. Alterations in the development of cognitive processes, for example in the attention-interference domain may link childhood adversity and psychopathology. Interfering stimuli can vary in their salience, i.e. ability to capture attentional focus, and valence. However, it is not known if interference by salience or valence is associated with self-reported adversity. In two independent study samples of healthy men (Study 1: n = 44; mean age [standard deviation (SD)] = 25.9 [3.4] years; Study 2: n = 37; 43.5 [9.7] years) we used the attention modulation task (AMT) that probed interference by two attention-modulating conditions, salience and valence separately across repeated target stimuli. The AMT measures the effects of visual distractors (pictures) on the performance of auditory discrimination tasks (target stimuli). We hypothesized that participants reporting higher levels of childhood adversity, measured with the childhood trauma questionnaire, would show sustained interference in trials with lower salience. Due to conflicting reports on the valence-modulation, we tested the valence condition in an exploratory manner. Linear mixed models revealed an interaction between reported childhood adversity and the salience condition across tone presentations in both study samples (Sample 1: p = .03; Sample 2: p = .04), while there were no effects for the valence condition across both studies. Our study suggests that higher self-reported childhood adversity is related to faster processing of target cues during high salience, but slower during low salience conditions. These results hint to the mechanisms linking childhood adversity and psychopathological symptoms in the attentional domain.

The influence of peripheral information on a proactive process during multitasking.

The aim of this study was to examine whether peripheral information facilitates proactive processes during multitasking. For this purpose, peripheral information was presented regularly during multitasking and its effects on the performance of a tracking task (main task: reactive process) and a discrimination task (sub-task: proactive process) were examined. Experiment 1 presented peripheral information (white circles) in the same sensory modality (visual) as the information used for multitasking and the number of circle presentations was manipulated. In Experiment 2, a pure tone (auditory) was presented as peripheral information. We found that, in both experiments, the difficulty of the tracking task influenced discrimination performance, showing that as the difficulty of the tracking task (reactive process) increased, more cognitive resources were consumed in the tracking task, resulting in a decrease in cognitive resources available for the discrimination task (proactive process). In addition, regular presentation of peripheral information facilitated discrimination task performance in both experiments. Interestingly, this peripheral information also facilitated the tracking task performance (reactive process) even if the tracking task was difficult. Moreover, this promoting effect of the peripheral information occurred regardless of the sensory modality. This study revealed that processing of peripheral information facilitates the proactive process even if more cognitive resources are consumed, and that this facilitating effect does not conflict with multitasking and provides a margin of cognitive resources and also facilitates the reactive process. Our results provide evidence of how peripheral information and cognitive resources are used during multitasking.

Chromatic discrimination in fixed saturation levels from tufted capuchin monkeys with different color vision genotypes.

Recent research has proposed new approaches to investigate color vision in Old World Monkeys by measuring suprathreshold chromatic discrimination. In this study, we aimed to extend this approach to New World Monkeys with different color vision genotypes by examining their performance in chromatic discrimination tasks along different fixed chromatic saturation axes. Four tufted capuchin monkeys were included in the study, and their color vision genotypes were one classical protanope, one classical deuteranope, one non-classical protanope, and a normal trichromat. During the experiments, the monkeys were required to perform a chromatic discrimination task using pseudoisochromatic stimuli with varying target saturations of 0.06, 0.04, 0.03, and 0.02 u'v' units. The number of errors made by the monkeys along different chromatic axes was recorded, and their performance was quantified using the binomial probability of their hits during the tests. Our results showed that dichromatic monkeys made more errors near the color confusion lines associated with their specific color vision genotypes, while the trichromatic monkey did not demonstrate any systematic errors. At high chromatic saturation, the trichromatic monkey had significant hits in the chromatic axes around the 180° chromatic axis, whereas the dichromatic monkeys had errors in colors around the color confusion lines. At lower saturation, the performance of the dichromatic monkeys became more challenging to differentiate among the three types, but it was still distinct from that of the trichromatic monkey. In conclusion, our findings suggest that high saturation conditions can be used to identify the color vision dichromatic phenotype of capuchin monkeys, while low chromatic saturation conditions enable the distinction between trichromats and dichromats. These results extend the understanding of color vision in New World Monkeys and highlight the usefulness of suprathreshold chromatic discrimination measures in exploring color vision in non-human primates.

The Relationship Between Dual Feedback and Self-Perception in Amplitude Discrimination Task Performance

Feedback and self-perception are often studied in relation to task performance as they are often associated with observable differences in performance. However, the way self-perception and feedback may affect each other and an individual has yet to be fully understood. Therefore, the purpose of this study is to determine whether there is a relationship between different types of feedback and subject self-perception, and to understand the effects of using different feedback types. A group of 39 young adults performed a series of amplitude discrimination tasks and were provided with three feedback conditions and completed a survey detailing their perception of their performance and the feedback provided. Results indicated that there is a difference in perception of feedback types, though there was no significant difference in performance between the feedback conditions. Additionally, there was some evidence that a pattern exists by which subjects with lower self-efficacy scores may be more susceptible to performance changes as feedback conditions change. These findings suggest that subjects are responsive to feedback, and that this responsivity could be related to subjects’ self-perception.

Context dependent mechanisms of time and numerosity during bisection and discrimination task performance

Context dependent mechanisms of time and numerosity during bisection and discrimination task performance

Inquiry of the orbitofrontal cortex role in incentive learning: An artificial neural networks simulation

This study evaluates, through artificial neural network (NN) simulations, the roles of amygdala (AMG) and orbitofrontal cortex (OFC) in reversal learning as responsible for assigning and updating incentive values, respectively, by taking into account some of its physiological characteristics and its connections with mesolimbic system structures. An architecture was built which contained modules of nodes representing OFC, amygdala (AMG), ventral tegmental area (VTA) and nucleus accumbens (NACC). Simulations were based on experimental responses of rats during a discrimination and reversal learning task in a T-maze. During simulations, intact NN responded similar to control rats. OFC showed retarded encoding in afferent connections as comparing with AMG nodes and an increase in the recruitment of neural nodes during reversal tasks. Activity of neural nodes plausibly emulates reinforcer preference during discriminations and reversals in AMG, COF and NACC. All these findings were disrupted by OFC’s inactivation. NN with OFC nodes inactivated (RN), just like rats with OFC inactivated, achieved discrimination learning although its reversal was impaired. As with rats, perseveration of incorrect responses was not found because subjects stop responding after a few incorrect trials. These findings are in accordance with the hypotheses of AMG as key in encoding novel predicting-outcome cues and OFC as critical for incentive value updating and the crucial role this prefrontal region plays for correct performance in discrimination tasks.

Columnar Lesions in Barrel Cortex Persistently Degrade Object Location Discrimination Performance.

Primary sensory cortices display functional topography, suggesting that even small cortical volumes may underpin perception of specific stimuli. Traditional loss-of-function approaches have a relatively large radius of effect (>1 mm), and few studies track recovery following loss-of-function perturbations. Consequently, the behavioral necessity of smaller cortical volumes remains unclear. In the mouse primary vibrissal somatosensory cortex (vS1), "barrels" with a radius of ∼150 μm receive input predominantly from a single whisker, partitioning vS1 into a topographic map of well defined columns. Here, we train animals implanted with a cranial window over vS1 to perform single-whisker perceptual tasks. We then use high-power laser exposure centered on the barrel representing the spared whisker to produce lesions with a typical volume of one to two barrels. These columnar-scale lesions impair performance in an object location discrimination task for multiple days without disrupting vibrissal kinematics. Animals with degraded location discrimination performance can immediately perform a whisker touch detection task with high accuracy. Animals trained de novo on both simple and complex whisker touch detection tasks showed no permanent behavioral deficits following columnar-scale lesions. Thus, columnar-scale lesions permanently degrade performance in object location discrimination tasks.

Discrimination of edge orientation by bumblebees.

Simple feature detectors in the visual system, such as edge-detectors, are likely to underlie even the most complex visual processing, so understanding the limits of these systems is crucial for a fuller understanding of visual processing. We investigated the ability of bumblebees (Bombus terrestris) to discriminate between differently angled edges. In a multiple-choice, “meadow-like” scenario, bumblebees successfully discriminated between angled bars with 7° differences, significantly exceeding the previously reported performance of eastern honeybees (Apis cerana, limit: 15°). Neither the rate at which bees learned, nor their final discrimination performance were affected by the angular orientation of the training bars, indicating a uniform performance across the visual field. Previous work has found that, in dual-choice tests, eastern honeybees cannot reliably discriminate between angles with less than 25° difference, suggesting that performance in discrimination tasks is affected by the training regime, and doesn’t simply reflect the perceptual limitations of the visual system. We used high resolution LCD monitors to investigate bumblebees’ angular resolution in a dual-choice experiment. Bumblebees could still discriminate 7° angle differences under such conditions (exceeding the previously reported limit for Apis mellifera, of 10°, as well as that of A. cerana). Bees eventually reached similar levels of accuracy in the dual-choice experiment as they did under multiple-choice conditions but required longer learning periods. Bumblebees show impressive abilities to discriminate between angled edges, performing better than two previously tested species of honeybee. This high performance may, in turn, support complex visual processing in the bumblebee brain.

Chromatic discrimination in fixed saturation levels from trichromats and subjects with congenital color vision deficiency

Color vision tests use estimative of threshold color discrimination or number of correct responses to evaluate performance in chromatic discrimination tasks. Both approaches have advantages and disadvantages. In the present investigation, we compared the number of errors during color discrimination task in normal trichromats and participants with color vision deficiency (CVD) using pseudoisochromatic stimuli at fixed saturation levels. We recruited 28 normal trichromats and eight participants with CVD. Cambridge Color Test was used to categorize their color vision phenotype, and those with a phenotype suggestive of color vision deficiency had their L- and M-opsin genes genotyped. Pseudoisochromatic stimuli were shown with target chromaticity in 20 vectors radiating from the background chromaticity and saturation of 0.06, 0.04, 0.03, 0.02, 0.01, and 0.005 u’v' units. Each stimulus condition appeared in four trials. The number of errors for each stimulus condition was considered an indicator of the participant's performance. At high chromatic saturation, there were fewer errors from both phenotypes. The errors of the normal trichromats had no systematic variation for high saturated stimuli, but below 0.02 u’v' units, there was a discrete prevalence of tritan errors. For participants with CVD, the errors happened mainly in red-green chromatic vectors. A three-way ANOVA showed that all factors (color vision phenotype, stimulus saturation, and chromatic vector) had statistically significant effects on the number of errors and that stimulus saturation was the most important main effect. ROC analysis indicated that the performance of the fixed saturation levels to identify CVD was better between 0.02 and 0.06 u’v’ units reaching 100%, while saturation of 0.01 and 0.005 u’v’ units decreased the accuracy of the screening of the test. We concluded that the color discrimination task using high saturated stimuli separated normal trichromats and participants with red-green color vision deficiencies with high performance, which can be considered a promising method for new color vision tests based in frequency of errors.

APOE‐ε4 status moderates the relationship between body mass index and hippocampal structure in older African Americans

AbstractBackgroundGrowing evidence suggests that traditional body mass index (BMI) cutoff values may overestimate adiposity and its health consequences in African Americans. Further, while obesity disproportionately affects African Americans, obesity is inconsistently associated with Alzheimer’s disease (AD) in older adulthood. Examining the influence of BMI and its interaction with the strongest genetic risk factor of AD, the APOE‐ε4 allele, on hippocampal‐dependent cognitive performance and medial temporal lobe (MTL) structure may provide insights into the complex relationship between obesity and AD in older African Americans.MethodAnalyses included 70 cognitively normal older African Americans (mean age=69.50 years, SD=7.18; mean education=14.12 years, SD 2; 38.60% APOE‐4 allele carriers) who completed cognitive testing, saliva sampling for APOE genotyping, and structural neuroimaging to extract MTL cortical region/hippocampal subfield volumes and surface areas. Cognitive tests included the following measures of generalization and episodic memory: Concurrent Discrimination and Transfer Task, Acquired Equivalence Task, and Rey Auditory Verbal Learning Test. ANCOVAs were used to compare BMI groups (normal: 18‐24.9 kg/m2; overweight: 25‐29.9 kg/m2; class 1 obesity: 30‐34.9 kg/m22) and to test for BMIxAPOE interactions on cognitive and neuroimaging outcomes, while controlling for age, sex, education, literacy, and depressive symptomology.ResultThere was a statistically significant difference between BMI groups on Concurrent Discrimination and Transfer Task performance, p=.01, partial η 2=.18. The normal and class 2 obesity group committed significantly greater errors than either the overweight or class 1 obesity group, ps < .05. Significant BMIxAPOE interactions were identified for the following hippocampal subfield volumes and surface areas: left DG/CA3 and left CA1, ps < .05. For APOE‐ε4 non‐carriers, the normal BMI group had significantly smaller left DG/CA3 and CA1 subfields than the other groups. Among APOE‐ε4 carriers, the class 2 obesity group had smaller left DG/CA3 and CA1 subfields than the other groups.ConclusionBeing overweight may confer cognitive protection in older African Americans. However, obesity appears to be selectively detrimental to hippocampal subfield structure among APOE‐ε4 carriers while normal BMI may be deleterious to hippocampal subfield structure among APOE‐ε4 non‐carriers.

Transcranial Magnetic Stimulation Over the Right Posterior Superior Temporal Sulcus Promotes the Feature Discrimination Processing.

Attention is the dynamic process of allocating limited resources to the information that is most relevant to our goals. Accumulating studies have demonstrated the crucial role of frontal and parietal areas in attention. However, the effect of posterior superior temporal sulcus (pSTS) in attention is still unclear. To address this question, in this study, we measured transcranial magnetic stimulation (TMS)-induced event-related potentials (ERPs) to determine the extent of involvement of the right pSTS in attentional processing. We hypothesized that TMS would enhance the activation of the right pSTS during feature discrimination processing. We recruited 21 healthy subjects who performed the dual-feature delayed matching task while undergoing single-pulse sham or real TMS to the right pSTS 300 ms before the second stimulus onset. The results showed that the response time was reduced by real TMS of the pSTS as compared to sham stimulation. N270 amplitude was reduced during conflict processing, and the time-varying network analysis revealed increased connectivity between the frontal lobe and temporo-parietal and occipital regions. Thus, single-pulse TMS of the right pSTS enhances feature discrimination processing and task performance by reducing N270 amplitude and increasing connections between the frontal pole and temporo-parietal and occipital regions. These findings provide evidence that the right pSTS facilitates feature discrimination by accelerating the formation of a dynamic network.

Automated Operant Conditioning Devices for Fish. Do They Work?

Simple SummaryAutomated training devices are commonly used for investigating learning, memory, and other cognitive functions in warm-blood vertebrates, whereas manual training procedures are the standard in fish and other lower vertebrates, thus limiting comparison among species. Here, we directly compared the two different approaches to training in guppies (Poecilia reticulata) by administering numerical discrimination tasks of increasing difficulty. The automated device group showed a much lower performance compared to the traditionally-trained group. We modified some features of the automated device in order to improve its efficiency. Increasing the decision time or inter-trial interval was ineffective, while reducing the cognitive load and allowing subjects to reside in the test tank improved numerical performance. Yet, in no case did subjects match the performance of traditionally-trained subjects, suggesting that small teleosts may be limited in their capacity to cope with operant conditioning devices.The growing use of teleosts in comparative cognition and in neurobiological research has prompted many researchers to develop automated conditioning devices for fish. These techniques can make research less expensive and fully comparable with research on warm-blooded species, in which automated devices have been used for more than a century. Tested with a recently developed automated device, guppies (Poecilia reticulata) easily performed 80 reinforced trials per session, exceeding 80% accuracy in color or shape discrimination tasks after only 3–4 training session, though they exhibit unexpectedly poor performance in numerical discrimination tasks. As several pieces of evidence indicate, guppies possess excellent numerical abilities. In the first part of this study, we benchmarked the automated training device with a standard manual training procedure by administering the same set of tasks, which consisted of numerical discriminations of increasing difficulty. All manually-trained guppies quickly learned the easiest discriminations and a substantial percentage learned the more difficult ones, such as 4 vs. 5 items. No fish trained with the automated conditioning device reached the learning criterion for even the easiest discriminations. In the second part of the study, we introduced a series of modifications to the conditioning chamber and to the procedure in an attempt to improve its efficiency. Increasing the decision time, inter-trial interval, or visibility of the stimuli did not produce an appreciable improvement. Reducing the cognitive load of the task by training subjects first to use the device with shape and color discriminations, significantly improved their numerical performance. Allowing the subjects to reside in the test chamber, which likely reduced the amount of attentional resources subtracted to task execution, also led to an improvement, although in no case did subjects match the performance of fish trained with the standard procedure. Our results highlight limitations in the capacity of small laboratory teleosts to cope with operant conditioning automation that was not observed in laboratory mammals and birds and that currently prevent an easy and straightforward comparison with other vertebrates.

The impact of feedback on tactile discrimination task performance

Research in the fields of psychology and neuroscience often rely on tasks that participants perform to fulfill the requirements of a study. These tasks are administered with either feedback, partial feedback, or no feedback given to the participant. The purpose of this study is to compare and contrast the impact of feedback vs. no feedback on a tactile discrimination task. The goal of providing feedback should, in theory, be to motivate participants while performing a task without altering the results. To test this hypothesis, a group of 22 participants was instructed to take two sequential amplitude discrimination tests using the Brain Gauge; one test with feedback and one without. The results show a clear indication that when presented with feedback, participants performed better than without feedback, and it was speculated that the improvement in performance was due to an improvement in motivation, which was supported by a simple survey. The study results suggest that future research should utilize feedback as a means for motivation in participants and should investigate the effects of only positive or negative feedback as well as how feedback would affect scores and motivation levels during long-term experiments.

Hippocampal subfield bold signal and mnemonic discrimination task performance in cognitive aging

AbstractBackgroundCognitive aging is associated with impaired episodic memory formation (Small et al., 1999), which requires the neurocomputational process of pattern separation to disambiguate similar stimulus input. Pattern separation relies on the dentate gyrus (DG) (Yassa & Stark, 2011), a hippocampal subfield that is susceptible to age‐related change (Small et al., 2011). Cognitive aging is also associated with impaired performance on putative measures of behavioral pattern separation (Yassa et al., 2010), called mnemonic discrimination tasks in humans. Prior work using high‐resolution fMRI suggests that age‐related impairments in mnemonic discrimination are linked to aberrant activation patterns in the DG/CA3 (Yassa et al., 2010). Whereas aging is associated with impaired DG integrity and mnemonic discrimination ability, cardiorespiratory fitness is associated with enhanced DG integrity and improved mnemonic discrimination ability. Given that cardiorespiratory fitness has been positively linked to DG/CA3 integrity in young adults (Nauer et al., 2019), it is conceivable that in older adults, cardiorespiratory fitness will modulate age‐related changes in DG/CA3 activation, which in turn, will dampen age‐related impairments in mnemonic discrimination.Methods18 older adults (55‐85 years) and 18 young adults (18‐35 years) underwent a submaximal treadmill test to estimate cardiorespiratory fitness and high‐resolution fMRI to examine hippocampal subfield BOLD signal during encoding and retrieval of a mnemonic discrimination task (MDT).ResultsIn older adults, we found increased right DG/CA3 BOLD signal in incorrect mnemonic discrimination trials contrasted with correct mnemonic discrimination trials, specifically during stimulus retrieval. Additionally, in both young and older adults, we found that right DG/CA3 BOLD signal in the mnemonic discrimination fMRI contrast during stimulus encoding marginally significantly predicted MDT corrected accuracy. Finally, in both young and older adults, fitness significantly negatively predicted left DG/CA3 BOLD signal in the mnemonic discrimination fMRI contrast during stimulus retrieval.ConclusionsThese results suggest that DG/CA3 BOLD signal relates to performance on a MDT designed to tax pattern separation, and that cardiorespiratory fitness modulates BOLD signal in these subregions. Altogether, these results suggest a link between fitness, DG/CA3 functional integrity, and mnemonic discrimination that may be critical to understanding how to dampen age‐related impairments in episodic memory.

Perceptual inference is impaired in individuals with ASD and intact in individuals who have lost the autism diagnosis

Beyond the symptoms which characterize their diagnoses, individuals with autism spectrum disorder (ASD) show enhanced performance in simple perceptual discrimination tasks. Often attributed to superior sensory sensitivities, enhanced performance may also reflect a weaker bias towards previously perceived stimuli. This study probes perceptual inference in a group of individuals who have lost the autism diagnosis (LAD); that is, they were diagnosed with ASD in early childhood but have no current ASD symptoms. Groups of LAD, current ASD, and typically developing (TD) participants completed an auditory discrimination task. Individuals with TD showed a bias towards previously perceived stimuli—a perceptual process called “contraction bias”; that is, their representation of a given tone was contracted towards the preceding trial stimulus in a manner that is Bayesian optimal. Similarly, individuals in the LAD group showed a contraction bias. In contrast, individuals with current ASD showed a weaker contraction bias, suggesting reduced perceptual inferencing. These findings suggest that changes that characterize LAD extend beyond the social and communicative symptoms of ASD, impacting perceptual domains. Measuring perceptual processing earlier in development in ASD will tap the causality between changes in perceptual and symptomatological domains. Further, the characterization of perceptual inference could reveal meaningful individual differences in complex high-level behaviors.

Resting EEG in alpha band predicts individual differences in visual size perception

Human visual size perception results from an interaction of external sensory information and internal state. The cognitive mechanisms involved in the processing of context-dependent visual size perception have been found to be innate in nature to some extent, suggesting that visual size perception might correlate with human intrinsic brain activity. Here we recorded human resting alpha activity (8–12 Hz), which is an inverse indicator of sustained alertness. Moreover, we measured an object’s perceived size in a two-alternative forced-choice manner and the Ebbinghaus illusion magnitude which is a classic illustration of context-dependent visual size perception. The results showed that alpha activity along the ventral visual pathway, including left V1, right LOC and bilateral inferior temporal gyrus, negatively correlated with an object’s perceived size. Moreover, alpha activity in the left superior temporal gyrus positively correlated with size discrimination threshold and size illusion magnitude. The findings provide clear evidence that human visual size perception scales as a function of intrinsic alertness, with higher alertness linking to larger perceived size of objects and better performance in size discrimination and size illusion tasks, and suggest that individual variation in resting-state brain activity provides a neural explanation for individual variation in cognitive performance of normal participants.

A Basal Ganglia Computational Model to Explain the Paradoxical Sensorial Improvement in the Presence of Huntington's Disease.

The basal ganglia (BG) represent a critical center of the nervous system for sensorial discrimination. Although it is known that Huntington's disease (HD) affects this brain area, it still remains unclear how HD patients achieve paradoxical improvement in sensorial discrimination tasks. This paper presents a computational model of the BG including the main nuclei and the typical firing properties of their neurons. The BG model has been embedded within an auditory signal detection task. We have emulated the effect that the altered levels of dopamine and the degree of HD affectation have in information processing at different layers of the BG, and how these aspects shape transient and steady states differently throughout the selection task. By extracting the independent components of the BG activity at different populations, it is evidenced that early and medium stages of HD affectation may enhance transient activity in the striatum and the substantia nigra pars reticulata. These results represent a possible explanation for the paradoxical improvement that HD patients present in discrimination task performance. Thus, this paper provides a novel understanding on how the fast dynamics of the BG network at different layers interact and enable transient states to emerge throughout the successive neuron populations.

Dichotic Perception of Lexical Tones in Cantonese-Speaking Congenital Amusics.

Congenital amusia is an inborn neurogenetic disorder of musical pitch processing, which also induces impairment in lexical tone perception. However, it has not been examined before how the brain specialization of lexical tone perception is affected in amusics. The current study adopted the dichotic listening paradigm to examine this issue, testing 18 Cantonese-speaking amusics and 18 matched controls on pitch/lexical tone identification and discrimination in three conditions: non-speech tone, low syllable variation, and high syllable variation. For typical listeners, the discrimination accuracy was higher with shorter RT in the left ear regardless of the stimulus types, suggesting a left-ear advantage in discrimination. When the demand of phonological processing increased, as in the identification task, shorter RT was still obtained in the left ear, however, the identification accuracy revealed a bilateral pattern. Taken together, the results of the identification task revealed a reduced LEA or a shift from the right hemisphere to bilateral processing in identification. Amusics exhibited overall poorer performance in both identification and discrimination tasks, indicating that pitch/lexical tone processing in dichotic listening settings was impaired, but there was no evidence that amusics showed different ear preference from controls. These findings provided temporary evidence that although amusics demonstrate deficient neural mechanisms of pitch/lexical tone processing, their ear preference patterns might not be affected. These results broadened the understanding of the nature of pitch and lexical tone processing deficiencies in amusia.

Cognitive Phenotype and Differential Gene Expression in a Hippocampal Homologue in Two Species of Frog.

The complexity of an animal's interaction with its physical and/or social environment is thought to be associated with behavioral flexibility and cognitive phenotype, though we know little about this relationship in amphibians. We examined differences in cognitive phenotype in two species of frog with divergent natural histories. The green-and-black poison frog (Dendrobates auratus) is diurnal, displays enduring social interactions, and uses spatially distributed resources during parental care. Túngara frogs (Physalaemus=Engystomops pustulosus) are nocturnal, express only fleeting social interactions, and use ephemeral puddles to breed in a lek-type mating system. Comparing performance in identical discrimination tasks, we find that D. auratus made fewer errors when learning and displayed greater behavioral flexibility in reversal learning tasks than túngara frogs. Further, túngara frogs preferred to learn beacons that can be used in direct guidance whereas D. auratus preferred position cues that could be used to spatially orient relative to the goal. Behavioral flexibility and spatial cognition are associated with hippocampal function in mammals. Accordingly, we examined differential gene expression in the medial pallium, the amphibian homolog of the hippocampus. Our preliminary data indicate that genes related to learning and memory, synaptic plasticity, and neurogenesis were upregulated in D. auratus, while genes related to apoptosis were upregulated in túngara frogs, suggesting that these cellular processes could contribute to the differences in behavioral flexibility and spatial learning we observed between poison frogs and túngara frogs.