Figure-ground Discrimination Research Articles

Ab. No. 42 Effect of Visual Perceptual Skills Training on Manual Dexterity and Functional Abilities in Children With Autism Spectrum Disorder: A Case Series

Introduction: Globally, prevalence of ASD is rising alarmingly. Evidence synthesis on effective intervention strategies is crucial to bridge the knowledge gap. In addition to disruption in communication and social interaction, motor signs like impaired manual dexterity are frequently associated in children with autism spectrum disorder (ASD). This study aims to investigate the positive impact of visual perceptual skills training along with functional training as these skills are closely related to daily activities and academic skills. Methods: Three school-aged children (between 8-12 years of age) diagnosed with ASD were included. Motor clumsiness was the primary concern of parents. Intervention was based on principles of sensory integration. It comprised functional training along with visual perceptual skills training including figure-ground discrimination, design copying, visual scanning, visual closure, and visual-motor integration. Manual dexterity was assessed by the Nine-Hole Peg Test (9HPT) and Box and Block Test (BBT) before intervention and after 12 weeks of intervention. Besides, functional changes in activities like feeding, buttoning, writing, and copying from the board at inclusive schools were gauged. Result: All children showed improvement in manual dexterity as assessed by the 9HPT scores that changed from 49 to 40 seconds, 42 to 35 seconds, 45 to 37 seconds, respectively. In addition, BBT scores improved from 38 to 44 blocks, 41 to 49 blocks and 39 to 46 blocks, respectively. Independence in feeding and buttoning increased, apart from better efficiency in copying from board and writing. Conclusion: Visual perceptual skills training helped in improving manual dexterity in children with ASD. Moreover, independence in daily activities and academic skills were enhanced. Implications: This case series reveals that the effect of this approach is clinically significant in real life settings. However, it must be investigated on a larger population.

Bioinspired figure-ground discrimination via visual motion smoothing

Flies detect and track moving targets among visual clutter, and this process mainly relies on visual motion. Visual motion is analyzed or computed with the pathway from the retina to T4/T5 cells. The computation of local directional motion was formulated as an elementary movement detector (EMD) model more than half a century ago. Solving target detection or figure-ground discrimination problems can be equivalent to extracting boundaries between a target and the background based on the motion discontinuities in the output of a retinotopic array of EMDs. Individual EMDs cannot measure true velocities, however, due to their sensitivity to pattern properties such as luminance contrast and spatial frequency content. It remains unclear how local directional motion signals are further integrated to enable figure-ground discrimination. Here, we present a computational model inspired by fly motion vision. Simulations suggest that the heavily fluctuating output of an EMD array is naturally surmounted by a lobula network, which is hypothesized to be downstream of the local motion detectors and have parallel pathways with distinct directional selectivity. The lobula network carries out a spatiotemporal smoothing operation for visual motion, especially across time, enabling the segmentation of moving figures from the background. The model qualitatively reproduces experimental observations in the visually evoked response characteristics of one type of lobula columnar (LC) cell. The model is further shown to be robust to natural scene variability. Our results suggest that the lobula is involved in local motion-based target detection.

Columnar neurons support saccadic bar tracking in Drosophila.

Tracking visual objects while maintaining stable gaze is complicated by the different computational requirements for figure-ground discrimination, and the distinct behaviors that these computations coordinate. Drosophila melanogaster uses smooth optomotor head and body movements to stabilize gaze, and impulsive saccades to pursue elongated vertical bars. Directionally selective motion detectors T4 and T5 cells provide inputs to large-field neurons in the lobula plate, which control optomotor gaze stabilization behavior. Here, we hypothesized that an anatomically parallel pathway represented by T3 cells, which provide inputs to the lobula, drives bar tracking body saccades. We combined physiological and behavioral experiments to show that T3 neurons respond omnidirectionally to the same visual stimuli that elicit bar tracking saccades, silencing T3 reduced the frequency of tracking saccades, and optogenetic manipulation of T3 acted on the saccade rate in a push-pull manner. Manipulating T3 did not affect smooth optomotor responses to large-field motion. Our results show that parallel neural pathways coordinate smooth gaze stabilization and saccadic bar tracking behavior during flight.

A Figure-Ground Discrimination Algorithm Inspired by Border-Ownership Selective Cells

A Figure-Ground Discrimination Algorithm Inspired by Border-Ownership Selective Cells

Clinical Screening for Posterior Cortical Atrophy.

Posterior cortical atrophy (PCA) is a progressive neurologic syndrome that presents with complex visual deficits. Although PCA is most commonly a form of Alzheimer disease (AD), its early diagnosis is usually delayed due to a lack of understanding for how best to clinically screen for the syndrome. To identify neurobehavioral screening tasks for PCA-beyond simple visual constructions-that can be administered in clinic or at bedside. We compared the performance of 12 individuals who met neuroimaging-supported consensus criteria for PCA with that of 12 matched individuals with typical AD (tAD) and 24 healthy controls (HC) on clinic/bedside tasks measuring (a) complex figure copying, (b) Balint syndrome, (c) visual object agnosia, (d) color identification, (e) figure-ground discrimination, (f) global-local processing, (g) dressing apraxia, (h) ideomotor apraxia, and (i) Gerstmann syndrome. All of the individuals with PCA were impaired on the figure-ground discrimination task compared with half of the tAD group and no HC. Approximately half of the PCA group had Balint syndrome, dressing apraxia, and ideomotor apraxia compared with none in the tAD group. Difficulty copying a complex figure, global-local processing impairment, and Gerstmann syndrome did not distinguish between the two dementia groups. The figure-ground discrimination task can be used successfully as an overall screening measure for PCA, followed by specific tasks for Balint syndrome and dressing and limb apraxia. Findings reinforce PCA as a predominant occipitoparietal disorder with dorsal visual stream involvement and parietal signs with spatiomotor impairments.

Visual Perceptual Skills as Predictors of Handwriting Skills of Children Grades 1-3

ABSTRACT The purposes of this study were to identify if correlations exist between the eight sub-components of visual perception including eye hand coordination, position in space, copying, figure ground discrimination, spatial relations, visual closure, visual motor speed and form constancy, and handwriting ability. The studies also further determined which sub-components of visual perception were best predictors of children’s handwriting abilities. In this descriptive correlational research design, 65 children in grades 1–3 were evaluated using the Evaluation Tool of Children’s Handwriting (ETCH) and the Developmental Test of Visual Perception-2 (DTVP-2) on two different occasions. The Pearson’s Product-Moment Correlation Coefficient (r) and Multiple Linear Regression: Stepwise method were used to analyze the data. The results revealed significant relationships between four subcomponents (eye-hand coordination, copying, figure-ground, and spatial relations) of visual perception and word legibility. Based on the stepwise regression analysis, the best predictors of handwriting legibility are spatial relations, visual closure, and position in space, respectively. This study can guide therapists/educators in determining which visual perceptual areas to focus on when working with children with handwriting difficulties. When evaluating children with poor handwriting, special attention should be paid to the areas of figure ground, spatial relations, visual closure, and copying as they were found to correlate significantly with handwriting legibility.

A systematic review and meta-analysis of older driver interventions

The purpose of this systematic review and meta-analysis was to summarize and quantify the effects of different driving interventions among older adults on outcomes of crashes, on-road driving performance, self-reported outcomes of errors and crashes, and driving simulator performance. Randomized controlled trials examining the effects of a driving intervention among older adults ≥ 50 years of age were included. Thirty-one studies were identified using a systematic literature review, and 26 were included in meta-analyses. The following types of driving interventions were identified: physical retraining/exercise (e.g., flexibility and coordination training); visual-perceptual training (e.g., improving figure-ground discrimination); cognitive training (e.g., Useful Field of View cognitive training); education (e.g., classroom driver refresher course); context-specific training (i.e., on-road training in car, driving simulator training); combined intervention approaches (e.g., education and context-specific training combined). Effect sizes were calculated for each driving intervention type relative to control groups using random-effects. Physical retraining/exercise, visual-perceptual training, and combined intervention approaches demonstrated medium to large effects on on-road driving performance, ds = 0.564–1.061, ps < .050. Cognitive training approaches reduced at-fault crashes by almost 30 %, OR = 0.729, 95 % CI [0.553, 0.962], p = .026. Education and context-specific approaches were not efficacious to improve driving safety outcomes, ps> .050. In summary, skill-specific interventions (physical retraining/exercise, visual-perceptual training, cognitive training) and combined intervention approaches improved on-road driving performance and reduced at-fault crashes. Optimizing interventions that target age-related functional declines and combined intervention approaches is recommended.

Population coding of figure and ground in natural image patches by V4 neurons.

Segmentation of a natural scene into objects and background is a fundamental but challenging task for recognizing objects. Investigating intermediate-level visual cortical areas with a focus on local information is a crucial step towards understanding the formation of the cortical representations of figure and ground. We examined the activity of a population of macaque V4 neurons during the presentation of natural image patches and their respective variations. The natural image patches were optimized to exclude the influence of global context but included various characteristics of local stimulus. Around one fourth of the patch-responsive V4 neurons exhibited significant modulation of firing activity that was dependent on the positional relation between the figural region of the stimulus and the classical receptive field of the neuron. However, the individual neurons showed low consistency in figure-ground modulation across a variety of image patches (55–62%), indicating that individual neurons were capable of correctly signaling figure and ground only for a limited number of stimuli. We examined whether integration of the activity of multiple neurons enabled higher consistency across a variety of natural patches by training a support vector machine to classify figure and ground of the stimuli from the population firing activity. The integration of the activity of a few tens of neurons yielded discrimination accuracy much greater than that of single neurons (up to 85%), suggesting a crucial role of population coding for figure-ground discrimination in natural images.

Dynamic cognitive remediation for a Traumatic Brain Injury (TBI) significantly improves attention, working memory, processing speed, and reading fluency.

Background:In the U.S. 3.8 million people have a Traumatic Brain Injury (TBI) each year. Rapid brain training exercises to improve cognitive function after a mild TBI are needed.Objective:This study determines whether cognitive remediation by discriminating the direction a test pattern moves relative to a stationary background (movement figure-ground discrimination) improves the vision and cognitive deficits that result from a TBI, providing a paradigm shift in treatment methods.Methods:Movement-discrimination neurotraining was used to remediate low-level visual timing deficits in the dorsal stream to determine whether it improved high-level cognitive functions, such as processing speed, reading fluency, and the executive control functions of attention and working memory in four men with a TBI between the ages of 15–68. Standardized tests, as well as Magnetoencephalography (MEG) brain imaging, were administered at the beginning and end of 8–16 weeks of intervention training to evaluate improvements in cognitive skills.Results:Movement-discrimination cognitive neurotraining remediated both low-level visual timing deficits and high-level cognitive functioning, including selective and sustained attention, reading fluency, processing speed, and working memory for all TBI patients we studied. MEG brain imaging, using the Fast-VESTAL procedure, showed that this movement-discrimination training improved time-locked activity in the dorsal stream, attention, and executive control networks.Conclusions:Remediating visual timing deficits in the dorsal stream revealed the causal role of visual movement discrimination training in improving high-level cognitive functions such as focusing and switching attention, working memory, processing speed, and reading. This study found that movement-discrimination training was very rapid and effective in remediating cognitive deficits, providing a new approach that is very beneficial for treating a mild TBI.

Corrigendum: Training on Movement Figure-Ground Discrimination Remediates Low-Level Visual Timing Deficits in the Dorsal Stream, Improving High-Level Cognitive Functioning, Including Attention, Reading Fluency, and Working Memory.

[This corrects the article DOI: 10.3389/fnhum.2017.00236.].

Pharmacological manipulation of GABA activity in nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS) impairs figure-ground discrimination in pigeons: Running head: SP/IPS in figure-ground segregation

Figure-ground segregation is a fundamental visual ability that allows an organism to separate an object from its background. Our earlier research has shown that nucleus rotundus (Rt), a thalamic nucleus processing visual information in pigeons, together with its inhibitory complex, nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS), are critically involved in figure-ground discrimination (Acerbo et al., 2012; Scully et al., 2014). Here, we further investigated the role of SP/IPS by conducting bilateral microinjections of GABAergic receptor antagonist and agonists (bicuculline and muscimol, respectively) and non-NMDA glutamate receptor antagonist (CNQX) after the pigeons mastered figure-ground discrimination task. We used two doses of each drug (bicuculline: 0.1 mM and 0.05 mM; muscimol: 4.4 mM and 8.8 mM; CNQX: 2.15 mM and 4.6 mM) in a within-subject design, and alternated drug injections with baseline (ACSF). The order of injections was randomized across birds to reduce potential carryover effects. We found that a low dose of bicuculline produced a decrement on figure trials but not on background trials, whereas a high dose impaired performance on background trials but not on figure trials. Muscimol produced an equivalent, dose-dependent impairment on both types of trials. Finally, CNQX had no consistent effect at either dose. Together, these results further confirm our earlier hypothesis that inhibitory projections from SP to Rt modulate figure-ground discrimination, and suggest that the Rt and the SP/IPS provide a plausible substrate that could perform figure-ground segregation in avian brain.

PROGRESSION OF VISUAL FIELDS IN POSTERIOR CORTICAL ATROPHY MIRRORS THAT OF COGNITIVE DEFICITS

The significance of visual field defects (VFD) in posterior cortical atrophy (PCA) has been questioned in face of coexisting higher-order visual disturbances. The relationship between pattern of VFDs and that of cognitive deficits may give insight into the mechanism of VFDs in PCA. Twenty-one patients with PCA had visual field tests performed using Humphrey automated perimetry at baseline and follow-up (mean duration 2.5 years; number of assessments 2–4). Mean deviation (MD) per hemifield was calculated and the ratio between MD in the right and left hemifield (R/LMDratio) established for every assessment. Cognitive measures consisted of scores created to summarise performance on tests of unilateral (Object Perception (OP); Space Perception (SP); Spelling; Arithmetic) and bilateral cognitive functions (Shape Detection (SD); Figure-Ground Discrimination (FGD)). Cognitive scores were compared with R/LMDratio at baseline using Spearman's correlation. Progression in cognitive tests was analysed according to time and contemporary R/LMDratio using mixed model linear regression. All patients had abnormal HFA at presentation, consisting of incomplete homonymous hemianopia (HH) more marked in one hemifield in all but one patient. The more affected hemifield was the left in 14 patients (66%). At baseline R/LMD did not correlate with score on OP (ρ=0.23,p<0.3), SP (ρ=0.12, p<0.6), Arithmetic (ρ =-0.24, p<0.28), or Spelling (ρ =-0.25, p<0.28). On the longitudinal analysis, increment of one unit in RLMDratio was associated with decrement of -0.78 in Spelling (p<0.01) and -0.83 in Arithmetic (p<0.02), but had no effect on OP or SP (slope 0.001, p<0.9; and 0.01, p<0.9, respectively). Increasing 1 unit on the log of RLMDratio absolute value (RLMD approached 1) was associated with decline of 0.73 (p<0.03) in FGD and 0.55 (p<0.04) in SD. Predominant right HH was associated with greater decline on cognitive functions relying on the left hemisphere, suggesting that VFDs result from extension of degeneration into the contralateral occipital lobe. This was further supported by the association between bilateral VFDs and deterioration on bilateral occipital lobe functions. Predominant left HH did not correlate with greater right hemisphere deficits, which may be explained by the occurrence of the latter in all patients, as a consequence of PCA case definition.

Training on Movement Figure-Ground Discrimination Remediates Low-Level Visual Timing Deficits in the Dorsal Stream, Improving High-Level Cognitive Functioning, Including Attention, Reading Fluency, and Working Memory.

The purpose of this study was to determine whether neurotraining to discriminate a moving test pattern relative to a stationary background, figure-ground discrimination, improves vision and cognitive functioning in dyslexics, as well as typically-developing normal students. We predict that improving the speed and sensitivity of figure-ground movement discrimination (PATH to Reading neurotraining) acts to remediate visual timing deficits in the dorsal stream, thereby improving processing speed, reading fluency, and the executive control functions of attention and working memory in both dyslexic and normal students who had PATH neurotraining more than in those students who had no neurotraining. This prediction was evaluated by measuring whether dyslexic and normal students improved on standardized tests of cognitive skills following neurotraining exercises, more than following computer-based guided reading (Raz-Kids (RK)). The neurotraining used in this study was visually-based training designed to improve magnocellular function at both low and high levels in the dorsal stream: the input to the executive control networks coding working memory and attention. This approach represents a paradigm shift from the phonologically-based treatment for dyslexia, which concentrates on high-level speech and reading areas. This randomized controlled-validation study was conducted by training the entire second and third grade classrooms (42 students) for 30 min twice a week before guided reading. Standardized tests were administered at the beginning and end of 12-weeks of intervention training to evaluate improvements in academic skills. Only movement-discrimination training remediated both low-level visual timing deficits and high-level cognitive functioning, including selective and sustained attention, reading fluency and working memory for both dyslexic and normal students. Remediating visual timing deficits in the dorsal stream revealed the causal role of visual movement discrimination training in improving high-level cognitive functions such as attention, reading acquisition and working memory. This study supports the hypothesis that faulty timing in synchronizing the activity of magnocellular with parvocellular visual pathways in the dorsal stream is a fundamental cause of dyslexia and being at-risk for reading problems in normal students, and argues against the assumption that reading deficiencies in dyslexia are caused by phonological or language deficits, requiring a paradigm shift from phonologically-based treatment of dyslexia to a visually-based treatment. This study shows that visual movement-discrimination can be used not only to diagnose dyslexia early, but also for its successful treatment, so that reading problems do not prevent children from readily learning.

The Comparison of Visual Perception Skills in 7 - 12-Year-Old Children With or Without Dyslexia Who have Attention Deficit Hyperactivity Disorder

Background: The recognition of problems occurring with ADHD comorbid disorders can largely facilitate their diagnosis and treat- ment. Objectives: The present study aims to compare the visual perception skills of 7 - 12-year-old children with or without dyslexia who have ADHD. Methods: This is a descriptive-comparative study that encompasses a statistical population of 7 - 12-year-old children with ADHD in Iran who were convenience-sampled in Tehran's therapeutic centers in 1394. The groups completed visual perception skills tests and the results were compared by independent T-test. Results: The results of the independent T-test demonstrate that the children with ADHD but without dyslexia had better form constancy, visual discrimination, visual closure, visual-spatial relationship, visual sequential memory, visual memory, and figure ground discrimination (P < 0.01). Conclusions: Due to the diculties suered by children with ADHD and dyslexia, we recommend early diagnosis, medical screen- ing, and use of suitable therapeutic methods to identify and minimize the number of children exposed to the high risks of undiag- nosed ADHD and dyslexia.

Neurons forming optic glomeruli compute figure-ground discriminations in Drosophila.

Many animals rely on visual figure-ground discrimination to aid in navigation, and to draw attention to salient features like conspecifics or predators. Even figures that are similar in pattern and luminance to the visual surroundings can be distinguished by the optical disparity generated by their relative motion against the ground, and yet the neural mechanisms underlying these visual discriminations are not well understood. We show in flies that a diverse array of figure-ground stimuli containing a motion-defined edge elicit statistically similar behavioral responses to one another, and statistically distinct behavioral responses from ground motion alone. From studies in larger flies and other insect species, we hypothesized that the circuitry of the lobula--one of the four, primary neuropiles of the fly optic lobe--performs this visual discrimination. Using calcium imaging of input dendrites, we then show that information encoded in cells projecting from the lobula to discrete optic glomeruli in the central brain group these sets of figure-ground stimuli in a homologous manner to the behavior; "figure-like" stimuli are coded similar to one another and "ground-like" stimuli are encoded differently. One cell class responds to the leading edge of a figure and is suppressed by ground motion. Two other classes cluster any figure-like stimuli, including a figure moving opposite the ground, distinctly from ground alone. This evidence demonstrates that lobula outputs provide a diverse basis set encoding visual features necessary for figure detection.

Figure-ground modulation in awake primate thalamus

Figure-ground discrimination refers to the perception of an object, the figure, against a nondescript background. Neural mechanisms of figure-ground detection have been associated with feedback interactions between higher centers and primary visual cortex and have been held to index the effect of global analysis on local feature encoding. Here, in recordings from visual thalamus of alert primates, we demonstrate a robust enhancement of neuronal firing when the figure, as opposed to the ground, component of a motion-defined figure-ground stimulus is located over the receptive field. In this paradigm, visual stimulation of the receptive field and its near environs is identical across both conditions, suggesting the response enhancement reflects higher integrative mechanisms. It thus appears that cortical activity generating the higher-order percept of the figure is simultaneously reentered into the lowest level that is anatomically possible (the thalamus), so that the signature of the evolving representation of the figure is imprinted on the input driving it in an iterative process.

Asymmetric Processing of Visual Motion for Simultaneous Object and Background Responses

Visual object fixation and figure-ground discrimination in Drosophila are robust behaviors requiring sophisticated computation by the visual system, yet the neural substrates remain unknown. Recent experiments in walking flies revealed object fixation behavior mediated by circuitry independent from the motion-sensitive T4-T5 cells required for wide-field motion responses. In tethered flight experiments under closed-loop conditions, we found similar results for one feedback gain, whereas intact T4-T5 cells were necessary for robust object fixation at a higher feedback gain and in figure-ground discrimination tasks. We implemented dynamical models (available at http://strawlab.org/asymmetric-motion/) based on neurons downstream of T4-T5 cells—one a simple phenomenological model and another, physiologically more realistic model—and found that both predict key features of stripe fixation and figure-ground discrimination and are consistent with a classical formulation. Fundamental to both models is motion asymmetry in the responses of model neurons, whereby front-to-back motion elicits stronger responses than back-to-front motion. When a bilateral pair of such model neurons, based on well-understood horizontal system cells, downstream of T4-T5, is coupled to turning behavior, asymmetry leads to object fixation and figure-ground discrimination in the presence of noise. Furthermore, the models also predict fixation in front of a moving background, a behavior previously suggested to require an additional pathway. Thus, the models predict several aspects of object responses on the basis of neurons that are also thought to serve a key role in background stabilization.

Bilateral lesions of nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS) selectively impair figure–ground discrimination in pigeons

Earlier, we reported that nucleus rotundus (Rt) together with its inhibitory complex, nucleus subpretectalis/interstitio-pretecto-subpretectalis (SP/IPS), had significantly higher activity in pigeons performing figure-ground discrimination than in the control group that did not perform any visual discriminations. In contrast, color discrimination produced significantly higher activity than control in the Rt but not in the SP/IPS. Finally, shape discrimination produced significantly lower activity than control in both the Rt and the SP/IPS. In this study, we trained pigeons to simultaneously perform three visual discriminations (figure-ground, color, and shape) using the same stimulus displays. When birds learned to perform all three tasks concurrently at high levels of accuracy, we conducted bilateral chemical lesions of the SP/IPS. After a period of recovery, the birds were retrained on the same tasks to evaluate the effect of lesions on maintenance of these discriminations. We found that the lesions of the SP/IPS had no effect on color or shape discrimination and that they significantly impaired figure-ground discrimination. Together with our earlier data, these results suggest that the nucleus Rt and the SP/IPS are the key structures involved in figure-ground discrimination. These results also imply that thalamic processing is critical for figure-ground segregation in avian brain.

Fonctions visuoperceptives chez les enfants IMC âgés de sept à 14 ans : groupement perceptif et discrimination figure–fond

Cognitive and perceptual disorders are commonly associated with the motor pathology in children with cerebral palsy (CP). Impairment of visual–perceptual functions is frequently reported in these children. These functions, however, play an important role in academic learning. Using the computerized battery BEVPS, we assessed three groups of children aged between 7 and 14 years, a CP group, a group matched on chronological age and a group matched for mental age (matched on Raven matrices) with CP group. In regarding to visuoperceptual functions, the perceptual grouping, figure–ground discrimination and local–global treatment processing abilities were assessed. The results showed that the perceptual grouping abilities of CP children were significantly lower in comparison with the children matched on chronological age and mental age when they had to process drawings silhouettes. In contrast, these performances are comparable between the three groups of children when they have to process line drawings. Furthermore, the deficits on figure–ground discrimination of CP children were observed when compared with children of the same chronological age for naming the drawings completely overlapping. Contrary, no difference was observed between the three groups for matching the drawings that were completely overlapping or for naming figures partially overlapping. Finally, the performances of the three groups were similar for the local and global information processing. These results therefore demonstrate the specificity of visual–perceptual impairment for these intermediate perceptual processing abilities in children with cerebral palsy, which seems to depend on the type of presentation of visual information.

Analogues of simple and complex cells in rhesus monkey auditory cortex

Receptive fields (RFs) of neurons in primary visual cortex have traditionally been subdivided into two major classes: "simple" and "complex" cells. Simple cells were originally defined by the existence of segregated subregions within their RF that respond to either the on- or offset of a light bar and by spatial summation within each of these regions, whereas complex cells had ON and OFF regions that were coextensive in space [Hubel DH, et al. (1962) J Physiol 160:106-154]. Although other definitions based on the linearity of response modulation have been proposed later [Movshon JA, et al. (1978) J Physiol 283:53-77; Skottun BC, et al. (1991) Vision Res 31(7-8):1079-1086], the segregation of ON and OFF subregions has remained an important criterion for the distinction between simple and complex cells. Here we report that response profiles of neurons in primary auditory cortex of monkeys show a similar distinction: one group of cells has segregated ON and OFF subregions in frequency space; and another group shows ON and OFF responses within largely overlapping response profiles. This observation is intriguing for two reasons: (i) spectrotemporal dissociation in the auditory domain provides a basic neural mechanism for the segregation of sounds, a fundamental prerequisite for auditory figure-ground discrimination; and (ii) the existence of similar types of RF organization in visual and auditory cortex would support the existence of a common canonical processing algorithm within cortical columns.