Brain network interactions in auditory, visual and linguistic processing

In the paper, we discuss the importance of network interactions between brain regions in mediating performance of sensorimotor and cognitive tasks, including those associated with language processing. Functional neuroimaging, especially PET and fMRI, provide data that are obtained essentially simultaneously from much of the brain, and thus are ideal for enabling one to assess interregional functional interactions. Two ways to use these types of data to assess network interactions are presented. First, using PET, we demonstrate that anterior and posterior perisylvian language areas have stronger functional connectivity during spontaneous narrative production than during other less linguistically demanding production tasks. Second, we show how one can use large-scale neural network modeling to relate neural activity to the hemodynamically-based data generated by fMRI and PET. We review two versions of a model of object processing - one for visual and one for auditory objects. The regions comprising the models include primary and secondary sensory cortex, association cortex in the temporal lobe, and prefrontal cortex. Each model incorporates specific assumptions about how neurons in each of these areas function, and how neurons in the different areas are interconnected with each other. Each model is able to perform a delayed match-to-sample task for simple objects (simple shapes for the visual model; tonal contours for the auditory model). We find that the simulated electrical activities in each region are similar to those observed in nonhuman primates performing analogous tasks, and the absolute values of the simulated integrated synaptic activity in each brain region match human fMRI/PET data. Thus, this type of modeling provides a way to understand the neural bases for the sensorimotor and cognitive tasks of interest.     

Context-sensitive binding by the laminar circuits of V1 and V2: A unified model of perceptual grouping,attention, and orientation contrast

A detailed neural model is presented of how the laminar circuits of visual cortical areas V1 and V2 implement context-sensitive binding processes such as perceptual grouping and attention. The model proposes how specific laminar circuits allow the responses of visual cortical neurons to be determined not only by the stimuli within their classical receptive fields, but also to be strongly influenced by stimuli in the extra-classical surround. This context-sensitive visual processing can greatly enhance the analysis of visual scenes, especially those containing targets that are low contrast, partially occluded, or crowded by distractors. We show how interactions of feedforward, feedback, and horizontal circuitry can implement several types of contextual processing simultaneously, using shared laminar circuits. In particular, we present computer simulations that suggest how top-down attention and preattentive perceptual grouping, two processes that are fundamental for visual binding, can interact, with attentional enhancement selectively propagating along groupings of both real and illusory contours, thereby showing how attention can selectively enhance object representations. These simulations also illustrate how attention may have a stronger facilitatory effect on low contrast than on high contrast stimuli, and how pop-out from orientation contrast may occur. The specific functional roles which the model proposes for the cortical layers allow several testable neurophysiological predictions to be made. The results presented here simulate only the boundary grouping system of adult cortical architecture. However, we also discuss how this model contributes to a larger neural theory of vision that suggests how intracortical and intercortical feedback help to stabilize development and learning within these cortical circuits. Although feedback plays a key role, fast feedforward processing is possible in response to unambiguous information. Model circuits are capable of synchronizing quickly, but context-sensitive persistence of previous events can influence how synchrony develops. Although these results focus on how the interblob cortical processing stream controls boundary grouping and attention, related modelling of the blob cortical processing stream suggests how visible surfaces are formed, and modelling of the motion stream suggests how transient responses to scenic changes can control long-range apparent motion and also attract spatial attention.     

Auditory distractor processing in sequential selection tasks

In this review, we analyze the cognitive processes contributing to selection in audition. In particular, we focus on the processing of auditory distractors in sequential selection paradigms in which target stimuli are accompanied by distractors. We review the evidence from two established tasks, namely the auditory negative priming and the auditory distractor–response binding task, and discuss the cognitive mechanisms contributing to the results typically observed in these tasks. In fact, several processes have been suggested as to explain how distractors are processed and handled in audition; that is, auditory distractors can be inhibited, encoded with a do-not-respond-tag, integrated into a stimulus–response episode containing the response to the target, or upheld in working memory and matched/mismatched with the following distractor. In addition, variables possibly modulating these cognitive processes are discussed. Finally, auditory distractor processing is compared with distractor processing in vision.     

Neurological basis of language and sequential cognition: evidence from simulation,aphasia, and ERP studies

The current research addresses the hypothesis that certain aspects of sequential cognition have made substantial contributions to the human language processing capability, from a functional neurophysiology perspective. We first describe a cognitive sequence processing model that was developed based on the functional neuroanatomy of primate cortex and basal ganglia. We demonstrate how this model is capable of simulating the behavior of human infants in extracting serial, temporal and abstract structure from language-like sound sequences as revealed in recent psycholinguistic experiments. We then demonstrate how, through training, this model can perform adult level syntactic comprehension, based on dissociated processing streams for open vs. closed class words. The model subsequently predicts: (1) that impaired syntactic processing (as in agrammatic aphasia) will be associated with impairments in corresponding non-linguistic cognitive sequencing tasks, and (2) that neurophysiological processes (as revealed by ERPs) involved in syntactic processing should also be involved in the corresponding non-linguistic cognitive sequencing tasks. Data confirming these predictions are reviewed. We conclude that the study of sequential cognition will provide a new paradigm for the investigation of the neurophysiological bases of language.     

What do dogs (<Emphasis Type="Italic">Canis familiaris</Emphasis>) see? A review of vision in dogs and implications for cognition research

Over the last 20 years, a large amount of research has been conducted in an attempt to uncover the cognitive abilities of the domestic dog. While substantial advancements have been made, progress has been impeded by the fact that little is known about how dogs visually perceive their external environment. It is imperative that future research determines more precisely canine visual processing capabilities, particularly considering the increasing number of studies assessing cognition via paradigms requiring vision. This review discusses current research on visual cognition and emphasizes the importance of understanding dog visual processing. We review several areas of vision research in domestic dogs, such as sensitivity to light, visual perspective, visual acuity, form perception, and color vision, with a focus on how these abilities may affect performance in cognition tasks. Additionally, we consider the immense diversity seen in dog morphology and explore ways in which these physical differences, particularly in facial morphology, may result in, or perhaps even be caused by, different visual processing capacities in dogs. Finally, we suggest future directions for research in dog vision and cognition.     

Latent relationships of fluid, visual, and simultaneous cognitive tasks

Horn's 1989 fluid intelligence and Luria's 1966 simultaneous processing have been represented in various cognitive assessment batteries. Although related, these concepts are purported to measure distinct cognitive functions; fluid intelligence refers to deductive reasoning whereas simultaneous processing refers to understanding complex relationships among gestalts. The current study explored the factor structure of known fluid and simultaneous tests along with visually complex new tests. A total of 56 children in Grades 1 through 5 were administered tests from the Kaufman Assessment Battery for Children, Elliott's Differential Abilities Scales, and two experimental tasks. Findings suggest that (1) the two experimental subtests were psychometrically viable, (2) when analyzed as a two-factor structure, fluid and visual processing components were pronounced, and (3) when analyzed as a single-factor structure, simultaneous processing emerged. These findings indicate simultaneous processing may be a blend of fluid and visual components.     

It's about time: revisiting temporal processing deficits in dyslexia

Temporal processing in French children with dyslexia was evaluated in three tasks: a word identification task requiring implicit temporal processing, and two explicit temporal bisection tasks, one in the auditory and one in the visual modality. Normally developing children matched on chronological age and reading level served as a control group. Children with dyslexia exhibited robust deficits in temporal tasks whether they were explicit or implicit and whether they involved the auditory or the visual modality. First, they presented larger perceptual variability when performing temporal tasks, whereas they showed no such difficulties when performing the same task on a non‐temporal dimension (intensity). This dissociation suggests that their difficulties were specific to temporal processing and could not be attributed to lapses of attention, reduced alertness, faulty anchoring, or overall noisy processing. In the framework of cognitive models of time perception, these data point to a dysfunction of the ‘internal clock’ of dyslexic children. These results are broadly compatible with the recent temporal sampling theory of dyslexia.     

The role of sensory factors in cognitive aging research.

Performance on complex, cognitive tasks often is sensitive to low-level sensory and perceptual factors. These relations are particularly important for cognitive aging researchers because aging is associated with a variety of changes in sensory and perceptual function. In the article that follows, I first selectively outline some relations between task performance and sensory function. Next, I summarize age-related changes in visual function and the implications of these changes for task performance, using the digit-symbol subtest of the WAIS as an example. I offer some reasons why age-related sensory decline may not be important to all cognitive tasks. Finally, I provide several recommendations for cognitive gerontologists who want to minimize the risk that the age differences they observe are sensory in nature.     

When meaning matters,look but don’t touch: The effects of posture on reading

Much of the reading that we do occurs near our hands. Previous research has revealed that spatial processing is enhanced near the hands, potentially benefiting several processes involved in reading; however, it is unknown whether semantic processing—another critical aspect of reading—is affected near the hands. While holding their hands either near to or far from a visual display, our subjects performed two tasks that drew on semantic processing: evaluation of the sensibleness of sentences, and the Stroop color-word interference task. We found evidence for impoverished semantic processing near the hands in both tasks. These results suggest a trade-off between spatial processing and semantic processing for the visual space around the hands. Readers are encouraged to be aware of this trade-off when choosing how to read a text, since both kinds of processing can be beneficial for reading.     

A computational framework for attentional object discovery in RGB-D videos

We present a computational framework for attention-guided visual scene exploration in sequences of RGB-D data. For this, we propose a visual object candidate generation method to produce object hypotheses about the objects in the scene. An attention system is used to prioritise the processing of visual information by (1) localising candidate objects, and (2) integrating an inhibition of return (IOR) mechanism grounded in spatial coordinates. This spatial IOR mechanism naturally copes with camera motions and inhibits objects that have already been the target of attention. Our approach provides object candidates which can be processed by higher cognitive modules such as object recognition. Since objects are basic elements for many higher level tasks, our architecture can be used as a first layer in any cognitive system that aims at interpreting a stream of images. We show in the evaluation how our framework finds most of the objects in challenging real-world scenes.     

The neuroanatomy and neuroendocrinology of fragile X syndrome

Fragile X syndrome (FXS), caused by a single gene mutation on the X chromosome, offers a unique opportunity for investigation of gene-brain-behavior relationships. Recent advances in molecular genetics, human brain imaging, and behavioral studies have started to unravel the complex pathways leading to the cognitive, psychiatric, and physical features that are unique to this syndrome. In this article, we summarize studies focused on the neuroanatomy and neuroendocrinology of FXS. A review of structural imaging studies of individuals with the full mutation shows that several brain regions are enlarged, including the hippocampus, amygdala, caudate nucleus, and thalamus, even after controlling for overall brain volume. These regions mediate several cognitive and behavioral functions known to be aberrant in FXS such as memory and learning, information and sensory processing, and social and emotional behavior. Two regions, the cerebellar vermis, important for a variety of cognitive tasks and regulation of motor behavior, and the superior temporal gyrus, involved in processing complex auditory stimuli, are reported to be reduced in size relative to controls. Functional imaging, typically limited to females, has emphasized that individuals with FXS do not adequately recruit brain regions that are normally utilized by unaffected individuals to carry out various cognitive tasks, such as arithmetic processing or visual memory tasks. Finally, we review a number of neuroendocrine studies implicating hypothalamic dysfunction in FXS, including abnormal activation of the hypothalamic-pituitary-adrenal (HPA) axis. These studies may help to explain the abnormal stress responses, sleep abnormalities, and physical growth patterns commonly seen in affected individuals. In the future, innovative longitudinal studies to investigate development of neurobiologic and behavioral features over time, and ultimately empirical testing of pharmacological, behavioral, and even molecular genetic interventions using MRI are likely to yield significant positive changes in the lives of persons with FXS, as well as increase our understanding of the development of psychiatric and learning problems in the general population.     

How human abilities affect component skills in word processing

Even simple tasks such as basic word processing can be quite complex. This paper argues that such tasks can be decomposed into a set of component skills and suggests how user abilities affect performance based on those skills. Special attention is given to spatial memory tests. It is argued that these tests actually assess two separable abilities: visual search and retention of order information. Skill acquisition can be facilitated by taking these abilities into account in system design: The importance of searching is decreased by providing context searches in which the system locates items in a text, and the importance of remembering the order of command sequences is improved by decreasing procedural complexity.     

Threaded cognition: an integrated theory of concurrent multitasking

The authors propose the idea of threaded cognition, an integrated theory of concurrent multitasking--that is, performing 2 or more tasks at once. Threaded cognition posits that streams of thought can be represented as threads of processing coordinated by a serial procedural resource and executed across other available resources (e.g., perceptual and motor resources). The theory specifies a parsimonious mechanism that allows for concurrent execution, resource acquisition, and resolution of resource conflicts, without the need for specialized executive processes. By instantiating this mechanism as a computational model, threaded cognition provides explicit predictions of how multitasking behavior can result in interference, or lack thereof, for a given set of tasks. The authors illustrate the theory in model simulations of several representative domains ranging from simple laboratory tasks such as dual-choice tasks to complex real-world domains such as driving and driver distraction.     

Individual differences and interrelationships among a select set of cognitive skills

An experiment was conducted to investigate individual differences and interrelationships in performance on three short-term memory processing and visual processing tasks. Parameters of models for these tasks were correlated. High correlations (.97 and .83) were obtained for some intertask parameters. indicating that elemental component processes for different tasks can be identified that are similar or highly related. Psychometric measures (SATM and SATV) were also correlated with the information processing model parameters. High multiple correlations of SATV and SATM were obtained using model parameters as predictors. when the data were analyzed separately for female and male subjects. The results are suggestive of sex differences in the interrelationships of the cognitive processes under investigation.     

Interdependence of Saccadic and Fixational Fluctuations

Recent research suggests that the different components of eye movements (fixations, saccades) are not strictly separate but are interdependent processes. This argument rests on observations that gaze-step sizes yield unimodal distributions and exhibit power-law scaling, indicative of interdependent processes coordinated across timescales. The studies that produced these findings, however, employed complex tasks (visual search, scene perception). Thus, the question is whether the observed interdependence is a fundamental property of eye movements or emerges in the interplay between cognitive processes and complex visual stimuli. In this study, we used a simple eye movement task where participants moved their eyes in a prescribed sequence at several different paces. We outlined diverging predictions for this task for independence versus interdependence of fixational and saccadic fluctuations and tested these predictions by assessing the spectral properties of eye movements. We found no clear peak in the power spectrum attributable exclusively to saccadic fluctuations. Furthermore, changing the pace of the eye movement sequence yielded a global shift in scaling relations evident in the power spectrum, not just a localized shift for saccadic fluctuations. These results support the conclusion that fixations and saccades are interdependent processes.     

The human Turing machine: a neural framework for mental programs

In recent years much has been learned about how a single computational processing step is implemented in the brain. By contrast, we still have surprisingly little knowledge of the neuronal mechanisms by which multiple such operations are sequentially assembled into mental algorithms. We outline a theory of how individual neural processing steps might be combined into serial programs. We propose a hybrid neuronal device: each step involves massively parallel computation that feeds a slow and serial production system. Production selection is mediated by a system of competing accumulator neurons that extends the role of these neurons beyond the selection of a motor action. Productions change the state of sensory and mnemonic neurons and iteration of such cycles provides a basis for mental programs.     

Influence of auditory-verbal, visual-verbal, visual, and visual-visual processing speed on reading and spelling at the end of Grade 1

This study examined cognitive processing speed through four modalities (auditory-verbal, visual-verbal, visual, and visual-visual) at the end of Grade 1 and how it influences reading and spelling. The subjects were 124 French-speaking children, selected for their contrasting performance on reading and spelling tasks. The children in the first group (N=69) were average readers; the second group of children (N=55) performed worse or much worse on all reading and spelling tasks. The experimental design consisted of a set of 10 tasks administered in two sessions. The major findings reveal that: (1) the children with reading difficulties displayed low and slow performance on most cognitive tasks, whatever the modality; (2) auditory-verbal and visual-verbal processing speed significantly predicted written language, which was not the case with the visual modalities; and (3) that visual problems did not appear to be a potential cause of reading problems in most delayed readers. The findings also confirm the independence of phonological and naming-speed skills in reading development and reading impairment.     

Selective impairment of auditory selective attention under concurrent cognitive load

Load theory predicts that concurrent cognitive load impairs selective attention. For visual stimuli, it has been shown that this impairment can be selective: Distraction was specifically increased when the stimulus material used in the cognitive load task matches that of the selective attention task. Here, we report four experiments that demonstrate such selective load effects for auditory selective attention. The effect of two different cognitive load tasks on two different auditory Stroop tasks was examined, and selective load effects were observed: Interference in a nonverbal-auditory Stroop task was increased under concurrent nonverbal-auditory cognitive load (compared with a no-load condition), but not under concurrent verbal-auditory cognitive load. By contrast, interference in a verbal-auditory Stroop task was increased under concurrent verbal-auditory cognitive load but not under nonverbal-auditory cognitive load. This double-dissociation pattern suggests the existence of different and separable verbal and nonverbal processing resources in the auditory domain.     

Sparse but not 'grandmother-cell' coding in the medial temporal lobe

Although a large number of neuropsychological and imaging studies have demonstrated that the medial temporal lobe (MTL) plays an important role in human memory, there are few data regarding the activity of neurons involved in this process. The MTL receives massive inputs from visual cortical areas, and evidence over the last decade has consistently shown that MTL neurons respond selectively to complex visual stimuli. Here, we focus on how the activity patterns of these cells might reflect the transformation of visual percepts into long-term memories. Given the very sparse and abstract representation of visual information by these neurons, they could in principle be considered as 'grandmother cells'. However, we give several arguments that make such an extreme interpretation unlikely.