Dorsal Visual Processing Stream Research Articles

Are some Gestalt principles deployed more readily than others during early development? The case of lightness versus form similarity.

Four experiments investigated how readily infants achieve perceptual organization by lightness and form similarity. Infants were (a) familiarized with elements that could be organized into rows or columns on the basis of lightness or form similarity and tested with vertical versus horizontal bars depicting the familiar versus novel organization or (b) familiarized with bars and tested with elements. For lightness similarity, generalization occurred in both tasks; however, for form similarity, generalization occurred only in the elements --> bars task. The findings indicate that lightness similarity is more readily deployed than form similarity and are discussed in the context of (a) whether the difference reflects speed of application or experience-based learning, (b) evidence from visual agnosic patients and the time course of application of the principles in healthy adults, and (c) development of dorsal and ventral visual processing streams.

TMS can reveal contrasting functions of the dorsal and ventral visual processing streams

In order to investigate the functional specificity of the dorsal and ventral visual processing steams we used transcranial magnetic stimulation (TMS) to briefly disrupt one or the other while subjects performed three tasks, involving discrimination of colour or shape or relative position. TMS was delivered over right posterior parietal cortex (PPC) or right lateral occipital (LO) cortex, regions known to have visuo-spatial and object processing properties respectively. LO but not PPC stimulation had a significant effect on reaction time when subjects were asked to make a discrimination of relative shape. PPC stimulation had a significant effect when subjects were asked to discriminate relative position of the same shapes. Stimulation of LO also lengthened reaction times on the position task. There were no effects of stimulation at either site on colour discrimination. Results are discussed within the framework of how the dorsal stream and ventral stream are dissociated following their damage in neurological patients and possible ways in which they may interact in the normal brain.

Intact automatic avoidance of obstacles in patients with visual form agnosia

In everyday life our reaching behaviour has to be guided not only by the location and properties of the target object, but also by the presence of potential obstacles in the workspace. Recent evidence from neglect and optic ataxia patients has suggested that this automatic obstacle avoidance is mediated by the dorsal, rather than the ventral, stream of visual processing. We tested this idea in two studies involving patients with visual form agnosia resulting from bilateral ventral-stream damage. In the first study, we asked patient DF to reach out and pick up a target object in the presence of obstacles placed at varying distances to the left or right of the target. We found that both DF and controls shifted their trajectories away from the potential obstacles and adjusted their grip aperture in such a way as to minimize risk of collision. In a second study, we asked DF and a second patient, SB, to either reach between, or to bisect the space between, two cylinders presented at varying locations. We found that both patients adjusted their reach trajectories to account for shifts in cylinder location in the reaching task, despite showing significantly worse performance than control subjects when asked to make a bisection judgement. Taken together, these data indicate that automatic obstacle avoidance behaviour is spared in our patients with visual form agnosia. We attribute their ability to the functional intactness of the dorsal stream of visual processing, and argue that the ventral stream plays no important role in automatic obstacle avoidance.

Cortical Control of Visually Guided Reaching: Evidence from Patients with Optic Ataxia

The dorsal stream of visual information processing connecting V1 to the parietal cortex is thought to provide a fast control of visually guided reaching. Important for this assumption was the observation that in both the monkey and the human, parietal lesions may provoke disturbance of visually goal-directed hand movements. In the human, severe misreaching termed 'optic ataxia' has been ascribed to lesions of the superior parietal lobule (SPL) and/or the intraparietal sulcus. Using new tools for lesion analysis, here we re-evaluated this view investigating the typical lesion location in a large group of unilateral stroke patients with optic ataxia, collected over a time period of 15 years. We found no evidence for the assumption that disruption of visually guided reaching in humans is associated with a lesion typically centering on the SPL on the convexity. In both left and right hemispheres, we found optic ataxia associated with a lesion overlap that affected the lateral cortical convexity at the occipito-parietal junction, i.e. the junction between the inferior parietal lobule (IPL) and superior occipital cortex and--in the left hemisphere even more posteriorly--also the junction between occipital cortex and the SPL. Via the underlying parietal white matter, the lesion overlap extended in both hemispheres to the medial cortical aspect, where it affected the precuneus close to the occipito-parietal junction. These lateral and medial structures seem to be integral to the fast control of visually guided reaching in humans.

What the hand can?t tell the eye: illusion of space constancy during accurate pointing

When we press an elevator button or pick up a coffee cup, different visual information is used to guide our reach and to form our conscious experience of these objects. But can the information guiding our hand be brought into awareness? The fact that we can see and feel our own hand in action suggests that it might be possible. However, the dual visual systems theory claims that on-line control of movement is governed by the dorsal stream of visual processing, which is largely unconscious. Two experiments are presented as strong tests of the hypothesis that the visual information guiding on-line pointing in healthy human adults is inaccessible for conscious report. Results show that participants are incapable of consciously accessing the information used in pointing, even though they can see and feel their hands in action and accurate performance depends on it.

Age differences in neural correlates of route encoding and route recognition

Spatial memory deficits are core features of aging-related changes in cognitive abilities. The neural correlates of these deficits are largely unknown. In the present study, we investigated the neural underpinnings of age-related differences in spatial memory by functional MRI using a navigational memory task with route encoding and route recognition conditions. We investigated 20 healthy young (18–29 years old) and 20 healthy old adults (53–78 years old) in a random effects analysis. Old subjects showed slightly poorer performance than young subjects. Compared to the control condition, route encoding and route recognition showed activation of the dorsal and ventral visual processing streams and the frontal eye fields in both groups of subjects. Compared to old adults, young subjects showed during route encoding stronger activations in the dorsal and the ventral visual processing stream (supramarginal gyrus and posterior fusiform/parahippocampal areas). In addition, young subjects showed weaker anterior parahippocampal activity during route recognition compared to the old group. In contrast, old compared to young subjects showed less suppressed activity in the left perisylvian region and the anterior cingulate cortex during route encoding. Our findings suggest that age-related navigational memory deficits might be caused by less effective route encoding based on reduced posterior fusiform/parahippocampal and parietal functionality combined with diminished inhibition of perisylvian and anterior cingulate cortices correlated with less effective suppression of task-irrelevant information. In contrast, age differences in neural correlates of route recognition seem to be rather subtle. Old subjects might show a diminished familiarity signal during route recognition in the anterior parahippocampal region.

The topography of metabolic deficits in posterior cortical atrophy (the visual variant of Alzheimer’s disease) with FDG-PET

Background:The term “posterior cortical atrophy” (PCA) refers to a clinical syndrome in which higher order visual processing is disrupted owing to a neurodegenerative disorder, the most commonly associated pathology being...

Graspability and object processing in infants

This review pursues the idea that a dual visual system approach is fruitful for interpreting work on infant cognition. We provide examples from the visual perception and cognition literature demonstrating that the potential graspability of stimuli typically used in infant studies influence how these stimuli are processed by the infant brain. Specifically, we argue that small, local, familiar and moving stimuli are more likely to be processed by the dorsal (how or action) stream of visual processing. In contrast, larger, stationary objects are likely to be processed by the ventral (what or perception) stream. This analysis clarifies apparently conflicting results in the literature.

Three streams of visual information processing in V2 of Cebus monkey.

Gattass and collaborators (Gattass R, Rosa MGP, Souza APB, Piñon MCG, Neuenschwander S [1990a] Braz J Med Biol Res 23:375-393) proposed that the dorsal stream of visual processing, as defined by Ungerleider and Mishkin (Ungerleider LG, Mishkin M [1982] In: Ingle DJ, Goodale MA, Mansfield RJW, editors. Analysis of visual behavior. Cambridge: Massachusetts Institute of Technology. p 549-586), can be subdivided into dorsolateral and dorsomedial streams, and suggested that they may be involved in different aspects of the processing of motion and spatial perception, respectively. The goal of the present study was to provide additional evidence for this hypothesis by using cytochrome oxidase immunohistochemistry combined with retrograde tracing techniques. In Old World monkeys, the locations of visual area 4 (V4; ventral stream) and middle temporal area (MT; dorsal stream) projecting neurons in V2 supports the hypothesis that the cytochrome oxidase (CytOx)-rich thin stripes and the CytOx-poor interstripes are associated with the ventral stream, and that the CytOx-rich thick stripes belong to the dorsal stream. In this study we describe, in the New World monkey Cebus, the distribution of retrogradely labeled cells in V2 relative to the CytOx compartments after fluorescent tracers were placed in areas V4, MT, and the parietooccipital area (PO). We found PO-projecting neurons in CytOx-rich thick stripes and CytOx-poor interstripes in V2, whereas MT-projecting neurons appeared almost exclusively in thick stripes. In contrast, V4-projecting neurons were located mostly in CytOx-poor interstripes and CytOx-rich thin stripes. In addition, V4- and MT-projecting neurons were located mainly in supragranular layers, whereas PO-projecting neurons were located in supragranular and infragranular layers. These results support the hypothesis for the existence of three distinct streams of visual processing: ventral (including V4), dorsolateral (including MT), and dorsomedial (including PO).

Visual processing of rapidly presented stimuli is normalized in Parkinson’s disease when proximal stimulus strength is enhanced

Deficient perception and cognition in Parkinson’s disease (PD) has been attributed to slow information processing, but an alternative explanation may be reduced signal strength. In 18 nondemented individuals with PD and 15 healthy adults, we enhanced the contrast level of rapidly flashed masked letters. The PD group required significantly higher contrast to reach criterion (80% accuracy). Normal motion detection in these participants indicated no gross, general dysfunction of the dorsal visual processing stream. These results suggest that putatively slowed processing in PD may be an artifact of reduced signal strength arising from depletion of dopamine in retina or cortical visual areas.

Know how, knowledge that and the requirement of conscious intent

The distinction between know how and knowledge that is one that has failed to draw much attention in philosophy, despite its importance in other fields. This distinction is explored and neuropsychological studies are presented that support this distinction. In particular, the dorsal and ventral visual processing streams are examined and shown to process information individually despite lesions to the other processing stream. Studies are also presented that further highlight the idea that the distinction between know how and knowledge that take place in decision-making and in judgements of how to act. These studies also contradict Carr's assessment that a necessary aspect of connecting know how with ability is conscious intent. The idea of a more general functional connection between know how and ability is explored and it is emphasized that this functional connection should include very basic neurobiological functions.

Flow of activation from V1 to frontal cortex in humans. A framework for defining "early" visual processing.

This study provides a time frame for the initial trajectory of activation flow along the dorsal and ventral visual processing streams and for the initial activation of prefrontal cortex in the human. We provide evidence that this widespread system of sensory, parietal, and prefrontal areas is activated in less than 30 ms, which is considerably shorter than typically assumed in the human event-related potential (ERP) literature and is consistent with recent intracranial data from macaques. We find a mean onset latency of activity over occipital cortex (C1(e)) at 56 ms, with dorsolateral frontal cortex subsequently active by just 80 ms. Given that activity in visual sensory areas typically continues for 100-400 ms prior to motor output, this rapid system-wide activation provides a time frame for the initiation of feedback processes onto sensory areas. There is clearly sufficient time for multiple iterations of interactive processing between sensory, parietal, and frontal areas during brief (e.g., 200 ms) periods of information processing preceding motor output. High-density electrical mapping also suggested activation in dorsal stream areas preceding ventral stream areas. Our data suggest that multiple visual generators are active in the latency range of the traditional C1 component of the ERP, which has often been taken to represent V1 activity alone. Based on the temporal pattern of activation shown in primate recordings and the evidence from these human recordings, we propose that only the initial portion of the C1 component (approximately the first 10-15 ms; C1(e)) is likely to represent a response that is predominated by V1 activity. These data strongly suggest that activity represented in the "early" ERP components such as P1 and N1 (and possibly even C1) is likely to reflect relatively late processing, after the initial volley of sensory afference through the visual system and involving top-down influences from parietal and frontal regions.

Defining the cortical visual systems: “What”, “Where”, and “How”

The visual system historically has been defined as consisting of at least two broad subsystems subserving object and spatial vision. These visual processing streams have been organized both structurally as two distinct pathways in the brain, and functionally for the types of tasks that they mediate. The classic definition by Ungerleider and Mishkin labeled a ventral “what” stream to process object information and a dorsal “where” stream to process spatial information. More recently, Goodale and Milner redefined the two visual systems with a focus on the different ways in which visual information is transformed for different goals. They relabeled the dorsal stream as a “how” system for transforming visual information using an egocentric frame of reference in preparation for direct action. This paper reviews recent research from psychophysics, neurophysiology, neuropsychology and neuroimaging to define the roles of the ventral and dorsal visual processing streams. We discuss a possible solution that allows for both “where” and “how” systems that are functionally and structurally organized within the posterior parietal lobe.

Representation of Manipulable Man-Made Objects in the Dorsal Stream

We used fMRI to examine the neural response in frontal and parietal cortices associated with viewing and naming pictures of different categories of objects. Because tools are commonly associated with specific hand movements, we predicted that pictures of tools, but not other categories of objects, would elicit activity in regions of the brain that store information about motor-based properties. We found that viewing and naming pictures of tools selectively activated the left ventral premotor cortex (BA 6). Single-unit recording studies in monkeys have shown that neurons in the rostral part of the ventral premotor cortex (canonical F5 neurons) respond to the visual presentation of graspable objects, even in the absence of any subsequent motor activity. Thus, the left ventral premotor region that responded selectively to tools in the current study may be the human homolog of the monkey canonical F5 area. Viewing and naming tools also selectively activated the left posterior parietal cortex (BA 40). This response is similar to the firing of monkey anterior intraparietal neurons to the visual presentation of graspable objects. In humans and monkeys, there appears to be a close link between manipulable objects and information about the actions associated with their use. The selective activation of the left posterior parietal and left ventral premotor cortices by pictures of tools suggests that the ability to recognize and identify at least one category of objects (tools) may depend on activity in specific sites of the ventral and dorsal visual processing streams.

Mapping the network for planning: a correlational PET activation study with the Tower of London task.

We used the Tower of London task (TOL) and H(2)(15)O-PET to map the network of brain structures involved in planning. Six healthy right-handed subjects had 12 measurements of relative regional cerebral blood flow (rrCBF) during six conditions, each performed twice. There was one rest condition, and five sets of TOL problems at different complexity levels, performed on a touch-sensitive computer monitor with the right arm. Complexity was defined as the number of moves required to solve each problem. Activation was analysed in two ways: a category analysis comparing levels of rrCBF during rest and task was done to identify all structures involved in performance of the TOL; and a correlation analysis was carried out to delineate a subset of structures where the levels of rrCBF correlated with task complexity. Activated brain areas in which rrCBF increases did not correlate with complexity could be grouped into: (i) regions belonging to the dorsal stream of visual input processing, namely visual cortical areas 17, 18 and 19, and posterior parietal cortical areas 7 and 40; and (ii) regions involved in the execution and sequencing of arm movements (right cerebellum, left primary motor cortex and supplementary motor area). Brain regions where levels of rrCBF correlated with task complexity included lateral premotor cortex (area 6), rostral anterior cingulate cortex (areas 32 and 24), dorsolateral prefrontal cortex (areas 9 and 46) bilaterally, and right dorsal caudate nucleus. We propose that dorsolateral prefrontal, lateral premotor, anterior cingulate and caudate areas form a network for the planning of movement that interacts with brain areas primarily involved in visual processing and movement execution.