Impaired delayed but preserved immediate grasping in a neglect patient with parieto-occipital lesions

Patients with optic ataxia, a deficit in visually guided action, paradoxically improve when pantomiming an action towards memorized stimuli. Visual form agnosic patient D.F. shows the exact opposite pattern of results: although being able to grasp objects in real-time she loses grip scaling when grasping an object from memory. Here we explored the dissociation between immediate and delayed grasping in a patient (F.S.) who after a parietal-occipital stroke presented with severe left visual neglect, a loss of awareness of the contralesional side of space. Although F.S. had preserved grip scaling even in his neglected field, he was markedly impaired when asked to pretend to grasp a leftward object from memory. Critically, his deficit cannot be simply explained by the absence of continuous on-line visual feedback, as F.S. was also able to grasp leftward objects in real-time when vision was removed. We suggest that regions surrounding the parietal-occipital sulcus, typically damaged in patients with optic ataxia but spared in F.S., seem to be essential for real-time actions. On the other hand, our data indicates that regions in the ventral visual stream, damaged in D.F but intact in F.S., would appear to be necessary but not sufficient for memory-guided action

Hand-selective visual regions represent how to grasp 3D tools: Brain decoding during real actions

Most neuroimaging experiments that investigate how tools and their actions are represented in the brain use visual paradigms where tools or hands are displayed as 2D images and no real movements are performed. These studies discovered selective visual responses in occipitotemporal and parietal cortices for viewing pictures of hands or tools, which are assumed to reflect action processing, but this has rarely been directly investigated. Here, we examined the responses of independently visually defined category-selective brain areas when participants grasped 3D tools (N = 20; 9 females). Using real-action fMRI and multivoxel pattern analysis, we found that grasp typicality representations (i.e., whether a tool is grasped appropriately for use) were decodable from hand-selective areas in occipitotemporal and parietal cortices, but not from tool-, object-, or body-selective areas, even if partially overlapping. Importantly, these effects were exclusive for actions with tools, but not for biomechanically matched actions with control nontools. In addition, grasp typicality decoding was significantly higher in hand than tool-selective parietal regions. Notably, grasp typicality representations were automatically evoked even when there was no requirement for tool use and participants were naive to object category (tool vs nontools). Finding a specificity for typical tool grasping in hand-selective, rather than tool-selective, regions challenges the long-standing assumption that activation for viewing tool images reflects sensorimotor processing linked to tool manipulation. Instead, our results show that typicality representations for tool grasping are automatically evoked in visual regions specialized for representing the human hand, the primary tool of the brain for interacting with the world

Improving psychological science: further thoughts, reflections and ways forward

Cogent Psychology is a pioneering and dynamic Open Access journal for the psychology community, publishing original research, reviews, and replications that span the full spectrum of psychological inquiry. In 2021, it relaunched with a new Editor-in-Chief and Section Editors with an exciting vision to combine open access publishing with open research practices. As such, the journal welcomes traditional and new article formats, including Registered Reports, Brief Replication Reports, Review Articles, and Brief Reports. This broader range of formats is designed to reflect the evolving nature of psychological research and open science approaches. To the best of our knowledge, no other psychology journal offers such a distinctive combination of article publishing formats. Moreover, we welcome submissions in nine key areas of psychological science: Clinical Psychology, Cognitive & Experimental Psychology, Developmental Psychology, Educational Psychology, Health Psychology, Neuropsychology, Personality & Individual Differences, Social Psychology and Work, Industrial & Organisational Psychology

Impaired peripheral reaching and on-line corrections in patient DF: optic ataxia with visual form agnosia

An influential model of vision suggests the presence of two visual streams within the brain: a dorsal occipito-parietal stream which mediates action and a ventral occipito-temporal stream which mediates perception. One of the cornerstones of this model is DF, a patient with visual form agnosia following bilateral ventral stream lesions. Despite her inability to identify and distinguish visual stimuli, DF can still use visual information to control her hand actions towards these stimuli. These observations have been widely interpreted as demonstrating a double dissociation from optic ataxia, a condition observed after bilateral dorsal stream damage in which patients are unable to act towards objects that they can recognize. In Experiment 1, we investigated how patient DF performed on the classical diagnostic task for optic ataxia, reaching in central and peripheral vision. We replicated recent findings that DF is remarkably inaccurate when reaching to peripheral targets, but not when reaching in free vision. In addition we present new evidence that her peripheral reaching errors follow the optic ataxia pattern increasing with target eccentricity and being biased towards fixation. In Experiments 2 and 3, for the first time we examined DF’s on-line control of reaching using a double-step paradigm in fixation-controlled and free-vision versions of the task. DF was impaired when performing fast on-line corrections on all conditions tested, similarly to optic ataxia patients. Our findings question the long-standing assumption that DF’s dorsal visual stream is functionally intact and that her on-line visuomotor control is spared. In contrast, in addition to visual form agnosia, DF also has visuomotor symptoms of optic ataxia which are most likely explained by bilateral damage to the superior parietal occipital cortex. We thus conclude that patient DF can no longer be considered as an appropriate single-case model for testing the neural basis of perception and action dissociations

Efficacy of home-based visuomotor feedback training in stroke patients with chronic hemispatial neglect

Hemispatial neglect is a severe cognitive condition frequently observed after a stroke, associated with unawareness of one side of space, disability and poor long-term outcome. Visuomotor feedback training (VFT) is a neglect rehabilitation technique that involves a simple, inexpensive and feasible training of grasping-to-lift rods at the centre. We compared the immediate and long-term effects of VFT vs. a control training when delivered in a home-based setting. Twenty participants were randomly allocated to an intervention (who received VFT) or a control group (n = 10 each). Training was delivered for two sessions by an experimenter and then patients self-administered it for 10 sessions over two weeks. Outcome measures included the Behavioural Inattention Test (BIT), line bisection, Balloons Test, Landmark task, room description task, subjective straight-ahead pointing task and the Stroke Impact Scale. The measures were obtained before, immediately after the training sessions and after four-months post-training. Significantly greater short and long-term improvements were obtained after VFT when compared to control training in line bisection, BIT and spatial bias in cancellation. VFT also produced improvements on activities of daily living. We conclude that VFT is a feasible, effective, home-based rehabilitation method for neglect patients that warrants further investigation with well-designed randomised controlled trials on a large sample of patients

Human see, human do? Viewing tool pictures evokes action-specific activity in visual hand-selective occipitotemporal cortex

Every day we have countless experiences with different types of objects. Amongst all the objects we encounter, tools are unique because they are tightly linked to predictable actions. Neuroimaging studies have consistently reported selective visual responses in occipitotemporal and parietal cortices for viewing pictures of tools or hands. The specificity of these responses, however, is unknown. Does viewing a tool picture evoke a response specific to the action associated with that tool? Here, we used fMRI and multivoxel pattern analysis to ask whether viewing tool pictures associated with specific actions can be decoded from these regions, and if so, are the patterns of neural activity elicited by viewing pictures and performing the corresponding actions similar? Participants (N=18) viewed tool pictures (while performing an orthogonal task) and, in separate runs, pantomimed tool use actions (without tool in hand) in response to tool names. Our stimulus set consisted of familiar tools (e.g., screwdriver or tongs) that differed in the tool use action (rotate or squeeze) but were carefully matched for low-level differences (e.g., grip, colour, orientation). We found that merely viewing tool pictures triggered automatic retrieval of action information associated with the depicted tools, within both ventral occipitotemporal and parietal areas, and even primary somatosensory cortex. However, the patterns of activity elicited by tool pictures and corresponding pantomime tool use actions were unrelated, thus suggesting a clear neural distinction between perceived tool action affordances and pantomimed tool use actions. Interestingly, visual hand-selective occipitotemporal cortex was the only region where tool use action decoding was higher than tool identity decoding for both viewing and pantomiming, suggesting that its response cannot be simply explained by shape differences. These data show that visual hand-selective cortex represents action-specific information associated with tool use, and that these representations are triggered by simply viewing pictures

Impact of aging and stroke on a new computerized test of visual attention in far space

In our everyday life we use visual search to locate people, places and objects around us and visual attention plays a pivotal role for efficient and successful visual search. Even though our visual attention operates to find stimuli in both near (within reach) and far (out of reach) space, most of the research in this area has been conducted in near space alone. Impairments in visual attention are very common following stroke with visual neglect as a classic manifestation. While visual neglect has been shown to dissociate between near and far space, currently there is no validated tool that measures visual attention in far space. We present a new simple, portable, and open-source automated test of visual attention in far space, the Computerized Extrapersonal Neglect Test (CENT). CENT consists of computerised versions of cancellation and line bisection tasks completed on a large screen in far space using a wireless remote. We tested 179 healthy controls (18-94 years old) and 55 stroke survivors using the CENT. Aging effects, normative data and internal consistency were established from the healthy control data. Convergent and divergent validity and sensitivity were assessed in 55 stroke survivors (compared to 58 age-matched controls) who completed the CENT and the gold standard validated measures of visual neglect, cognition, and quality of life. Aging was accompanied by slower search speed and poorer quality of search and both these variables were significantly impaired in stroke survivors. The CENT demonstrated good internal consistency, convergent and divergent validity. Importantly, stroke survivors with neglect were specifically impaired in CENT when compared to other stroke survivors. In fact, the CENT presented higher sensitivity to attentional deficits when compared to gold standard measures. The CENT is a brief, automated, easy to administer tool, sensitive to age-related decline, brain injury and attentional impairments

The neural basis of visuomotor deficits in hemispatial neglect

We have recently reported that patients with hemispatial neglect demonstrate increased terminal errors when performing delayed leftward reaches and that right-brain damaged patients (irrespective of neglect) take longer to complete their movements [Rossit, S., Muir, K., Reeves, I., Duncan, G., Birschel, P., & Harvey, M. (2009). Immediate and delayed reaching in hemispatial neglect. Neuropsychologiaa 47, 1563–1573]. Here we conducted an initial voxel-based lesion-symptom analysis to examine the neural basis of such deficits in 21 right-brain damaged subjects with 11 patients suffering from hemispatial neglect (2 more than in Rossit et al. [Rossit S., Muir K., Reeves I., Duncan, G., Birschel, P., & Harvey, M. (2009). Immediate and delayed reaching in hemispatial neglect. Neuropsychologia 47, 1563–1573] and 10 control patients without the condition. We found that the accuracy impairments in delayed leftward reaches were associated with damage to occipito-temporal areas. In contrast, the movement time slowing was related to more anterior lesions in the frontal lobe. These findings agree with the view that neglect affects actions thought to depend on the processing carried out by the ventral visual stream. In addition, we suggest that the timing impairments which are not neglect-specific maybe be driven by frontal structures

Attention in action: Evidence from on-line corrections in left visual neglect

It is widely accepted that the posterior parietal cortex is critical for the on-line control of action and optic ataxia patients are unable to correct their movements in-flight to changes in target position. The current study investigated on-line correction in patients with left visual neglect, right brain damaged patients without neglect and healthy controls. Participants were asked to reach towards a central target that could jump unexpectedly, at movement onset, to the right or left sides of space. In response to the jump, participants were asked either to follow the target or to stop their movement. Neglect patients were able to correct their ongoing movements smoothly and accurately towards right and left target jumps. They did so even when told to stop their movement, indicating that these corrections occurred automatically (i.e., without instruction). However, the timing of corrections to the left was delayed in neglect patients and this produced a drastic increase in movement time. To our surprise, we also found that neglect patients were impaired at stopping their ongoing reaches, when compared to the control groups, in response to either left or right jump trials. We suggest that the ‘automatic pilot’ system for the hand is spared in neglect, but its processing speed is unilaterally slowed due to a deficit in orienting of attention to the contralesional side. We relate these findings to the breakdown of a system that combines information for attention, perception and action. Damage to this system may not only slow corrective movements to the contralesional side, but also produce non-lateralized deficits in interrupting an ongoing reach

Immediate and delayed reaching in hemispatial neglect

Milner and Goodale (The visual brain in action, Oxford: Oxford University Press, 1995; The visual brain in action, 2nd ed., Oxford: Oxford University Press, 2006) propose a model of vision that makes a distinction between vision for perception and vision for action. One strong claim of the model is that the dorsal stream's control of action is designed for dealing with target stimuli in the ‘here and now’, yet when time is allowed to pass and a reaction has to be made on the basis of a visual memory, the ventral stream is required for successful performance. Regarding the syndrome of hemispatial neglect, Milner and Goodale further claim that the visual dorsal stream is relatively spared in these patients. In the current study we tested whether neglect patients would indeed be unimpaired in immediate pointing, yet show inaccurate pointing in a condition where a delay is interposed between the presentation of the stimulus and the response signal (in particular in left space). We tested the ability of nine neglect patients (and healthy and right hemisphere no neglect control groups) to perform reaches towards immediate and delayed targets, placed in left, central and right locations. Neglect patients showed no accuracy impairments when asked to perform an immediate action. Conversely, when pointing towards remembered leftward locations, they markedly overshoot the target or failed to initiate a reach altogether. These results confirm that patients with neglect are not specifically impaired when performing ‘here and now’ actions, but rather present deficits when the visuomotor task taps into more perceptual ‘off-line’ representations thought to depend on ventral visual stream activation