Effects of parietal injury on covert orienting of attention (original) (raw)
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A review of the evidence for a disengage deficit following parietal lobe damage
Neuroscience & Biobehavioral Reviews, 2001
We review the literature on response times to ipsilesional and contralesional targets following spatial precues in patients with damage involving the left-and right-parietal lobes with the aim of appraising the`disengage de®cit' reported initially by Posner and colleagues (Posner MI, Cohen A, Rafal RD. Neural systems control of spatial orienting. Proceedings of the Royal Society of London, B 1982;298:187±98). The data of individual subjects from a sub-sample of studies were submitted to analyses of variance, and data from all studies meeting our selection criteria were submitted to meta-analytic procedures (Hunter JE, Schmidt FL. Methods of metaanalysis: correcting error and bias in research. Newberg Park: Sagge Publications, 1990). Findings from both types of analysis conducted on data from patients with right-hemisphere lesions indicate that: (1) the disengage de®cit phenomenon is robust following peripheral cues, but not following central cues; (2) the disengage de®cit is large at shorter cue-target stimulus onset asynchronies (SOAs), and decreases as SOA increases; (3) the disengage de®cit is larger in patients with a diagnosis of hemispatial neglect; and (4) although the magnitude of the disengage de®cit appears to increase with increases in lesion size, multilobar vs unilobar involvement did not signi®cantly alter the pattern of the disengage de®cit. We also show that responses to validly cued targets in the contralesional hemispace were signi®cantly slower than for validly cued targets in ipsilesional hemispace. Similar, but usually smaller, effects were observed in patients with homologous left-hemisphere damage. The implications of these results for current models of the role of the parietal lobes in attentional orienting are discussed. q
Effects of left parietal injury on covert orienting of attention
Journal of Neurology, Neurosurgery & Psychiatry, 2002
Objective: To assess the effects of left parietal injury on covert visual attention during a detection task and a pointing task. Methods: The Posner's paradigm was given to a patient who was found at the age of 74 to have spent all his life without the left parietal lobe as a result of a congenital perinatal insult and to a control subject. In one session subjects were required to provide an arbitrary response at stimulus appearance (key press). In another session subjects were required to point to the stimulus. Results: The patient was able to disengage covert attention from a cued position when the task was to provide an arbitrary key press response in a similar fashion to a control subject with no neurological deficits. By contrast, he was impaired in disengaging attention from a cued position when the task was to reprogramme an overt pointing action.
Inhibitory processing following damage to the parietal lobe
Neuropsychologia, 2003
We investigated inhibitory properties of spatial attention in a group of four patients with lesions involving the posterior parietal lobe. In a first experiment, a double cue inhibition of return (IOR) procedure was employed. The parietal patients showed an IOR effect only when they had to detect targets that appeared on the contralesional side. In a second experiment, we combined an IOR procedure with a Stroop task [Psychon. Bull. Rev. 8 (2001) 315] to explore the neural basis of "inhibitory tagging" as described by Fuentes et al. [Q. J. Exp. Psychol. Hum. Exp. Psychol. 52 ]. The results from the control participants replicated the findings of Vivas and Fuentes, Stroop interference was reduced at the cued location, relative to the uncued location. The parietal patients showed a similar result, but only for contralesional targets. These findings suggest that IOR is modulated by the parietal lobe, and that, through this process, the parietal cortex influences the application of inhibitory tagging to stimuli.
Isolating attentional systems: A cognitive-anatomical analysis
Psychobiology, 1987
Each of these operations appears to be affected by a different form of brain injury. Damage to the parietal lobe can produce a severe deficit in the ability to disengage attention from a visual location, without any loss in efficiency of the move or engage operations (posner, Walker, Friedrich, & Rafal, 1984). Our results show only small
Attentional responses to unattended stimuli in human parietal cortex
Brain, 2005
Right-sided parietal lesions lead to lateralized attentional deficits which are most prominent with bilateral stimulation. We determined how an irrelevant stimulus in the unattended hemifield alters attentional responses in parietal cortex during unilateral orienting. A trial consisted of a central spatial cue, a delay and a test phase during which a grating was presented at 9 deg eccentricity. Subjects had to discriminate the orientation of the grating. The unattended hemifield was either empty or contained a second, irrelevant grating. We carried out a series of functional MRI (fMRI) studies in 35 healthy volunteers (13 men and 22 women, aged between 19 and 30 years) as well as a behavioural and structural lesion mapping study in 17 righthemispheric lesion patients, 11 of whom had neglect. In the patients with but not in those without neglect, the addition of a distractor in the unattended hemifield significantly impaired performance if attention was directed contralesionally but not if it was directed ipsilesionally. In the healthy volunteers, we discerned two functionally distinct areas along the posterior–anterior axis of the intraparietal sulcus (IPS). The posterior, descending IPS segment in both hemispheres showed attentional enhancement of responses during contralateral attentional orienting and was unaffected by the presence of an irrelevant stimulus in the ignored hemifield. In contrast, the right-sided horizontal IPS segment showed a strong attentional response when subjects oriented to a stimulus in the relevant hemifield and an irrelevant stimulus was simultaneously present in the ignored hemifield, compared with unilateral stimulation. This effect was independent of the direction of attention. The symmetrical left-sided horizontal IPS segment showed the highest responses under the same circumstances, in combination with a contralateral bias during unilateral stimulation conditions. None of the six patients without neglect had a lesion of the horizontal IPS segment. In four of the 11 neglect patients, the lesion overlapped with the horizontal IPS activity cluster and lay in close proximity to it in another four. The remaining three patients had a lesion at a distance from the parietal cortex. Our findings reconcile the role of the IPS in endogenous attentional control with the clinically significant interaction between direction of attention and bilateral stimulation in right parietal lesion patients. Functional imaging in neglect patients will be necessary to assess IPS function in those cases where the structural lesion spares the middle IPS segment.
Attentional Functions of Parietal and Frontal Cortex
Cerebral Cortex, 2005
A model of normal attentional function, based on the concept of competitive parallel processing, is used to compare attentional deficits following parietal and frontal lobe lesions. Measurements are obtained for visual processing speed, capacity of visual shortterm memory (VSTM), spatial bias (bias to left or right hemifield) and top-down control (selective attention based on task relevance). The results show important differences, but also surprising similarities, in parietal and frontal lobe patients. For processing speed and VSTM, deficits are selectively associated with parietal lesions, in particular lesions of the temporoparietal junction. We discuss explanations based on either grey matter or white matter lesions. In striking contrast, measures of attentional weighting (spatial bias and topdown control) are predicted by simple lesion volume. We suggest that attentional weights reflect competition between broadly distributed object representations. Parietal and frontal mechanisms work together, both in weighting by location and weighting by task context. a Scores \0.5 show bias to right; scores [0.5 show bias to left.
The role of human parietal cortex in attention networks
Brain, 2003
The parietal cortex has been proposed as part of the neural network for guiding spatial attention. However, it is unclear to what degree the parietal cortex contributes to the attentional modulations of activities of the visual cortex and the engagement of the frontal cortex in the attention network. We recorded behavioural performance and haemodynamic responses using functional MRI from a patient with focal left parietal damage in covert visual orienting tasks requiring detection of targets at the attended or unattended locations. While the patient's reaction times to left visual ®eld stimuli were speeded by valid relative to invalid cues, attention to LVF stimuli was associated with enhanced activities in the right extrastriate cortex, right parietal and cingulate cortices, and bilateral frontal cortices. However, the patient's behavioural and neural responses to right visual ®eld stimuli were not in¯uenced by cue validity. The results are discussed in terms of the role of human parietal cortex in the neural network underlying voluntary attentional control.
Current Opinion in Neurobiology, 2004
The parietal lobe forms about 20% of the human cerebral cortex and is divided into two major regions, the somatosensory cortex and the posterior parietal cortex. Posterior parietal cortex, located at the junction of multiple sensory regions, projects to several cortical and subcortical areas and is engaged in a host of cognitive operations. One such operation is selective attention, the process where by the input is filtered and a subset of the information is selected for preferential processing. Recent neuroimaging and neuropsychological studies have provided a more fine-grained understanding of the relationship between brain and behavior in the domain of selective attention.
Transient neural activity in human parietal cortex during spatial attention shifts
Nature Neuroscience, 2002
Natural scenes contain more information than the human visual system can efficiently process at once. Visual attention is the perceptual mechanism by which observers select important aspects of a scene for further cognitive processing 1-5 . Evidence from neurophysiology and functional neuroimaging shows that the neural representation of a visual object is suppressed when it is presented along with other competing objects, relative to when it is presented alone, reflecting competitive interactions among sensory representations. This competitive suppression is thought to occur through inhibitory neural connections. When an object is attended through the action of a top-down biasing signal, this suppression is effectively lifted, and the item is 'selected' 6-8 .