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The parietal cortex and saccade planning: lessons from human lesion studies.

Ptak R, Müri RM - Front Hum Neurosci (2013)

Bottom Line: The parietal cortex is a critical interface for attention and integration of multiple sensory signals that can be used for the implementation of motor plans.Many neurons in this region exhibit strong attention-, reach-, grasp- or saccade-related activity.However, these patients also show bilateral impairments of saccade initiation and control that are difficult to explain in the context of their lateralized deficits of visual attention.

View Article: PubMed Central - PubMed

Affiliation: Division of Neurorehabilitation, University Hospitals Geneva Geneva, Switzerland ; Laboratory of Cognitive Neurorehabilitation, Faculty of Medicine, University of Geneva Geneva, Switzerland ; Faculty of Psychology and Educational Sciences, University of Geneva Geneva, Switzerland.

ABSTRACT
The parietal cortex is a critical interface for attention and integration of multiple sensory signals that can be used for the implementation of motor plans. Many neurons in this region exhibit strong attention-, reach-, grasp- or saccade-related activity. Here, we review human lesion studies supporting the critical role of the parietal cortex in saccade planning. Studies of patients with unilateral parietal damage and spatial neglect reveal characteristic spatially lateralized deficits of saccade programming when multiple stimuli compete for attention. However, these patients also show bilateral impairments of saccade initiation and control that are difficult to explain in the context of their lateralized deficits of visual attention. These findings are reminiscent of the deficits of oculomotor control observed in patients with Bálint's syndrome consecutive to bilateral parietal damage. We propose that some oculomotor deficits following parietal damage are compatible with a decisive role of the parietal cortex in saccade planning under conditions of sensory competition, while other deficits reflect disinhibition of low-level structures of the oculomotor network in the absence of top-down parietal modulation.

No MeSH data available.


Related in: MedlinePlus

A simplified scheme showing the main cortical regions and subcortical structures involved in the control of saccadic eye movements (DLPFC, dorsolateral prefrontal cortex; FEF, frontal eye field; PEF, parietal eye field; PPRF, paramedian pontine reticular formation; SC, superior colliculus).
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Figure 1: A simplified scheme showing the main cortical regions and subcortical structures involved in the control of saccadic eye movements (DLPFC, dorsolateral prefrontal cortex; FEF, frontal eye field; PEF, parietal eye field; PPRF, paramedian pontine reticular formation; SC, superior colliculus).

Mentions: Visual, visuomotor and fixation activity is predominant in area 7a (whose human homologue is probably the angular gyrus) and the lateral intraparietal area (LIP), whose homologue in humans has been termed the parietal eye field (PEF; Figure 1). Functional imaging studies have localized the PEF in the posterior IPS (Müri et al., 1996; Culham and Kanwisher, 2001; Pierrot-Deseilligny et al., 2004). This region is highly active when subjects execute saccadic eye movements, or when they shift their attention without shifting the gaze, making it difficult to distinguish between mechanisms involved in saccade planning and the orienting of attention (Corbetta et al., 1998; Perry and Zeki, 2000). In saccade tasks the PEF is activated together with the frontal eye field (FEF; see Grosbras et al., 2005 for a review of functional imaging studies), which is located in dorsal premotor cortex (Paus, 1996). Fronto-parietal connections between the posterior parietal and premotor/prefrontal cortex form a network that is involved in the filtering of sensory contents and the covert and overt guidance of spatial attention (Gottlieb, 2007; Corbetta et al., 2008; Ptak, 2012). The PEF and FEF both have direct and independent connections to the superior colliculus, which is the primary mesencephalic structure playing a crucial role in saccade initiation and the maintenance of fixation (Wurtz and Mohler, 1976; Munoz and Wurtz, 1992). The cortical saccade network is thus directly linked to mesencephalic centers that trigger the execution of saccades (Figure 1).


The parietal cortex and saccade planning: lessons from human lesion studies.

Ptak R, Müri RM - Front Hum Neurosci (2013)

A simplified scheme showing the main cortical regions and subcortical structures involved in the control of saccadic eye movements (DLPFC, dorsolateral prefrontal cortex; FEF, frontal eye field; PEF, parietal eye field; PPRF, paramedian pontine reticular formation; SC, superior colliculus).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3675316&req=5

Figure 1: A simplified scheme showing the main cortical regions and subcortical structures involved in the control of saccadic eye movements (DLPFC, dorsolateral prefrontal cortex; FEF, frontal eye field; PEF, parietal eye field; PPRF, paramedian pontine reticular formation; SC, superior colliculus).
Mentions: Visual, visuomotor and fixation activity is predominant in area 7a (whose human homologue is probably the angular gyrus) and the lateral intraparietal area (LIP), whose homologue in humans has been termed the parietal eye field (PEF; Figure 1). Functional imaging studies have localized the PEF in the posterior IPS (Müri et al., 1996; Culham and Kanwisher, 2001; Pierrot-Deseilligny et al., 2004). This region is highly active when subjects execute saccadic eye movements, or when they shift their attention without shifting the gaze, making it difficult to distinguish between mechanisms involved in saccade planning and the orienting of attention (Corbetta et al., 1998; Perry and Zeki, 2000). In saccade tasks the PEF is activated together with the frontal eye field (FEF; see Grosbras et al., 2005 for a review of functional imaging studies), which is located in dorsal premotor cortex (Paus, 1996). Fronto-parietal connections between the posterior parietal and premotor/prefrontal cortex form a network that is involved in the filtering of sensory contents and the covert and overt guidance of spatial attention (Gottlieb, 2007; Corbetta et al., 2008; Ptak, 2012). The PEF and FEF both have direct and independent connections to the superior colliculus, which is the primary mesencephalic structure playing a crucial role in saccade initiation and the maintenance of fixation (Wurtz and Mohler, 1976; Munoz and Wurtz, 1992). The cortical saccade network is thus directly linked to mesencephalic centers that trigger the execution of saccades (Figure 1).

Bottom Line: The parietal cortex is a critical interface for attention and integration of multiple sensory signals that can be used for the implementation of motor plans.Many neurons in this region exhibit strong attention-, reach-, grasp- or saccade-related activity.However, these patients also show bilateral impairments of saccade initiation and control that are difficult to explain in the context of their lateralized deficits of visual attention.

View Article: PubMed Central - PubMed

Affiliation: Division of Neurorehabilitation, University Hospitals Geneva Geneva, Switzerland ; Laboratory of Cognitive Neurorehabilitation, Faculty of Medicine, University of Geneva Geneva, Switzerland ; Faculty of Psychology and Educational Sciences, University of Geneva Geneva, Switzerland.

ABSTRACT
The parietal cortex is a critical interface for attention and integration of multiple sensory signals that can be used for the implementation of motor plans. Many neurons in this region exhibit strong attention-, reach-, grasp- or saccade-related activity. Here, we review human lesion studies supporting the critical role of the parietal cortex in saccade planning. Studies of patients with unilateral parietal damage and spatial neglect reveal characteristic spatially lateralized deficits of saccade programming when multiple stimuli compete for attention. However, these patients also show bilateral impairments of saccade initiation and control that are difficult to explain in the context of their lateralized deficits of visual attention. These findings are reminiscent of the deficits of oculomotor control observed in patients with Bálint's syndrome consecutive to bilateral parietal damage. We propose that some oculomotor deficits following parietal damage are compatible with a decisive role of the parietal cortex in saccade planning under conditions of sensory competition, while other deficits reflect disinhibition of low-level structures of the oculomotor network in the absence of top-down parietal modulation.

No MeSH data available.


Related in: MedlinePlus