Magnetic Misreaching

Carey, David P.; Coleman, Richard; Sala, Sergio Della

doi:10.1016/s0010-9452(08)70722-6

Cited by 77 publications

(45 citation statements)

References 42 publications

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“…This suggests that also the greater severity of the deficits observed for canonical reaches in peripheral vision might depend on the disjunction of gaze orientation and hand movement direction, rather than or in addition to the higher computational and metabolic (Beurze, Toni, Pisella, & Medendorp, 2010) demands required when planning reaches toward targets located in the periphery of the visual field. This conclusion is in line with the reported cases of magnetic misreaching observed in parietal patients, in which the hand is attracted toward a "magnetic" fixation point (Carey, Coleman, & Della Sala, 1997;Jackson et al, 2005), probably as a result of an inability to decouple eye and hand movements. This might reflect a difficulty in the computation required to determine the position of the hand relative to that of the gaze.…”

Section: The Role Of Eye-hand Decouplingsupporting

confidence: 91%

A visuomotor disorder in the absence of movement: Does Optic Ataxia generalize to learned isometric hand action?

et al. 2014

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Section: The Role Of Eye-hand Decouplingsupporting

confidence: 91%

A visuomotor disorder in the absence of movement: Does Optic Ataxia generalize to learned isometric hand action?

et al. 2014

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“…6G, 9A). This resembles the gaze-dependent deviation in reaching induced by TMS over PPC by van Donkelaar and Adams (2005) and the inability of patients with OA (damage to PPC) to decouple reach from gaze (Carey et al, 1997;Jackson et al, 2005;Granek et al, 2009). This effect is expected if foveal representations are preserved at the expense of disrupted peripherally retinal representations (Crawford et al, 2004) and is Comparison between data (magnitude of parietal rTMS-induced effects) obtained in experiment 1 (no visual feedback of hand) and experiment 3 (visual feedback of hand) for reaches with the right hand (same subjects, n ϭ 6).…”

Section: Goal Encoding Vs Reach Vector Encodingmentioning

confidence: 81%

Specificity of Human Parietal Saccade and Reach Regions during Transcranial Magnetic Stimulation

Vesia

Prime²,

Yan³

et al. 2010

J. Neurosci.

142

159

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Single-unit recordings in macaque monkeys have identified effector-specific regions in posterior parietal cortex (PPC), but functional neuroimaging in the human has yielded controversial results. Here we used on-line repetitive transcranial magnetic stimulation (rTMS) to determine saccade and reach specificity in human PPC. A short train of three TMS pulses (separated by an interval of 100 ms) was delivered to superior parieto-occipital cortex (SPOC), a region over the midposterior intraparietal sulcus (mIPS), and a site close to caudal IPS situated over the angular gyrus (AG) during a brief memory interval while subjects planned either a saccade or reach with the left or right hand. Behavioral measures then were compared to controls without rTMS. Stimulation of mIPS and AG produced similar patterns: increased end-point variability for reaches and decreased saccade accuracy for contralateral targets. In contrast, stimulation of SPOC deviated reach end points toward visual fixation and had no effect on saccades. Contralateral-limb specificity was highest for AG and lowest for SPOC. Visual feedback of the hand negated rTMS-induced disruptions of the reach plan for mIPS and AG, but not SPOC. These results suggest that human SPOC is specialized for encoding retinally peripheral reach goals, whereas more anterior-lateral regions (mIPS and AG) along the IPS possess overlapping maps for saccade and reach planning and are more closely involved in motor details (i.e., planning the reach vector for a specific hand). This work provides the first causal evidence for functional specificity of these parietal regions in healthy humans.

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“…23 24 Mechanisms of optic ataxia in patients with Bálint's syndrome could overlap those of magnetic misreaching, as in "Ms D" who had progressive parietal lobe degeneration and reached "slavishly" toward objects in central fixation when directed to reach toward targets eccentric to fixation. 191 Impaired reaching behaviours in Bálint's syndrome may reflect the interaction among different hypothetical parietal lobe and frontal lobe mechanisms for vision and action. 192 Lesion of the right frontal lobe may impair monitoring of information related to self generated arm movements.…”

Section: Awareness Of Visual Impairmentsmentioning

confidence: 99%

Psychoanatomical substrates of Balint's syndrome

Rizzo

Vecera

2002

Journal of Neurology, Neurosurgery &Amp; Psychiatry

195

115

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Objectives: From a series of glimpses, we perceive a seamless and richly detailed visual world. Cerebral damage, however, can destroy this illusion. In the case of Bálint's syndrome, the visual world is perceived erratically, as a series of single objects. The goal of this review is to explore a range of psychological and anatomical explanations for this striking visual disorder and to propose new directions for interpreting the findings in Bálint's syndrome and related cerebral disorders of visual processing. Methods: Bálint's syndrome is reviewed in the light of current concepts and methodologies of vision research. Results: The syndrome affects visual perception (causing simultanagnosia/visual disorientation) and visual control of eye and hand movement (causing ocular apraxia and optic ataxia). Although it has been generally construed as a biparietal syndrome causing an inability to see more than one object at a time, other lesions and mechanisms are also possible. Key syndrome components are dissociable and comprise a range of disturbances that overlap the hemineglect syndrome. Inouye's observations in similar cases, beginning in 1900, antedated Bálint's initial report. Because Bálint's syndrome is not common and is difficult to assess with standard clinical tools, the literature is dominated by case reports and confounded by case selection bias, non-uniform application of operational definitions, inadequate study of basic vision, poor lesion localisation, and failure to distinguish between deficits in the acute and chronic phases of recovery. Conclusions: Studies of Bálint's syndrome have provided unique evidence on neural substrates for attention, perception, and visuomotor control. Future studies should address possible underlying psychoanatomical mechanisms at "bottom up" and "top down" levels, and should specifically consider visual working memory and attention (including object based attention) as well as systems for identification of object structure and depth from binocular stereopsis, kinetic depth, motion parallax, eye movement signals, and other cues.

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Magnetic Misreaching

Cited by 77 publications

References 42 publications

A visuomotor disorder in the absence of movement: Does Optic Ataxia generalize to learned isometric hand action?

A visuomotor disorder in the absence of movement: Does Optic Ataxia generalize to learned isometric hand action?

Specificity of Human Parietal Saccade and Reach Regions during Transcranial Magnetic Stimulation

Psychoanatomical substrates of Balint's syndrome

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