Posterior parietal stroke impairs post-saccadic updating of visual space in both hemifields and reaction to visual stimuli in the contralesional hemifield

2007 ◽  
Vol 118 (4) ◽  
pp. e99
Author(s):  
A. Sprenger ◽  
A. Hinz ◽  
H. Deubel ◽  
D. Kömpf ◽  
W. Heide
Keyword(s):  
Visual Stimuli ◽  
Visual Space ◽  
Posterior Parietal

The Posterior Parietal Cortex in Humans and Monkeys

Physiology ◽  
1997 ◽  
Vol 12 (4) ◽  
pp. 166-171 ◽  
Author(s):  
C Galletti ◽  
PP Battaglini ◽  
P Fattori
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Visual Space ◽  
Superior Parietal Lobule ◽  
Monkey Brain ◽  
Posterior Parietal ◽  
Parietal Lobule

The recently reported existence of neurons able to encode visual space in the superior parietal lobule of the monkey brain suggests that human and monkey superior parietal lobules are homologous structures.

Deficits of visual attention and saccadic eye movements after lesions of parietooccipital cortex in monkeys

1989 ◽  
Vol 61 (1) ◽  
pp. 74-90 ◽  
Author(s):  
J. C. Lynch ◽  
J. W. McLaren
Keyword(s):  
Visual Attention ◽  
Visual Stimuli ◽  
Severe Form ◽  
Inferior Parietal Lobule ◽  
Cortical Lesions ◽  
Visual Extinction ◽  
Prestriate Cortex ◽  
Posterior Parietal ◽  
Parietal Lobule ◽  
Visual Inattention

1. Visual attention is often profoundly disturbed in humans after damage to the cortex of the posterior parietal lobe, particularly of the minor hemisphere, with some patients being totally unaware of visual stimuli in the hemifield of extrapersonal space contralateral to the cortical damage. This severe form of visual inattention is usually called contralateral neglect and has occasionally been reported following posterior parietal lesions in monkeys. However, in monkeys, only qualitative observations have been published and those reports are not in agreement concerning the severity of the deficit. The present experiments were designed to measure quantitatively the amount of disruption of selective visual attention which is produced by lesions of posterior parietal and parietooccipital cortical lesions in monkeys. 2. Five monkeys were trained to visually fixate and follow with their gaze a small visual stimulus as it suddenly moved varying distances (8, 16, or 24 degrees) from the midline into the left or right visual hemifields. Two animals then received a unilateral cortical lesion limited to the inferior parietal lobule (IPL). Three animals received unilateral lesions which included both the inferior parietal lobule and a portion of adjacent dorsal prestriate cortex (IPL-PS). 3. Visual inattention is commonly divided into two levels of severity. The more severe form, contralateral neglect, is the complete absence of behavioral response to a stimulus in the visual field contralateral to hemisphere damage. The less severe deficit, usually called visual extinction, is a tendency to ignore the contralateral of two visual stimuli when they appear simultaneously and symmetrically placed with respect to the center of the subject's surroundings. The five monkeys in this study were tested on a stimulus paradigm which simultaneously measured the severity of visual neglect and also the amount and duration of visual extinction which were produced by the cortical lesions. 4. All monkeys displayed contralateral visual extinction after unilateral posterior parietal or parietooccipital lesions. Three of the five monkeys showed a reversal of the visual extinction after a second, symmetrical lesion was placed in the opposite hemisphere. No monkey showed evidence of full-blown contralateral neglect after lesions limited to the parietooccipital cortex, either in the formal testing situation or during informal neurological examinations. The severity of the observed inattention did not appear to be related to the size of the cortical lesions.(ABSTRACT TRUNCATED AT 400 WORDS)

Contributions of cat posterior parietal cortex to visuospatial discrimination

2000 ◽  
Vol 17 (5) ◽  
pp. 701-709 ◽  
Author(s):  
STEPHEN G. LOMBER ◽  
BERTRAM R. PAYNE
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Food Reward ◽  
Visual Space ◽  
Visual Orienting ◽  
Area 7 ◽  
Visuospatial Processing ◽  
Posterior Parietal ◽  
Cooling Loops ◽  
Significant Bearing

The purpose of the present study was to examine the contributions made by cat posterior parietal cortex to the analyses of the relative position of objects in visual space. Two cats were trained on a landmark task in which they learned to report the position of a landmark object relative to a right or left food-reward chamber. Subsequently, three pairs of cooling loops were implanted bilaterally in contact with visuoparietal cortices forming the crown of the middle suprasylvian gyrus (MSg; architectonic area 7) and the banks of the posterior-middle suprasylvian sulcus (pMS sulcal cortex) and in contact with the ventral-posterior suprasylvian (vPS) region of visuotemporal cortex. Bilateral deactivation of pMS sulcal cortex resulted in a profound impairment for all six tested positions of the landmark, yet bilateral deactivation of neither area 7 nor vPS cortex yielded any deficits. In control tasks (visual orienting and object discrimination), there was no evidence for any degree of attentional blindness or impairment of form discrimination during bilateral deactivation of pMS cortex. Therefore, we conclude that bilateral cooling of pMS cortex, but neither area 7 nor vPS cortex, induces a specific deficit in spatial localization as examined with the landmark task. These observations have significant bearing on our understanding of visuospatial processing in cat, monkey, and human cortices.

scholarly journals Spike-field activity in parietal area LIP during coordinated reach and saccade movements

2012 ◽  
Vol 107 (5) ◽  
pp. 1275-1290 ◽  
Author(s):  
Maureen A. Hagan ◽  
Heather L. Dean ◽  
Bijan Pesaran
Keyword(s):  
Firing Rate ◽  
Posterior Parietal Cortex ◽  
Field Potential ◽  
Visual Space ◽  
Synaptic Activity ◽  
Visually Guided ◽  
Correlated Activity ◽  
Field Activity ◽  
Posterior Parietal ◽  
Field Coherence

The posterior parietal cortex is situated between visual and motor areas and supports coordinated visually guided behavior. Area LIP in the intraparietal sulcus contains representations of visual space and has been extensively studied in the context of saccades. However, area LIP has not been studied during coordinated movements, so it is not known whether saccadic representations in area LIP are influenced by coordinated behavior. Here, we studied spiking and local field potential (LFP) activity in area LIP while subjects performed coordinated reaches and saccades or saccades alone to remembered target locations to test whether activity in area LIP is influenced by the presence of a coordinated reach. We find that coordination significantly changes the activity of individual neurons in area LIP, increasing or decreasing the firing rate when a reach is made with a saccade compared with when a saccade is made alone. Analyzing spike-field coherence demonstrates that area LIP neurons whose firing rate is suppressed during the coordinated task have activity temporally correlated with nearby LFP activity, which reflects the synaptic activity of populations of neurons. Area LIP neurons whose firing rate increases during the coordinated task do not show significant spike-field coherence. Furthermore, LFP power in area LIP is suppressed and does not increase when a coordinated reach is made with a saccade. These results demonstrate that area LIP neurons display different responses to coordinated reach and saccade movements, and that different spike rate responses are associated with different patterns of correlated activity. The population of neurons whose firing rate is suppressed is coherently active with local populations of LIP neurons. Overall, these results suggest that area LIP plays a role in coordinating visually guided actions through suppression of coherent patterns of saccade-related activity.

Covert attention suppresses neuronal responses in area 7a of the posterior parietal cortex

1994 ◽  
Vol 72 (2) ◽  
pp. 1020-1023 ◽  
Author(s):  
M. A. Steinmetz ◽  
C. E. Connor ◽  
C. Constantinidis ◽  
J. R. McLaughlin
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Potential Role ◽  
Visual Stimuli ◽  
Covert Attention ◽  
Neuronal Responses ◽  
Central Target ◽  
Match To Sample ◽  
Area 7A ◽  
Posterior Parietal

1. The effect of covert attention was studied in area 7a of the posterior parietal cortex of rhesus monkeys performing a spatial match-to-sample task. The task required the animals to fixate a central target light, to detect and remember the location of a transient spatial cue, and to respond when one of a series of stimuli appeared at the cued location. Neuronal responses evoked by the visual stimuli were recorded during each behavioral trial. 2. Thirty-eight percent of the neurons isolated and studied in these experiments responded to visual stimuli. The responses of 55% of the neurons tested were suppressed, and 5% enhanced for stimuli presented at the attended location. Responses in the remaining neurons (40%) were unaffected by shifts in attention. 3. Activity in 57% of the suppressed neurons was reduced to rates not significantly different from spontaneous activity. 4. The extent of suppression for individual neurons was often restricted to the attended portion of the receptive field. 5. These data suggest a potential role for these neurons in the redirection of visual attention.

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