scholarly journals The posterior parietal cortex contributes to visuomotor processing for saccades in blindsight macaques

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Rikako Kato ◽  
Takuya Hayashi ◽  
Kayo Onoe ◽  
Masatoshi Yoshida ◽  
Hideo Tsukada ◽  
...  
Keyword(s):  
Visual Field ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Visual Awareness ◽  
Functional Brain Imaging ◽  
Intraparietal Sulcus ◽  
Visual Responses ◽  
Primate Model ◽  
Positron Emission ◽  
Posterior Parietal

AbstractPatients with damage to the primary visual cortex (V1) lose visual awareness, yet retain the ability to perform visuomotor tasks, which is called “blindsight.” To understand the neural mechanisms underlying this residual visuomotor function, we studied a non-human primate model of blindsight with a unilateral lesion of V1 using various oculomotor tasks. Functional brain imaging by positron emission tomography showed a significant change after V1 lesion in saccade-related visuomotor activity in the intraparietal sulcus area in the ipsi- and contralesional posterior parietal cortex. Single unit recordings in the lateral bank of the intraparietal sulcus (lbIPS) showed visual responses to targets in the contralateral visual field on both hemispheres. Injection of muscimol into the ipsi- or contralesional lbIPSs significantly impaired saccades to targets in the V1 lesion-affected visual field, differently from previous reports in intact animals. These results indicate that the bilateral lbIPSs contribute to visuomotor function in blindsight.

scholarly journals Topographic Organization for Delayed Saccades in Human Posterior Parietal Cortex

2005 ◽  
Vol 94 (2) ◽  
pp. 1372-1384 ◽  
Author(s):  
Denis Schluppeck ◽  
Paul Glimcher ◽  
David J. Heeger
Keyword(s):  
Visual Field ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Target Location ◽  
Critical Role ◽  
Topographic Maps ◽  
Field Orientation ◽  
Topographic Organization ◽  
Motor Intention ◽  
Posterior Parietal

Posterior parietal cortex (PPC) is thought to play a critical role in decision making, sensory attention, motor intention, and/or working memory. Research on the PPC in non-human primates has focused on the lateral intraparietal area (LIP) in the intraparietal sulcus (IPS). Neurons in LIP respond after the onset of visual targets, just before saccades to those targets, and during the delay period in between. To study the function of posterior parietal cortex in humans, it will be crucial to have a routine and reliable method for localizing specific parietal areas in individual subjects. Here, we show that human PPC contains at least two topographically organized regions, which are candidates for the human homologue of LIP. We mapped the topographic organization of human PPC for delayed (memory guided) saccades using fMRI. Subjects were instructed to fixate centrally while a peripheral target was briefly presented. After a further 3-s delay, subjects made a saccade to the remembered target location followed by a saccade back to fixation and a 1-s inter-trial interval. Targets appeared at successive locations “around the clock” (same eccentricity, ≈30° angular steps), to produce a traveling wave of activity in areas that are topographically organized. PPC exhibited topographic organization for delayed saccades. We defined two areas in each hemisphere that contained topographic maps of the contra-lateral visual field. These two areas were immediately rostral to V7 as defined by standard retinotopic mapping. The two areas were separated from each other and from V7 by reversals in visual field orientation. However, we leave open the possibility that these two areas will be further subdivided in future studies. Our results demonstrate that topographic maps tile the cortex continuously from V1 well into PPC.

Directional Selectivity of BOLD Activity in Human Posterior Parietal Cortex for Memory-Guided Double-Step Saccades

2006 ◽  
Vol 95 (3) ◽  
pp. 1645-1655 ◽  
Author(s):  
W. Pieter Medendorp ◽  
Herbert C. Goltz ◽  
Tutis Vilis
Keyword(s):  
Visual Field ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Target Location ◽  
Double Step ◽  
Fmri Signal ◽  
Posterior Parietal ◽  
Visual Hemifields ◽  
Target Locations

We used functional magnetic resonance imaging (fMRI) to investigate the role of the human posterior parietal cortex (PPC) in storing target locations for delayed double-step saccades. To do so, we exploited the laterality of a subregion of PPC that preferentially responds to the memory of a target location presented in the contralateral visual field. Using an event-related design, we tracked fMRI signal changes in this region while subjects remembered the locations of two sequentially flashed targets, presented in either the same or different visual hemifields, and then saccaded to them in sequence. After presentation of the first target, the fMRI signal was always related to the side of the visual field in which it had been presented. When the second target was added, the cortical activity depended on the respective locations of both targets but was still significantly selective for the target of the first saccade. We conclude that this region within the human posterior parietal cortex not only acts as spatial storage center by retaining target locations for subsequent saccades but is also involved in selecting the target for the first intended saccade.

scholarly journals Single-unit activity in marmoset posterior parietal cortex in a gap saccade task

2020 ◽  
Vol 123 (3) ◽  
pp. 896-911 ◽  
Author(s):  
Liya Ma ◽  
Janahan Selvanayagam ◽  
Maryam Ghahremani ◽  
Lauren K. Hayrynen ◽  
Kevin D. Johnston ◽  
...  
Keyword(s):  
Parietal Cortex ◽  
Unit Activity ◽  
Single Unit ◽  
Posterior Parietal Cortex ◽  
Common Marmoset ◽  
Gap Effect ◽  
Oculomotor Control ◽  
Single Unit Activity ◽  
Primate Model ◽  
Posterior Parietal

Abnormal saccadic eye movements can serve as biomarkers for patients with several neuropsychiatric disorders. The common marmoset ( Callithrix jacchus) is becoming increasingly popular as a nonhuman primate model to investigate the cortical mechanisms of saccadic control. Recently, our group demonstrated that microstimulation in the posterior parietal cortex (PPC) of marmosets elicits contralateral saccades. Here we recorded single-unit activity in the PPC of the same two marmosets using chronic microelectrode arrays while the monkeys performed a saccadic task with gap trials (target onset lagged fixation point offset by 200 ms) interleaved with step trials (fixation point disappeared when the peripheral target appeared). Both marmosets showed a gap effect, shorter saccadic reaction times (SRTs) in gap vs. step trials. On average, stronger gap-period responses across the entire neuronal population preceded shorter SRTs on trials with contralateral targets although this correlation was stronger among the 15% “gap neurons,” which responded significantly during the gap. We also found 39% “target neurons” with significant saccadic target-related responses, which were stronger in gap trials and correlated with the SRTs better than the remaining neurons. Compared with saccades with relatively long SRTs, short-SRT saccades were preceded by both stronger gap-related and target-related responses in all PPC neurons, regardless of whether such response reached significance. Our findings suggest that the PPC in the marmoset contains an area that is involved in the modulation of saccadic preparation. NEW & NOTEWORTHY As a primate model in systems neuroscience, the marmoset is a great complement to the macaque monkey because of its unique advantages. To identify oculomotor networks in the marmoset, we recorded from the marmoset posterior parietal cortex during a saccadic task and found single-unit activities consistent with a role in saccadic modulation. This finding supports the marmoset as a valuable model for studying oculomotor control.

scholarly journals Dynamic changes in spatial representation within the posterior parietal cortex in response to visuomotor adaptation

2021 ◽  
Author(s):  
Selene Schintu ◽  
Dwight J. Kravitz ◽  
Edward H. Silson ◽  
Catherine A. Cunningham ◽  
Eric M. Wassermann ◽  
...  
Keyword(s):  
Visual Cortex ◽  
Visual Field ◽  
Receptive Field ◽  
Parietal Cortex ◽  
Spatial Representation ◽  
Posterior Parietal Cortex ◽  
Visuomotor Adaptation ◽  
Prism Adaptation ◽  
Attentional Deployment ◽  
Posterior Parietal

Recent studies used fMRI population receptive field (pRF) mapping to demonstrate that retinotopic organization extends from primary visual cortex to ventral and dorsal visual pathways by quantifying visual field maps, receptive field size, and laterality throughout multiple areas. Visuospatial representation in the posterior parietal cortex (PPC) is modulated by attentional deployment, raising the question of whether spatial representation in the PPC is dynamic and flexible and that this flexibility contributes to visuospatial learning. To answer this question, changes in spatial representation within PPC, as measured with pRF mapping, were recorded before and after visuomotor adaptation. Visuospatial input was laterally manipulated, rightward or leftward, via prism adaptation, a well-established visuomotor technique that modulates visuospatial performance. Based on existing models of prism adaptation mechanism of action, we predicted left prism adaptation to produce a right visuospatial bias via an increasing pRF size in the left parietal cortex. However, our hypothesis was agnostic as to whether right PPC will show an opposite effect given the bilateral bias to right visual field. Findings show that adaptation to left-shifting prisms increases pRF size in both PPCs, while leaving space representation in early visual cortex unchanged. This is the first evidence that prism adaptation drives a dynamic reorganization of response profiles in the PPC. Our results show that spatial representation in the PPC not only reflects changes driven by attentional deployment but dynamically changes in response to visuomotor adaptation. Furthermore, our results provide support for using prism adaptation as a tool to rehabilitate visuospatial deficits.

Remapping the Remembered Target Location for Anti-Saccades in Human Posterior Parietal Cortex

2005 ◽  
Vol 94 (1) ◽  
pp. 734-740 ◽  
Author(s):  
W. Pieter Medendorp ◽  
Herbert C. Goltz ◽  
Tutis Vilis
Keyword(s):  
Visual Field ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Target Location ◽  
Functional Magnetic Resonance ◽  
Posterior Parietal ◽  
Saccade Task ◽  
Anti Saccades ◽  
Do So

We used functional magnetic resonance imaging (fMRI) to investigate the role of the human posterior parietal cortex (PPC) in anti-saccades. To do so, we exploited the laterality of a subregion of the PPC for remembered target location. Using an event-related design, we tracked fMRI signal changes in this region while subjects remembered the location of a flashed target, then were instructed to plan either an anti- or pro-saccade to that location, and finally were instructed to execute the movement. At first, the region responded preferentially to the memory of a target location presented in the contralateral visual field. However, when an anti-cue specified a saccadic response into the opposite visual field, we observed a dynamic shift in cortical activity from one hemisphere to the other. This shows that this region within the human posterior parietal cortex codes the target location for an upcoming saccade, rather than the location of the remembered visual stimulus in an anti-saccade task.

Task-specific reversal of visual hemineglect following bilateral reversible deactivation of posterior parietal cortex: A comparison with deactivation of the superior colliculus

2001 ◽  
Vol 18 (3) ◽  
pp. 487-499 ◽  
Author(s):  
STEPHEN G. LOMBER ◽  
BERTRAM R. PAYNE
Keyword(s):  
Visual Field ◽  
Superior Colliculus ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Light Emitting Diode ◽  
Spatial Relations ◽  
High Contrast ◽  
Reversible Deactivation ◽  
Posterior Parietal ◽  
The Impact

The purpose of the present study was to compare and contrast behavioral performance on three different tasks of spatial cognition during unilateral and bilateral reversible deactivation of posterior parietal cortex. Specifically, we examined posterior middle suprasylvian (pMS) sulcal cortex in adult cats during temporary and reversible cooling deactivation. In Task 1, the cats oriented to a high-contrast, black visual stimulus moved into the visual field periphery. In Task 2, the cats oriented to a static light-emitting diode (LED). Task 3 examined the cats' ability to determine whether a black-and-white checkered, landmark box was closer to the right or left side of the testing apparatus. Following training on all tasks, cryoloops were implanted bilaterally within the pMS sulcus. Unilateral deactivation of pMS sulcal cortex resulted in virtually no responses to either moved or static stimuli and virtually no responses to landmarks presented in the contralateral hemifield, and a profound contralateral hemifield neglect was induced. Responses to stimuli and landmarks presented in the ipsilateral hemifield were unimpaired. Additive, bilateral cooling of the homotopic region in the contralateral hemisphere, but not an adjacent region, resulted in reversal of the initial hemineglect for the moved stimulus, yet induced a complete failure to orient to peripheral static LED stimuli. Bilateral cooling also reversed the contralateral neglect of the landmark, but then cats could not accurately determine position of the landmark anywhere in the visual field because performance was reduced to chance levels for all landmark loci in both hemifields. In this instance, as the contralateral neglect disappeared during bilateral cooling of pMS cortex, a new spatial discrimination deficit was revealed across the entire visual field. We conclude that pMS cortex contributes in multiple ways to the analyses of space, and that these contributions cannot be safely predicted from analyses of unilateral deactivations or from one task to another. Moreover, it is clear that other structures are capable of guiding orienting to high contrast, moved targets when pMS cortex is eliminated from brain circuitry. However, these same structures are incapable of supporting either orienting to static stimuli or analyses of spatial relations as tested with the landmark task. The impact of reversible deactivation of the superior colliculus on these same tasks is discussed.

scholarly journals Topographic Maps of Visual Spatial Attention in Human Parietal Cortex

2005 ◽  
Vol 94 (2) ◽  
pp. 1358-1371 ◽  
Author(s):  
Michael A. Silver ◽  
David Ress ◽  
David J. Heeger
Keyword(s):  
Visual Field ◽  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Visual Stimulation ◽  
Covert Attention ◽  
Topographic Maps ◽  
Cortical Areas ◽  
Visual Spatial ◽  
Temporal Phase ◽  
Posterior Parietal

Functional magnetic resonance imaging (fMRI) was used to measure activity in human parietal cortex during performance of a visual detection task in which the focus of attention systematically traversed the visual field. Critically, the stimuli were identical on all trials (except for slight contrast changes in a fully randomized selection of the target locations) whereas only the cued location varied. Traveling waves of activity were observed in posterior parietal cortex consistent with shifts in covert attention in the absence of eye movements. The temporal phase of the fMRI signal in each voxel indicated the corresponding visual field location. Visualization of the distribution of temporal phases on a flattened representation of parietal cortex revealed at least two distinct topographically organized cortical areas within the intraparietal sulcus (IPS), each representing the contralateral visual field. Two cortical areas were proposed based on this topographic organization, which we refer to as IPS1 and IPS2 to indicate their locations within the IPS. This nomenclature is neutral with respect to possible homologies with well-established cortical areas in the monkey brain. The two proposed cortical areas exhibited relatively little response to passive visual stimulation in comparison with early visual areas. These results provide evidence for multiple topographic maps in human parietal cortex.

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