scholarly journals Spatial orientation and the representation of space with parietal lobe lesions

1997 ◽  
Vol 352 (1360) ◽  
pp. 1411-1419 ◽  
Author(s):  
Hans–Otto Karnath
Keyword(s):  
Parietal Cortex ◽  
Neural Control ◽  
Parietal Lobe ◽  
Peripersonal Space ◽  
Spatial Neglect ◽  
Neural Representation ◽  
Space Representation ◽  
Control Mechanisms ◽  
Optic Ataxia ◽  
Representation Of Space

Damage to the human parietal cortex leads to disturbances of spatial perception and of motor behaviour. Within the parietal lobe, lesions of the superior and of the inferior lobule induce quite different, characteristic deficits. Patients with inferior (predominantly right) parietal–lobe lesions fail to explore the contralesional part of space by eye or limb movements (spatial neglect). In contrast, superior parietal lobe lesions lead to specific impairments of goal–directed movements (optic ataxia). The observations reported in this paper support the view of dissociated functions represented in the inferior and the superior lobule of the human parietal cortex. They suggest that a spatial reference frame for exploratory behaviour is disturbed in patients with neglect. Data from these patients’ visual search argue that their failure to explore the contralesional side is due to a disturbed input transformation leading to a deviation of egocentric space representation to the ipsilesional side. Data further show that this deviation follows a rotation around the earth–vertical body axis to the ipsilesional side rather than a translation towards that side. The results are in clear contrast to explanations that assume a lateral gradient ranging from a minimum of exploration in the extreme contralesional to a maximum in the extreme ipsilesional hemispace. Moreover, the failure to orient towards and to explore the contralesional part of space appears to be distinct from those deficits observed once an object of interest has been located and releases reaching. Although patients with neglect exhibit a severe bias of exploratory movements, their hand trajectories to targets in peripersonal space may follow a straight path. This result suggests that (i) exploratory and (ii) goal–directed behaviour in space do not share the same neural control mechanisms. Neural representation of space in the inferior parietal lobule seems to serve as a matrix for spatial exploration and for orienting in space but not for visuomotor processes involved in reaching for objects. Disturbances of such processes rather appear to be prominent in patients with more superior parietal lobe lesions and optic ataxia.

Neural Representation of Space Using Sinusoidal Arrays

1993 ◽  
Vol 5 (6) ◽  
pp. 869-884 ◽  
Author(s):  
David S. Touretzky ◽  
A. David Redish ◽  
Hank S. Wan
Keyword(s):  
Computer Simulations ◽  
Parietal Cortex ◽  
Spatial Information ◽  
Sine Wave ◽  
Spiking Neurons ◽  
Neural Representation ◽  
Temporal Dimension ◽  
Response Properties ◽  
Representation Of Space

O'Keefe (1991) has proposed that spatial information in rats might be represented as phasors: phase and amplitude of a sine wave encoding angle and distance to a landmark. We describe computer simulations showing that operations on phasors can be efficiently realized by arrays of spiking neurons that recode the temporal dimension of the sine wave spatially. Some cells in motor and parietal cortex exhibit response properties compatible with this proposal.

Strategies for the Control of Balance During Locomotion

2018 ◽  
Vol 7 (1) ◽  
pp. 18-25 ◽  
Author(s):  
Hendrik Reimann ◽  
Tyler Fettrow ◽  
John J. Jeka
Keyword(s):  
Degrees Of Freedom ◽  
Neural Control ◽  
Control Strategies ◽  
Mechanical Effect ◽  
Space Representation ◽  
Control Mechanisms ◽  
Step Width ◽  
Foot Placement ◽  
The Central Nervous System ◽  
Phase Space Representation

The neural control of balance during locomotion is currently not well understood, even in the light of considerable advances in research on balance during standing. In this paper, we lay out the control problem for this task and present a list of different strategies available to the central nervous system to solve this problem. We discuss the biomechanics of the walking body, using a simplified model that iteratively gains degrees of freedom and complexity. Each addition allows for different control strategies, which we introduce in turn: foot placement shift, ankle strategy, hip strategy, and push-off modulation. The dynamics of the biomechanical system are discussed using the phase space representation, which allows illustrating the mechanical effect of the different control mechanisms. This also enables us to demonstrate the effects of common general stability strategies, such as increasing step width and cadence.

scholarly journals Temporal preparation in patients with Neglect syndrome

2020 ◽  
Vol 41 (1) ◽  
pp. 66-83
Author(s):  
Mónica Triviño ◽  
Estrella Ródenas ◽  
Ángel Correa
Keyword(s):  
Parietal Cortex ◽  
Parietal Lobe ◽  
Causal Relation ◽  
Spatial Location ◽  
Control Mechanisms ◽  
Subcortical Structures ◽  
Sequential Effects ◽  
Temporal Preparation ◽  
Attentional Deficits ◽  
Neglect Syndrome

AbstractThe right parietal cortex has been widely associated with a spatial orienting network. Its damage frequently produces the Neglect syndrome consisting in deficits in spatial attention to the left hemifield. Neglect has also been related to temporal deficits (such as the estimation of the duration of a stimulus or the discrimination of two stimuli that occur at the same spatial location but at different time intervals). Such attentional deficits have been much less studied in the temporal as compared to the spatial domain. The current research focused on the study of temporal attention processes in patients with Neglect syndrome, specifically, on temporal preparation. We recruited 10 patients with Neglect syndrome, 10 patients without Neglect syndrome, as well as 11 healthy individuals. Each participant completed an experimental task which measures three main temporal preparation effects described in the literature: Temporal orienting and Foreperiod effects (both related to control mechanisms and prefrontal areas) and Sequential effects (automatic in nature and related to parietal and subcortical structures). The results showed a deficit in the sequential effects only in those patients who suffered from Neglect syndrome. The results suggest a causal relation between Neglect syndrome and the automatic mechanisms of temporal preparation. Since our sample of Neglect patients had suffered lesions mainly in the parietal cortex, the results are discussed taking into account the role of the parietal lobe in the processing of time and the models explaining sequential effects.

scholarly journals A spatial memory signal shows that the parietal cortex has access to a craniotopic representation of space

eLife ◽  
2018 ◽  
Vol 7 ◽  
Author(s):  
Mulugeta Semework ◽  
Sara C Steenrod ◽  
Michael E Goldberg
Keyword(s):  
Spatial Memory ◽  
Parietal Cortex ◽  
Receptive Fields ◽  
Spatial Location ◽  
Visual Response ◽  
Lateral Intraparietal Area ◽  
Memory Response ◽  
Representation Of Space ◽  
Present Trial

Humans effortlessly establish a gist-like memory of their environment whenever they enter a new place, a memory that can guide action even in the absence of vision. Neurons in the lateral intraparietal area (LIP) of the monkey exhibit a form of this environmental memory. These neurons respond when a monkey makes a saccade that brings the spatial location of a stimulus that appeared on a number of prior trials, but not on the present trial, into their receptive fields (RFs). The stimulus need never have appeared in the neuron’s RF. This memory response is usually weaker, with a longer latency than the neuron’s visual response. We suggest that these results demonstrate that LIP has access to a supraretinal memory of space, which is activated when the spatial location of the vanished stimulus can be described by a retinotopic vector from the center of gaze to the remembered spatial location.

scholarly journals Dynamical Latent State Computation in the Posterior Parietal Cortex

2022 ◽  
Author(s):  
Kaushik J Lakshminarasimhan ◽  
Eric Avila ◽  
Xaq Pitkow ◽  
Dora E Angelaki
Keyword(s):  
Parietal Cortex ◽  
Posterior Parietal Cortex ◽  
Target Location ◽  
Neural Representation ◽  
World Model ◽  
Population Activity ◽  
The World ◽  
Neural Interactions ◽  
Posterior Parietal ◽  
Hidden States

Success in many real-world tasks depends on our ability to dynamically track hidden states of the world. To understand the underlying neural computations, we recorded brain activity in posterior parietal cortex (PPC) of monkeys navigating by optic flow to a hidden target location within a virtual environment, without explicit position cues. In addition to sequential neural dynamics and strong interneuronal interactions, we found that the hidden state -- monkey's displacement from the goal -- was encoded in single neurons, and could be dynamically decoded from population activity. The decoded estimates predicted navigation performance on individual trials. Task manipulations that perturbed the world model induced substantial changes in neural interactions, and modified the neural representation of the hidden state, while representations of sensory and motor variables remained stable. The findings were recapitulated by a task-optimized recurrent neural network model, suggesting that neural interactions in PPC embody the world model to consolidate information and track task-relevant hidden states.

Visuotactile Representation of Peripersonal Space: A Neural Network Study

2010 ◽  
Vol 22 (1) ◽  
pp. 190-243 ◽  
Author(s):  
Elisa Magosso ◽  
Melissa Zavaglia ◽  
Andrea Serino ◽  
Giuseppe di Pellegrino ◽  
Mauro Ursino
Keyword(s):  
Neural Network ◽  
Peripersonal Space ◽  
Sensitivity Analyses ◽  
Neurological Deficits ◽  
Inhibitory Synapses ◽  
Space Representation ◽  
Emergent Properties ◽  
Bilateral Stimulation ◽  
The Right ◽  
Parameter Values

Neurophysiological and behavioral studies suggest that the peripersonal space is represented in a multisensory fashion by integrating stimuli of different modalities. We developed a neural network to simulate the visual-tactile representation of the peripersonal space around the right and left hands. The model is composed of two networks (one per hemisphere), each with three areas of neurons: two are unimodal (visual and tactile) and communicate by synaptic connections with a third downstream multimodal (visual-tactile) area. The hemispheres are interconnected by inhibitory synapses. We applied a combination of analytic and computer simulation techniques. The analytic approach requires some simplifying assumptions and approximations (linearization and a reduced number of neurons) and is used to investigate network stability as a function of parameter values, providing some emergent properties. These are then tested and extended by computer simulations of a more complex nonlinear network that does not rely on the previous simplifications. With basal parameter values, the extended network reproduces several in vivo phenomena: multisensory coding of peripersonal space, reinforcement of unisensory perception by multimodal stimulation, and coexistence of simultaneous right- and left-hand representations in bilateral stimulation. By reducing the strength of the synapses from the right tactile neurons, the network is able to mimic the responses characteristic of right-brain-damaged patients with left tactile extinction: perception of unilateral left tactile stimulation, cross-modal extinction and cross-modal facilitation in bilateral stimulation. Finally, a variety of sensitivity analyses on some key parameters was performed to shed light on the contribution of single-model components in network behaviour. The model may help us understand the neural circuitry underlying peripersonal space representation and identify its alterations explaining neurological deficits. In perspective, it could help in interpreting results of psychophysical and behavioral trials and clarifying the neural correlates of multisensory-based rehabilitation procedures.

Resituating cognitive mechanisms within heterarchical networks controlling physiology and behavior

2019 ◽  
Vol 29 (5) ◽  
pp. 620-639 ◽  
Author(s):  
William Bechtel
Keyword(s):  
Cognitive Control ◽  
Cognitive Science ◽  
Neural Control ◽  
Science Research ◽  
Control Mechanisms ◽  
Cognitive Mechanisms ◽  
Physiological Processes ◽  
High Level ◽  
And Behavior ◽  
Production Mechanisms

Cognitive science has traditionally focused on mechanisms involved in high-level reasoning and problem-solving processes. Such mechanisms are often treated as autonomous from but controlling underlying physiological processes. I offer a different perspective on cognition which starts with the basic production mechanisms through which organisms construct and repair themselves and navigate their environments and then I develop a framework for conceptualizing how cognitive control mechanisms form a heterarchical network that regulates production mechanisms. Many of these control mechanisms perform cognitive tasks such as evaluating circumstances and making decisions. Cognitive control mechanisms are present in individual cells, but in metazoans, intracellular control is supplemented by a nervous system in which a multitude of neural control mechanisms are organized heterarchically. On this perspective, high-level cognitive mechanisms are not autonomous, but are elements in larger heterarchical networks. This has implications for future directions in cognitive science research.

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