scholarly journals Short-term saccadic adaptation in the macaque monkey: a binocular mechanism

2013 ◽  
Vol 109 (2) ◽  
pp. 518-545 ◽  
Author(s):  
K. P. Schultz ◽  
C. Busettini
Keyword(s):  
Saccadic Eye Movements ◽  
Initial Response ◽  
Macaque Monkey ◽  
Double Step ◽  
Adaptive Process ◽  
Adaptive Mechanisms ◽  
Second Shift ◽  
The Subject ◽  
The Brain ◽  
Saccadic Responses

Saccadic eye movements are rapid transfers of gaze between objects of interest. Their duration is too short for the visual system to be able to follow their progress in time. Adaptive mechanisms constantly recalibrate the saccadic responses by detecting how close the landings are to the selected targets. The double-step saccadic paradigm is a common method to simulate alterations in saccadic gain. While the subject is responding to a first target shift, a second shift is introduced in the middle of this movement, which masks it from visual detection. The error in landing introduced by the second shift is interpreted by the brain as an error in the programming of the initial response, with gradual gain changes aimed at compensating the apparent sensorimotor mismatch. A second shift applied dichoptically to only one eye introduces disconjugate landing errors between the two eyes. A monocular adaptive system would independently modify only the gain of the eye exposed to the second shift in order to reestablish binocular alignment. Our results support a binocular mechanism. A version-based saccadic adaptive process detects postsaccadic version errors and generates compensatory conjugate gain alterations. A vergence-based saccadic adaptive process detects postsaccadic disparity errors and generates corrective nonvisual disparity signals that are sent to the vergence system to regain binocularity. This results in striking dynamical similarities between visually driven combined saccade-vergence gaze transfers, where the disparity is given by the visual targets, and the double-step adaptive disconjugate responses, where an adaptive disparity signal is generated internally by the saccadic system.

Neuronal death of the cancellation theory?

1994 ◽  
Vol 17 (2) ◽  
pp. 274-275
Author(s):  
Claude Prablanc
Keyword(s):  
Eye Movements ◽  
Clinical Observation ◽  
Saccadic Eye Movements ◽  
Analytic Solutions ◽  
Visual Stability ◽  
Perceptual Stability ◽  
Stable Representation ◽  
The Subject ◽  
The Stability ◽  
The Brain

The question of how the brain can construct a stable representation of the external world despite eye movements is a very old one. If there have been some wrong statements of problems (such as the inverted retinal image), other statements are less naive and have led to analytic solutions possibly adopted by the brain to counteract the spurious effects of eye movements. Following the MacKay (1973) objections to the analytic view of perceptual stability, Bridgeman et al. claim that the idea that signals canceling the effects of saccadic eye movements are needed is also a misconception, as is the claim that stability and position encoding are two distinct problems. It must be remembered, however, that what made the theory of “cancellation” formulated by von Holst and Mittelstaedt (1950) so appealing was the clinical observation of perceptual instability following ocular paralysis. Following the concept of corollary discharge, the theory of efference copy had the advantage of simultaneously solving three problems: the stability of the visual world during the saccade, the same visual stability across saccades, and the visual constancy problem of allowing the subject to know where an object in space is.

scholarly journals An architectonic type principle in the development of laminar patterns of cortico-cortical connections

2021 ◽  
Author(s):  
Sarah F. Beul ◽  
Alexandros Goulas ◽  
Claus C. Hilgetag
Keyword(s):  
Structural Connectivity ◽  
Macaque Monkey ◽  
Brain Regions ◽  
Adult Brain ◽  
Mammalian Brain ◽  
Cortical Connections ◽  
Cortical Projections ◽  
Structural Connections ◽  
High Degree ◽  
The Brain

AbstractStructural connections between cortical areas form an intricate network with a high degree of specificity. Many aspects of this complex network organization in the adult mammalian cortex are captured by an architectonic type principle, which relates structural connections to the architectonic differentiation of brain regions. In particular, the laminar patterns of projection origins are a prominent feature of structural connections that varies in a graded manner with the relative architectonic differentiation of connected areas in the adult brain. Here we show that the architectonic type principle is already apparent for the laminar origins of cortico-cortical projections in the immature cortex of the macaque monkey. We find that prenatal and neonatal laminar patterns correlate with cortical architectonic differentiation, and that the relation of laminar patterns to architectonic differences between connected areas is not substantially altered by the complete loss of visual input. Moreover, we find that the degree of change in laminar patterns that projections undergo during development varies in proportion to the relative architectonic differentiation of the connected areas. Hence, it appears that initial biases in laminar projection patterns become progressively strengthened by later developmental processes. These findings suggest that early neurogenetic processes during the formation of the brain are sufficient to establish the characteristic laminar projection patterns. This conclusion is in line with previously suggested mechanistic explanations underlying the emergence of the architectonic type principle and provides further constraints for exploring the fundamental factors that shape structural connectivity in the mammalian brain.

scholarly journals VI. On the comparative structure of the brain in rodents

1882 ◽  
Vol 33 (216-219) ◽  
pp. 15-21
Keyword(s):  
Olfactory Organ ◽  
Cortical Surface ◽  
Complex Relationship ◽  
Comparative Structure ◽  
The Subject ◽  
The Brain

I have endeavoured in this abstract to summarise the results of my recent researches into the minute structure of the brain in the smaller Rodents. The pig and sheep, which were the subjects of my former memoir, possess a highly developed olfactory apparatus conjoined to a well convoluted cortical surface; but in the smaller animals now under consideration the surface of the hemispheres is almost perfectly smooth, while the olfactory organ, from its comparative size and complex relationship, has an important part to play in the architecture of the brain. Animals possessing the latter type of cerebrum have been classed together as the Osmatic Lissencéphales, in contradistinction to those which were the subject of my former enquiries, the Osmatic Gyren-céphales. My researches into the structure of the brain of prominent members of the former group, viz., the rabbit and rat, may be considered under two heads:— ( a .) The histology of the complete cortical envelope.

Transfer of consciousness. Considering its possibility or fantasy from the religious and scientific perspectives

DIALOGO ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 189-200
Author(s):  
Tudor-Cosmin Ciocan ◽  
Any Docu Axelerad ◽  
Maria CIOCAN ◽  
Alina Zorina Stroe ◽  
Silviu Docu Axelerad ◽  
...  
Keyword(s):  
Artificial Intelligence ◽  
Eternal Life ◽  
Human Consciousness ◽  
Religious Believer ◽  
Actual Knowledge ◽  
Holistic Understanding ◽  
The World ◽  
The Subject ◽  
Human Feature ◽  
The Brain

Ancient beliefs such as astral projection, human possession, abduction and other similar are not only universal, taught by all religions, but also used as premises for core believes/expectations, such as after-life, eternal damnation, reincarnation, and many others. Transferring Consciousness to a Synthetic Body is also a feature of interest in our actual knowledge, both religious as for science. If immortality were an option, would you take it into consideration more seriously? Most people would probably dismiss the question since immortality isn’t a real deal to contract. But what if having eternal life was a possibility in today’s world? The possibility of the transfer of human consciousness to a synthetic body can soon become a reality, and it could help the world for the better. Thus, until recently, the subject was mostly proposed by religion(s) and saw as a spiritual [thus, not ‘materially real’ or ‘forthwith accomplishable’] proposal therefore not really fully engaged or trust if not a religious believer. Now, technology is evolving, and so are we. The world has come to a point where artificial intelligence is breaking the boundaries of our perception of human consciousness and intelligence. And with this so is our understanding about the ancient question ‘who are we?’ concerning consciousness and how this human feature sticks to our body or it can become an entity beyond the material flesh. Without being exhaustive with the theme's development [leaving enough room for further investigations], we would like to take it for a spin and see how and where the religious and neuroscience realms intersect with it for a global, perhaps holistic understanding. Developments in neurotechnology favor the brain to broaden its physical control further the restraints of the human body. Accordingly, it is achievable to both acquire and provide information from and to the brain and also to organize feedback processes in which a person's thoughts can influence the activity of a computer or reversely.

scholarly journals Astrocytes: Heterogeneous and Dynamic Phenotypes in Neurodegeneration and Innate Immunity

2018 ◽  
Vol 25 (5) ◽  
pp. 455-474 ◽  
Author(s):  
Colm Cunningham ◽  
Aisling Dunne ◽  
Ana Belen Lopez-Rodriguez
Keyword(s):  
Neural Circuit ◽  
Phenotypic Diversity ◽  
Significant Heterogeneity ◽  
Therapeutic Implications ◽  
Numerous Cell ◽  
Health And Disease ◽  
The Subject ◽  
The Brain ◽  
Substantial Heterogeneity ◽  
Homogenous Population

Astrocytes are the most numerous cell type in the brain and perform several essential functions in supporting neuronal metabolism and actively participating in neural circuit and behavioral function. They also have essential roles as innate immune cells in responding to local neuropathology, and the manner in which they respond to brain injury and degeneration is the subject of increasing attention in neuroscience. Although activated astrocytes have long been thought of as a relatively homogenous population, which alter their phenotype in a relatively stereotyped way upon central nervous system injury, the last decade has revealed substantial heterogeneity in the basal state and significant heterogeneity of phenotype during reactive astrocytosis. Thus, phenotypic diversity occurs at two distinct levels: that determined by regionality and development and that determined by temporally dynamic changes to the environment of astrocytes during pathology. These inflammatory and pathological states shape the phenotype of these cells, with different consequences for destruction or recovery of the local tissue, and thus elucidating these phenotypic changes has significant therapeutic implications. In this review, we will focus on the phenotypic heterogeneity of astrocytes in health and disease and their propensity to change that phenotype upon subsequent stimuli.

Lantern Demonstration of Gross Lesions of the Cerebrum

1901 ◽  
Vol 47 (199) ◽  
pp. 729-737 ◽  
Author(s):  
Joseph Shaw Bolton
Keyword(s):  
Cerebral Cortex ◽  
Dura Mater ◽  
Royal Society ◽  
Mental Disease ◽  
Post Mortem ◽  
Pyramidal Layer ◽  
Gross Lesions ◽  
The Subject ◽  
The Brain ◽  
Morbid Conditions

This demonstration was a further report on the subject laid before the Association at the meeting at Claybury in February last, viz., the morbid changes occurring in the brain and other intra-cranial contents in amentia and dementia. In a paper read before the Royal Society in the spring of 1900, and subsequently published in the Philosophical Transactions, it was stated, as the result of a systematic micrometric examination of the visuo-sensory (primary visual) and visuo-psychic (lower associational) regions of the cerebral cortex, that the depth of the pyramidal layer of nerve-cells varies with the amentia or dementia existing in the patient. At the meeting of the Association referred to it was further shown, from an analysis, clinical and pathological, of 121 cases of insanity which appeared consecutively in the post-mortem room at Claybury, that the morbid conditions inside the skull-cap in insanity, viz., abnormalities in the dura mater, the pia arachnoid, the ependyma and intra-cranial fluid, etc., are the accompaniments of and vary in degree with dementia alone, and are independent of the duration of the mental disease. Since that date the pre-frontal (higher associational) region has been systematically examined in nineteen cases, viz., normal persons and normal aments (infants), and cases of amentia, of chronic and recurrent insanity without appreciable dementia, and of dementia, and the results obtained form the subject of the present demonstration. A paper on the whole subject will shortly be published in the Archives of the Claybury Laboratory.

Phosphodiesterase-5 inhibitors oppose hyperoxic vasoconstriction and accelerate seizure development in rats exposed to hyperbaric oxygen

2009 ◽  
Vol 106 (4) ◽  
pp. 1234-1242 ◽  
Author(s):  
Ivan T. Demchenko ◽  
Alex Ruehle ◽  
Barry W. Allen ◽  
Richard D. Vann ◽  
Claude A. Piantadosi
Keyword(s):  
Hyperbaric Oxygen ◽  
Positive Function ◽  
Initial Response ◽  
Brain Regions ◽  
No Production ◽  
No Donor ◽  
Mean Values ◽  
Brain Nitric Oxide ◽  
The Brain ◽  
Phosphodiesterase 5

Oxygen is a potent cerebral vasoconstrictor, but excessive exposure to hyperbaric oxygen (HBO2) can reverse this vasoconstriction by stimulating brain nitric oxide (NO) production, which increases cerebral blood flow (CBF)—a predictor of O2 convulsions. We tested the hypothesis that phosphodiesterase (PDE)-5 blockers, specifically sildenafil and tadalafil, increase CBF in HBO2 and accelerate seizure development. To estimate changes in cerebrovascular responses to hyperoxia, CBF was measured by hydrogen clearance in anesthetized rats, either control animals or those pretreated with one of these blockers, with the NO inhibitor Nω-nitro-l-arginine methyl ester (l-NAME), with the NO donor S-nitroso- N-acetylpenicillamine (SNAP), or with a blocker combined with l-NAME. Animals were exposed to 30% O2 at 1 atm absolute (ATA) (“air”) or to 100% O2 at 4 or 6 ATA. EEG spikes indicated central nervous system CNS O2 toxicity. The effects of PDE-5 blockade varied as a positive function of ambient Po2. In air, CBF did not increase significantly, except after pretreatment with SNAP. However, at 6 ATA O2, mean values for CBF increased and values for seizure latency decreased, both significantly; pretreatment with l-NAME abolished these effects. Conscious rats treated with sildenafil before HBO2 were also more susceptible to CNS O2 toxicity, as demonstrated by significantly shortened convulsive latency. Decreases in regional CBF reflect net vasoconstriction in the brain regions studied, since mean arterial pressures remained constant or increased throughout. Thus PDE-5 blockers oppose the protective vasoconstriction that is the initial response to hyperbaric hyperoxia, decreasing the safety of HBO2 by hastening onset of CNS O2 toxicity.

Context dependence of receptive field remapping in superior colliculus

2011 ◽  
Vol 106 (4) ◽  
pp. 1862-1874 ◽  
Author(s):  
Jan Churan ◽  
Daniel Guitton ◽  
Christopher C. Pack
Keyword(s):  
Receptive Field ◽  
Superior Colliculus ◽  
Visual Stimulation ◽  
Receptive Fields ◽  
Spatial Location ◽  
Macaque Monkey ◽  
Visual Signals ◽  
Perceptual Stability ◽  
Visual Background ◽  
The Brain

Our perception of the positions of objects in our surroundings is surprisingly unaffected by movements of the eyes, head, and body. This suggests that the brain has a mechanism for maintaining perceptual stability, based either on the spatial relationships among visible objects or internal copies of its own motor commands. Strong evidence for the latter mechanism comes from the remapping of visual receptive fields that occurs around the time of a saccade. Remapping occurs when a single neuron responds to visual stimuli placed presaccadically in the spatial location that will be occupied by its receptive field after the completion of a saccade. Although evidence for remapping has been found in many brain areas, relatively little is known about how it interacts with sensory context. This interaction is important for understanding perceptual stability more generally, as the brain may rely on extraretinal signals or visual signals to different degrees in different contexts. Here, we have studied the interaction between visual stimulation and remapping by recording from single neurons in the superior colliculus of the macaque monkey, using several different visual stimulus conditions. We find that remapping responses are highly sensitive to low-level visual signals, with the overall luminance of the visual background exerting a particularly powerful influence. Specifically, although remapping was fairly common in complete darkness, such responses were usually decreased or abolished in the presence of modest background illumination. Thus the brain might make use of a strategy that emphasizes visual landmarks over extraretinal signals whenever the former are available.

The Brain Stem Saccadic Burst Generator Encodes Gaze in Three-Dimensional Space

2008 ◽  
Vol 99 (5) ◽  
pp. 2602-2616 ◽  
Author(s):  
Marion R. Van Horn ◽  
Pierre A. Sylvestre ◽  
Kathleen E. Cullen
Keyword(s):  
Eye Movements ◽  
Brain Stem ◽  
Dimensional Space ◽  
Three Dimensional ◽  
Saccadic Eye Movements ◽  
Three Dimensions ◽  
Related Information ◽  
Computer Based ◽  
Different Depths ◽  
The Brain

When we look between objects located at different depths the horizontal movement of each eye is different from that of the other, yet temporally synchronized. Traditionally, a vergence-specific neuronal subsystem, independent from other oculomotor subsystems, has been thought to generate all eye movements in depth. However, recent studies have challenged this view by unmasking interactions between vergence and saccadic eye movements during disconjugate saccades. Here, we combined experimental and modeling approaches to address whether the premotor command to generate disconjugate saccades originates exclusively in “vergence centers.” We found that the brain stem burst generator, which is commonly assumed to drive only the conjugate component of eye movements, carries substantial vergence-related information during disconjugate saccades. Notably, facilitated vergence velocities during disconjugate saccades were synchronized with the burst onset of excitatory and inhibitory brain stem saccadic burst neurons (SBNs). Furthermore, the time-varying discharge properties of the majority of SBNs (>70%) preferentially encoded the dynamics of an individual eye during disconjugate saccades. When these experimental results were implemented into a computer-based simulation, to further evaluate the contribution of the saccadic burst generator in generating disconjugate saccades, we found that it carries all the vergence drive that is necessary to shape the activity of the abducens motoneurons to which it projects. Taken together, our results provide evidence that the premotor commands from the brain stem saccadic circuitry, to the target motoneurons, are sufficient to ensure the accurate control shifts of gaze in three dimensions.

scholarly journals Context-Based Filtering for Assisted Brain-Actuated Wheelchair Driving

2007 ◽  
Vol 2007 ◽  
pp. 1-12 ◽  
Author(s):  
Gerolf Vanacker ◽  
José del R. Millán ◽  
Eileen Lew ◽  
Pierre W. Ferrez ◽  
Ferran Galán Moles ◽  
...  
Keyword(s):  
Control System ◽  
Shared Control ◽  
Eeg Signals ◽  
Intelligent Processing ◽  
Intelligent Wheelchair ◽  
Brain Signals ◽  
Brain Interface ◽  
The Subject ◽  
Electroencephalogram Eeg ◽  
The Brain

Controlling a robotic device by using human brain signals is an interesting and challenging task. The device may be complicated to control and the nonstationary nature of the brain signals provides for a rather unstable input. With the use of intelligent processing algorithms adapted to the task at hand, however, the performance can be increased. This paper introduces a shared control system that helps the subject in driving an intelligent wheelchair with a noninvasive brain interface. The subject's steering intentions are estimated from electroencephalogram (EEG) signals and passed through to the shared control system before being sent to the wheelchair motors. Experimental results show a possibility for significant improvement in the overall driving performance when using the shared control system compared to driving without it. These results have been obtained with 2 healthy subjects during their first day of training with the brain-actuated wheelchair.

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