bluuebunny/crossref_metadata_2025 huggingface dataset:
Selection of the optimal pulse sequence for functional MRI
Authors: Bandettini Peter A.
Published: April 2012

This chapter assists the functional magnetic resonance imaging (fMRI) user in making an informed decision regarding the choice of functional MRI pulse sequence, and presents the pulse sequence choices against a wider backdrop of relevant variables, ranging from paradigm timing to available hardware. It explores the variables that can be optimized in typical functional MRI experiments, which include: information content, sensitivity, acquisition speed, image resolution, brain coverage and anatomical image quality. Summaries and discussions of the tradeoffs regarding the variables described are also included, and some of the issues relating to selection of the possible and the optimal temporal resolution and spatial resolution in fMRI experiments are considered. The rapid rate of improvement in pulse sequence design, data processing, information content, data interpretation and paradigm design can be overwhelming to the novice and even to the advanced user. The hope is to build a broader perspective of what the limits and possibilities of fMRI are.
Registration, atlases and cortical flattening
Authors: Jenkinson Mark
Published: April 2012

This chapter discusses the details of structural analysis methods in functional magnetic resonance imaging (fMRI) to interpret, relate and compare spatial locations, beginning with a description of some preliminary and related processing methods. It proceeds with a discussion of registration including both manual and automatic registration, and gives a brief overview of the important concepts and various approaches involved in registration. The chapter also discusses the two basic tasks for which an atlas is helpful, and mentions that when analysing the functional response of the brain, it is the spatial relationships between different parts of the cortical surface which are of interest. Therefore, an understanding and analysis of these spatial relationships is critical for the knowledge of cognitive function. Analysing the spatial relations in three dimensions, however, is complicated. It is more natural to express the relations in a two-dimensional representation, since the cortical grey matter is in effect a folded two-dimensional surface. Cortical flattening provides a way of creating such a two-dimensional map from the three-dimensional images of the brain. Finally, the chapter discusses the three main applications of structural analysis in fMRI
Extracting brain connectivity
Authors: Büchel Christian , Friston Karl
Published: April 2012

This chapter shows that new methods for measuring effective connectivity allow us to characterize the interactions between brain regions which underlie the complex interactions among different processing stages of functional architectures. It reviews the basic concepts of effective connectivity in neuroimaging. The methods introduced to assess effective connectivity are multiple linear regression, covariance structural equation modelling and variable parameter regression. The first example demonstrates that non-linear interactions can be characterized using simple extensions of linear models, while in the second, structural equation modelling is introduced as a device that allows one to combine observed changes in cortical activity and anatomical models. Finally, the chapter concludes that the approach to neuroimaging data and regional interactions is an exciting endeavour, which is starting to attract more attention.
Clinical applications of mapping neurocognitive processes in the human brain with functional MRI
Authors: Thulborn Keith R. , Gisbert Antonio
Published: April 2012

A critical issue in functional magnetic resonance imaging (fMRI) is to ensure that the subject is performing the required task. This can be important particularly in clinical studies. Clinical applications of fMRI conducted thus far can be summarized in three general areas. This chapter deals with aspects of these applications along with special problems associated with patient studies, and presents strategies that serve to meet these challenges. Quality control of the imaging environment, patient preparation and selection, as well as appropriately calibrated paradigms, are also discussed. The chapter reviews quality assurance and considers several aspects of the fMRI examination to ensure this level of success, concluding that fMRI has now become an exciting window onto brain function in many patient populations currently thought to be inappropriate for imaging.
Dynamic functional neuroimaging integrating multiple modalities
Authors: George John S. , Schmidt David M. , Rector David M. , Wood Chris
Published: April 2012

This chapter discusses the relative importance of imaging technologies and the need to integrate information from multiple methods. It deals with several classes of computational techniques that allow the integration of data from magnetoencephalography (MEG) and magnetic resonance imaging (MRI) to improve the accuracy and reliability of functional neuroimaging by MEG. The chapter analyses the integrated application of two powerful paradigms for functional neuroimaging, exploiting the strengths and minimizing the weaknesses of each. Furthermore, it illustrates that because of the ambiguity associated with the neural electromagnetic inverse problem, a number of investigators have pursued the strategy of using fMRI to define the locations of activation while using MEG or EEG to estimate time-courses. Finally, the chapter mentions the need to expand the arsenal of methods available to the neuroscientist or physician for understanding the architecture and dynamic function of the human brain.
The Upright Head in Hominid Evolution
Authors: Tobias Phillip V.
Published: April 2012

Human uprightness and its anatomic basis are among the most outstanding features that differentiate the living man from the apes of Africa and Asia. The manner in which the body has modified its structure and biomechanics to the new forms of uprightness and bipedalism is only short of ingenious. After more than 4 to 5 million years, humans have not yet evolved a mechanism that is free of errors and vexatious problems. Our bodies are still subject to what Sir Arthur Keith termed the ills of uprightness. These include flat feet, slipped disks, hernias, prolapses, malposture, malocclusion, and painful cephalocervical pathology showing itself as headaches, hypertonicity of the neck muscles, and effects of pressure on motor and sensory nerves.
The Head-Neck System of the BlowflyCalliphora:1. Anatomic Organization of Neck Muscles, Motoneurons, and Multimodal and Visual Inputs
Authors: Strausfeld Nicholas J.
Published: April 2012

Insects offer highly accessible model systems for the study of neural integration and the design of circuits underlying compensatory and voluntary orbital movement. One advantage of such circuitry is that it is simpler in design than in an animal that can move its head and eyes separately. The two eyes of an insect are part of its exoskeleton and their major excursions in the horizontal and vertical planes are conjugate. This chapter tackles the skeletal and neuromuscular organization of the head-neck system in Calliphora erythrocephala, outlines its major sensory neurons and interneurons, and predicts the functional organization of the system by connecting the organization of retinitopic visual neurons to specific neck muscle pathways.
Control of Gaze in Salamanders
Authors: Manteuffel Gerhard
Published: April 2012

Studies of amphibian gaze control stems back to the 1930s and 1940s, when Birukow and Sperry investigated the optokinetic reflex in anurans and newts. In these initial researches, they discovered such fundamental properties as the unidirectionality of nystagmus under monocular vision. Birukow found the rostral in the frog Rana temporaria and presented indirect proof of the presence of an optokinetic after-reaction abolishing vestibular after-nystagmus. On the basis of optic nerve regeneration, Sperry found that retinal position and velocity signals rule the direction of gaze movements, even after functionally inadequate regeneration. Main visual relays in the control of optokinetic nystagmus are situated in the pretectum and the accessory optic nucleus. Vertical directional preferences in the accessory optic system and horizontal directional selectivity corroborate the lesion results.
Development of the Vertebral Joints (C3 through T2) in Man
Authors: Putz Reinhard
Published: April 2012

The wide range of literature on the primary development of the vertebral column is mainly concerned with the vertebral bodies and the intervertebral disks. The earliest conclusive document of the reorganization of the vertebral column was given by Sensenig. Tondury focused himself majorly on the time and order of appearance of the centers of ossification in the vertebrae, and the fusion of the neural arches with the bodies. It was Verbout who finally provided a clear view of the definitive segmentation of the elements of the vertebral column. Regarding clinical literature, a huge amount of work exists on the functional interpretation of the vertebral joints, which are referred as the “guide rails of movement.”
Head-Trunk Coordination and Locomotor Equilibrium in 3-to 8-Year-Old Children
Authors: Assaiante Christine , Amblard and Bernard
Published: April 2012

Thirty-six healthy normal children from three to eight years of age joined in this experiment. Six age groups of six children each were formed. The subjects were asked to walk normally on flat ground on a straight line drawn on flat ground or on a beam. Each of these locomotory tasks was made twice according to pseudorandom plan, so that for a particular task, the results of two trials with each subject could be averaged. The kinematics of the locomotor movements was analyzed through an optical automatic TV image processor. Three markers were arranged on a frame fixed to the subject's left shoulder to calculate positions and orientations of the trunk. The last marker was placed on the ankle joint in order to monitor stepping.
Relationship between Force and Cross-Sectional Area of Postcervical Muscles in Man: Influence of Variations in the Morphology of the Neck
Authors: Mayoux-Benhamou Marie-Anne , Wybier Marc , Barbet Jacques Patrick , Labbé Sylvain , Revel Michel
Published: April 2012

Neck muscles have both dynamic and static functionalities, since they move the head in all directions and since they also have a postural role as antagonists of gravity. The static function depends on the strength and endurance of these muscles. The spine is a single weight-bearing column, and it depends solely upon muscular strength for both its lateral and its anteroposterior stabilization. The normal curvature observed in the sagittal plane is constantly subject to gravitational torques, which tends to increase lordosis and cause the head to fall forward. The neck muscles must work against these two effects of gravity. Calculating the absolute force given by neck muscles in static situations needs an accurate knowledge of forces present and of lever arms involved.
Multidimensional Geometry Intrinsic to Head Movements around Distributed Centers of Rotation: A Neurocomputer Paradigm
Authors: Pellionisz Andáas J. , Goff Bertrand Le , Laczkó Jozsef
Published: April 2012

Neuroscience has increasingly polarized during the past decade. The narrowly focused searchlight targeted at the domain of microscopic components unmasked small details. As a result, molecular neurobiology has prospered. In turn, system neuroscience underwent a re-evaluation of its scope, its mathematical methods, and even its philosophical and theoretical foundation. The direction in which this broad searchlight should be targeted in order to illuminate overall neural net function has been questioned. A trend toward clarification has only recently started to unfold, under intense pressure from technologic implications in the quickly developing field of microcomputing. Research on neurocomputing aspects of gaze may thus significantly contribute to a rejuvenation of system neuroscience as it meets some important challenges.
Vestibular and Optokinetic Asymmetries in the Ocular and Cervical Reflexes
Authors: Pettorossi Vito E. , Errico Pierangelo , Ferraresi Aldo , Draicchio Francesco , Santarelli Rosa Maria , Bruni Rosa
Published: April 2012

Asymmetries of the vertical optokinetic reflex (VOKR) and the vertical vestibulo-ocular reflex (VVOR) have been observed in many species. Gains of upward OKR slow phases were higher than those of downward OKR slow phases. An upward preponderance was also observed in the VVOR of cats. This difference between upward and downward eye responses has been shown to be largely affected by gravity. Gravity also affects the VVOR response because the animals should be pitched around the interaural axis to a 90-degree incline to reveal such vertical vestibular asymmetry. In this condition, the vertical canals were stimulated without activating the otolithic receptors since the direction of gravity's action on the maculae was constant.
Cervicovestibular Interactions in Coriolis-Like Effects
Authors: Bles Willem , Bos Jelte E.
Published: April 2012

Human cervical mechanisms are very deeply connected to the vestibular system, and the contribution of the neck reflexes in postural control is mostly hidden. Consequently, neck reflexes are a subject of minor interest in neurology; clinical practice does not provide methodology to evaluate the contribution of the neck. However, because of the increasing number of patients with cervical ataxia due to acceleration trauma, research on the topic of cervicovestibular interactions is needed in order to find a methodology to sort out the contribution of the neck and the vestibular system in postural control. As a first approach to this research field, the authors did two pilot studies on horizon perception in healthy subjects.
Head Position versus Head Motion in the Inhibition of Horizontal Postrotary Nystagmus
Authors: Koenig Eberhard , Dengler Wilhelm , Fetter Michael , Hann Asta , Dichgans Johannes
Published: April 2012

A tilt from the prior erect position to a horizontal head position stimulates not only the otoliths but also the vertical semicircular canals and neck afferents. To clarify further the inputs needed for inhibition, the authors compared static head tilts having only one dynamic component with head movements giving predominantly dynamic components. In addition, intermittent head tilts of different durations and at different times after the stop were used to study the dynamics of the “dumping” process. Head tilts after the presumed end of the peripheral input were used to study whether the effect of the inhibitory stimulus changes in the absence of peripheral input from the horizontal semicircular canals.
Organization of the Motor Nuclei Innervating Epaxial Muscles in the Neck and Back
Authors: Sugiuchi Yuriko , Shinoda Yoshikazu
Published: April 2012

The epaxial muscles are axial muscles innervated by the dorsal rami of the spinal nerves. These muscles demonstrate continued action in such a way as to counteract gravity in a decerebrate preparation, and thus they are classified as physiologic extensors. The epaxial muscles, neck muscles in particular, are under the strong influence of long descending motor tracts, especially the vestibulospinal and reticulospinal tracts, and play a significant role in control of postures in standing, in locomotion, and even during voluntary movements of extremities. A relatively small phylogenetic change of the epaxial musculature has occurred from the lower vertebrates to the mammals, as compared with the striking phylogenetic transformation of the hypaxial musculature among vertebrates.
Electrophysiology and Pharmacology of Two Types of Neurons in the Medial Vestibular Nucleus and Nucleus Gigantocellularis of the Guinea Pig In Vitro
Authors: Serafin Mauro , Khateb Asaid , Waele Catherine De , Vidal Pierre Paul , Mühlethaler Michel
Published: April 2012

The importance of intrinsic membrane properties in shaping the firing pattern of neurons in the mammalian central nervous system is well recognized. Despite a significant literature in vivo, neither the vestibular system nor the reticulospinal systems have yet been investigated in this respect. It is of interest to identify whether such neurons are endowed with complex intrinsic properties, because they might play a crucial role in some aspects of sensory-motor transformations. The authors restricted themselves to neurons either of the medial vestibular nucleus (MVN) or the nucleus gigantocellularis (NCG). The latter were documented in an area situated above the inferior olive that is known to contain mostly reticulospinal neurons.
Spatial Innervation Patterns of Single Vestibulospinal Axons in Neck Motor Nuclei
Authors: Shinoda Yoshikazu , Ohgaki Tohru , Sugiuchi Yuriko , Futami Takahiro
Published: April 2012

Eye and head position control is an ideal paradigm for studying how central nervous system mechanisms interact to stabilize a multidimensional motor system. Head movement signals detected by the semicircular canals are mediated through vestibulo-ocular and vestibulocollic pathways that line each of the three semicircular canals to a set of eye and head muscles. For tasks needing compensatory eye and head movements, the central nervous system will program muscles to respond in particular combinations rather than to generate an infinite variety of muscle contraction patterns. Single unit recording in animals engaging in motor behavior made it possible to analyze temporal and quantitative aspects of neuronal activities in different parts of the CNS with regard to various movement parameters.
Single Vestibular Unit Recordings in the Alert Cat during Active and Passive Head Movements
Authors: Fuller James H.
Published: April 2012

Recordings of single neurons in conscious animals started over three decades ago. In unrestrained animals, this activity was documented extracellularly and the recorded neuron was referred to as a “single unit.” Shortly after, single units were recorded in sensory-motor areas of the brain in which timing was often used to differentiate motor from sensory neuronal activity. If a cell's firing rate was systematically modified and tightly coupled to a short interval before the onset of the movement, it was assumed to be linked with motor activity. If it started after movement and/or synchronized with the leading edge or onset of a stimulus, it was assumed to be linked with sensory events.
Reticulospinal Control of Head Movements in the Cat
Authors: Sasaki Shigeto
Published: April 2012

When a new object appears in the periphery of the visual field, animals direct their head and eyes to it (orienting movements). Movements of the head play a critical role in the orienting movements, especially in animals such as cats, in which the range of oculomotor movements is restricted. The superior colliculus and frontal oculomotor areas have been shown to be in involved in the control of orienting movements. Stimulations of the tectum and the cerebral peduncle have been shown to evoke disynaptic excitatory postsynaptic potentials (EPSPs) in neck motoneurons in cats. The tectal and pyramidal EPSPs are mediated by common relay neurons in the lower brain stem.
Contribution of Reticulospinal Neurons to the Dynamic Control of Head Movements: Presumed Neck Bursters
Authors: Grantyn Alexey , Berthoz Alain , Hardy Olivier , Gourdon Antoine
Published: April 2012

This chapter only deals with the immediate premotor neuronal organization of this coordination at the level of the brain stem. It is known that the activity of the superior colliculus contributes to the initial saccade and the head movement. The afferent collicular neurons of the crossed tectoreticulospinal pathways activate a network of neurons in the brain stem that produces the premotor neuronal signals. It is well established that the signals that are carried by descending tectoreticulospinal neurons (TRSNs) are mainly phasic bursts. It is discussed that their firing rate is related to either eye velocity or dynamic motor error signals.
Control of Vertical Head Movement via Forel's Field H
Authors: Isa Tadashi , Itouji Toru , Sasaki Shigeto
Published: April 2012

Reticulospinal neurons (RSNs) in the medial pontomedullary reticular formation have been suggested as being the relay station of the disynaptic pathways from the superior colliculus and the cerebral cortex to the dorsal neck motoneurons. A unilateral lesion of the nucleus reticularis pontis caudalis (NRPC) and the rostral part of the nucleus reticularis gigantocellularis (NRG) produced by kainic acid injection resulted in a severe impairment of ipsiversive orienting movements of the eyes and head in the horizontal direction. This suggests that this region plays a vital role in controlling horizontal orienting movement. However, vertical orienting movement appeared to be unfazed after the lesion, suggesting that it is regulated by separate pathways.
Role of the Lateral Mesencephalic Reticular Formation in the Control of Head Movements
Authors: Hardy Olivier , Mirenowicz Jacques
Published: April 2012

It is possible to consider that there are two types of combined eye and head movements involved in two behavioral strategies. In one, the objective of slow eye movements is to compensate head movements. For that aim, the eyes move in the direction opposite to head turning, stabilizing the visual world on the retina. In the second strategy, the eyes and the head rapidly move in the same direction in order to orient the gaze toward a visual stimulus or a particular direction of space but without any strict fixation constraint. Compared to the former, the rapid eye movement can be characterized as anticompensatory because the eyes move in the same direction as the head.
Brain Stem Control of Coordinated Eye-Head Gaze Shifts
Authors: Tomlinson R. David , Bance Manohar
Published: April 2012

Recent experiments have proven that the vestibulo-ocular reflex (VOR) does not simply sum with vestibular eye movement commands during combined eye-head gaze saccades. Instead, if VOR gain is measured during combined eye-head gaze shifts, the gain is found to be a function of amplitude, decreasing from near unity during small-amplitude saccades to near zero at large amplitudes. In spite of this observation, large-amplitude saccades remain precise even if the head is perturbed during the movement. Since the VOR is not functional during these perturbed saccades, the eye trajectory does not change in response to this perturbation. Instead, the maintenance of saccadic accuracy is made by the changes in the movement duration.
Non-linear Dynamics of Involuntary Head Movements
Authors: Goldberg Jefim
Published: April 2012

This chapter discusses the sensory-motor origins of involuntary head movements. These movements can be regarded as a continuous sequence of deviations and succeeding corrections effected by sensory-motor mechanisms. This is important in the maintenance of static equilibrium in the vertical posture. The concept of pendulum models of equilibrium dynamics is also discussed in this chapter. It is used to represent the whole-body equilibrium in the upright posture. This model belongs to the general class of second-order dynamic systems. Moreover, the spectral analysis of involuntary head movements is also employed in this chapter. Utilizing the Fourier spectral methods, the head movement is decomposed into a sum of sinusoidal components of different frequencies and amplitudes. Based on the discussion of results, it is concluded that quantitative analysis of movement behaviors would provide a more useful measure of understanding dynamic properties than Fourier methods or other methods.
Active Head Movement Analysis of Vestibulo-ocular Reflex Dynamics
Authors: OʼLeary Dennis P. , Davis Linda L.
Published: April 2012

The primary role of the vestibulo-ocular reflex (VOR) is to stabilize the eyes for clear vision throughout angular eye movements. Another alternative approach to VOR testing at higher frequencies is to use active head oscillations in which a rotational sensor attached to a head strap would monitor head movement. This method needs the use of a computer and other technology in its implementation. In this chapter, the use of active head oscillations for VOR testing is reviewed in laboratories. Previous research on active head movements are also presented in the chapter. These previous studies employed active head movements at frequencies both below and above 2 Hz with an earth-fixed visual target. Certain physiologic considerations in using active head movements in place of passive chair rotations are also clarified in this chapter. The methods, test protocol, and data acquisition and analysis in VOR testing are sequentially explained. Meniere's disease is also briefly discussed.
Effect of Freeing the Head on Eye Movement Characteristics during Three-Dimensional Shifts of Gaze and Tracking
Authors: Collewijn Han , Steinman Robert M. , Erkelens Casper J. , Pizlo Zygmunt , Steen Johannes Van Der
Published: April 2012

This chapter considers the primary method used in studying the binocular control of gaze while an unrestrained subject viewed close target objects. Also presented here is the first comparative analysis of two types of oculomotor performance: performance in a head-free condition versus performance in a “bite board” (head fixed condition). The subjects made saccades between two stationary targets and tracked a target that moved both in a lateral direction and in depth. This chapter also shows that head-free saccades are faster than saccades made using the head on a bite board, and head-free three-dimensional pursuit does not differ significantly from the pursuit with the head on a bite board. This work has concluded that it is feasible to record binocular gazed behaviors in unrestrained subjects. Another conclusion is that the performance of oculomotor control is excellent in generally natural conditions.
Coordination of Head and Eyes during the Performance of Natural (and Unnatural) Visual Tasks
Authors: Kowler Eileen , Pizlo Zygmunt , Zhu Guo-Liang , Erkelens Casper J. , Steinman Robert M. , Collewijn Han
Published: April 2012

According to Lashley, the key in achieving coordinated patterns of action was to program diverse motor responses with reference to a single, central spatial map and a single internal clock. This chapter studies the coordinated head and eye movements during natural and unusual performance of visual tasks, and the results of the investigations in scanning the unusual head-eye movement combinations. Three characteristics were revealed regarding the normal coordination of head and eye movements. The first one is that moving the head can increase saccades rate. The second is that the ability to perform unusual patterns of head and eye movements is different during a task with clear cognitive components than during less natural tasks when the observer tries to direct the eye to an eccentric target without cognitive significance. Lastly, there is a natural tendency to program head and eye movements concurrently in similar spatial and temporal patterns.
Gaze Saccades to Visual Targets: Does Head Movement Change the Metrics?
Authors: Becker Wolfgang , Jürgens Reinhard
Published: April 2012

In this chapter, the authors addressed the question of the degree to which gaze saccades executed under natural conditions are modulated by concomitant head movements by creating a “quasi-natural” situation. Head-fixed saccades were compared to head-free saccades. The first experiment in this study cannot prove or disprove the validity of Bizzi's classical summation hypothesis for human gaze saccades confined to the oculomotor range. It rather demonstrates that the presence of a classical VOR is irrelevant for the velocity of such gaze saccades since the concurrent head movement starts too late and is too slow to impart to the saccade a significant gain in velocity in the event of a disconnected VOR. The second experiment confirms that the factor of greater importance for the dynamics of head-free saccades is the orbital eccentricity and direction of the EiH contribution to saccades.
Eye-Head Coordination During Active and Passive Head Rotations in the Dark
Authors: Schmid Roberto , Zambarbieri Daniela
Published: April 2012

Vestibular nystagmus is believed to be related to a strategy of eye-head coordination aimed to quickly orient the gaze toward a point of interest. This was suggested by Melvill Jones in 1964. Thus, in order to give further support for the interpretation of vestibular nystagmus, the authors compared eye-head coordination during active and passive head rotations in the dark by adopting similar profiles of head movement. The experiments involved subjects that were seated in the dark wearing lightweight helmets with lamps. The subjects were advised to slowly orient their heads to a position while the profiles of their head movements were recorded. The results in this study support the hypothesis that the orienting saccades observed during active head rotation is of the same nature with the fast phases of vestibular nystagmus evoked by passive rotation.
Identification of Peripheral Visual Images in a Laterally Restricted Gaze Field
Authors: Semmlow John L. , Gauthier Gabriel M. , Vercher Jean-Louis
Published: April 2012

The study in this chapter aims to assess the effects of degraded peripheral vision on visual performance. A series of preliminary psychological experiments were conducted to evaluate identification task performance in unrestricted viewing conditions in terms of the required time to identify a peripherally located three-digit number. This study is inspired by the case of decreased performance and discomfort of patients wearing corrective lenses with distorted peripheral fields. The experiments in the study involve three subjects whose head and eye movements were simultaneously recorded using an infrared reflection technique and an ultrasonic head movement monitor, respectively. A block diagram of a model to represent the task of identifying eccentric targets during restricted peripheral vision is constructed in this chapter. It is concluded that identification of peripheral targets when peripheral vision is restricted requires a coordinated and precise motor response from head and eyes.
Visual and Vestibular Contributions to Head-Eye Coordination during Head-Free Pursuit
Authors: Barnes Graham R. , Lawson Jane F.
Published: April 2012

This chapter presents the results of the experiments that indicate that there is little evidence to support the existence of a central cancellation mechanism of the VOR in normal human subjects, as proposed by Robinson. The changes in gaze velocity with the frequency composition of the stimulus are discussed in this chapter. The enhancement of the highest frequency component is presented. The role of the vestibulo-ocular reflex during head-free pursuit is analyzed and investigated here. It is concluded that although there is little evidence to support the central cancellation hypothesis, other nonvisual mechanisms may have a role in vestibulo-ocular reflex suppression.
Mathematical Modeling of Visual and Nonvisual Mechanisms of Head-Eye Coordination
Authors: Barnes Graham R.
Published: April 2012

The gain of eye velocity during head-fixed pursuit is significantly modified by the frequency composition of a mixed-frequency, pseudorandom stimulus. The model of the visual and nonvisual control of smooth eye movement that has been developed is discussed here, as well as the results of a series of experiments related to head-eye coordination. In order to simulate the changes in gain and phase of eye velocity that occur during a number of oculomotor tasks, a model of oculomotor control is presented here. The results of the experiment indicate that there are two separate mechanisms involved in the visual control of eye movement. Evidence suggests that optimal VOR suppression can be achieved only through visual feedback.
Timing of Coordinated Head and Eye Movements during Changes in the Direction of Gaze
Authors: Steen Johannes Van Der
Published: April 2012

The objective of this chapter is to present the effects of voluntary control and stimulus conditions on three types of oculomotor behavior that were previously regarded as different subsystems. Examples are given in this chapter to illustrate that performance is determined by stimulus conditions and voluntary processes. The primary contribution of head movements to saccadic gaze shifts is a reduction of the duration of the gaze shift that results in different characteristics of the velocity profile. These experiments aim to study interactions between saccades and vergence or pursuit and vergence, and to give more insight into the degree to which the performance of the head motor systems and oculomotor behavior is determined by processing in modular subsystems.
Decoding of Optic Flow by the Primate Optokinetic System
Authors: Miles Frederick A. , Schwarz Urs , Busettini Claudio
Published: April 2012

The major concern in this chapter is the review of the recent argument of Miles which explains that the visual backup to the two labyrinth reflexes (rotational vestibulo-ocular reflex (RVOR) and translational vestibulo-ocular reflex (TVOR)) is provided by two individual tracking systems. One tracking system is the classical optokinetic system (OKR), which provides backup to canal-ocular reflexes and mainly deals with rotational disturbances of gaze. The other one provides the backup to otolith-ocular reflexes and mainly deals with translational disturbances of gaze. This chapter also offers some cautionary words concerning the decomposition of optic flow into rotational and translational components. It is suggested that the pursuit system be deployed by some attentional focusing mechanism.
Perception of Liminal and Supraliminal Whole-Body Angular Motion
Authors: Benson Alain J. , Brown Sally F.
Published: April 2012

Understanding the head-neck system involves knowledge about the sensitivity and dynamics of the ampullary receptors of the semicircular canals, the macular receptors of the otolith organs, and the cervical mechanoreceptors. This chapter deals with the perception of sensory information from the semicircular canals engendered by whole-body angular motion stimuli. Thresholds for the detection of discrete angular movements in x, y, and z axes are presented in this chapter. Moreover, the effects of head-fixed visual display and stimulus duration on thresholds are discussed. It is concluded that although there is a complex interrelationship between velocity, acceleration, and frequency in determining the subjective intensity of whole-body angular acceleration, the experiments using supraliminal stimuli are in agreement with the studies about thresholds.
Cortical Representation of Head-in-Space Movement and Same Psychophysical Experiments on Head Movement
Authors: Grüsser Otto-Joachim , Guldin Wolfgang , Harris Lawrence , Lefèbre Johann-Christoph , Pause Max
Published: April 2012

The contribution of multimodal signals to the perception of head movements is discussed in this chapter. The experimental methods and the anatomic connections of the parieto-insular vestibular cortex (PVIC) in primates are presented here, as well as the description of the responses of single nerve cells in the PIVC to visual, vestibular, and somatosensory stimulation. The second part of this chapter contains a discussion of the latest psychophysical experiments performed in the laboratory with results that indicate the functional involvement of the PVIC beyond vection by optokinetic stimulation. It is concluded that the neurophysiological experiments performed provided strong evidence for the existence of a complex cortical neuronal network in the primate monitoring of the rotary movements of the head in space.
Eye-Head Coordination in Oblique Gaze Shifts in Cats
Authors: Roucoux André , Crommelinck Marc , Borel and Liliane
Published: April 2012

This chapter focuses on the discussion of the characteristics of neck muscle command signals and the descriptions of the aspects of head movement trajectories, eye saccades, and the coordination in visually triggered oblique gaze shifts by trained cats. The methods in the eye and head movement recording and the training procedure and experimental paradigm are presented. The results of the activity are explained in detail in this chapter, including (1) the timing of the neck muscle discharge as a function of the orientation of the head movement and (2) the temporal aspects of eye-head component coordination.
Vestibulo-Ocular Reflex Inhibition Mechanism during Goal-Directed Saccades in Man
Authors: Pélisson Denis , Prablanc Claude
Published: April 2012

It has been shown from recent studies that concurrent head velocity affects gaze shift kinematics due to an inhibition of the VOR during the saccade in man. The goal of this study is to quantify the VOR-saccade interactions during small gaze shifts. A procedure of passive head rotation is thus designed to be able to quantify VOR gain associate with gaze shifts of even smaller amplitude. The main findings are summarized in the gaze velocity profiles. It was found that when saccadic response is executed when the head is moving in the same direction, gaze velocity is faster than when the head is fixed. Another finding is that the gaze shift duration is inversely related to gaze shift velocity.
Do Head Position and Active Head Movements Influence Postural Stability?
Authors: Straube Andreas , Paulus Walter , Brandt Thomas
Published: April 2012

The differential effects of voluntary head movements (horizontal oscillations about the z axis) and varying head positions on postural sway are investigated in this chapter. The methods of the experiments are presented here. Ten subjects took part in the experiments, where their head movements were recorded using a head-fixed angular accelerometer. The main finding of the experiment is that the differential effects of varying head positions were surprisingly small. Moreover, the body sway does not significantly increase with head rotation and that indicated the precise reevaluation of head sway with respect to the head position relative to the trunk.
Influence of Tactile Cues on Visually Induced Postural Reactions
Authors: Young Lawrence R. , Standish Gail
Published: April 2012

The primary focus of this study is multi-sensory integration and its motor control and behavioral consequences. The series of experiments involve moving a spatial visual stimulus provided by a roughly hemispherical “rotating dome” filling the subject's field of view. It is discussed in this chapter how elementary reflexes that act to maintain an animal's head in the upright position depend upon numerous sensory inputs acting independently or in a group. This study demonstrates that the presence of lateral forces on the shoulders is enough to inhibit visually induced motion and the associated postural reactions of the neck and trunk.
Differential Influence of Vertical Head Posture during Walking
Authors: Zangemeister Wolfgang H. , Bulgheroni Maria V. , Pedotti Antonio
Published: April 2012

This study involves a kinematic analysis based on the examination of trajectories, velocities, and accelerations of all markers. The two questions pursued in this study are: (1) would it be possible to distinguish responses from subjects when normal humans walked under three different conditions of vertical head posture? (2) how could results fit into recent observations on the linkage between gaze position, otolith influences, and neck muscles as the uppermost part of the truncal/skeletal muscles? The results showed that the otolith input appears to dominate particularly neck prioceptive and gaze motor influences during normal gait. Thus, postural control depends on the integration of vestibular, somatosensory, and visual orientation signals.
Head-Shaking Nystagmus—A Tool to Detect Vestibular Asymmetries in Patients
Authors: Koenig Eberhard , Fetter Michael , Takahashi Sachiko , Dichgans Johannes
Published: April 2012

Head-shaking nystagmus (HSN) is a transient nystagmus which is a result of a unilateral peripheral hypofunction based on Ewald's second law. This law states that there will be a stronger response of a labyrinth to excitatory than to inhibitory inputs with high-velocity stimuli. This chapter aims to understand the degree to which the HSN may be explained by the two hypotheses — unilateral peripheral hypofunction or asymmetry of central velocity storage — and to evaluate the correlation between HSN and SPN. It is concluded that the horizontal head-shaking maneuver is a highly sensitive method for detecting vestibular asymmetries resulting from the unilateral vestibular hypofunction or imbalance in the central velocity storage.
Effect of Peripheral Vestibular Disorders on Head-Trunk Coordination during Postural Sway in Humans
Authors: Shupert Charlotte L. , Horak Fay Bahling , Black F. Owen
Published: April 2012

The experiments in this study were performed to analyze how head motion is controlled during postural sway in two groups of patients with vestibular disorders and in normal subjects. The subjects were tested in conditions that resulted in postural sway primarily about the ankles, with little motion of the trunk, and in conditions that led to large motions of the body about the hips, with substantial motion of the trunk. The results have shown that the head and trunk movements are uncoordinated in normal subjects and patients with severe bilateral deficits. The results also indicated that when postural sway results in large movements of the trunk, the head movements of the normal subjects are controlled in a way that provides a stable platform for the vestibular and visual systems.
Eye-Head Coordination in Normal and Hemilabyrinthectomized Cats
Authors: Borel Liliane , Lacour Michel
Published: April 2012

This chapter studies the properties and the functional coupling of four sensory-motor subsystems that contribute to the head and eye stabilization during linear motion in the vertical plane. The problems investigated in this chapter include the way the reflexes interact and are functionally coupled and the solutions relating to the central nervous system (CNS) when the there is an impaired eye-head coordination. The dynamics of the vestibulocollic reflex, oculocollic coupling, and the compensatory eye movements are discussed here. It is concluded that tight coupling between the visual and vestibular systems in head postural control and gaze stabilization also operates during linear motion in the vertical plane.
Vestibular Compensation: Sensitive Period and Role of Sensory-Motor Activity in Substitution Processes
Authors: Zennou-Azogui Yohʼi , Xerri Christian
Published: April 2012

This chapter discusses vestibular compensation as a multisensory substitution process. The contribution of somatosensory afferents, the remaining labyrinthine afferents, and the visual afferents are also explained in this chapter. The authors also studied the effect of sensory motor restriction (SMR) on the recovery of locomotor equilibrium after unilateral vestibular neurectomy. The behavioral and neurophysiologic studies show the critical part that a substitution process can play in vestibular compensation. It is concluded that the sensory data transmitted to the central nervous system (CNS) could play a substitutive role in the recovery of dynamic function if they are available at an early and delimited period of compensation.
Response Characteristics of Central Vestibular Neurons and Compensatory Mechanisms following Hemilabyrinthectomy
Authors: Chan Ying-Sing , Hwang Joseph C.
Published: April 2012

The changes in vestibular neuronal activities that accompany hemilabyrinthectomy (HL) are the main focus of this study. The emphasis is on the acute and chronic changes in relation to the otolith system in response to HL. The compensatory process after HL is also discussed in relation to the involvement of neural structures and changes in synaptic mechanisms. The semicircular canal system and the otolith system are discussed in this chapter. The acute hemilabyrinthectomy, otolith function with bilateral labyrinths intact, and the response sensitivity and spatial coding properties of central vestibular units in the lesioned side are also described. The findings imply that inputs from the intact otoliths and/or semicircular canals in the lesioned animals are operative at the level of the vestibular nuclei bilaterally during natural head movements.
Vestibular N-Methyl-d-Aspartate Receptors in Normal and Compensated Guinea Pigs
Authors: Waele Catherine De , Vibert Nicholas , Berthoz Alain , Vidal Pierre Paul
Published: April 2012

The postural syndromes observed after unilateral global and selective lesions of the vestibular apparatus are discussed in the first part of this chapter. The second part includes the results that suggest that N-methyl-D-aspartate (NMDA) receptors contribute to the resting discharge of the vestibular neurons in normal guinea pigs in vivo. The third part contains the recommendation to increase the number and/or sensitivity of NMDA receptors on deafferented neurons in order to create denervation hypersensitivity. This could contribute to the functional recovery of the static reflexes in hemilabyrinthectomized guinea pigs.
Effects ofN-Methyl-d-Aspartate Receptor Antagonists on Vestibular Compensation in the Guinea Pig: In Vivo and In Vitro Studies
Authors: Smith Paul F. , Darlington Cynthia L.
Published: April 2012

This study investigates the contribution of NMDA receptors to vestibular compensation for UL in the guinea pig using the NMDA receptor/channel antagonists. Three experimental approaches were taken to examine the effect of NMDA antagonists on vestibular compensation. The results imply that NMDA receptor antagonists interfere with vestibular compensation during a limited period following UL. It is found that noncompetitive NMDA antagonists MK801 have a binding site similar to dissociative anesthetics such as ketamine.
Subjective Visual Vertical and Eye-Head Coordination (Roll) with Brain Stem Lesions
Authors: Marianne Dieterich , Brandt Thomas
Published: April 2012

The ocular tilt reaction (OTR) models a fundamental pattern of coordinated eye-head roll motion based on utricular/saccular as well as vertical canal input, made by the gaviceptive pathways from the labyrinths via pontomedullary vestibular nuclei to the rostral midbrain tegmentum. The direction of eye-head tilt in roll with brain stem lesions and the skew deviation and cyclorotation is discussed in this chapter. It is concluded that all patients with the OTR showed significant deviations of the subjective visual vertical (SVV) in the direction of the head tilt. The single features of the OTR, perceptual and oculomotor, can be induced separately depending on the site of the lesion.
Cervical Contribution to Balance: Cervical Vertigo
Authors: Brown Jeffrey J.
Published: April 2012

Dizziness is described as any alteration or perversion of the sense of balance. In this chapter, the evidence to support the diagnosis of the syndrome of imbalance that resulted from disturbance of cervical joint receptors is presented and tackled. Various experimental supports are presented in this chapter. Also, cervical vertigo syndrome is discussed in detail, including its definition and symptoms. The diagnostic dilemmas are also briefly discussed, such as the complaints that complicate the diagnosis of cervical vertigo due to the subjective signs of the disease. It is recommended from experimental evidence that there should be a validity of the diagnosis of cervical vertigo because of the increasing number of patients with characteristic syndrome.