Gross Anatomy of the Parietal Operculum

A precise anatomical localization of SII within the inferior parietal lobule must consider the sulcal arrangement surrounding the parietal operculum. On average, the anterior and posterior borders of the parietal operculum are, respectively, the central sulcus and posterior ascending ramus of the Sylvian fissure.218 An imaginary lateral extension of the postcentral sulcus points to the middle of the parietal oper-culum, which is relatively co-extensive with the horizontal ramus of the Sylvian...

Ji

Schematic illustration of a parabolic flight maneuver (above) and a typical trace of the gravitoinertial force level (below). Each parabola contains approximately 20 s of steady 0 g and 1.8 g. B. In the free-fall phase of parabolic flight, the aircraft and passengers are accelerating toward earth at the same rate so it is possible to float. Lack of contact leads to loss of orientation relative to the aircraft if the eyes are closed. C. A sense of orientation is restored and...

The Somatosensory System In Prosimian Primates

Prosimian primates are varied in appearance and lifestyle (Wolfheim, 1983 Fleagle, 1999). They include lemurs, lorises, and galagos. Tarsiers have also been classified with prosimians, but form a distinctly separate line of primate evolution, one of a specialized, visual, nocturnal predator. Of the prosimians, the somatosensory system has been significantly studied only in galagos. There have been limited studies of S1 organization in other prosimians (Krishnamurti et al., 1976 Carlson and...

Remote Touch In Medicine

The results of our ongoing research program on remote touch also have potentially significant implications for the practice of medicine in the future. Physical contact offers powerful evidence that an object exists. Only haptics reliably and unambiguously convey information about the forces and vibrations arising from direct mechanical contact between the perceiver actor and objects in the environment. We describe such immediate contact between skin and surface as non-remote. Because contact...

The Computational Argument In Favor Of A Recurrent View Of Touch

Perhaps the most important computational advantage gained by having a recurrent model of touch is the demonstration that learning can be much more effective and general in these networks than in classical feedforward network architectures. An interesting discussion of this issue has been presented by Grossberg in a recent review article.47 By comparing two types of artificial networks (feedforward self-organizing and recurrent networks), Grossberg notes that classical feedforward...

Plasticity In Si Maps

2.7.1 Evidence from Animals Shows that SI Maps Can Change Related to difficulties in demonstrating detailed somatotopic maps in humans are possible effects due to the mechanisms responsible for cortical reorganization in adults after injuries (see reviews in References 53, 64, 120, 154, 155, and 193) or use and experience-dependent Of greatest significance are demonstrations that maps may be dynamic since reorganization can be immediate following local anesthesia64 or temporally timed...

Receptors Involved In The Control Of Locomotion

Sherrington (1906) elaborated on muscle sense, and defined proprioceptors as receptors mediating the conscious sensation of the body's own movements. He assumed proprioception to be mediated by receptors in muscles, joints, and ligaments (Sherrington 1906 Sherrington 1947). From the 1930s to the 1960s, physiologists (but not clinicians) came to believe that muscle receptor activity and therefore proprio-ception did not involve conscious sensation, but this view had to be reversed again when it...

The Potential Role Of Corticothalamic Feedback Projections In Tactile Information Processing

The FF model of touch completely ignores the fact that, like all other mammalian sensory systems, the somatosensory system also contains massive corticocortical and corticofugal feedback projections. For instance, in primates, feedforward soma-tosensory pathways terminate in four distinct somatosensory areas located in the anterior parietal cortex (areas 3a, 3b, 1, and 2). These areas are connected through feedforward corticocortical projections. Projections from the anterior parietal cortex...

References

Adams, N.C., Lozsadi, D.A., and Guillery, R.W., Complexities in the thalamocortical and corticothalamic pathways, European Journal of Neuroscience, 9, 204, 1997. 2. Albe-Fessard, D., Condes-Lara, M., Kesar, S., and Sanderson, P., Tonic cortical controls acting on spontaneous and evoked thalamic activity. In G. Macchi, A. Rus-tioni, and R. Spreafico, Eds., Somatosensory Integration in the Thalamus A Reevaluation Based on New Methodological Approaches, Elsevier, Amsterdam, 1983. 3. Andersen, P.,...

The Simian Elaboration

The somatosensory system is more complex in monkeys than in prosimian primates at the cortical level and perhaps at the thalamic level (Kaas and Pons, 1988 Kaas, 1993). At the level of the thalamus, we distinguish a ventroposterior nucleus (VP), a ventroposterior inferior nucleus (VPI), and a ventroposterior superior nucleus (VPS) as the main relay nuclei of the somatosensory information (Figure 1.4 Dykes et al., 1981 Nelson et al., 1981 Kaas et al., 1984 Cusick et al., 1985 Krubitzer and Kaas,...

The Problem Of Detecting Brain Plasticity

Important modifications in brain circuits can be quite difficult to detect. Small changes in synaptic strength, when distributed across many synapses and neurons, can be difficult to measure and quantify. Thus, plasticity is often demonstrated under rather unnatural conditions with the assumption that similar but less obvious changes occur under more natural conditions. One form of synaptic plasticity, long-term potentiation or LTP, for example, is typically studied in living slices of brain...

Central Pattern Generators And Sensory Feedback

6.7.1 Cyclical Motor Patterns Generated without Sensory Input Literally hundreds of studies in which sensory input has been reduced or abolished by deafferentation have since demonstrated beyond doubt that isolated neuronal networks in the CNS can generate the basic rhythmical motor patterns involved not only in walking but also in the activities of breathing, chewing, swimming, flying, scratching, paw-shaking, and autonomic functions such as micturition and sexual reflexes (Grillner 1975...

Neurophysiological Studies Of Tactile Attention

In this section, we briefly review the ascending and central pathways of the somatosensory system. We will later show that neurons at practically all stages within the system, starting at the level of the brain stem nuclei, have responses that are affected by the animal's focus of attention with neurons at higher levels of the central nervous system showing greater effects than neurons closer to the peripheral inputs. Afferent fibers entering the spinal cord separate into two parallel paths...