In this book Professor Holmes discusses some of the evidence relating to one of the most baffling problems yet recognized by biologists-the factors involved in the regulation of growth and form. A wide range of possible influences, from enzymes to cellular competition, is considered. Numerous experiments and theories are described, with or without bibliographic citation. There is a list of references for each chapter and an index. The subject from a scientific standpoint is an exceedingly difficult one, for the reason that very little indeed is understood regarding such phenomena as differentiation. It follows that the problem offers fine opportunities for intellectual jousting by mechanists and vitalists, that hypotheses and theories must often be the weapons of choice, and philosophy the armor. Professor Holmes gives us a good seat from which to watch the combats, explains clearly what is going on, and occasionally slips away to enter the lists himself. This stereoscopic atlas of anatomy was designed as an aid in teaching neuro-anatomy for beginning medical students and as a review for physicians taking Board examinations in Psychiatry and Neurology. Each plate consists of a pair of stereoscopic photographs and a labelled diagram of the important parts seen in the photograph. Perhaps in this day of scarcity of materials, particularly of human brains hardened for dissection, photographs of this kind conceivably can be used as a substitute. Successive stages of dissection are presented in such a fashion that, used in conjunction with the dissecting manual, a student should be able to identify most of the important components of the nervous system without much outside help. The area covered is limited to the gross features of the brain and brain stem and perhaps necessarily does not deal with any of the microscopic structure. So much more can be learned from the dissection of the actual brain that it is doubtful if this atlas would be useful except where brains are not available. A good deal of effort has been spent on the preparation of this atlas, with moderately successful results.

The Integrative Action of the Nervous System.

Modulating the experience of agency: a positron emission tomography study.

It is well accepted that pain is a multidimensional experience, but little is known of how the brain represents these dimensions. We used positron emission tomography (PET) to indirectly measure pain-evoked cerebral activity before and after hypnotic suggestions were given to modulate the perceived intensity of a painful stimulus. These techniques were similar to those of a previous study in which we gave suggestions to modulate the perceived unpleasantness of a noxious stimulus. Ten volunteers were scanned while tonic warm and noxious heat stimuli were presented to the hand during four experimental conditions: alert control, hypnosis control, hypnotic suggestions for increased-pain intensity and hypnotic suggestions for decreased-pain intensity. As shown in previous brain imaging studies, noxious thermal stimuli presented during the alert and hypnosis-control conditions reliably activated contralateral structures, including primary somatosensory cortex (S1), secondary somatosensory cortex (S2), anterior cingulate cortex, and insular cortex. Hypnotic modulation of the intensity of the pain sensation led to significant changes in pain-evoked activity within S1 in contrast to our previous study in which specific modulation of pain unpleasantness (affect), independent of pain intensity, produced specific changes within the ACC. This double dissociation of cortical modulation indicates a relative specialization of the sensory and the classical limbic cortical areas in the processing of the sensory and affective dimensions of pain.

https://www.physiology.org/doi/pdf/10.1152/jn.2001.86.1.402

Cortical Representation of the Sensory Dimension of Pain

Touching warm and cool bars that are spatially interlaced produces a painful burning sensation resembling that caused by intense, noxious cold. We demonstrated previously that this thermal grill illusion can be explained as an unmasking phenomenon that reveals the central inhibition of pain by thermosensory integration. In order to localize this unmasking in the human brain, we have used positron emission tomography (PET) to compare the cortical activation patterns evoked by the thermal grill and by cool, warm, noxious cold and noxious heat stimuli. The thermal grill illusion produces activation in the anterior cingulate cortex, whereas its component warm and cool stimuli do not. This area is also activated by noxious heat or cold. Thus, increased activity in the anterior cingulate cortex appears to be selectively associated with the perception of thermal pain. Disruption of thermosensory and pain integration may account for the central pain syndrome that can occur after stroke damage.

Functional imaging of an illusion of pain.

Unmyelinated afferents constitute a second system coding tactile stimuli of the human hairy skin. Impulses were recorded from unmyelinated afferents innervating the forearm skin of human subjects u...

https://www.physiology.org/doi/pdf/10.1152/jn.1999.81.6.2753

Unmyelinated afferents constitute a second system coding tactile stimuli of the human hairy skin.

Structural basis of information processing and neocortical neurotransmitters.- Divergence of thalamocortical projections and limits on somatosensory cortical plasticity.- Inhibitory circuitry in relation to the functional organization of somatosensory cortex.- Pain, temperature, and the sense of the body.- The functional role of a noninactivating sodium current in neocortical neurons.- Psychophysics of somatosensation.- Information processing channels in the sense of touch.- A novel approach for studying direction discrimination.- Tactile directional sensibility theoretical and functional aspects.- Experimental assessment of the temporal hypothesis of velocity scaling.- Vibrotactile adaptation of the RA system: A psychophysical analysis.- Tactile neural codes for the shapes and orientations of objects.- Tactual discrimination of softness: Abilities and mechanisms.- Representation of the shape and contact force of handled objects in populations of cutaneous afferents.- Haptic object processing I: Early perceptual features.- Haptic object identification II: Purposive exploration.- Cortical representation of somatosensation.- The somatosensory cortex.- The organization of lateral somatosensory cortex in primates and other mammals.- Serial processing in the somatosensory system of macaques.- Parallel processing in somatosensory areas I and II of the cerebral cortex.- Linearity as the basic law of psychophysics: Evidence from studies of the neural mechanisms of roughness magnitude estimation.- Form processing and attention effects in the somatosensory system.- Functional plasticity of cortical representations of the hand.- Sensory-motor interface.- Somatosensory signals and sensorimotor transformations in reactive control of grasp.- Strain-sensitive mechanoreceptors in the human skin provide kinaesthetic information.- A second tactile system in the human skin with unmyelinated primary afferents.- Factors influencing the perception of tactile stimuli during movement.- Changing the intended direction of movement.- Disturbances of motor behavior after parietal lobe lesions in the human.- Neuronal population behavior: Imaging techniques.- PET and fMRI scans of the cerebral cortex in humans and single neuron responses from SI in monkeys to rubbing embossed dot and grating patterns across a fingerpad.- Magnetic resonance functional mapping of cortical activation associated with differing sensorimotor hand paradigms.- Whole-head neuromagnetic recordings of human somatosensory cortical functions.- Optical imaging of intrinsic signals in somatosensory cortex.- Somatosensory and frontal cortical processing during pain experience.- Cortical Neurocomputation and modelling.- Local receptive field diversity within cortical neuronal populations.- Functional segregation and integration in the nervous system: Theory and models.

L. Terenius

Papers

Somesthesis and the neurobiology of the somatosensory cortex