Co-Planar Stereotaxic Atlas of the Human Brain—3-Dimensional Proportional System: An Approach to Cerebral Imaging, J. Talairach, P. Tournoux. Georg Thieme Verlag, New York (1988), 122 pp., 130 figs. DM 268

I have developed "tennis elbow" from lugging this book around the past four weeks, but it is worth the pain, the effort, and the aspirin. It is also worth the (relatively speaking) bargain price. Including appendixes, this book contains 894 pages of text. The entire panorama of the neural sciences is surveyed and examined, and it is comprehensive in its scope, from genomes to social behaviors. The editors explicitly state that the book is designed as "an introductory text for students of biology, behavior, and medicine," but it is hard to imagine any audience, interested in any fragment of neuroscience at any level of sophistication, that would not enjoy this book. The editors have done a masterful job of weaving together the biologic, the behavioral, and the clinical sciences into a single tapestry in which everyone from the molecular biologist to the practicing psychiatrist can find and appreciate his or

Principles of Neural Science

Brain-computer interfaces for communication and control.

The emergence of a unified cognitive moment relies on the coordination of scattered mosaics of functionally specialized brain regions. Here we review the mechanisms of large-scale integration that counterbalance the distributed anatomical and functional organization of brain activity to enable the emergence of coherent behaviour and cognition. Although the mechanisms involved in large-scale integration are still largely unknown, we argue that the most plausible candidate is the formation of dynamic links mediated by synchrony over multiple frequency bands.

The brainweb: phase synchronization and large-scale integration.

Prelude. Cycle 1. Introduction. Cycle 2. Structure defines function. Cycle 3. Diversity of cortical functions is provided by inhibition. Cycle 4. Windows on the brain. Cycle 5. A system of rhythms: from simple to complex dynamics. Cycle 6. Synchronization by oscillation. Cycle 7. The brain's default state: self-organized oscillations in rest and sleep. Cycle 8. Perturbation of the default patterns by experience. Cycle 9. The gamma buzz: gluing by oscillations in the waking brain. Cycle 10. Perceptions and actions are brain state-dependent. Cycle 11. Oscillations in the "other cortex:" navigation in real and memory space. Cycle 12. Coupling of systems by oscillations. Cycle 13. The tough problem. References.

Rhythms of the brain

The potential for peripheral nerve injury to reorganize motor cortical representations was investigated in adult rats. Maps reflecting functional connections between the motor cortex and somatic musculature were generated with intracortical electrical stimulation techniques. Comparison of cortical somatotopic maps obtained in normal rats with maps generated from rats with a facial nerve lesion indicated that the forelimb and eye/eyelid representations expanded into the normal vibrissa area. Repeated testing from an electrode placed chronically in the motor cortex showed a shift from vibrissa to forelimb within hours after facial nerve transection. These comparatively quick changes in motor cortex representation pattern suggest that synaptic relations between motor cortex and somatic musculature are continually reshaped in adult mammals.

Rapid reorganization of adult rat motor cortex somatic representation patterns after motor nerve injury.

The present study examined whether premovement central neural processing in Parkinson9s disease was related to functional motor disability and plasma L-dopa concentration. Reaction time (RT) performance in simple and choice RT tasks was assessed while plasma L-dopa levels were controlled by continuous IV L-dopa infusion in five parkinsonian patients. Five age-matched controls performed the same RT tasks for comparison. Simple RT for the patients was longer than the normal control RT at all infusion levels (p ≤ 0. 005). However, choice RT was normal when the patients were “on,” but became prolonged as plasma L-dopa levels decreased (p ≤ 0. 01). The results show that there are abnormalities of premovement central neural processing in Parkinson9s disease, and that simple and choice RTs are differentially affected by L-dopa replacement. This suggests that different neural mechanisms may be involved in the processing of these tasks.

Dopaminergic effects on simple and choice reaction time performance in Parkinson's disease.

The motor cortex includes several areas in the frontal agranular cortex. These areas receive inputs from sensory pathways, motor control structures, other cortical areas, and from "modulatory" pathways. Motor cortical outputs are widely distributed to many other parts of the nervous system and can thereby influence each of the major descending motor control pathways and spinal motor circuitry. The most intensively studied motor areas, the premotor area (PMA), supplementary motor area (SMA), and primary motor cortex (MI), appear to have different roles in movement. PMA is involved in coupling arbitrary cues to motor acts, whereas SMA appears to participate more in internal guidance or planning of movement. While MI has been implicated in control of muscle force or length, more recent data suggest that it encodes higher order parameters, such as movement direction. Two new views of motor cortex are presented. First, it is argued that MI contains functional subdivisions of the face, arm, and leg, and that each subdivision contains a highly overlapping, extensively interconnected and non-topographic internal organization. Second, motor representations can reorganize rapidly as a consequence of experience or peripheral lesions. These changes may arise through modifications in synaptic coupling among motor cortex neurons. These features of motor cortex suggest a role for motor cortex in learning and in performing voluntary movements.

Motor areas of the cerebral cortex.

Rapid voluntary limb movements are accompanied by a triphasic electromyogram (EMG): the agonist muscle discharges briefly to generate the initial limb displacement and then, in sequence, an antagonist and second agonist burst occur. The origins of these bursts of EMG have been attributed to both peripheral and central sources. We attempted to determine in human subjects whether somesthetic afferent inputs related to passive muscle stretch or joint rotation were necessary for the appearance of the three bursts. EMGs were recorded while subjects performed rapid isotonic movements before and after forearm afferent function was blocked by ischemia. EMG patterns were also studied during phasic and sustained isometric contractions of forearm muscles. When the forearm was ischemically deafferented the triphasic EMG pattern persisted though the amplitudes of the three bursts were modified. In separate experiments, a similar three burst pattern was also observed while phasic isometric contractions were performed but not when rapid-onset sustained isometric contractions were executed. These data support the view that somesthetic afferent information related to muscle length or joint rotation is not necessary for the occurrence of the three burst pattern during rapid motor behaviors. Since bursts of EMG activity were observed when torque rose and fell quickly during fast isotonic movements and phasic isometric contractions, the triphasic pattern appears to be a fundamental property of the central program underlying such rapid motor behaviors.

Centrally programmed patterns of muscle activity in voluntary motor behavior of humans.

Cortical areas engaged in knowledge manipulation during reasoning were identified with functional magnetic resonance imaging (MRI) while participants performed transitive inference (TI) on an ordered list of 11 items (e.g. if A < B and B < C, then A < C). Initially, participants learned a list of arbitrarily ordered visual shapes. Learning occurred by exposure to pairs of list items that were adjacent in the sequence. Subsequently, functional MR images were acquired as participants performed TI on non-adjacent sequence items. Control tasks consisted of height comparisons (HT) and passive viewing (VIS). Comparison of the TI task with the HT task identified activation resulting from TI, termed 'reasoning', while controlling for rule application, decision processes, perception, and movement, collectively termed 'support processes'. The HT-VIS comparison revealed activation related to support processes. The TI reasoning network included bilateral prefrontal cortex (PFC), pre-supplementary motor area (preSMA), premotor area (PMA), insula, precuneus, and lateral posterior parietal cortex. By contrast, cortical regions activated by support processes included the bilateral supplementary motor area (SMA), primary motor cortex (M1), somatic sensory cortices, and right PMA. These results emphasize the role of a prefrontal-parietal network in manipulating information to form new knowledge based on familiar facts. The findings also demonstrate PFC activation beyond short-term memory to include mental operations associated with reasoning.

/pdf/frontal-and-parietal-lobe-activation-during-transitive-2msohw00jf.pdf

Jerome N. Sanes

Papers

Rapid reorganization of adult rat motor cortex somatic representation patterns after motor nerve injury.

Dopaminergic effects on simple and choice reaction time performance in Parkinson's disease.

Motor areas of the cerebral cortex.

Centrally programmed patterns of muscle activity in voluntary motor behavior of humans.

Frontal and Parietal Lobe Activation during Transitive Inference in Humans