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

Positron emission tomography (PET) and functional magnetic resonance imaging (fMRI) have been extensively used to explore the functional neuroanatomy of cognitive functions. Here we review 275 PET and fMRI studies of attention (sustained, selective, Stroop, orientation, divided), perception (object, face, space/motion, smell), imagery (object, space/ motion), language (written/spoken word recognition, spoken/ no spoken response), working memory (verbal/numeric, object, spatial, problem solving), semantic memory retrieval (categorization, generation), episodic memory encoding (verbal, object, spatial), episodic memory retrieval (verbal, nonverbal, success, effort, mode, context), priming (perceptual, conceptual), and procedural memory (conditioning, motor, and nonmotor skill learning). To identify consistent activation patterns associated with these cognitive operations, data from 412 contrasts were summarized at the level of cortical Brodmann's areas, insula, thalamus, medial-temporal lobe (including hippocampus), basal ganglia, and cerebellum. For perception and imagery, activation patterns included primary and secondary regions in the dorsal and ventral pathways. For attention and working memory, activations were usually found in prefrontal and parietal regions. For language and semantic memory retrieval, typical regions included left prefrontal and temporal regions. For episodic memory encoding, consistently activated regions included left prefrontal and medial-temporal regions. For episodic memory retrieval, activation patterns included prefrontal, medial-temporal, and posterior midline regions. For priming, deactivations in prefrontal (conceptual) or extrastriate (perceptual) regions were consistently seen. For procedural memory, activations were found in motor as well as in non-motor brain areas. Analysis of regional activations across cognitive domains suggested that several brain regions, including the cerebellum, are engaged by a variety of cognitive challenges. These observations are discussed in relation to functional specialization as well as functional integration.

Imaging Cognition II: An Empirical Review of 275 PET and fMRI Studies

Imaging the premotor areas.

One fundamental function of primary motor cortex (MI) is to control voluntary movements. Recent evidence suggests that this role emerges from distributed networks rather than discrete representations and that in adult mammals these networks are capable of modification. Neuronal recordings and activation patterns revealed with neuroimaging methods have shown considerable plasticity of MI representations and cell properties following pathological or traumatic changes and in relation to everyday experience, including motor-skill learning and cognitive motor actions. The intrinsic horizontal neuronal connections in MI are a strong candidate substrate for map reorganization: They interconnect large regions of MI, they show activity-dependent plasticity, and they modify in association with skill learning. These findings suggest that MI cortex is not simply a static motor control structure. It also contains a dynamic substrate that participates in motor learning and possibly in cognitive events as well.

https://www.uta.edu/rfmems/Telemetry/Implant%20Sensor/47185_Plasticity%20and%20primary%20motor%20cortex.pdf

Plasticity and primary motor cortex.

Deep brain stimulation (DBS) has provided remarkable benefits for people with a variety of neurologic conditions. Stimulation of the ventral intermediate nucleus of the thalamus can dramatically relieve tremor associated with essential tremor or Parkinson disease (PD). Similarly, stimulation of the subthalamic nucleus or the internal segment of the globus pallidus can substantially reduce bradykinesia, rigidity, tremor, and gait difficulties in people with PD. Multiple groups are attempting to extend this mode of treatment to other conditions. Yet, the precise mechanism of action of DBS remains uncertain. Such studies have importance that extends beyond clinical therapeutics. Investigations of the mechanisms of action of DBS have the potential to clarify fundamental issues such as the functional anatomy of selected brain circuits and the relationship between activity in those circuits and behavior. Although we review relevant clinical issues, we emphasize the importance of current and future investigations on these topics.

/pdf/deep-brain-stimulation-262qpo74ya.pdf

Deep Brain Stimulation

van Mier, H, L W Tempel, J S Perlmutter, M E Raichle, and S E Petersen Changes in brain activity during motor learning measured with PET: effects of hand of performance and practice J N

Changes in brain activity during motor learning measured with PET: effects of hand of performance and practice.

We evaluated sensorimotor processing in patients with writer9s cramp using PET and H 2 15 O blood flow scans. The study included six right-handed patients with unilateral writer9s cramp and eight right-handed normals. Subjects had blood flow scans at rest and during vibration of either the “affected” or “unaffected” hand. Vibration produced a consistent peak response in primary sensorimotor area (PSA) and supplementary motor area (SMA), both contralateral to the vibrated hand. Both responses were significantly reduced approximately 25% in patients with writer9s cramp (PSA, p = 0.002; SMA, p = 0.02) whether vibrating the affected or unaffected hand. This indicates that patients with unilateral writer9s cramp have bilateral brain dysfunction. These data provide objective evidence of abnormal central sensorimotor processing in writer9s cramp.

Abnormal cortical responses in patients with writer's cramp.

Previous studies of cerebral oxygen metabolism and extraction in patients with subarachnoid hemorrhage (SAH) have yielded conflicting results. We used positron emission tomography (PET) to measure ...

https://journals.sagepub.com/doi/pdf/10.1038/jcbfm.1991.143

Cerebral Oxygen Metabolism after Aneurysmal Subarachnoid Hemorrhage

The importance of hemodynamic factors in the pathogenesis and treatment of ischemic cerebrovascular disease is not clear. We have investigated the relationship between cerebral hemodynamics and the subsequent risk of stroke in 30 medically treated patients with symptomatic occlusion or greater than 75% intracranial stenosis of the carotid arterial system. Positron emission tomography (PET) was used to evaluate the regional hemodynamic status of the cerebral circulation. Clinical follow-up to 1 year post-PET was available for all patients. The incidence at 1 year of all strokes was 1/9 for patients with normal hemodynamics and 1/21 for patients with abnormal hemodynamics. The 1-year incidence of ipsilateral ischemic stroke was 1/9 for hemodynamically normal patients and 0/21 in the abnormal group. The 21 patients in the abnormal group fulfilled entry criteria for the Extracranial-Intracranial Bypass Trial. The 0/21 incidence of ipsilateral ischemic stroke at 1 year was compared with the 1-year rate of 0.109 for the 714 medically treated patients from the Bypass Trial. We were able to reject with better than 90% certainty (p = 0.089) the hypothesis that our sample of patients came from a population with an ipsilateral ischemic stroke rate of 0.109 or greater. Thus, in this small sample, we found no evidence that PET evidence of abnormal cerebral hemodynamics identifies a subgroup of patients at higher risk for early stroke if treated medically with antithrombotic drugs.

Influence of cerebral hemodynamics on stroke risk: One‐year follow‐up of 30 medically treated patients

Task-induced changes in regional CBF (rCBF) can be measured with positron emission tomography (PET) and provide a powerful tool to map brain function. Many studies using these techniques have investigated responses in healthy young subjects. Since many pathological conditions occur more commonly in older subjects, it is necessary to compare blood flow responses in these patients with appropriately age-matched controls. Furthermore, the effects of normal aging on such blood flow responses remain unknown. For both reasons, we designed this study to determine whether vibration-induced CBF responses change with advancing age in normals. CBF was measured with PET and bolus-administered H2(15)O in 26 subjects from 20 to 72 years old (mean = 39; SD = 19). Regional responses were identified by subtraction-image analysis. Left and right hand vibration produced consistent responses in contralateral primary sensorimotor area (PSA) and supplementary motor area (SMA). Response magnitudes were compared to age by linear regression. There were no substantial relationships between age and responses to vibration for PSA or SMA (PSA r = -0.28, p = 0.054; SMA r = -0.33, p = 0.13). Power analysis demonstrates a high degree of confidence (99.7% for PSA and 87% for SMA) for detecting at least a moderate correlation (r = 0.6) between response magnitude and age. We conclude that the rCBF responses to vibrotactile hand stimulation do not change with normal aging.

Lee W. Tempel

Papers

Changes in brain activity during motor learning measured with PET: effects of hand of performance and practice.

Abnormal cortical responses in patients with writer's cramp.

Cerebral Oxygen Metabolism after Aneurysmal Subarachnoid Hemorrhage

Influence of cerebral hemodynamics on stroke risk: One‐year follow‐up of 30 medically treated patients

Vibration-induced regional cerebral blood flow responses in normal aging.