[Cortical localizations seen by the dynamic gamma-camera : a new approach in neuropsychology].

We present here the results obtained in the study of normal brain functions, in normal awake man performing normal voluntary tasks, by mean of new approach developed in our laboratory. Its principle lies on the fact that focal changes in cortical blood flow during brain function are due to the coupling between local function aand metabolism, which has been demonstrated in man during hand movement by Olesen (1971) and by Raichle and associates (1976). So far as the changes are focal (uni- or multifocal) they can be assessed by external measurement of focal cerebral blood flow (rCBF) with the 133Xenon clearance technique, provided that the detection apparatus used yields a proper spatial and temporal resolution. A temporal resolution of 45 sec. is made possible by the initial slope calculation of Olesen and coll. (1971), using intracarotid injection of isotope. The spatial resolution has been improved by the design of a special system using 254 scintillation detectors with individual collimation, each 8 mm ø, connected to individual ratemeters (Sveinsdottir et al., 1975). This allows the simultaneous processing of the 254 clearance curves by a small on-line Varian computer. The results are displayed as functional colour pictures of the brain on a T.B. screen, less than 3 min. after isotope injection. The studies have been performed to date in more than 200 patients, usually in connection with carotid angiography. 84 subjects could be classified as "normals+ because of lack of detectable brain lesion and of permanent symptoms, and they constitute the reference material for exploring normal brain functions. In each case one or two "rest" studies have been made for comparison with the test situations. The following observations were made: Resting pattern: with the patients lying in a quiet dark room with minimal sensory input the normal pattern is much the same in both hemispheres and it is characterized by higher flows in the anterior upper parts of the frontal lobes (fig. 1 a). The percent variation in a given area during two different rest studies is about 5 percent (fig. 1 b). Primary sensory inputs. Auditory and visual inputs activate the corresponding parts of temporal and occipital regions (fig. 2 and 3). Simple cutaneous stimulation such as touch or vibrations do not change the rest pattern. Moderate pain gives a global increase of CBF, pre-dominantly in the frontal regions (Ingvar, 1976). Vestibular stimulation with cold or warm water in the ear gives an increase of rCBF in the parietal regions. Simple movements. Movements of mouth, eyes, hand or foot clearly activate the corresponding parts of the central region, with an increase of rCBF up to 50--100% (Sveinsdottir et al., 1975). When the movement is repetitive there is in all cases an additional clearcut increase in the upper premotor region, probably including the supplementary motor area. This last region is activated alone when the subject tries to imagine a movement without actually moving (fig. 5 a, b, c). Sensory discrimination...