Resonance Imaging In Healthy Volunteers Research Articles

CORTICAL REPRESENTATION OF THE URGE TO VOID: A FUNCTIONAL MAGNETIC RESONANCE IMAGING STUDY

The urge to void generally increases with bladder distention but the relationship between the 2 factors is complex. When the bladder is moderately filled, the desire to void can be called forth deliberately but it can also be suppressed. To elucidate human brain mechanisms that are active during such intentional modulations of the desire to void we performed functional magnetic resonance imaging in healthy volunteers. Brain activity was studied in 22 young women. At moderate bladder filling (about 350 ml) they periodically suppressed or enhanced the urge to void without allowing urine to pass. A manual task with a dynamometer, in which the current urge to void was expressed as grip force, demonstrated that the intensity of sensations could be influenced voluntarily. We also examined brain activity during repetitive (1 Hz) contractions of pelvic floor muscles after the bladder was emptied. Significant brain activity associated with an increased urge to void was found in the insular cortex, frontal opercula, supplementary motor area (SMA), cingulate motor area (CMA), right posterior parietal cortex, left prefrontal cortex and cerebellum. Trends toward activation were detected in the thalamus, peri-aquaeductal gray matter and ventral pons. Suppression of the urge to void significantly activated the left superior frontal lobe. The SMA and CMA were active during voluntary rhythmical contractions of pelvic floor muscles. Sensation intensity of the desire to void can be influenced intentionally. Frontoparietal cortical areas and the SMA/CMA seem to be involved in this process.

Pain-related Cerebral Activation Characterized by Magnetic Resonance Imaging in Healthy Volunteers.

Pain-related Cerebral Activation Characterized by Magnetic Resonance Imaging in Healthy Volunteers. Gretchen Henkel; Anesthesiology

Ideographic characters call for extra processing to correspond with phonemes.

Cortical areas used in the copying of Japanese ideographic characters and syllabic characters were studied using functional magnetic resonance imaging in healthy volunteers. Complexity of characters was controlled to illustrate differences resulting from character to sound conversion differences between the ideographic and syllabic characters. Statistical comparisons indicated extensive activation in the fusiform gyrus, posterior portions around the intraparietal sulcus and in the conjunction area of BA 6, 9 and 44 (which is assumed to be Exner's area) during the copying of ideographic characters. These findings suggested that indirectness between ideographic characters and their pronunciation demands extra processing such as semantic mediation and intensive grapheme processing in comparison with syllabic characters.

Somatotopy in human primary motor and somatosensory hand representations revisited.

High-resolution functional magnetic resonance imaging of healthy volunteers was used to study the functional anatomy of the human primary motor (M1) and somatosensory (S1) cortical hand representations during simple movements of thumb, little finger and wrist and a sequential movement of the middle three fingers. Rest served as a control state. The results demonstrated an orderly somatotopy in both M1 and S1, even though the cortical areas active with individual movements significantly overlapped. Moreover, the activation patterns in M1 and S1 differed in three aspects: (i) S1 activation was distributed into significantly more clusters than M1 and the primary cluster was smaller; (ii) the overlaps of areas active with different movements were significantly larger in M1 than in S1; (iii) the difference between the three-finger sequential movement and the single-finger movements was more pronounced in S1 than in M1. The sequence-activated S1 cortex was distributed into significantly more clusters. There was also a trend for a bigger volume difference between sequence and the single finger movements in S1 than M1. These data suggest that while the distributed character dominates in M1 and S1, a somatotopic arrangement exists for both M1 and S1 hand representations, with the S1 somatotopy being more discrete and segregated, in contrast to the more integrated and overlapping somatotopy in M1.

Measurement of atrial volumes by magnetic resonance imaging in healthy volunteers and in patients with myocardial infarction

Magnetic resonance imaging was used to measure atrial volumes and emptying fractions in healthy volunteers to establish normal ranges and also in patients with myocardial infarction. Fourteen healthy volunteers (age mean +/- SD, 47 +/- 13 years) and 14 patients (age 56 +/- 9) with previous myocardial infarction were studied. All patients were in sinus rhythm, had competent cardiac valves and no heart failure. Atrial and ventricular volumes were measured from a set of cardiac gated transverse spin echo images (TE 40 ms) covering the heart and acquired at the end of ventricular systole and diastole. Ventricular ejection fractions and atrial emptying fractions were calculated. In patients with myocardial infarction, left atrial end-diastolic and systolic volumes were significantly higher (P < 0.001), and the emptying fraction significantly lower (P < 0.001) than in the control group. The right atrial end-diastolic volume was also significantly higher (P < 0.05) and the emptying fraction significantly lower (P < 0.01) than those in the control group. These findings are likely to be due to abnormal left ventricular long axis dynamics caused by damage to the myocardium, and reflect the abnormal systolic and diastolic functions of the left ventricle which contribute to atrial filling and emptying, respectively. Changes in atrial volumes can be measured non-invasively by magnetic resonance imaging. Using this method we have studied the normal ranges and demonstrated abnormalities in patients with myocardial infarction. Thus this imaging method may prove to be useful for studying atrial function under different physiological and pathological conditions and for evaluating the effect of therapeutic interventions on atrial function.