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Digitale Medien

Unit activity in monkey parietal cortex related to haptic perception and temporary memory (1989)

Koch, K. W. ; Fuster, J. M.

Springer

Experimental brain research 76 (1989), S. 292-306

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Details

ISSN: 1432-1106

Schlagwort(e): Parietal cortex ; Haptic perception ; Memory ; Unit activity ; Monkeys

Quelle: Springer Online Journal Archives 1860-2000

Thema: Medizin

Notizen: Summary The neural responses of 456 single units were recorded in parietal cortex of behaving monkeys during a haptic delayed matching-to-sample task. (1) In areas 2 and 5 together, 22% of the neurons were activated by the auditory cue that signalled the beginning of a trial. Virtually all of these cells were also activated during the arm movements required by the task. These neurons, showing both auditory-related and movement-related responses, may function in sensorimotor integration. (2) Responses related to arm projection frequently began before movement onset, sometimes as much as 320 ms before. Such “premovement” responses were approximately equally common, and showed the same latency distribution, in areas 2, 5a, and 5b. (3) There was a topographic rostral-to-caudal gradient of decreasing neural responsiveness to the animal's manipulation of the cue (sample) objects. Eleven percent of manipulation-activated cells responded preferentially to one of the sample objects. (4) Many cells showed sustained (〉 3 s) activation during the delay period (the time between handling of the sample object and palpation of the choice objects), even though at that time the monkey was sitting quietly and without stimulation. (5) Cells with sustained activation throughout most or all of the 18-s delay period were rare in all areas tested except area 5a. These cells, especially those that were preferentially activated depending on which sample object was palpated, may function in the temporary retention of haptic attributes. (6) The population of cells activated during sample manipulation was largely distinct from the population of cells showing sustained activation during the delay period. These two cell populations may represent different but complementary aspects of haptic perception. (7) The most common response during the delay period was sustained inhibition. This may be an expression of a nonspecific mechanism for decreasing background noise and enhancing neural responses to an anticipated perceptual event. (8) Relatively little evidence was found to support a functional distinction between the neural response properties of areas 2 and 5 a. This suggests that area 2 may be at a higher level in the somatosensory heirarchy of the posterior parietal cortex than usually considered.

Materialart: Digitale Medien

URL: http://dx.doi.org/10.1007/BF00247889

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Digitale Medien

Determination of the various phases of aluminium in steel by x-ray fluorescence spectrometryDedicated to Prof. Dr F. Huber on the occasion of his 60th birthday. Presented at the 17th Spektrometertagung, Lugano, 1988. (1989)

Klockenkämper, R. ; Koch, K. H.

New York, NY [u.a.] : Wiley-Blackwell

X-Ray Spectrometry 18 (1989), S. 177-181

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Details

ISSN: 0049-8246

Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy

Quelle: Wiley InterScience Backfile Collection 1832-2000

Thema: Physik

Notizen: The total content of aluminium in steel can be determined from the Kα line in the x-ray spectrum with a detection limit of 0.001%. However, aluminium is generally present in three phases, as metal, as nitride and as oxide; these different phases are of metallurgical significance and have to be distinguished. This is possible from their different kβ bands in the x-ray spectrum, which were found at 1555.3 1553.9 and 1552.5 eV, respectively. The physical bandwidth of about x-ray 7 eV, however, causes overlapping of the peaks, so that an unfolding procedure is needed. The defection limit of the different phases was determined to be 0.06% which, unfortunately, is above the region of interest for modern steel analysis. In addition, the analysis time of about 3 min is too long for use in process control, so that the classical methods for pahse determination cannot be replaced by x-ray fluorescence analysis.

Zusätzliches Material: 5 Ill.