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Biomedical subjects

B Dreher

Publications and source records attributed to B Dreher.

At least 91 records · Page 5Linked to original sources
PubMed1973

Receptive field analysis: responses to moving visual contours by single lateral geniculate neurones in the cat.

1. Responses of single geniculate cells to moving light and dark bars and light/dark edges were studied in cats anaesthetized with nitrous oxide/oxygen (70%/30%).2. Over 95% (230 out of 241) of geniculate cells had antagonistic centre-surround receptive fields. Their responses could be characterized as centre-activated or centre-suppressed depending on the receptive field type (ON- or OFF-centre) and the contrast between stimulus and the background (brighter or darker than the background). Moving light and dark edges evoked responses which were very similar to the responses evoked by these stimuli in simple cells of striate cortex.3. A number of cells (45) with antagonistic centre-surround receptive fields were classified according to their X/Y (sustained/transient) properties. Units with sustained properties (X-cells) did not increase their firing rate with an increase of stimulus velocity and some of them showed a clear-cut preference for slow movement (around 1-2 degrees /sec). On the other hand, units with transient properties (Y-cells) showed a clear-cut preference for fast-moving stimuli (50-100 degrees /sec.)4. Elongation of the stimulus beyond the antagonistic surround in both X- and Y-cells produced a clear-cut reduction of amplitude of both centre and surround components of the response. Thus the existence of a suppressive field component beyond the antagonistic surround is confirmed.5. About 5% of cells had receptive fields which did not have an antagonistic centre-surround organization but gave a mixed ON-OFF discharge from the central region of the field. Around the central region there was a silent suppressive zone. These units were not directionally selective, responded preferentially to fast-moving stimuli (25-100 degrees /sec) and had a substantial (spontaneous) maintained activity.

Action Potentials↗
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Lymphatic metastasis; lymphangiochemotherapy of mammary cancer: ascitic form of rat mammary adenocarcinoma 13762.

When 5 million cells of the ascitic form of the RMT 13762 are injected into syngeneic F344 rat footpads there is consistent metastasis to the popliteal node more rapidly than when the solid form is used. A greater number of tumor cells escapes from the footpad to the draining node via the afferent lymph than with the solid tumor. Local intralymphatic injection of 5FU produces cure or retardation of nodal metastasis in a significant number of animals (p less than 0.002).

Adenocarcinoma↗
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Aged↗
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Processing of form and motion in area 21a of cat visual cortex.

Extracellular recordings from single neurons have been made from presumed area 21a of the cerebral cortex of the cat, anesthetized with N2O/O2/sodium pentobarbitone mixture. Area 21a contains mainly a representation of a central horizontal strip of contralateral visual field about 5 deg above and below the horizontal meridian. Excitatory discharge fields of area 21a neurons were substantially (or slightly but significantly) larger than those of neurons at corresponding eccentricities in areas 17, 19, or 18, respectively. About 95% of area 21a neurons could be activated through either eye and the input from the ipsilateral eye was commonly dominant. Over 90% and less than 10% of neurons had, respectively, C-type and S-type receptive-field organization. Virtually all neurons were orientation-selective and the mean width at half-height of the orientation tuning curves at 52.9 deg was not significantly different from that of neurons in areas 17 and 18. About 30% of area 21a neurons had preferred orientations within 15 deg of the vertical. The mean direction-selectivity index (32.8%) of area 21a neurons was substantially lower than the indices for neurons in areas 17 or 18. Only a few neurons exhibited moderately strong end-zone inhibition. Area 21a neurons responded poorly to fast-moving stimuli and the mean preferred velocity at about 12.5 deg/s was not significantly different from that for area 17 neurons. Selective pressure block of Y fibers in contralateral optic nerve resulted in a small but significant reduction in the preferred velocities of neurons activated via the Y-blocked eye. By contrast, removal of the Y input did not produce significant changes in the spatial organization of receptive fields (S or C type), the size of the discharge fields, the width of orientation tuning curves, or direction-selectivity indices. Our results are consistent with the idea that area 21a receives its principal excitatory input from area 17 and is involved mainly in form rather than motion analysis.

Animals↗