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A M Mass

Publications and source records attributed to A M Mass.

At least 19 recordsLinked to original sources
PubMed2000

Ganglion cells density and retinal resolution in the sea otter, Enhydra lutris.

The topographic distribution, density, and size of ganglion cells were studied in retinal wholemounts of the sea otter, Enhydra lutris. The cell distribution showed a well defined horizontal streak of higher cell density, and within this streak, a narrow area of the highest cell density. The peak cell density in this area ranged from 4050 to 4400 cells/mm(2), with a mean of 4225 cells/mm(2). The ganglion cell size ranged from 7 microm to 47 microm but the majority of cells were 7 to 30 microm. Cell size distribution revealed three size groups: 7-16, 17-28, and 29-47 microm. The highest-density area contained mainly small (7-16 microm) cells. The cell-density data predict a retinal resolution around 7' in water. Retinal organization in the sea otter exhibits more properties common with terrestrial rather than aquatic mammals, both in terms of ganglion cell characteristics and in terms of their topographic distribution.

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PubMed1995

Ganglion cell topography of the retina in the bottlenosed dolphin, Tursiops truncatus.

The distribution and size of ganglion cells in the retina of the bottlenosed dolphin are described. Ganglion cells concentrate at two spots of the highest density in the nasal and temporal quadrants, 15 to 16 mm (50 to 55 degrees) from the optic disk. The mean peak cell density in both spots is about 670 cells/mm2. With a posterior nodal distance of 14.5 mm (under water), this corresponds to 43 cells/deg2, which provides a retinal resolution of about 9' in water and 12' in air. Mean cell size was from 26 to 31 microns in various parts of the retina.

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PubMed1992

Peak density, size and regional distribution of ganglion cells in the retina of the fur seal Callorhinus ursinus.

The total number, size, topographic distribution and peak density of ganglion cells were studied in retinal wholemounts of the fur seal, Callorhinus ursinus. The cell distribution showed a distinct zone of high ganglion cell density. It was located in the temporal retinal quadrant, near the horizontal meridian, 10-12 mm (25-31 degrees) from the optic disk. The peak cell density in this zone was 812-1332 cells/mm2 (mean 1053 cells/mm2), i.e. 125-205 cells/deg2 (mean 162 cells/deg2). These data predict a retinal resolution of 5.6-7.1 cycle/deg. The ganglion cell soma size ranged from 10 to 50 microns. Cell size histograms were bimodal in shape with modes below and above 30 microns.

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PubMed1983

[Laminar distribution of current sources in the superior colliculi of the rabbit upon stimulation of the optic nerve].

The evoked potential field in the rabbit superior colliculus was subjected to the current source density analysis to determine the location and sequence of the current sinks and sources after electrical stimulation of the optic nerve. The earliest current sink was observed in the middle part of the stratum griseum superficiale. The later and the most prominent current sinks were observed in the upper part and in the deep part of the stratum griseum superficiale. The time course of the current sinks and sources was in correspondence with the main components of the evoked potential. The results permit indicating the location of afferent synapses and sequence of their activation.

Animals↗
PubMed1979

[Configuration of the electrical field of an evoked potential in in the superiod colliculus of the rabbit brain upon punctiform afferent stimulation].

Evoked potentials were studied in the rabbit superior colliculus to punctiform light stimulation of the receptive field. The evoked potentials were of negative polarity and did not show potential reversion. The depths of recordings were from 0.1 to 1 mM. The 4-6 degrees shift of the punctiform stimulus from the optimal position led to the disappearance of the evoked potential. If large (more than 5-6 degrees) or diffuse stimuli were used the evoked potentials reversed from surface-negative to deep-positive at a depth of 0.3-0.4 mM. It is suggested that the evoked potential to punctiform stimuli indicate more precisely the location of afferent synapses.

Animals↗
PubMed1977

[Organization of the afferent input to the superior colliculus of the rabbit brain].

The organization of afferent input to superior colliculus was studied in unanesthetized paralyzed rabbits. Two groups of afferent fibres with the average conduction velocities 3 and 6 m per s were determined. It was found that C1 and C2 components of the evoked potential reflect postsynaptic activity of collicular neurons activated by these groups of optic nerve fibres. The existence in rabbit of direct retino-tectal input to the superior colliculus is supposed.

Animals↗
PubMed1975

[The existence of recurrent inhibition in the superior collicus of the rabbit].

The optic nerve stimulation entailed inhibition of the unit responses for 200-300 msec, suppression of testing unit responses and of evoked potentials. When the testing responses to repeated stimuli were suppressed, the subsequent inhibition was suppressed also, and the next response was suppressed a little or not at all. The observed inhibition is supposed to be of a recurrent character.

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