Low calcium, high magnesium, and cobalt hyperpolarize the horizontal cell membrane and suppress the response to light, but only partially affect the response of receptor cells. These observations are consistent with the interpretation that a depolarizing transmitter is released by photoreceptors in darkness. The hyperpolarizing response to light of the horizontal cells would then result from a reduction in the amount of transmitter released.

Action Potentials↗

PubMed1974

Visuovestibular interactions in the cat superior colliculus.

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Action Potentials↗

PubMed1973

The contrast sensitivity of the cat.

1. The experiments were carried out on pretrigeminal cats.2. By recording potentials evoked from the visual cortex by a grating stimulus, it was established that there was a linear relation between the voltage generated and the logarithm of the contrast of the grating.3. The voltage evoked by the grating was independent of the orientation of the grating.4. It has previously been shown in man that, if the contrast is determined by an extrapolation to the point at which a zero voltage occurs, this value corresponds to the psychophysical threshold. On the assumption that the threshold of the cat also occurs at zero voltage, thresholds for a number of spatial frequencies and orientations were determined.5. When the threshold sensitivity function for the cat is compared with man it is found to be displaced to lower spatial frequencies by a factor of about ten. This means that while the cat cannot see such high spatial frequencies as man, it can see lower frequencies better than man.

Animals↗

PubMed1972

Variations of the visual responses of the superior colliculus in relation to body roll.

A large percentage of the directional units of the superior colliculus of the curarized cat modify their response to a particular moving visual stimulus as a function of the position of rotation of the animal about its longitudinal axis.

Action Potentials↗

PubMedDate not supplied

Horizontal cells of turtle retina: a neurotransmitter control of electrical junctions?

Recent experiments suggest that GABA and dopamine can modulate the permeability of the electrical junctions between horizontal cells of the turtle retina. The possible significance and functional advantages of a chemical control of the electrical junctions are briefly discussed. A similar mechanism could combine in a network of interacting elements the low energy cost and low intrinsic noise typical of the electrical synapses with the great functional plasticity typical of the chemical transmission.

Animals↗