On the Organization of Receptive Fields of Orientation-Selective Units Recorded in the Fish Tectum

Abstract

Responses from two types of orientation-selective units of retinal origin (detectors of horizontal lines and detectors of vertical lines) were recorded extracellularly from their axon terminals in the medial sublamina of tectal retinorecipient layer of immobilized cyprinid fish Carassius gibelio. Excitatory and inhibitory influences across receptive fields of orientation-selective units were evaluated. Positions, sizes and forms of the responsive parts of the receptive field were estimated by moving edges and flashing narrow light and dark stripes. It was shown that the orientation-selective units in fish are characterized by small responsive receptive fields with mean width of 4.8 +/- 1.6 degrees (n = 176). The comparison of different types of orientation-selective units revealed that the responsive receptive fields of detectors of vertical lines are significantly wider (13%) than those of detectors of horizontal lines. Statistically significant difference was also found between sizes of responsive receptive fields evaluated by light and dark edges. Mean responsive receptive field width, estimated for light edges (ON responses) were wider than those evaluated for dark edges (OFF responses). Inhibition in the receptive field of orientation-selective units was evaluated on the basis of two experimental methods. Evidence that signals are not linearly summed across the receptive field was derived from experimental results. Inhibitory influences, recorded in the receptive field of orientation-selective units, always initiated inside the responsive receptive field area and spread towards the periphery. Results of the study indicate that receptive fields cannot be defined as homogeneous sensory zone driven by a linear mechanism of response generation. The receptive fields of orientation-selective units, in fish appear to be composed of subunits sensitive to the appropriately oriented stimuli.

Cardinal difference between the orientation-selective retinal ganglion cells projecting to the fish tectum and the orientation-selective complex cells of the mammalian striate cortex

“…reduced by the in°uence of the second (peripheral) stimulus presented at the other locations within the RF. Strong evidences for lateral inhibitory in°uences in the¯sh OS GC RF were already given in our former study (Damjanović et al, 2009b). In experiments with stimulation by two stripes of the same sign of contrast (both of them light, or both dark), the inhibitory in°uences of the lateral stripe were always initiated inside the RRF area.…”

“…Stimulation outside the RRF, causing no response in itself, nevertheless a®ects the behavior of the cells. In particular, an investigation using pairs of stationary stripes of optimal orientation that°ashed synchronously at di®erent distances from each other revealed mutual inhibition (Damjanović et al, 2009b). In the experiments, the stripes were of the same sign of contrast relative to the background (both of them light or both dark).…”

“…With this method, OS GCs were investigated in pike and gold¯sh (Zenkin & Pigarev, 1969, 1970, in some marine¯sh (Maximova et al, 1971), in trout (Galand & Li ege, 1975), in crucian carp and common carp (Maximova & Maximov, 1981;Maximova, 1999) and in Japanese dace (Kawasaki & Aoki, 1983). A detailed classi¯cation of the OS GCs and investigation of the interaction of signals within their receptive¯eld (RF) in the Carassius gibelio were made in recent studies Damjanović et al, 2009b). It was shown that OS GCs comprised two physiological types that di®er in preferred orientations close to vertical and horizontal.…”

Visual receptive field properties of cells in the optic tectum of the archer fish

“…Several studies have tested the functional properties of cells in the optic tectum of the goldfish (Damjanović et al 2009a(Damjanović et al , 2009bJacobson and Gaze 1964;Maximov et al 2005). In their study, Maximov et al (2005) explored the responses of cells to a moving bar stimulus.…”

On the organization of receptive fields of retinal spot detectors projecting to the fish tectum: Analogies with the local edge detectors in frogs and mammals

“…Both are indifferent to the sign of the contrast of stimulus, that is, they are ON–OFF type units. They mark this sublaminae (Damjanović, Maximova, & Maximov, ; Maximov, ; Maximov et al, ; Maximova & Maximov, ). And finally, when the electrode is guided deeper than the OS units, sustained activity of another two types of GCs are regularly recorded.…”