During spatial summation, signals from multiple photoreceptors converge onto which intermediate neuron before reaching the ganglion cells?

During spatial summation, signals from multiple photoreceptors converge onto which intermediate neuron before reaching the ganglion cells?

• A. Amacrine cells
• B. Bipolar cells
• C. Ganglion cells
• D. Horizontal cells

Answer: (B)

Spatial summation in the retina involves pooling input from several photoreceptors to influence a downstream neuron. The first interneurons that receive signals from photoreceptors and pass them toward ganglion cells are the bipolar cells, which collect input from multiple photoreceptors within a receptive field and transmit it onward to the ganglion cells. Horizontal cells contribute to shaping the receptive field through lateral interactions (surround), but they are not the main conduit for the direct feedforward summation to ganglion cells. Amacrine cells modulate signals later in the circuit, primarily affecting timing and complex processing in the inner retina, not the primary spatial pooling step. So the intermediate neuron that handles spatially summed input from photoreceptors before reaching the ganglion cells is the bipolar cell.

Spatial summation in the retina involves pooling input from several photoreceptors to influence a downstream neuron. The first interneurons that receive signals from photoreceptors and pass them toward ganglion cells are the bipolar cells, which collect input from multiple photoreceptors within a receptive field and transmit it onward to the ganglion cells. Horizontal cells contribute to shaping the receptive field through lateral interactions (surround), but they are not the main conduit for the direct feedforward summation to ganglion cells. Amacrine cells modulate signals later in the circuit, primarily affecting timing and complex processing in the inner retina, not the primary spatial pooling step. So the intermediate neuron that handles spatially summed input from photoreceptors before reaching the ganglion cells is the bipolar cell.