[Types of receptive field in the external geniculate body and its functional model]

The functional differences between receptive fields of types I and II of lateral geniculate nucleus were investigated in cat. Some characteristics of these fields are shown to coincide with transient (Y-type ) and sustanied (X-type) receptive fields. Receptive fields of type I possess a limited range for transmission of information on luminance, those of type II--a normal dynamic range (2 log. unit). The investigation of a dynamic functional model showed that type of the receptive field is determined by the depth of inhibition mediated through an interneuron. The depth of inhibition is larger in type I. Types I and II have different frequency characteristics. It is suggested that receptive fields of type I serve to transmit information on the shape of the image (spatial and time contrasts) and those of type II on luminance.