[Comparative electrophysiologic characteristics of afferent representation in the cortical and striatal portions of the turtle forebrain].

Visual and somatic representations are established in the subcortical striatal sections of the forebrain (pallial thickening, dorsal ventricular ridge and putamen) of immobilized weakly anaesthetized turtles. According to electrophysiological characteristics they are similar to the corresponding sensory representations in the general cortex. The absence of reliable discrepancy between the latencies of potentials in the cortex and striatum evoked by light flash or by the electric stimulation of the dorsal thalamus indicates that visual projectional fibres ascending from the lateral geniculate nucleus terminate both in cortical and striatal structures. Differences in the latency distribution of single unit responses in the cortex and striatum to visual and thalamic stimulations can be due to the existence, besides the geniculo-telencephalic pathway, of a rotundo-telencephalic visual channel having direct connections with the striatum and polysynaptic ones with the general cortex. Significant differences in latency between the evoked potentials and neuronal responses in cortical and subcortical structures to electric stimulation of the skin shows that somatic projectional fibres on their way to the cortex are relayed in the striatum, thus indicating a lower corticolization degree of the somatosensory system as compared with that of the visual one.