Thalamocortical specificity and the synthesis of sensory cortical receptive fields.
A persistent and fundamental question in sensory cortical physiology concerns the manner in which receptive fields of layer-4 neurons are synthesized from their thalamic inputs. According to a hierarchical model proposed more than 40 years ago, simple receptive fields in layer 4 of primary visual cortex originate from the convergence of highly specific thalamocortical inputs (e.g., geniculate inputs with on-center receptive fields overlap the on subregions of layer 4 simple cells). Here, we summarize studies in the visual cortex that provide support for this high specificity of thalamic input to visual cortical simple cells. In addition, we review studies of GABAergic interneurons in the somatosensory "barrel" cortex with receptive fields that are generated by a very different mechanism: the nonspecific convergence of thalamic inputs with different response properties. We hypothesize that these 2 modes of thalamocortical connectivity onto subpopulations of excitatory and inhibitory neurons constitute a general feature of sensory neocortex and account for much of the diversity seen in layer-4 receptive fields.
Alonso
Jose-Manuel
JM
Department of Biological Sciences, State University of New York--State College of Optometry, 33 West 42nd Street, New York, New York 10036, USA. jalonso@sunyopt.edu
Swadlow
Harvey A
HA
D000818:Animals; D008959:Models, Neurological; D009474:Neurons / Q000502:physiology*; D012680:Sensitivity and Specificity; D013788:Thalamus / Q000166:cytology / Q000502:physiology*; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*; D014795:Visual Pathways / Q000502:physiology*