Relationships of local inhibitory and excitatory circuits to orientation preference maps in ferret visual cortex.
The contribution and precise role of intracortical circuits in generating orientation tuned responses in visual cortical neurons is still controversial. To address this question, the relationship between excitatory and inhibitory synaptic connections and orientation maps in ferret striate cortex was investigated by combining in vivo optical imaging and in vitro scanning laser photostimulation. Excitatory and inhibitory inputs to pyramidal cells originated preferentially from regions with similar orientation preference. Prominent cross-orientation inhibition was not observed, arguing against cross-orientation models of orientation selectivity. The tuning of inhibitory inputs was significantly broader in both layer 2/3 and layer 5/6 pyramidal neurons compared to the tuning of excitatory inputs. Local excitatory inputs were more prominent in the 0-20 degrees tuning difference range between pre- and postsynaptic cells than inhibitory inputs, whereas inhibition dominated in the 20-40 degrees tuning difference range. These differences in tuning of excitatory and inhibitory inputs onto individual cells are consistent with the predictions of recurrent models of orientation selectivity.
Roerig
B
B
Department of Anatomy and Neurobiology, School of Medicine, University of Maryland at Baltimore, 685 West Baltimore Street, Baltimore, MD 21201-1509, USA. broer001@umaryland.edu
Chen
B
B
D000818:Animals; D001931:Brain Mapping; D005289:Ferrets; D009433:Neural Inhibition / Q000502:physiology*; D009949:Orientation / Q000502:physiology*; D010775:Photic Stimulation; D017966:Pyramidal Cells / Q000502:physiology; D013569:Synapses / Q000502:physiology; D014793:Visual Cortex / Q000166:cytology / Q000502:physiology*; D014795:Visual Pathways / Q000166:cytology / Q000502:physiology