title: 'Simplification' of responses of complex cells in cat striate cortex: suppressive surrounds and 'feedback' inactivation.
abstract: In mammalian striate cortex (V1), two distinct functional classes of neurones, the so-called simple and complex cells, are routinely distinguished. They can be quantitatively differentiated from each other on the basis of the ratio between the phase-variant (F1) component and the mean firing rate (F0) of spike responses to luminance-modulated sinusoidal gratings (simple, F1/F0 > 1; complex, F1/F0 < 1). We investigated how recurrent cortico-cortical connections affect the spatial phase-variance of responses of V1 cells in the cat. F1/F0 ratios of the responses to optimally oriented drifting sine-wave gratings covering the classical receptive field (CRF) of single V1 cells were compared to those of: (1) responses to gratings covering the CRFs combined with gratings of different orientations presented to the 'silent' surrounds; and (2) responses to CRF stimulation during reversible inactivation of postero-temporal visual (PTV) cortex. For complex cells, the relative strength of the silent surround suppression on CRF-driven responses was positively correlated with the extent of increases in F1/F0 ratios. Inactivation of PTV cortex increased F1/F0 ratios of CRF-driven responses of complex cells only. Overall, activation of suppressive surrounds or inactivation of PTV 'converted' substantial proportions (50 and 30%, respectively) of complex cells into simple-like cells (F1/F0 > 1). Thus, the simple-complex distinction depends, at least partly, on information coming from the silent surrounds and/or feedback from 'higher-order' cortices. These results support the idea that simple and complex cells belong to the same basic cortical circuit and the spatial phase-variance of their responses depends on the relative strength of different synaptic inputs.
authors.affiliation: Discipline of Anatomy and Histology, School of Medical Sciences and Bosch Institute (F13), The University of Sydney, NSW 2006, Australia.
authors.forename: Cedric
authors.initials: C
authors.lastname: Bardy
authors.forename: Jin Yu
authors.initials: JY
authors.lastname: Huang
authors.forename: Chun
authors.initials: C
authors.lastname: Wang
authors.forename: Thomas
authors.initials: T
authors.lastname: FitzGibbon
authors.forename: Bogdan
authors.initials: B
authors.lastname: Dreher
mesh_terms: D000200:Action Potentials / Q000502:physiology*; D000818:Animals; D002415:Cats; D005074:Evoked Potentials, Visual / Q000502:physiology*; D005246:Feedback / Q000502:physiology; D005260:Female; D008297:Male; D009433:Neural Inhibition / Q000502:physiology*; D009474:Neurons / Q000145:classification / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods*; D014793:Visual Cortex / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology