Neuronal correlates of perception in early visual cortex.
We used functional magnetic resonance imaging (fMRI) to measure activity in human early visual cortex (areas V1, V2 and V3) during a challenging contrast-detection task. Subjects attempted to detect the presence of slight contrast increments added to two kinds of background patterns. Behavioral responses were recorded so that the corresponding cortical activity could be grouped into the usual signal detection categories: hits, false alarms, misses and correct rejects. For both kinds of background patterns, the measured cortical activity was retinotopically specific. Hits and false alarms were associated with significantly more cortical activity than were correct rejects and misses. That false alarms evoked more activity than misses indicates that activity in early visual cortex corresponded to the subjects' percepts, rather than to the physically presented stimulus.
Ress
David
D
Department of Psychology, Stanford University, 450 Serra Mall, Bldg. 420/400, Stanford, California 94309, USA. ress@stanford.edu
Heeger
David J
DJ
D000200:Action Potentials / Q000502:physiology; D016477:Artifacts; D006801:Humans; D008279:Magnetic Resonance Imaging; D009474:Neurons / Q000502:physiology*; D010364:Pattern Recognition, Visual / Q000502:physiology; D010775:Photic Stimulation; D011930:Reaction Time / Q000502:physiology; D014793:Visual Cortex / Q000502:physiology*; D014794:Visual Fields / Q000502:physiology; D014795:Visual Pathways / Q000502:physiology*; D014796:Visual Perception / Q000502:physiology*