title: Neural dynamics underlying target detection in the human brain.
abstract: Sensory signals must be interpreted in the context of goals and tasks. To detect a target in an image, the brain compares input signals and goals to elicit the correct behavior. We examined how target detection modulates visual recognition signals by recording intracranial field potential responses from 776 electrodes in 10 epileptic human subjects. We observed reliable differences in the physiological responses to stimuli when a cued target was present versus absent. Goal-related modulation was particularly strong in the inferior temporal and fusiform gyri, two areas important for object recognition. Target modulation started after 250 ms post stimulus, considerably after the onset of visual recognition signals. While broadband signals exhibited increased or decreased power, gamma frequency power showed predominantly increases during target presence. These observations support models where task goals interact with sensory inputs via top-down signals that influence the highest echelons of visual processing after the onset of selective responses.
authors.affiliation: Department of Ophthalmology, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, Department of Neurosurgery, Brigham and Women's Hospital, Boston, Massachusetts 02115, Department of Neurosurgery, Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115, and Center for Brain Science and Swartz Center for Theoretical Neuroscience, Harvard University, Cambridge, Massachusetts 02138.
authors.forename: Arjun K
authors.initials: AK
authors.lastname: Bansal
authors.forename: Radhika
authors.initials: R
authors.lastname: Madhavan
authors.forename: Yigal
authors.initials: Y
authors.lastname: Agam
authors.forename: Alexandra
authors.initials: A
authors.lastname: Golby
authors.forename: Joseph R
authors.initials: JR
authors.lastname: Madsen
authors.forename: Gabriel
authors.initials: G
authors.lastname: Kreiman
mesh_terms: D000293:Adolescent; D000328:Adult; D001288:Attention / Q000502:physiology; D001921:Brain / Q000502:physiology*; D002648:Child; D003627:Data Interpretation, Statistical; D004567:Electrodes, Implanted; D004569:Electroencephalography; D004827:Epilepsy / Q000523:psychology; D005133:Eye Movements / Q000502:physiology; D005260:Female; D006040:Goals; D006801:Humans; D008297:Male; D008875:Middle Aged; D010775:Photic Stimulation; D011597:Psychomotor Performance / Q000502:physiology*; D021641:Recognition, Psychology / Q000502:physiology*; D014793:Visual Cortex / Q000502:physiology; D014796:Visual Perception / Q000502:physiology*; D055815:Young Adult
keywords: attentional modulation; cognitive neuroscience; extrastriate cortex; human neurophysiology; target detection; visual recognition