Stimulus Load and Oscillatory Activity in Higher Cortex.
Exploring and exploiting a rich visual environment requires perceiving, attending, and remembering multiple objects simultaneously. Recent studies have suggested that this mental "juggling" of multiple objects may depend on oscillatory neural dynamics. We recorded local field potentials from the lateral intraparietal area, frontal eye fields, and lateral prefrontal cortex while monkeys maintained variable numbers of visual stimuli in working memory. Behavior suggested independent processing of stimuli in each hemifield. During stimulus presentation, higher-frequency power (50-100 Hz) increased with the number of stimuli (load) in the contralateral hemifield, whereas lower-frequency power (8-50 Hz) decreased with the total number of stimuli in both hemifields. During the memory delay, lower-frequency power increased with contralateral load. Load effects on higher frequencies during stimulus encoding and lower frequencies during the memory delay were stronger when neural activity also signaled the location of the stimuli. Like power, higher-frequency synchrony increased with load, but beta synchrony (16-30 Hz) showed the opposite effect, increasing when power decreased (stimulus presentation) and decreasing when power increased (memory delay). Our results suggest roles for lower-frequency oscillations in top-down processing and higher-frequency oscillations in bottom-up processing.
Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Simon
S
Kornblith
Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA Princeton Neuroscience Institute, Department of Psychology, Princeton University, Princeton, NJ 08540, USA.
Timothy J
TJ
Buschman
Department of Brain and Cognitive Sciences, The Picower Institute for Learning and Memory, Massachusetts Institute of Technology, Cambridge, MA 02139, USA.
Earl K
EK
Miller
D000818:Animals; D001288:Attention / Q000502:physiology*; D001683:Biological Clocks / Q000502:physiology*; D058256:Brain Waves / Q000502:physiology*; D002540:Cerebral Cortex / Q000502:physiology*; D003071:Cognition / Q000502:physiology*; D006801:Humans; D008252:Macaca fascicularis; D008253:Macaca mulatta; D008297:Male; D008570:Memory, Short-Term / Q000502:physiology*; D011939:Mental Recall / Q000502:physiology; D009415:Nerve Net / Q000502:physiology; D010364:Pattern Recognition, Visual / Q000502:physiology*; D010775:Photic Stimulation / Q000379:methods; D013647:Task Performance and Analysis; D014794:Visual Fields / Q000502:physiology
frontal eye fields; lateral intraparietal area; power; prefrontal cortex; synchrony; working memory