Abstract
Short-term memory requires the coordination of sub-processes like encoding, retention, retrieval and comparison of stored material to subsequent input. Neuronal oscillations have an inherent time structure, can effectively coordinate synaptic integration of large neuron populations and could therefore organize and integrate distributed sub-processes in time and space. We observed field potential oscillations (14–95 Hz) in ventral prefrontal cortex of monkeys performing a visual memory task. Stimulus-selective and performance-dependent oscillations occurred simultaneously at 65–95 Hz and 14–50 Hz, the latter being phase-locked throughout memory maintenance. We propose that prefrontal oscillatory activity may be instrumental for the dynamical integration of local and global neuronal processes underlying short-term memory.
Highlights
The maintenance of information during short-term memory (STM) has originally been associated with sustained firing of cells in prefrontal cortex (PFC) (Fuster and Alexander, 1971; GoldmanRakic, 1995; Miller et al, 1996; Rainer and Miller, 2000)
Stimulus-selective and performance-dependent oscillations occurred simultaneously at 65–95 Hz and 14–50 Hz, the latter being phase-locked throughout memory maintenance.We propose that prefrontal oscillatory activity may be instrumental for the dynamical integration of local and global neuronal processes underlying short-term memory
If oscillatory activity is involved in the organization of STM, the question arises whether oscillations participate in the coding of specific content as has been suggested previously (Lisman and Idiart, 1995; Singer, 1999) and which has been shown for parietal (Pesaran et al, 2002) and extrastriate visual cortex (Lee et al, 2005), or, whether they reflect unspecific arousal due to behavioral demands, or provide a temporal reference signal for the coordination of distributed representations (Lisman and Idiart, 1995; Sommer and Wennekers, 2001)
Summary
The maintenance of information during short-term memory (STM) has originally been associated with sustained firing of cells in prefrontal cortex (PFC) (Fuster and Alexander, 1971; GoldmanRakic, 1995; Miller et al, 1996; Rainer and Miller, 2000). Reverberating neuronal activity that could serve the maintenance of stimulus information has been proposed to express itself in common rate modulations (Golomb et al, 1990) or irregular (Compte et al, 2003) or oscillatory activity patterns (Compte et al, 2000). If oscillatory activity is involved in the organization of STM, the question arises whether oscillations participate in the coding of specific content as has been suggested previously (Lisman and Idiart, 1995; Singer, 1999) and which has been shown for parietal (Pesaran et al, 2002) and extrastriate visual cortex (Lee et al, 2005), or, whether they reflect unspecific arousal due to behavioral demands, or provide a temporal reference signal for the coordination of distributed representations (Lisman and Idiart, 1995; Sommer and Wennekers, 2001). Physiological evidence for neuronal oscillations participating in STM has been obtained in parietal (Pesaran et al, 2002) and extrastriate temporal cortex (Tallon-Baudry et al, 2004), but not for prefrontal cortex
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