Christos Constantinidis

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An important question in neuroscience is whether and how temporal patterns and fluctuations in neuronal spike trains contribute to information processing in the cortex. We have addressed this issue in the memory-related circuits of the prefrontal cortex by analyzing spike trains from a database of 229 neurons recorded in the dorsolateral prefrontal cortex(More)
Neurophysiological recordings have revealed that the discharges of nearby cortical cells are positively correlated in time scales that range from millisecond synchronization of action potentials to much slower firing rate co-variations, evident in rates averaged over hundreds of milliseconds. The presence of correlated firing can offer insights into the(More)
A conspicuous feature of cortical organization is the wide diversity of inhibitory interneurons; their differential computational functions remain unclear. Here we propose a local cortical circuit in which three major subtypes of interneurons play distinct roles. In a model designed for spatial working memory, stimulus tuning of persistent activity arises(More)
The prefrontal cortex is important in guiding or inhibiting future responses, which requires the temporal integration of events and which provides continuity to the thought process. No cellular mechanism has been proposed to explain how the mental representation of a response or idea is linked to the next. Using simultaneous recordings in monkeys, we(More)
A long-standing issue concerning the function of the primate dorsolateral prefrontal cortex is whether the activity of prefrontal neurons reflects the perceived sensory attributes of a remembered stimulus, or the decision to execute a motor response. To distinguish between these possibilities, we recorded neuronal activity from monkeys trained to make a(More)
1. Neuronal activity was recorded from area 7a of monkeys performing a delayed match-to-sample task requiring release of a behavioral key when a visual stimulus appeared at a remembered spatial location. 2. Activity in the delay periods was significantly elevated in 28% of 405 neurons studied and could be classified as either sustained or anticipatory in(More)
Neurons with directional specificities are active in the prefrontal cortex (PFC) during tasks that require spatial working memory. Although the coordination of neuronal activity in PFC is thought to be maintained by a network of recurrent connections, direct physiological evidence regarding such networks is sparse. To gain insight into the functional(More)
The primate posterior parietal cortex (PPC) plays an important role in representing and recalling spatial relationships and in the ability to orient visual attention. This is evidenced by the parietal activation observed in brain imaging experiments performed during visuo- spatial tasks, and by the contralateral neglect syndrome that often accompanies(More)
Working memory has long been associated with the prefrontal cortex, since damage to this brain area can critically impair the ability to maintain and update mnemonic information. Anatomical and physiological evidence suggests, however, that the prefrontal cortex is part of a broader network of interconnected brain areas involved in working memory. These(More)
1. The effect of covert attention was studied in area 7a of the posterior parietal cortex of rhesus monkeys performing a spatial match-to-sample task. The task required the animals to fixate a central target light, to detect and remember the location of a transient spatial cue, and to respond when one of a series of stimuli appeared at the cued location.(More)