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...erties could be to consider the overall level of synaptic activity. The local field potential (LFP) provides an easily obtainable measure of the activity in a local population—an ensemble—of neurons (=-=Pesaran et al. 2002-=-), which can be compared with spike activity measured simultaneously at the same site. The LFP is defined as the low-frequency (below �250 Hz) components of the raw field potential. These low-frequenc...

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...ent y-axis scaling for each panel. Grey lines are sigmoidal fits to data in each panel (firing rate = a * tanh [β(f1 – θ)] + c); error bars, in this and in subsequent figures, are standard errors. (c) Firing rate as a function of f1 averaged over the entire delay period. β = 0.11 s/pulse, θ = 24 pulses/s. at C old Spring H arbor L aboratory on A pril 2, 2013 http://cercor.oxfordjournals.org/ D ow nloaded from Cerebral Cortex November 2003, V 13 N 11 1199 ence or absence of oscillations within a particular frequency band), rather than firing rate per se, that encode the memory of the stimulus (Pesaran et al., 2002). Temporal encoding has been observed coexisting with labelled-line firing rate encoding (Pesaran et al., 2002). Whether one causes the other is not yet clear. We selected those neurons that were classified as persistent [see Materials and Methods; n = 126 out of 557 (23%) delay period stimulus-dependent neurons] and fit their firing rates, averaged over the whole delay period, as either linear (2 degrees of freedom) or sigmoidal (4 degrees of freedom) functions of f1. Taking into account both the number of degrees of freedom and the quality of the fit, neurons were classified as either linear...

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... probe should be emphasized because local inhomogeneities in field potential generation and the contribution of unit discharge patterns to the generation of local field can now be rigorously studied (=-=Pesaran et al. 2002-=-). Probes with on-chip active circuitry had two major advantages in chronically implanted animals. First, the preamplifier head-stage was eliminated, and therefore the rat had to carry substantially l...

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...ntrol signals for the manipulation of the external world. A variety of recording technologies are employed in neural prosthetic applications and, more widely, for the study of neural coding. Tetrodes =-=[19, 20]-=-, microwires [27, 28], and micro-arrays [21] have all been exploited to derive control signals. Current implantable prostheses exploit hundreds of electrodes which produce large volumes of data that m...

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...ggesting that oscillatory firing may be especially significant in neuronal discharges associated with active memory maintenance in delayed response tasks, compared with baseline spontaneous activity (=-=Pesaran et al. 2002-=-; Tallon-Baudry et al. 2001). Persistent activity during the memory period is believed to be sustained by reverberatory Address for reprint requests and other correspondence: A. Compte, Instituto de N...

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...morize it (Tallon-Baudry, Bertrand, Henaff, Isnard, & Fischer, 2005; Shibata et al., 1999). Last, memory formation or maintenance is accompanied by gamma oscillatory synchrony (Gruber & Muller, 2005; =-=Pesaran, Pezaris, Sahani, Mitra, & Andersen, 2002-=-; Fell et al., 2001; TallonBaudry, Bertrand, Peronnet, & Pernier, 1998), and the strength of this synchrony is modulated by memory load (Howard et al., 2003; De Pascalis & Ray, 1998). However, in all ...

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...ular and close to a Poisson process, even when the local field potential recordings exhibit coherent fast oscillations such as gamma oscillations (40–80 Hz) (Destexhe et al. 1999; Fries et al. 2001b; =-=Pesaran et al. 2002-=-) and sharp-wave ripples (100–200 Hz) (Buzsáki et al. 1992; Csicsvari et al. 1998, 1999a). In such oscillatory episodes, single-cell discharge rates are typically much lower than the oscillation frequ...