7,225 research outputs found
The Local Field Potential Reflects Surplus Spike Synchrony
The oscillatory nature of the cortical local field potential (LFP) is
commonly interpreted as a reflection of synchronized network activity, but its
relationship to observed transient coincident firing of neurons on the
millisecond time-scale remains unclear. Here we present experimental evidence
to reconcile the notions of synchrony at the level of neuronal spiking and at
the mesoscopic scale. We demonstrate that only in time intervals of excess
spike synchrony, coincident spikes are better entrained to the LFP than
predicted by the locking of the individual spikes. This effect is enhanced in
periods of large LFP amplitudes. A quantitative model explains the LFP dynamics
by the orchestrated spiking activity in neuronal groups that contribute the
observed surplus synchrony. From the correlation analysis, we infer that
neurons participate in different constellations but contribute only a fraction
of their spikes to temporally precise spike configurations, suggesting a dual
coding scheme of rate and synchrony. This finding provides direct evidence for
the hypothesized relation that precise spike synchrony constitutes a major
temporally and spatially organized component of the LFP. Revealing that
transient spike synchronization correlates not only with behavior, but with a
mesoscopic brain signal corroborates its relevance in cortical processing.Comment: 45 pages, 8 figures, 3 supplemental figure
Active C4 electrodes for local field potential recording applications
Extracellular neural recording, with multi-electrode arrays (MEAs), is a powerful method used to study neural function at the network level. However, in a high density array, it can be costly and time consuming to integrate the active circuit with the expensive electrodes. In this paper, we present a 4 mm × 4 mm neural recording integrated circuit (IC) chip, utilizing IBM C4 bumps as recording electrodes, which enable a seamless active chip and electrode integration. The IC chip was designed and fabricated in a 0.13 μm BiCMOS process for both in vitro and in vivo applications. It has an input-referred noise of 4.6 μV rms for the bandwidth of 10 Hz to 10 kHz and a power dissipation of 11.25 mW at 2.5 V, or 43.9 μW per input channel. This prototype is scalable for implementing larger number and higher density electrode arrays. To validate the functionality of the chip, electrical testing results and acute in vivo recordings from a rat barrel cortex are presented.R01 NS072385 - NINDS NIH HHS; 1R01 NS072385 - NINDS NIH HH
Frequency dependence of signal power and spatial reach of the local field potential
The first recording of electrical potential from brain activity was reported
already in 1875, but still the interpretation of the signal is debated. To take
full advantage of the new generation of microelectrodes with hundreds or even
thousands of electrode contacts, an accurate quantitative link between what is
measured and the underlying neural circuit activity is needed. Here we address
the question of how the observed frequency dependence of recorded local field
potentials (LFPs) should be interpreted. By use of a well-established
biophysical modeling scheme, combined with detailed reconstructed neuronal
morphologies, we find that correlations in the synaptic inputs onto a
population of pyramidal cells may significantly boost the low-frequency
components of the generated LFP. We further find that these low-frequency
components may be less `local' than the high-frequency LFP components in the
sense that (1) the size of signal-generation region of the LFP recorded at an
electrode is larger and (2) that the LFP generated by a synaptically activated
population spreads further outside the population edge due to volume
conduction
Local field potential measurement with low-power analog integrated circuit
Journal ArticleLocal field potentials (LFPs) in the brain are an important source of information for basic research and clinical (i.e., neuroprosthetic) applications. The energy contained in certain bands of LFPs in the 10-100 Hz range has been shown to correlate with specific arm movement parameters in nonhuman primates. In the near future, implantable devices will need to transmit neural information from hundreds of microelectrodes, and transcutaneous data transfer will become a significant bottleneck. Here we present a low-power, fully integrated circuit that performs on-site data reduction by isolating LFPs and measuring their signal energy. The resulting analog VLSI circuit consumes 586 μm × 79 μm of silicon area and dissipates only 5 nanowatts of power. We show that the chip performs similarly to state-of-the-art signal processing algorithms
Spatial Resolution of Local Field Potential Signals in Macaque V4
A main challenge for the development of cortical visual prostheses is to
spatially localize individual spots of light, called phosphenes, by assigning
appropriate stimulating parameters to implanted electrodes. Imitating the
natural responses to phosphene-like stimuli at different positions can help in
designing a systematic procedure to determine these parameters. The key
characteristic of such a system is the ability to discriminate between
responses to different positions in the visual field. While most previous
prosthetic devices have targeted the primary visual cortex, the extrastriate
cortex has the advantage of covering a large part of the visual field with a
smaller amount of cortical tissue, providing the possibility of a more compact
implant. Here, we studied how well ensembles of Multiunit activity (MUA) and
Local Field Potentials (LFPs) responses from extrastriate cortical visual area
V4 of a behaving macaque monkey can discriminate between two-dimensional
spatial positions. We found that despite the large receptive field sizes in V4,
the combined responses from multiple sites, whether MUA or LFP, has the
capability for fine and coarse discrimination of positions. We identified a
selection procedure that could significantly increase the discrimination
performance while reducing the required number of electrodes. Analysis of noise
correlation in MUA and LFP responses showed that noise correlations in LFP
responses carry more information about the spatial positions. Overall, these
findings suggest that spatial positions could be localized with patterned
stimulation in extrastriate area V4
Chronic neural probe for simultaneous recording of single-unit, multi-unit, and local field potential activity from multiple brain sites
Drug resistant focal epilepsy can be treated by resecting the epileptic focus
requiring a precise focus localization using stereoelectroencephalography
(SEEG) probes. As commercial SEEG probes offer only a limited spatial
resolution, probes of higher channel count and design freedom enabling the
incorporation of macro and microelectrodes would help increasing spatial
resolution and thus open new perspectives for investigating mechanisms
underlying focal epilepsy and its treatment. This work describes a new
fabrication process for SEEG probes with materials and dimensions similar to
clinical probes enabling recording single neuron activity at high spatial
resolution. Polyimide is used as a biocompatible flexible substrate into which
platinum electrodes and leads are...
The resulting probe features match those of clinically approved devices.
Tests in saline solution confirmed the probe stability and functionality.
Probes were implanted into the brain of one monkey (Macaca mulatta), trained to
perform different motor tasks. Suitable configurations including up to 128
electrode sites allow the recording of task-related neuronal signals. Probes
with 32 and 64 electrode sites were implanted in the posterior parietal cortex.
Local field potentials and multi-unit activity were recorded as early as one
hour after implantation. Stable single-unit activity was achieved for up to 26
days after implantation of a 64-channel probe. All recorded signals showed
modulation during task execution. With the novel probes it is possible to
record stable biologically relevant data over a time span exceeding the usual
time needed for epileptic focus localization in human patients. This is the
first time that single units are recorded along cylindrical polyimide probes
chronically implanted 22 mm deep into the brain of a monkey, which suggests the
potential usefulness of this probe for human applications
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