Local Field Potential Review

What is LFP

Origin of LFP

Different Frequency Bands

Paper Review-1

Paper Review-2

Paper Review-3

Paper Review-4

1/31/2015 1Presented by: Md. Kafiul Islam

Local Field Potential

Neural recordings from intracortical extracellular microelectrodes consist of two components superimposed on each other:

Action potentials/spikes from single & multi unit activity (300Hz –5kHz)

Slow varying field potentials (1-250 Hz).

http://www.youtube.com/watch?v=Un3LpObsCm4

• The LFP relates well to sub-threshold integrative processes in dendrites

• It represents the summation of excitatory and inhibitory dendriticsignals and other types of slow activity such as voltage dependent membrane oscillations or spike afterpotentials

1/31/2015 2Presented By: Md. Kafiul Islam

Origin of LFP

LFP mostly represents the inputs to a particular brain region and local processing taking place around the recording electrode, while the spikes represent the outputs generated by the region.

Belitski et al. examined correlations between the stimulus and spikes and LFP recorded on the same electrode in the visual cortex of an anesthetized macaque while presenting a color movie [later slide].

Nicolelis et al. reported correlations between spikes and the 8-10 Hz LFP signal.1/31/2015 3Presented By: Md. Kafiul Islam

Different Frequency Bands

Band Frequency

Range

Theta 4-10 Hz

Beta 15-45 Hz

Gamma 50-90 Hz

1/31/2015 4Presented By: Md. Kafiul Islam

Our knowledge about the information content in LFPs is limited compared to

the current understanding of neural spiking patterns. Recent work has shown

many correlations between oscillations in the LFP bands and behavior, and

new properties of the signal have been discovered.

LFP and spike responses

during movie stimulation (Belitski

et al. 2008, JNS)Observations:

•1–5 and 72–76 Hz LFPs show

high and significant modulations

of power at several points of the

movie.

•Spike rates clearly encoded the

movie. The high spike rate

episodes appeared to be

associated more

closely with episodes of high

LFP power in the high-gamma

LFP

frequency range than at lower

LFP frequencies.

Conclusion:

•Gamma LFPs may be more

closely related the stimulus

modulated

spiking activity than low LFP

1/31/2015 5Presented By: Md. Kafiul Islam

LFP and Spike responses

during movie stimulation (Belitski et

al.): Cont…oThe highest LFP power was at

low frequencies (8 Hz), & the

power decreased steeply at

increasing frequencies.

oThere was an increase of

power of 4 dB with movie

stimulation at very low

frequencies (12 Hz).

oThe evoked and spontaneous

LFP spectrograms were similar

at

frequencies between 12-24 Hz.

oThe most substantial power

increase over spontaneous

activity of the movie-evoked

LFP is in the gamma frequency

region 40–120 Hz1/31/2015 6Presented By: Md. Kafiul Islam

Some Findings:First, we found that LFP frequencies<40 Hz do not share any substantial signal

or noise correlations with higher LFP frequencies or with spikes. This suggests that the power of LFP fluctuations <40 Hz reflect different neural processes from those giving rise to higher-frequency LFPs and to spikes, and that these processes are mostly decoupled in naturalistic stimulation conditions.

Second, we found that LFP bands in the low-frequency range (1–24 Hz) had the strongest noise correlations of the whole LFP frequency range studied, and had relatively little signal correlations. The comparably small amount of signal correlation (i.e. the weak similarity in stimulus selectivity) explains why, although they share a substantial amount of stimulus unrelated variability, the joint information carried by two low LFP frequencies is almost equal to the sum of the two information carried by the individual frequencies.

Third, we found that LFP in the 60–100 Hz high-gamma band shared very little noise correlation during visual stimulation, but shared the highest observed signal correlation across all LFP frequencies. The 60–100 Hz LFP band also had the highest proportional power increase during visual stimulation, and also had a substantial signal correlation with spikes, because a local stimulus-related input would affect both the amount of spiking activity of pyramidal neurons and the engagement of the recurrent loop in the region around the tip of the electrode, which in turn reflects into the high gamma LFP power.

1/31/2015 Presented By: Md. Kafiul Islam 7

Neuronal Shot Noise and

Brownian 1/f2 Behavior in the LFP (Milstein et al. 2009)

1/31/2015 Presented By: Md. Kafiul Islam 8

The model gives way to two analytically tractable

solutions, both displaying Brownian noise:

1) Uncorrelated cells that display sharp

initial activity, whose extracellular fields slowly

decay in time: (Slow Dendro-Synaptic Decay)

2) Rapidly firing, temporally correlated

cells that generate UP-DOWN states (like Brownian

noise in telegraph process ) :

LFP as an input to BMI (MS Thesis by

Gireeja, 2009, UCB)

Coherence calculations show that beta oscillations are pervasive in

the cortex during the hold period of Manual Control (MC).

The power in the beta band of the LFP is significantly modulated by

direction during MC

Beta oscillations can be used to predict the stationarity of the task

cursor in both MC and BC

1/31/2015 Presented By: Md. Kafiul Islam 9

**Power in frequency bands of

the LFP and evoked potentials

are modulated with movement

direction

LFP as an input to BMI: Different Oscillations

Beta Oscillations:

We still lack a clear understanding of the functionality of beta oscillations. Results obtained

so far suggest that beta oscillations may serve as:

idle oscillations, a default state that the cortex reverts to when no other important

events are happening

a carrier wave for communication

a timing signal for spike synchronization across brain regions

a ‘planning’ oscillation

Gamma Oscillations:

Gamma coherence relates to behavior and information transfer

Spike-field coherence and oscillatory synchrony may sub serve neuronal communication

Gamma band spike-field coherence in the visual cortex has been shown to increase with

attention to a stimulus

The degree of gamma synchronization prior to and during a behavioral change was

correlated with response times to that change.

Gamma frequency oscillations may also predict spike response latency.

1/31/2015 10Presented By: Md. Kafiul Islam

Neuronal Oscillations in Cortical

Networks (Science; Buzsáki, et al. 2004)

Mammalian cortical neurons form behavior-

dependent oscillating networks of various sizes

covering freq from 0.05 Hz to 500 Hz.

Recent findings indicate that network oscillations

bias input selection, temporally link neurons into

assemblies, and facilitate synaptic plasticity.

Even single neurons are capable with complex

dynamics, including their intrinsic abilities to

resonate and oscillate at multiple frequencies,

which suggests that precise timing of their activity

within neuronal networks could represent

information.

1/31/2015 Presented By: Md. Kafiul Islam 11

Neuronal Oscillations in Cortical

Networks (Science; Buzsáki, et al. 2004): Cont…

A. Depression (low-pass filtering)

and facilitation (high-pass

filtering) of IPSP by two

interneurons converging onto

the same neocortical

pyramidal cell.

B. Band-stop (notch) filtering of

EPSP at gamma frequency

(15 to 30 ms).

C. Band-pass filtering of spike

transmission and transmission

probability peaks at 10 Hz.

D. Voltage-dependent,

subthreshold oscillation at 8

Hz.

1/31/2015 Presented By: Md. Kafiul Islam 12