Biomedical Engineering Reference
In-Depth Information
simultaneously recorded spike trains in the mo-
tor area of rhesus monkeys trained to produce a
series of visually guided hand movements ac-
cording to changes in the target locations (Lee,
2002, 2003).
The first studies about the wavelet coherence
are very recent (Grinsted et al., 2004; Klein et
al., 2006; Lachaux et al., 2002; Le Van Quyen
et al., 2001). The wavelet coherence, similarly to
the spectral coherence, infers on the functional
coupling between e.g. stimulus and neural re-
sponse, but additionally it also provides the tem-
poral structure of the coupling. Li et al. (2007)
investigated the temporal interaction in CA1 and
CA3 regions in rats with induced epilepsy using
the wavelet coherence. In previous works (Pavlov
et al., 2006, 2007) we advocated and illustrated
the use of the wavelet transform for analysis of
neural spike trains recorded in the trigeminal
nuclei under tactile whisker stimulation.
Unit Recordings and Sensory
Stimulation
Tungsten microelectrodes (2-5 M
Ω
; World Pre-
cission Instruments) were used to obtain single
unit recordings in the SP5C (A: -14.3 mm, L: 3
mm from the bregma; H: 0.5 to 2 mm from the
surface of the nucleus; according to the atlas of
Paxinos and Watson 1986). Unit firing was filtered
(0.3-3 KHz), amplified via an AC preamplifier
(DAM80; World Precision Instruments) and fed
into a personal computer (sample rate: 12 KHz)
for off-line analysis using Spike 2 software (Cam-
bridge Electronic Design, UK). Tactile stimula-
tion was performed by an electronically gated
solenoid with a probe of 1 mm in diameter that
produced <0.5 mm whisker deflections. To avoid
complex responses due to multiple deflections
of the vibrissae, these were cut to 2 mm long, so
the stimulation was reproducible and responses
could be compared.
MAIN THRUST OF THE CHAPTER
Experimental Protocol
Previous results suggest that the temporal ar-
chitecture of the spike response of a neuron is
crucial to determine facilitation or depression of
a postsynaptic neuron. To test this hypothesis we
studied the response of trigeminal SP5 neurons to
tactile stimulus and its modification when a novel,
distracter stimulus appears simultaneously.
Spontaneous spiking activity of the neuron was
recorded during 30 s. Then neural response to
deflections of the principal whisker was recorded
in three following conditions:
a.
Control stimulation.
Tactile stimulation
consisted in a sequence of 30 tactile pulses
lasting 20 ms and delivered at the RF at 1 Hz
rate was applied to the principal whisker.
Methods
b.
Ipsilateral sensory-interference.
During
tactile stimulation of the principal whisker
with the same characteristics as in (a) another
tactile distracter stimulus was continuously
applied with a hand-held brush to whiskers
located outside of the RF of the recorded
neuron.
Data were obtained from 20 urethane-anaesthe-
tized (1.6 g/Kg i.p.) young adult Wistar rats of
either sex, weighting 180-250 g (from Iffa-Credo,
France). Animals were placed in a stereotaxic
device and the body temperature was maintained
at 37°C. Supplemental doses of the anesthetic
were given when a decrease in the amplitude of
the EEG delta waves was observed. Experiments
were carried out in accordance with the European
Communities Council Directive (86/609/EEC).
c.
Contralateral sensory-interference.
The
same as in (b) but the distracter stimulus was
applied to the skin area that the recorded
neuronal RF but located in the contralateral
side of the body.
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