Biomedical Engineering Reference
In-Depth Information
ral stimulus coherence over scales in a narrow
band around the stimulus period. An estimate
of the band limits can be obtain from (3):
1
Sensory-Interference
Simultaneous application of another distractive
tactile stimulus (a gentle tickling with a paint-
brush for 30 s) on the contralateral whiskers
reduced tactile responses from 2.1±0.4 spikes/
stimulus to 1.7±0.3 spikes/stimulus (81% from
control value; p= 0.02) in 16 out of 23 neurons
(70%; Figure 1). We termed this decrease in
tactile responses caused by the application of the
distracter stimulus in the contralateral whiskers
as contralateral sensory-interference, as it has
been also described in the SI cortex (Alenda and
Nuñez, 2004, 2007). The response of the remain-
ing neurons was either not modified (n=2; 9%) or
increased (n=5; 21%).
A similar sensory-interference effect was
observed when the distracter tactile stimulus
was applied on the ipsilateral whiskers during
simultaneous stimulation of the principal whis-
ker (ipsilateral sensory-interference). Tactile re-
sponses from the principal whisker were reduced
to 1.6±0.5 spikes/stimulus (76% from control
value; p=0.01) in 19 out of 23 neurons (82% of
neurons; Figure 1). The remained four neurons
were not affected. Figure 2 illustrates PSTHs of a
typical neuron response in the three experimental
−
−
1
p
∈
(1
+
c
/ 2
k
)
, (1
−
c
/ 2
k
)
, which for
c
=
2 gives [0.86, 1.2] s. We shall refer to this band
as the stimulus period band. Obtained this way
coherence is a function of time
C
(
t
), which then
can be used to evaluate the power spectrum by
the conventional Fourier transform.
0
0
RESULTS
Neuronal Population
Tactile responses were studied in the SP5C
nucleus, whose participation in the sensory pro-
cessing is less known. Twenty three single neu-
ronal recordings in SP5C nucleus were included
in this study. Selected neurons were silent under
spontaneous conditions or displayed a low mean
firing rate (0.9±0.89 spikes/s), and had a RF that
corresponded to one or two whiskers. Tactile
stimuli (pulses of 20 ms duration) deflecting the
principal whisker evoked 2.1±0.4 spikes/stimulus
in the control stimulation conditions with a mean
latency of 20.1±0.9ms.
Figure 1. Percentage of I (sensory response Increase effect), D (sensory response Decrease effect) and
No change in the cases for ipsilateral (black box) and contralateral (grey box) distraction with respect
to control according the number of spikes evoked by each stimuli.
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