Healthcare and Medicine Reference
In-Depth Information
All cells have
>1 input
100
TTX ( )
80
TTX cuff
60
Control ( )
40
20
0
All cells have
only 1 input
6
8
10
12
14
16
18
20
Age (postnatal day)
TTX
FIGURE 9.14 Decreased activity prevents synapse elimination. At the rat nerve-muscle junction,
polyneuronal innervation declines between 10 and 15 days postnatal (green line). When a TTX cuff was placed
around the motor nerve root from postnatal day 9-19 and action potentials were eliminated, polyneuronal
innervation remained high (red circles). (Adapted from Thompson et al., 1979)
All cells have
>1 input
Control ( )
100
80
60
Stimulation ( )
40
20
Stimulator
0
All cells have
only 1 input
6
8
10
12
14
16
18
20
Age (postnatal day)
Stimulation
FIGURE 9.15 Increased muscle activity accelerates synapse elimination. Most rat soleus muscles are
polyneuronally innervated between postnatal days 8-10 (green line). When a stimulating electrode was
implanted in the leg to activate the sciatic nerve and muscle from postnatal days 6-8, there was a severe
decline in the number of polyneuronally innervated muscle cells (red circles). (Adapted from O'Brien
et al., 1978)
sharpening of tuning curves was prevented (Figure
9.16D). Noise pulse-rearing had no effect on tuning
curves from mice older than 30 days, suggesting a spe-
cific developmental effect (Zhang et al., 2002). There-
fore, when afferents all have the identical pattern of
activity, they are apparently unable to segregate prop-
erly along the frequency axis.
A similar finding is obtained in cats that were deaf-
ened by damaging the inner hair cells, and then stim-
ulated electrically within the cochlea. This is a highly
relevant experimental model because children with
profound hearing loss are now routinely implanted
with cochlear prostheses, and they hear the acoustic
world via electrical stimulation of their cochlea
Search Pocayo ::




Custom Search