Modulation of amplitude sensitivity by bilateral collicular interaction among different frequency laminae

Plastic Change in the Auditory Minimum Threshold Induced by Intercollicular Effects in Mice

“…The inhibitory and facilitatory CoIC has been proven to interconnect the two ICs on both sides of the dorsal midbrain [ 24 – 26 ]; hence, the above-mentioned study findings are likely due to the fact that IC ES focal electrical stimulation weakens and strengthens the effectiveness of a given sound stimulus through inhibition and excitation of inhibited and facilitated IC Mdu neurons, respectively. These inhibitory and facilitatory types of modulation activated by the 30 min IC ES focal electrical stimulation are similar to those demonstrated in a previous work [ 20 , 21 ]. In the mentioned real-time study, intercollicular effects were shown to be mediated through widespread inhibition and focused facilitation [ 20 , 21 ].…”

“…These inhibitory and facilitatory types of modulation activated by the 30 min IC ES focal electrical stimulation are similar to those demonstrated in a previous work [ 20 , 21 ]. In the mentioned real-time study, intercollicular effects were shown to be mediated through widespread inhibition and focused facilitation [ 20 , 21 ]. In the current study, most of the facilitated IC Mdu neurons displayed BF differences smaller than 2 kHz, whereas the inhibited IC Mdu neurons showed a wide range of BF differences (0–8 kHz) ( Figure 2(a) ).…”

“…MT shifts with BF differences ≤2 kHz in the IC Mdu neurons were larger than those with BF differences >2 kHz ( Figure 2(a) ). According to the topographical organization of the CoIC between the ICs, the commissural neurons in the central nucleus of IC send divergent projections to the equivalent frequency laminae in the central nucleus of the opposite IC [ 20 ]. Moreover, the density of this projection is greatest between the corresponding points [ 20 ].…”

“…According to the topographical organization of the CoIC between the ICs, the commissural neurons in the central nucleus of IC send divergent projections to the equivalent frequency laminae in the central nucleus of the opposite IC [ 20 ]. Moreover, the density of this projection is greatest between the corresponding points [ 20 ]. Therefore, the intercollicular effects evoked by focal electrical stimulation should be stronger in the equivalent frequency laminae between two ICs.…”

Neural interactions in unilateral colliculus and between bilateral colliculi modulate auditory signal processing

“…Conversely, the inhibitory modulation of bilateral collicular interaction sharpens the RIFs and FTCs of inhibited IC neurons but increased the slope of their RIFs and Q 10 value of their FTCs for sharper sensitivity to sound amplitude and frequency (Mei et al, 2012b; Cheng et al, 2013). It is also suggested that the small proportion of bilateral collicular excitatory interactions between neurons in corresponding frequency laminae and the large proportion of bilateral collicular inhibitory interactions between neurons in different frequency laminae may be involved in the formation of binaural neurons (i.e., excitation–excitation, EE neurons that can be excited by same BF sound stimulation to either ear; excitation–inhibition, EI neurons that are strongly excited by sound stimulation to the contralateral ear and are inhibited by sound stimulation to the ipsilateral ear; Mei et al, 2012a). The possible neural pathway may be described that the excitation from ipsilateral ear can cross to the contralateral IC in a lower auditory nucleus and then to the ipsilateral IC via facilitatory or inhibitory CoIC, respectively.…”