Neural Inhibition in Forward Masking of the Mouse Inferior Collicular Neurons: In vivo Intracellular Recording

Under free field stimulation condition, the forward masking of inferior collicular (IC) neurons of mouse (Mus musculus, Km) was examined by a pair of sound stimuli with different gap and fixed amplitude (80 dB SPL) in the present study. Total 32 IC neurons were obtained and the forward masking of 24 among these neurons was studied. The action potential (AP) firing to the probe in 58.3% of IC neurons could be completely recovery to the same degree with single tone stimulus when the gap of paired sound was longer than the duration of inhibitory postsynaptic potential (IPSP) evoked by masker occurring at post-AP. The AP firing to the probe in the remaining (41.7%) IC neurons could be completely recovery at paired sound gap less than or equal to the duration of the masker-evoked IPSP occurring at post-AP. However, the response latency to the probe could be just completely recovery when paired sound gap was longer than the duration of maskerevoked IPSP occurring at post-AP in almost all the IC neurons (23/24, 95.8%, P<;0.05). These results suggested that membrane potential state of the IC neurons, IPSP and synaptic depression might participate in the generation of forward masking.