Editing Animal echolocation (section)

===== Inferior colliculus =====

In the [[Inferior colliculus]], a structure in the bat's midbrain, information from lower in the auditory processing pathway is integrated and sent on to the auditory cortex. As George Pollak and others showed in a series of papers in 1977, the [[interneurons]] in this region have a very high level of sensitivity to time differences, since the time delay between a call and the returning echo tells the bat its distance from the target object. While most neurons respond more quickly to stronger stimuli, collicular neurons maintain their timing accuracy even as signal intensity changes.<ref name="Pollak Marsh 1977"/> These interneurons are specialized for time sensitivity in several ways. First, when activated, they generally respond with only one or two [[action potential]]s. This short duration of response allows their action potentials to give a specific indication of the moment when the stimulus arrived, and to respond accurately to stimuli that occur close in time to one another. The neurons have a very low threshold of activation – they respond quickly even to weak stimuli. Finally, for FM signals, each interneuron is tuned to a specific frequency within the sweep, as well as to that same frequency in the following echo. There is specialization for the CF component of the call at this level as well. The high proportion of neurons responding to the frequency of the acoustic fovea actually increases at this level.<!--<ref name="Carew_2001"/>--><ref name="Pollak Marsh 1977">{{cite journal |last1=Pollak |first1=George |last2=Marsh |first2=David |last3=Bodenhamer |first3=Robert |last4=Souther |first4=Arthur |title=Echo-detecting characteristics of neurons in inferior colliculus of unanesthetized bats |journal=Science |volume=196 |issue=4290 |pages=675–678 |date=May 1977 |pmid=857318 |doi=10.1126/science.857318 |bibcode=1977Sci...196..675P }}</ref>