Figure 2.

Types of neuronal response patterns evoked by broadband noise. A–F show PSTHs (bin width, 5 ms) of selected neurons from six temporal response types in response to 250 ms broadband noise pulses. Gray shaded areas indicate the duration of the stimulus. All neurons were recorded from aged animals. A, Onset (on) neuron, discharging during the first 50 ms of stimulus presentation. B, Spontaneously (spont.) active primary-like neuron (plb), responding ≥30% stronger during stimulus onset (first 50 ms) than during the later portion of the stimulus. Note that this neuron (in contrast to the neuron presented in D) does not show a dip in discharge after stimulus offset (arrows in B and D). This behavior was exclusively observed for aged neurons. C, Sustained neuron (sus). This type of neuron showed a sustained discharge pattern during the entire sound presentation. D, Spontaneously active primary-like neuron (plb), which discharged with a primary-like pattern during sound presentation, paused, and recovered spontaneous activity during the silent interval between noise burst presentations. E, Late sustained/build-up neuron (lsus). This type of neuron exhibited a build-up or a sustained discharged pattern after a latency of ≥50 ms. F, Offset/inhibitory neuron (off); neurons from this class either suppressed discharge below spontaneous activity during stimulus presentation or exclusively discharged after stimulus presentation. G, Absolute time of first action potential after stimulus offset (mean ± SD over repetitions) versus rate of discharge between stimuli for spontaneously active neurons. Response types of neurons are coded in colors: onset (on), primary-like (plb), sustained (sub), late sustained (lsus), offset (off), and sparse (spa) cells that showed spontaneous activity. Whereas in young adult animals, only offset neurons strongly discharged within 150 ms after stimulus offset, in aged animals, primary-like and offset neurons strongly discharged within 150 ms in aged animals (gray shaded areas).