Development of spectral and temporal response selectivity in the auditory cortex

Abstract

The mechanisms by which hearing selectivity is elaborated and refined in early development are very incompletely determined. In this study, we documented contributions of progressively maturing inhibitory influences on the refinement of spectral and temporal response properties in the primary auditory cortex. Inhibitory receptive fields (IRFs) of infant rat auditory cortical neurons were spectrally far broader and had extended over far longer duration than did those of adults. The selective refinement of IRFs was delayed relative to that of excitatory receptive fields by an Ϸ2-week period that corresponded to the critical period for plasticity. Local application of a GABA A receptor antagonist revealed that intracortical inhibition contributes to this progressive receptive field maturation for response selectivity in frequency. Conversely, it had no effect on the duration of IRFs or successive-signal cortical response recovery times. The importance of exposure to patterned acoustic inputs was suggested when both spectral and temporal IRF maturation were disrupted in rat pups reared in continuous, moderate-intensity noise. They were subsequently renormalized when animals were returned to standard housing conditions as adults.

A synaptic memory trace for cortical receptive field plasticity

“…These data are reminiscent of recent findings showing that the timing of the AI critical period can be altered by exposure to different auditory environments 10,12 .…”

Enduring effects of early structured noise exposure on temporal modulation in the primary auditory cortex

“…By contrast, previous studies that applied continuous noise exposure during the critical period reported that noise-rearing did not necessarily permanently impair cortical temporal processing into adulthood; the cortex returned to ''normal'' after animals were returned to a normal acoustic environment (13,14). A similar difference in the duration of exposure-induced plasticity has been reported in spectral domain development of A1 when rats were exposed to pulsed (11,12) or continuous (13) noise during the critical-period epoch.…”

“…Using a two-tone stimulus paradigm, it has been shown that the duration of poststimulation suppression significantly influences the ability of cortical neurons to respond to successive acoustic stimuli (14). Here, we estimate the dynamics of cortical excitability, using compound PSTHs generated by tonal stimuli.…”

“…Two of these studies did report that continuous noise exposure early in life altered temporal response properties of cortical neurons. Those changes were reversed after exposed rats were returned to normal environments (13,14). The effects on cortical spectral processing induced by exposing rats to sounds with different spectrotemporal structures have varied substantially as a function of the temporal features of the applied stimuli (10-13).…”

Paravalbumin-Containing Interneuron Connectivity and Critical Period Modulation

“…Moreover, changes in PV connectivity during postnatal development may allow for the maturation of simple receptive field organization. For instance, appropriate developmental inhibitory receptor activation is necessary for the normal reduction in spatial extent and temporal duration of receptive fields in primary sensory cortex (Chang et al, 2005).…”