Abstract
The representation of acoustic cues involves regions downstream from the auditory cortex (ACx). One such area, the perirhinal cortex (PRh), processes sensory signals containing mnemonic information. Therefore, our goal was to assess whether PRh receives auditory inputs from the auditory thalamus (MG) and ACx in an auditory thalamocortical brain slice preparation and characterize these afferent-driven synaptic properties. When the MG or ACx was electrically stimulated, synaptic responses were recorded from the PRh neurons. Blockade of type A gamma-aminobutyric acid (GABA-A) receptors dramatically increased the amplitude of evoked excitatory potentials. Stimulation of the MG or ACx also evoked calcium transients in most PRh neurons. Separately, when fluoro ruby was injected in ACx in vivo, anterogradely labeled axons and terminals were observed in the PRh. Collectively, these data show that the PRh integrates auditory information from the MG and ACx and that auditory driven inhibition dominates the postsynaptic responses in a non-sensory cortical region downstream from the ACx.
Highlights
The representation of auditory experience involves downstream processing beyond the auditory cortex (ACx)
The mean stimulation evoked a slow excitatory postsynaptic potential amplitude was greater in P24–34 neurons (P12–21: 3.3 ± 0.9 Hz, n = 15 vs. P24–34: 3.9 ± 0.4 Hz, n = 15; Shapiro-Wilk: W = 0.81, p = 0.0001, n = 30; Mann Whitney rank sum test, X2 = 4.22, p = 0.04)
Our primary finding is that perirhinal cortex (PRh), a key interface between sensory cortices and the hippocampus, is synaptically driven by both the auditory thalamus (MG) and cortex (ACx)
Summary
The representation of auditory experience involves downstream processing beyond the auditory cortex (ACx). PRh lesions disrupt behaviors that involve auditory cues (Corodimas and LeDoux, 1995; Kholodar-Smith et al, 2008a,b; Bang and Brown, 2009a,b; Gastelum et al, 2012). These observations motivated us to characterize the synaptic drive to the PRh from auditory regions in previously developed thalamocortical brain slice preparation (Cruikshank et al, 2002; Kotak et al, 2005). We used a peri-horizontal brain slice preparation known to preserve functional connections between the MG and ACx (Cruikshank et al, 2002; Kotak et al, 2005)
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