Neuroscience
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Functional interactions between dopaminergic and noradrenergic systems occur in many brain areas, including the prefrontal cortex (PFC). Biochemical, electrophysiological and behavioral data indicate crosstalk between D1 dopamine receptor (D1R) and α1-adrenergic receptor (α1AR) signaling in the PFC. However, it is unknown whether these interactions occur within the same neurons, or between neurons expressing either receptor. ⋯ Our data also showed that the ratio of plasma membrane-bound to intracellular α1ARs is significantly reduced in D1R-expressing dendrites. Similar results were obtained using either a pan-α1AR or a selective α1bAR antibody to label noradrenergic receptors. Thus, these results demonstrate that D1Rs and α1ARs co-localize in PFC dendrites, thereby suggesting that the catecholaminergic effects on PFC function may be driven, at least in part, by cell-autonomous D1R-α1AR interactions.
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The intrinsic properties of spherical neurons play a fundamental role in the sensory processing of self-generated signals along a fast electrosensory pathway in electric fish. Previous results indicate that the spherical neuron's intrinsic properties depend mainly on the presence of two resonant currents that tend to clamp the voltage near the resting potential. ⋯ We also show that the low-threshold potassium current also causes the long refractory period, explaining the necessary properties that implement the dynamic filtering of the self-generated signals previously described. Comparative data from other fish and from the auditory system indicate that other single spiking onset neurons might differ in the channel repertoire observed in the spherical neurons of Gymnotus omarorum.
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Psychostimulant reward, as assessed via the conditioned place preference (CPP) paradigm, exhibits a daily rhythm with peaks in the late dark and early light periods, and a nadir near the light-to-dark transition. While this diurnal rhythm is correlated with neural activity in several corticolimbic structures, the brain regions mediating this behavioral rhythm remain unknown. Here, we examine the role of the ventral medial prefrontal cortex (mPFC). ⋯ Inactivation of the ventral mPFC at either of these phases also eliminated the daily rhythm in amphetamine-induced CPP via an increase in drug-paired chamber dwell time at the baseline nadir. Together, these results indicate that the ventral mPFC plays a critical role in mediating the diurnal rhythm in amphetamine CPP during both the acquisition and expression of learned reward-context associations. Moreover, as the loss of rhythmicity occurs via an increase at the nadir point, these results suggest that excitatory output from the ventral mPFC normally inhibits context-elicited reward seeking prior to the light-to-dark transition.
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The majority of work examining the nucleus accumbens core (NAc) has focused on functions pertaining to behaviors guided by appetitive outcomes. These studies have pointed to the NAc as being critical for motivating behavior toward desirable outcomes. ⋯ To address this issue we asked if NAc lesions impact performance on a two-way active avoidance task in which rats must learn to shuttle back and forth in a behavioral training box in order to avoid a footshock predicted by an auditory tone. Although bilateral NAc lesions initially impaired reward-guided decision-making, we found that the same lesions improved acquisition and retention of two-way active avoidance.
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We have developed a classifier capable of locating and identifying speech sounds using activity from rat auditory cortex with an accuracy equivalent to behavioral performance and without the need to specify the onset time of the speech sounds. This classifier can identify speech sounds from a large speech set within 40 ms of stimulus presentation. ⋯ Our results demonstrate that the spatiotemporal patterns generated in primary auditory cortex can be used to quickly and accurately identify consonant sounds from a continuous speech stream without prior knowledge of the stimulus onset times. Improved understanding of the neural mechanisms that support robust speech processing in difficult listening conditions could improve the identification and treatment of a variety of speech-processing disorders.